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Management of Aquatıc Plants College of Agricultural Sciences Under ideal conditions, limited amounts of aquatic vegetation add to the aesthetic beauty of the pond and the ecosystem balance among the pond’s aquatic life Introduction If you build it, they will come That can be said of ponds and aquatic plants Just as grass and weeds will grow quickly on exposed soil, aquatic plants and algae will colonize new ponds in short order While these plants and algae can grow abundantly and interfere with various pond uses, they also provide many benefits to the pond if their growth is limited The first step in assessing the importance of aquatic plants to your pond is to determine your intended primary use(s) for the pond Ponds are frequently used in several ways to satisfy more than one objective For example, having water available in the pond for fire protection may satisfy one objective without interfering or conflicting with other objectives such as swimming or fishing Multiple-use ponds are fine as long as the uses are compatible When conflicting or incompatible uses are desired, it is necessary to assign priorities to the owner’s objectives For example, the objective of providing an If you build it, they will come area for swimming may conflict directly with the objective of having water available for irrigation Irrigation needs may lower the water level to a point where swimming is not possible at a time when swimming is most wanted For this reason, you should list and prioritize specific objectives for your pond This publication is intended to help pond owners understand the importance and benefits of aquatic plants and algae When plant and algae growth reach nuisance levels, pond owners have many options to restore balance to the pond ecosystem Too often, pond owners reach for quick fixes like aquatic herbicides If not used properly, herbicides may eliminate too much vegetation or beneficial plants along with the targeted weeds Herbicides are just one method of controlling unwanted plants and algae Nonchemical methods may provide longer and more permanent control and should be considered when developing a pond vegetation management strategy Information in this publication will help pond owners properly identify aquatic plants, understand their benefits, and choose appropriate control strategies (where necessary) to minimize damage to the pond ecosystem The Role of Aquatic Plants in Natural Pond Ecology Ponds are most healthy when there is a balanced ecosystem of insects, plants, fish, and animals otherwise known as a “food web.” A balanced food web includes some planktonic algae and aquatic plants at the top, which serve as a food source for small zooplankton and aquatic insects The zooplankton and insects in turn provide food for the smallest fish in the pond These then become prey for larger fish, which finally may be taken by raccoons, bears, or fishermen Under ideal conditions, pond plants also provide oxygen to the water during the day as a result of photosynthesis Some of this oxygen is then used to support the same plants during nighttime respiration In the winter, water temperatures get much colder and ice may cover the top of the pond for an extended period of time Most aquatic plants become dormant or produce seeds and die before winter, but a few plants are capable of remaining green and growing all winter long These plants are usually able to get enough light through Aquatic plants serve as important habitat for insects and other pond life the ice to cause some photosynthesis and help support pond life during the harsh winter conditions The optimum amount of aquatic vegetation for a given pond is difficult to identify because it depends on the preferred use of the pond Generally, aquatic vegetation should cover 20 to 40 percent of the pond area (bottom and top) to provide a healthy pond ecosystem The smaller percentage is preferable for boating, irrigation, and swimming, while the larger percentages are best for ponds intended primarily for fishing recreation Benefits of Plants and Algae A recent survey of Pennsylvania pond owners found that nearly two-thirds felt that aesthetic beauty was the main reason for building a pond on their property Part of the picturesque view of a pond includes at least some aquatic vegetation and the beauty it can impart The aesthetic beauty of water features with aquatic plants is one of the main reasons backyard ponds have become so popular in the last decade Besides their aesthetic beauty, plants and algae provide many benefits to the pond ecosystem Both the roots and leaves of aquatic plants can reduce muddy water conditions The roots of submerged and floating plants stabilize the bottom sediments while the dense leaves of submerged plants trap floating debris and sediment The plants also remove nutrients from the water column, thereby reducing the availability of nutrients to cause nuisance algae blooms The nutrients are stored in the plants until fall when much of the nutrient load falls to the pond sediments as the plants die Around the edge of the pond, the roots of emergent plants also stabilize the pond banks and reduce erosion Under the water surface, the dense stems, roots, and leaves of aquatic plants serve as excellent habitat for insects and invertebrates including snails, leeches, and crayfish The plant structure traps organic material and promotes the growth of periphyton (attached algae) and attracts zooplankton (barely visible aquatic animals) that serve as important food sources for Overabundant Aquatic Plant Growth Many of the same benefits provided to ponds by optimum levels of plant growth can be taken away by overabundant plant growth Nuisance plant and algae growth can ruin the aesthetic appeal of the pond, degrade water quality, and even kill aquatic life Unfortunately, nuisance plant growth is a common complaint among pond owners in Pennsylvania (Figure 1) Healthy pond fish populations depend on aquatic vegetation for food, cover, and reproduction 60 Pond Owners (Percent) these scavengers Aquatic insects also perch on aquatic plants and filter the surrounding water for food The benefit of aquatic algae and plants to the pond fishery cannot be overestimated, especially since more than 50 percent of pond owners in Pennsylvania consider fishing recreation a major use of their ponds A healthy and well-balanced fish population is more attainable if significant aquatic plant beds exist in the pond Many pond fish use weed areas as nesting beds to provide cover for their young Some feed directly on the plant leaves or the insects resting on the leaves All fish use the cover provided by vegetation to stalk prey Small fish hide from larger fish in underwater plants to prevent predation As a result, the amount and type of vegetation will affect the fish population structures Too much vegetation will allow many young fish to survive, making it difficult for larger fish to grow Too little vegetation allows predator fish to easily capture smaller fish In this case, fish may grow quickly until they consume all the smaller fish in the pond In addition to fish, other types of wildlife thrive in the pond environment In fact, pond owners are often surprised at the number and diversity of wildlife that is attracted to a pond, especially if the pond is constructed in an area that is otherwise lacking water resources Part of this attraction is the type of aquatic plants present in the pond.Various aquatic plants are a vital component in the diet of ducks and geese They not only eat the plants themselves but also devour the insects that live on the plant surfaces Emergent plants around the pond edge also serve as important nesting areas that provide dense cover for waterfowl.Various mammals also use aquatic plants For example, muskrats prefer ponds with cattail beds for food and cover Many pond owners are also surprised to see whitetail deer occasionally feeding on various pondweed species in and around the pond Last but not least, amphibians and reptiles such as turtles, salamanders, and snakes rely on pond plants for food and shelter 40 20 Plants/ Nuisance Leaks algae wildlife Water Fish quality kills Figure The prevalence of various pond problems based on a survey of Pennsylvania pond owners Overabundant plant and algae growth ruin the aesthetic beauty of the pond Aquatic plants and algae grow abundantly in certain settings for many reasons The simplest explanation is an overabundance of nutrients, primarily phosphorus and nitrogen A pond begins with mostly water, few nutrients, and little aquatic life As a result, a newly created, deep, springfed pond may have little life of any kind because of the lack of nutrients available to support pond life Over time, the pond accumulates nutrients in a process known as “eutrophication.” The addition of nutrients stimulates increased growth of algae, plankton, and aquatic plants, which grow, mature, and die Their remains decay and the nutrients are released back into the water of the pond to keep the cycle going A shallow, nutrient-rich pond exposed to sunlight with little water flowing through it will be teeming with algae and aquatic plants Eventually, though, material that resists decay will accumulate and the pond will fill up and become a bog or wetland This process of conversion to a bog or wetland can happen in a decade or may take centuries Humans greatly accelerate the eutrophication process through landuse activities Nearby fertilizer applications, septic systems, urban runoff, animal manure, erosion, and waterfowl can all add significant amounts of nutrients to a pond Too many plants are discouraging to the pond owner and are also detrimental to the pond ecosystem For example, a pond completely covered with water lilies will shade the pond enough to prevent other vegetation from growing under the water The shade will also be sufficient to reduce the growth of planktonic algae that serve as the base of the pond food web The resulting situation is a pond that is very unproductive for anything besides water lilies Similarly, a pond covered with duckweed or watermeal will also shade out any life beneath the surface In some cases, duckweed and watermeal may grow so quickly that they cause submerged plants to die prematurely due to shading The decay of the dead submerged plants can result in reduced dissolved oxygen and the death of fish and other pond life Complete coverage of the pond by floating plants can also eliminate oxygenation of the water and kill pond life by maintaining a complete separation of the water surface from the atmosphere Important Pond Measures and Features Related to Aquatic Plants Strategies to manage aquatic plants and algae require an understanding of several features related to the pond structure Some of these are basic measurements or observations that are rarely done by pond owners but can be easily accomplished.You might be surprised what you learn about your pond in the process Watershed and Water Source The pond “watershed” is an important concept that must be understood to determine the sources of nutrients that may be causing excessive plant growth The watershed includes the area of land surrounding the pond that contributes water to it Identifying the pond watershed is important because anything that occurs within this area can impact the pond Locating a pond in an undisturbed area and minimizing disturbance and land-use changes within the pond watershed are important components of protecting a pond A pond’s watershed is determined by the source of water feeding the pond Ponds that collect surface drainage will have a simple watershed boundary that includes all the land that drains surface water toward the pond Ponds that collect stream or spring water will have more complex and larger watershed boundaries that include all the area that drains into the respective stream or spring that feeds the pond The source of water feeding the pond can be important to the resulting growth of plants and algae in the pond A pond with a continuous supply of water is almost always going to be a more satisfactory pond than one with an intermittent water supply The nutrient conditions in a pond with a continuous overflow are likely to be better because excess nutrients will leave with the overflow water In contrast, a pond having intermittent flows only has a chance to purge excess nutrients during storm events Such ponds are prone to accumulate nutrients—resulting in excessive plant growth— much more rapidly than their overflowing cousins Pond water can be tested for nutrients like nitrate and phosphate to determine if excessive levels are accumulating in the pond Land-use activities that occur near the pond or within the watershed of the pond source (spring, stream, etc.) will largely determine the amount of nutrients that enter the pond and the resulting amount of plant and algae growth Identify and protect the land areas directly adjacent to the pond and the land areas surrounding the water sources that feed the pond Special care should be taken to avoid polluting activities such as applying fertilizers and animal manures or placing septic systems around the pond and its water sources Pond Surface Area The importance of getting an accurate measurement of your pond surface area cannot be overestimated The majority of pond owners visually estimate their pond area, which usually results in an overestimate of the true pond surface area Rather, the pond area should be calculated based on some simple measurements The effort necessary to estimate pond surface area is directly related to your pond’s shape and uniformity The simplest method—using basic equations for common shapes—can be applied if your pond closely resembles a circle, square, or rectangle in shape The area of a circular pond can be estimated by measuring the distance around the pond shoreline in feet Square the shoreline distance and divide by 547,390 to get the pond area in acres For example, a pond that is 450 feet around the shoreline would have an area of 0.37 acres [(450 feet)2 ÷ 547,390 = 0.37 acres] The area of a rectangular or square pond is estimated by simply measuring the length and width of the pond sides in feet Multiply the length by the width to get the square feet of surface area This value can be converted to acres by dividing by 43,560 square feet per acre So, a pond that measures 150 feet long and 100 feet wide would have an area of 0.34 acres (150 feet x 100 feet = 15,000 ft2 or 0.34 acres) Most ponds have an irregular shape for which the surface area cannot be adequately estimated using the formulas for common geometric shapes Three methods can be used in this case depending on the degree of accuracy you desire Keep in mind that the accuracy of your pond surface area estimate may be very important, especially for the safe use of aquatic herbicides The three methods are described in order from least to most accurate.You should strive to use the most accurate method that you can reasonably accomplish Nutrient levels in pond water can be easily determined using test kits available at most pet stores Land uses near the pond and within the pond watershed can cause excessive aquatic plant growth 20' 46' 48' 80' 70' 43' 42' 88' 108' 134' 163' 137' Figure An irregular-shaped pond broken into six trapezoids for estimation of pond surface area Handheld GPS units are one method to measure pond area 159' Average Length and Width Method Take numerous measurements to determine the average length and width Make certain you get both the longest and shortest distances in calculating the average length, as well as the widest and narrowest distances for determining the average width The more measurements you make, the more accurate your result will be The area is then calculated by multiplying the average width by the average length If you your measurements in feet, your result will be in square feet.You can convert square feet into acres by dividing it by 43,560 square feet per acre Depending on the number of width and length measurements you make, the final area will probably be within about ±20 percent of the actual pond surface area “waypoints,” can be stored in the GPS unit for use with mapping software that either accompanies the unit or can be purchased separately The software can connect the waypoints and calculate the area inside the resulting shape You can estimate pond surface area by walking the perimeter of the pond and stopping at various waypoint locations along the pond shoreline If waypoints are stored at each location where the pond shape changes, the resulting area will be extremely accurate, probably within percent of the actual pond area Even if you not own a GPS system, friends or family members that enjoy outdoor recreation may own a unit that you can use to estimate your pond surface area Multiple Trapezoids Method A more accurate method to determine the area of an odd-shaped pond is to divide the pond into multiple trapezoid shapes A new trapezoid is defined anywhere the shoreline makes a rapid change in direction Figure shows an irregular pond shape divided into six trapezoids (shown in dotted lines) Note that instead of horizontal transects, this method requires measuring the distance between each vertical transect This is most easily done during winter when the pond is frozen and the transects can be easily laid out and measured This method requires more measurement and effort, but the final area estimate will probably be within about ±5 to 10 percent of the actual pond area For the pond in Figure 2, multiplying the length and width of each trapezoid and then summing the area for all six trapezoids results in a pond area of 34,792 square feet, or about 0.80 acres The volume of water in ponds is often expressed in units called “acre-feet.” An acrefoot represents one surface acre that is one foot deep To calculate the acre-feet of water in a pond, you’ll need the surface area in acres as calculated above and an average depth of water in the pond For a typical bowl-shaped pond, the average depth can be estimated as 0.4 times the maximum depth So, a pond with a maximum depth of 12 feet would have an average depth of about 4.8 feet A more accurate method for calculating average depth is to make many measurements and calculate an average This is most often done by measuring the pond depth along two transects—one along the width and one along the length Make sure to pick transects that represent the shallow and deep portions of the pond Depths can be measured easily from a canoe or boat using a weight and a string marked in feet The more depth measures you make, the more accurate your final average will be An even better way to calculate an average pond depth is to divide the pond into numerous (at least four) subareas (much as we did in the trapezoid method) Take at least one depth within each of the subareas and use these to calculate the overall average pond depth This method is especially good if the pond bottom is irregular rather than bowl shaped For the pond example Global Positioning Systems (GPS) Handheld GPS systems have become quite common over the past five years as they have become more affordable They are now routinely used for outdoor recreation (hunting, hiking, camping, etc.) and navigation GPS units allow you to determine your exact location on Earth using multiple satellites in space.Various locations, or Pond Volume given in Figure 2, water depths measured in each of the six trapezoids resulted in an average pond depth of 4.5 feet Multiplying this depth by the area of the pond in acres provides the pond water volume in acrefeet (4.5 feet x 0.80 acres = 3.6 acre-feet) Residence Time The residence time of a pond measures the average length of time it takes for a molecule of water to pass through the pond from its entry to the overflow pipe Knowing this characteristic of your pond may be critical, especially for the use of some herbicides In some cases, herbicides will not be effective unless they are present in the pond water for some period of time For example, some herbicides suggest thirty days of contact time with the targeted plant to achieve effective control If the residence time of a pond is only seven days, using this herbicide would not be successful in achieving control The residence time is easy to calculate Simply calculate the pond volume in acrefeet as described above and measure the rate that water leaves the pond in gallons per minute (gpm) The outflow can be estimated using a simple bucket and stopwatch to catch water leaving the pond through the outlet of the overflow pipe The residence time in days can be calculated as follows: residence time = 226 x [pond volume] ÷ overflow rate For example, a one-acre pond with an average depth of feet and an overflow rate of 10 gallons per minute would have a residence time of 113 days [226 x (5 acre-feet) ÷ 10 gpm = 113 days] Other Pond Characteristics That Affect Plant Growth Numerous physical features of the pond are important in affecting the amount and diversity of aquatic plant and algae growth You should inspect each of these pond features annually to determine if changes are needed before resorting to other plantcontrol strategies Pond Depth and Slope Most plant and algae growth begins in less than feet of water This water depth allows sufficient sunlight to penetrate to the pond bottom to allow plant growth to begin from the sediment This is true of all kinds of aquatic plants, including submerged, emergent, floating, and algae Minimizing the area of the pond that has less than feet of water will minimize the area that can be colonized by plants and algae This is most easily done during pond construction by shaping pond banks to have a 1:3 bank slope or greater (i.e., a water depth of at least feet at a point feet from the shoreline) As the pond fills in over time, pond depths will decrease, leading to greater plant growth Dredging can be used to restore deeper water and reduce plant growth Overflow and Drain Pipes Most ponds have a vertical overflow drain pipe that controls the level of the pond water This L-shaped pipe moves water and associated nutrients under the dam and out of the pond to a receiving stream The overflow pipe is sized based on the pond’s drainage area, inflow, and water-storage characteristics It is especially important to inspect the overflow pipe and remove debris in or near the pipe Obstructions of this pipe may result in increased retention of water in the pond and greater sediment buildup on the pond bottom Blockage of the overflow pipe may also cause increased erosion and sedimentation from bank sediments Depending on the construction, a drainpipe may also be installed in the pond to allow for easy manipulation of the pond water level (called “drawdown”), which can be helpful in controlling plant growth around the edges of the pond Steep slopes along pond banks will prevent most aquatic plant growth An annual pond inspection might reveal structural problems (such as a clogged overflow pipe in this picture) that can be quickly fixed before they cause serious problems Types of Aquatic Plants and Algae Plankton algae Successful control of aquatic plants and algae always begins with accurate identification of the plants that exist in the pond or lake Dozens of aquatic plant and algae species occur in Pennsylvania—some are unique and easy to identify, while others are very difficult to accurately identify They may change their appearance at different times of the year and many not have conspicuous flowers or seeds to assist with identification All aquatic plants can be separated into one of four categories: algae, submerged aquatic vegetation, floating plants, and emergent plants Algae Filamentous algae Chara Nitella Leafy pondweed Algae occur in all ponds and frequently grow to nuisance levels due to excessive amounts of phosphorus and nitrogen in the pond water In fact, surveys of pond and lake owners in Pennsylvania have found that algae are the most common nuisance aquatic plant Algae are important to the pond ecosystem, providing food for insects that are fed upon by fish and other pond wildlife However, excessive growth of algae can ruin the aesthetic appeal of the pond and also have devastating effects on pond life when it dies in the fall of the year Algae occur in three different types— plankton, filamentous, and an attached branched form Plankton algae (phytoplankton) are the minute, single-celled suspended types that usually make the water pea-soup green, reddish, or brown Ponds with excessive plankton algae will usually have clear water during the cold, winter months, but the water will quickly cloud up during spring and summer as plankton algae grow in response to warm water The exact species of plankton algae in a pond can only be identified using a microscope Filamentous algae are the most common algae complaint among pond and lake owners These algae begin to grow on the bottom of the pond, usually in shallow water less than feet deep As the algae grow, they produce oxygen, which becomes trapped in the filaments, causing the algae to float toward the pond surface Once enough oxygen becomes trapped in the algae, a large mat will break loose and spread across the surface Although all filamentous algae begin to grow in shallow water, they can quickly cover the entire pond surface as mats break loose and become free floating Filamentous algae are easily distinguished from all other plants and algae, but a microscope is usually necessary to identify the exact species Attached branched algae look very much like a plant They are anchored to the bottom just like a submerged plant, but they have no true root system Two common attached branched algae are Chara and Nitella Chara usually grows in ponds and lakes with hard water in areas underlain by limestone It is gritty to touch and has a skunklike odor when crushed Nitella is soft and usually found in higher elevation ponds and lakes with soft water It is difficult to distinguish from several rooted, submerged aquatic plants Submerged Aquatic Vegetation Submerged plants are the most diverse group of aquatic plants with many special features They generally have submerged leaves that are flexible and small to reduce drag from underwater currents The leaves tend to be buoyant with air vacuoles that allow them to capture the maximum light in the water column The leaf surface is usually thin and without a waxy surface to allow for gas exchange from the surrounding water Many submerged plants have multiple types and shapes of leaves (submersed and floating) to maximize their ability to capture energy from sunlight, making them difficult to identify The stems of these plants are flexible and buoyant to allow the plant to float well within the water column Stems also often contain chlorophyll to assist the plant in capturing the limited sunlight under the water Most submerged aquatic plants grow in shallow water less than feet deep where sunlight penetrates to the bottom of the pond A few plants have the ability to grow in dimmer light conditions in very deep water Aquatic Plant Growth Prevention and Control Preventing Aquatic Plant and Algae Growth The old saying “an ounce of prevention is worth a pound of cure” also applies to controlling aquatic plants and algae in ponds and lakes Reacting to overabundant growth, once it has occurred, is simply a band-aid approach that often involves perpetual treatment to control the plant But several strategies can be used to prevent plant and algae growth before it occurs Pond Construction Features Most plant and algae growth begins in shallow water less than feet deep where sunlight can reach the pond bottom Therefore, limiting the amount of shallow water in the pond will control the amount of plants and algae that can grow As was mentioned earlier, this can be achieved by constructing the pond so the water is at least feet deep at a point feet from the shoreline (a 1:3 bank slope) If the pond will be used for swimming, you may wish to construct a small area with a gentler slope to allow for easy and safe entry into the pond For existing ponds with gentle bank slopes and extensive shallow water, dredg- A simple strip of unmowed grass around the pond edge, like this buffer around a golf course pond, can reduce aquatic plant and algae growth in the pond by reducing nutrients delivered to the pond 12 ing can be used to deepen the pond edges and prevent future plant and algae growth (see “Dredging” section later in this publication) Nutrient Control Strategies As was previously discussed, aquatic plants and algae grow to nuisance levels in response to excess levels of phosphorus and nitrogen in the pond water Thus, strategies that reduce nutrient entry into the pond will have the benefit of preventing future plant and algae growth Nutrient control strategies are rarely employed by pond owners because they are often perceived as too difficult and expensive, and they also not provide an immediate reduction in plant growth Rather, nutrient reductions will lead to a gradual and long-term reduction in plant and algae growth In an era of quick fixes for all problems, pond owners are unfortunately more likely to choose other approaches, such as herbicides, to control plants and algae Buffer Strips Perhaps the easiest method to control nutrients entering a pond is to establish a buffer strip of vegetation Maintaining a strip of vegetation around the pond and also around streams and springs that feed the pond is very beneficial for capturing nutrients before they enter the water Buffer strips act to slow water down and encourage infiltration of the water into the soil where the plant roots can capture and utilize nitrogen and phosphorus Buffers also act to remove sediment from the water by slowing water velocity The composition of a buffer does not need to be fancy A simple, 30-foot wide strip of taller grass will often suffice on gentle slopes around the pond A wider buffer with more diverse vegetation is better, especially on steeper slopes that provide runoff to the pond Buffer strips planted with native vegetation and wildflowers can also attract wildlife to the pond area A buffer area that includes larger vegetation capable of shading some of the pond water will also help reduce plant growth by limiting direct sun and cooling the water temperature Erosion and Sediment Control Most phosphorus enters a pond attached to soil particles that are suspended in water entering the pond Practices that reduce erosion near the pond and sediment delivery to the pond through the water supply can be effective in reducing aquatic plant and algae growth Reducing sediment delivery also prevents the pond from becoming shallower and thus reduces aquatic plant growth Erosion control around the pond involves the creation and maintenance of the vegetated buffer strip as described above Reducing sediment delivery to the pond through surface runoff or surface streams is more difficult The processes that cause sediment delivery to streams and springs are often large-scale land-use activities that are out of the pond owner’s control (e.g., stormwater runoff from housing developments and shopping centers upstream) Assuming that sediment cannot be reduced in the incoming runoff water, the pond owner can reduce the impact of sediment on the pond by creating a small sediment pond or shallow pool at the inlet of the main pond Water passing through this sediment pond or pool on its way to the pond will have an opportunity to drop its sediment load in the pool This pool should be of such dimensions that it can be easily cleaned with a backhoe A sedimentation pool helps the pond in the same way that sediment is removed by buffer strips Limit Fertilizer and Manure Applications Fertilizers and manures applied to lawns, golf courses, and farm fields may run off into adjacent ponds and lakes Some of the nutrients contained in these products may run off from the land where they are applied because plants are never able to utilize 100 percent of the nutrients Heavy rain immediately after application of fertilizers and manures is especially likely to cause runoff of nutrients into nearby ponds and lakes Just as these fertilizers are intended to stimulate growth of grass and crops, they also act to stimulate growth of aquatic plants and algae in receiving waters Reducing fertilizer and manure application rates on lands near ponds and prohibiting use of these products within the buffer area around the pond will reduce nutrients entering the pond Limit Other Nutrient Sources Other sources of nutrients to ponds can often be controlled or diverted Barnyards, feedlots, and pastures may contain high amounts of animal wastes rich in nutrients Fencing ponds and streams to limit animal access will help reduce nutrient runoff and soil erosion into ponds and the streams that feed them Just as domestic animals may contribute nutrients to ponds, excessive amounts of wildlife can also be problematic. The most likely cause for concern is large flocks of Canada geese A recent study in the northeastern United States found that Canada geese can be a large contributor to phosphorus additions to ponds. A flock of 200 geese were found to produce about 100 grams of phosphorus each day, enough to stimulate large quantities of algae. Approaches to limit the numbers of geese and the length of time that they visit the pond will reduce the nutrient load to the pond   Finally, human wastes can be a significant source of nutrients to some ponds and lakes Care should be taken to locate septic systems as far from the pond or lake shore as possible Homeowners with septic systems need to properly maintain the system to ensure that malfunctions don’t occur that could cause nutrient pollution into nearby ponds In the absence of strategies to control nutrients entering ponds, many pond owners are limited to reacting to excessive growth after it has started It is important to realize that acting to reduce plant and algae growth without addressing the underlying cause may simply create alternate problems For example, reducing submerged and floating aquatic plants may lead to increased algae growth by releasing nutrients formerly bound up in living plant material A truly integrated approach is usually necessary that incorporates water quality measurements, pond construction features, and physical, biological, and chemical controls to create a balanced aquatic plant management plan Sediment and nutrient levels in farm ponds can be greatly reduced by fencing the pond and piping drinking water to troughs Canada geese can increase aquatic plant and algae growth through their wastes 13 Physical Control Strategies Physical control strategies are akin to pulling weeds from your flower beds Many of these processes are time consuming and labor intensive, but they often have longerterm benefits than chemical control That’s because removal of plants and algae from the pond also removes the nutrients associated with the plants, which makes fewer nutrients available for future plant growth Raking and other physical removal of plants can be advantageous because they also remove nutrients from the pond Harvesting Physical harvesting of aquatic plants and algae can be very effective, especially for small quantities of plants near the shorelines Also, unlike many other aquatic plant control strategies, hand or mechanized removal of aquatic plants and algae does not require a state permit Many pond owners have developed innovative tools and techniques to accomplish aquatic plant harvesting All these methods involve some type of cutting, mowing, raking, digging, skimming, or pulling Harvesting techniques must often be repeated several times each growing season to eliminate new growth as it appears On larger lakes, consultants can be hired to mechanically remove large amounts of aquatic plant growth with plant harvesters 14 Many submerged aquatic plants can reproduce through fragmentation As a result, attempts to cut and harvest these plants can result in increased growth due to sprouting from fragments left behind Before attempting to harvest submerged plants, make sure you properly identify the plant and determine if it can spread through fragmentation If the problem plant is known to reproduce from fragments, avoid attempting to harvest the plant and focus on other physical, biological, or chemical control techniques Plants and algae that are harvested from the pond should be removed from the vicinity of the pond edge This will prevent the nutrients released from the decay of the plants from being washed back into the pond water In larger ponds and lakes, mechanized harvesters may be used to remove aquatic plants and algae These mechanized harvesters can be expensive because of high maintenance costs The most widely used type of mechanized equipment is called a plant harvester (weed cutter) Plant harvesters are used mainly on large lakes and cut off the underwater rooted vegetation to feet below the water surface As with hand removal of plants, mechanized removal offers the advantages of removing much of the nutrients associated with the aquatic vegetation, thus reducing future plant growth Mechanized weed cutters that not harvest or collect the weeds for transport to shore are not recommended because plant fragments can live for long periods of time, develop root systems, and grow in areas that previously were unaffected with a weed problem Aeration Aeration can be beneficial to the overall health of some ponds and lakes, but it should be viewed as part of an integrated management plan to reduce plant and algae growth rather than a solution to the problem The most efficient type of aeration involves introducing air bubbles at the bottom of the lake or pond through diffusers or hoses with small holes This type of aeration, called diffuse aeration, requires electric power and some installation by a profes- sional The air bubbles rising from the diffusers on the bottom of the pond oxygenate the water and push the oxygen-poor water to the surface where it is reaerated through an exchange with atmospheric oxygen In addition, some oxygen is directly transferred from the air bubbles to the surrounding water The resulting aeration of the bottom pond water activates a number of complex processes that can help control algae by precipitating phosphorus out of solution and keeping phosphorus bound to the bottom sediments Aeration of the bottom water layers can also be beneficial to reduce the depth of the organic muck layer that forms on the bottom of the pond Aerobic (oxygen-loving) bacteria work much faster than anaerobic bacteria in breaking down organic material on the bottom of the pond The other type of pond aeration involves surface aeration through fountains Fountains generally only aerate a shallow layer of water near the pond surface, so they have little or no benefit to reduce phosphorus levels and control algae The mechanical agitation of the pond surface by the fountain will reduce the growth of some floating plants, such as water lily and duckweed, that prefer to grow in stagnant water Drawdown Most aquatic plants and algae begin growing in shallow water near the pond edge Partially draining the pond to expose these shallow areas—called drawdown— is another physical method to reduce the growth of aquatic plants Drawdown is usually done during the fall to expose pond sediments to freezing temperatures during the winter The degree of plant control from a drawdown depends on the plant species present and the minimum winter temperatures A drawdown accompanied by below-freezing temperatures provides the greatest aquatic plant control Drawdown is often difficult for pond owners to accomplish because they cannot easily draw the water level down and keep it lower for an extended time over the winter More often, drawdown is done on larger lakes and reservoirs that can easily control the water level A permit for drawing down an impoundment is required for ponds larger than one acre or for any pond drawdown to conduct an activity that requires another state permit, such as a Pennsylvania Department of Environmental Protection Waterways Obstruction and Encroachment Permit Additional information is available through your local office of the Pennsylvania Fish and Boat Commission and the Pennsylvania Department of Environmental Protection Dredging As sediment and organic debris enter the pond, they will settle to the bottom and reduce the water depth This sedimentation process occurs quickly in ponds that receive erosion and stormwater from disturbed areas and slowly in ponds that are spring fed in undisturbed areas Shallower water from sedimentation allows sunlight to reach more of the pond bottom, resulting in increased plant and algae growth Dredging sediment from the pond can be a remedy to reduce plant growth, albeit a time-consuming and expensive one The first steps in any dredging project should be to locate where the sediment originates and then determine how the sediment delivery may be controlled Restoration of a pond to its original configuration usually provides significant benefits, but they can be short lived if the sedimentation is allowed to continue Dredging is a regulated activity that may require a drawdown permit and a dredging permit before proceeding Pond owners should consult the local office of the Department of Environmental Protection before beginning any dredging project Diffuse aeration Fountain aeration Biological Control Strategies Many pond owners desire biological or “natural” techniques to control unwanted aquatic plants These methods are less physically demanding than mechanical control strategies described above and are usually less damaging to the pond ecosystem when compared to the chemical control strategies described in the next section Drawdown of lakes and ponds will reduce plant growth by freezing bottom sediments during winter 15 Triploid Grass Carp Grass carp are a nonnative, plant-eating fish that can be stocked in ponds and lakes to provide control of some aquatic plants They have been used successfully on many ponds and lakes throughout Pennsylvania to control abundant aquatic plant growth When used improperly, however, they can have negative impacts such as increased growth of algae, muddying of water, or no control of unwanted plants Several steps should be followed to maximize the success of grass carp in your pond Plant identification is absolutely essential when considering the use of grass carp These fish will voraciously eat some aquatic plants while ignoring others Grass carp can be very effective at controlling most varieties of submerged aquatic vegetation The table below lists some of the common likes and dislikes of grass carp Plants Preferred by Grass Carp Pondweeds (many Potamogeton species) Elodea Coontail Naiad Duckweed Muskgrass (Chara) Water milfoil Bladderwort Water-stargrass Plants Not Preferred by Grass Carp Filamentous algae Planktonic algae Cattail Bulrush Arrowhead Watershield Large-leaf pondweed Water lily Spatterdock Grass carp can be very effective in controlling some rooted aquatic plants 16 Acquire a state permit Once you have determined that the nuisance plant in your pond is a species preferred by grass carp, you must obtain a state permit through the Pennsylvania Fish and Boat Commission (PFBC) to purchase grass carp Grass carp stocked in Pennsylvania waters must be triploid, or sterile, nonreproducing fish This genetically altered carp was created by exposing the fertilized eggs to heat shock, causing both sexes of the fish to have three sets of chromosomes (triploid) rather than the normal two (diploid) The permit application has a small fee and must include a photo of the outflow structure of the pond In some cases, you may be required to install a device over the outflow to prevent the grass carp from escaping For lakes larger than acres, a more detailed environmental assessment must be done before grass carp can be stocked The permit application along with other grass carp information can be downloaded from the Penn State Water Resources Extension Web site at water.cas.psu.edu or obtained from your local PFBC office Purchase and stock the fish Once you have obtained the state permit, you can purchase grass carp for stocking in your pond A limited number of hatcheries sell grass carp (list available on the Web site shown above) and you must show the permit to purchase fish from the approved hatcheries Grass carp are typically sold as 10- to 12-inch fish to maximize their chances of survival after stocking Up to fifteen grass carp may be stocked for each acre of pond, but starting with an initial stocking of just a few fish per acre is usually best Monitor and alter management Grass carp will live for up to fifteen years after stocking, although their ability to consume aquatic plants declines markedly after ten years For that reason, large grass carp are often removed and replaced with a restocking of smaller fish Grass carp should also be removed if they overcontrol aquatic plants and muddy the water looking for additional plants—a common problem if too many are stocked in the pond Other Plant-Eating Fish (Not Recommended) Other fish species, including koi, common carp, and Israeli carp, are sometimes marketed for control of aquatic plants and algae While these fish occasionally nibble on plants and algae, they are not exclusive plant eaters and may cause more problems than they solve As a result, they are not recommended for aquatic plant control Biological Additives Various pond additives have recently been developed that may reduce plant and algae growth through biological processes These products normally contain various microbes or enzymes that feed on or consume nutrients (nitrogen and phosphorus), making them unavailable for plant growth In other words, they outcompete plants and algae for available nutrients in the pond Currently, no permit requirements exist to use these products in Pennsylvania and success has been mixed Some products are expensive and may require multiple applications during each year, and their results may be affected by the water quality conditions in each pond Still, as these products are further developed, they appear to be a promising alternative to the use of chemicals in aquatic plant control Barley Straw Barley straw has been used for many years with some controversy to control filamentous algae Some pond owners claim remarkable control with barley straw while others report no effect or increased algae growth The mechanism by which barley straw inhibits algae growth is poorly understood, but it is thought to be related to the release of hydrogen peroxide Barley straw should be applied to the pond during the fall or winter prior to the plants’ growing season As it decays, it may prevent algae growth in the following spring and summer It does not kill existing algae Approximately three to five bales of barley straw should be used per acre of pond area The bales should be broken apart and submerged in cages, nets, or other containers that will allow water to move through the straw The containers should be placed where maximum water movement is occurring in the pond (near the spring or stream that feeds the pond, if possible) Keep these three key points about barely straw in mind: • It is only used for prevention of filamentous algae (not for other aquatic plants) • It must be applied weeks before algae growth begins • It doesn’t always work and should be viewed as an inexpensive alternative that might be worth a try Chemical Control Strategies When aquatic plants and algae appear at nuisance levels, pond owners often turn to aquatic herbicides Herbicides are effective and usually provide quick solutions to aquatic plant problems Aquatic herbicides fall into two categories: contact and systemic Systemic herbicides are absorbed through leaves or roots and then transported within the treated plant Contact pesticides are not absorbed by the treated plants; they must directly touch the plant to be effective The use of aquatic herbicides has some disadvantages Aquatic plants often have to be treated every year to keep them under control Some chemicals can be quite costly and, if used incorrectly, may be hazardous to the applicator and the pond environment The preceding sections of this publication have demonstrated the multitude of options that exist for aquatic plant control in addition to aquatic herbicides The use of aquatic herbicides should only be undertaken after these other options have been investigated Keep in mind that effective control of aquatic plants and algae usually integrates nutrient management into the control plan Carefully follow each of the steps listed below if you are using an aquatic herbicide Barley straw submerged in bags may help prevent growth of some filamentous algae Aquatic herbicides can be effective, but they must be used with extreme care Properly identify your aquatic plant No single aquatic herbicide will kill every aquatic plant In fact, most herbicides have a relatively small number of plants that they will effectively control Therefore, it is imperative that you accurately identify the offending plant and choose the cor17 Trout are especially sensitive to aquatic herbicides Careful measurement of pond area and depth is critical to determine the proper amount of aquatic herbicide to apply to your pond 18 rect herbicide that will control it Use the information and links provided above for assistance with proper plant identification Example A nearly rectangular pond measures 275 feet long and 110 feet wide Select appropriate herbicide Once the plant is properly identified, the next step is to select an appropriate herbicide for control Several herbicides are available for any given aquatic plant found in ponds The selection of the “best” herbicide should be based on a number of variables: • effect on the target plant needing control • effect on other nontarget plants in the pond • presence of sensitive fish (like trout) or other aquatic life • water use restrictions for the herbicide • cost Appendix of this publication provides a description of the most common aquatic herbicides used in Pennsylvania and a table showing which plants each will control effectively Water use restrictions should be carefully evaluated before choosing an herbicide For example, a pond owner that needs a pond for irrigation would not want to choose an herbicide that has a thirty-day irrigation restriction after application Pond area = 275 feet x 110 feet = 30,250 square feet (ft2) There are 43,560 square feet in one acre, so this pond is 0.69 acres (30,250 ft2 ÷ by 43,560ft2) Calculate correct herbicide dose Earlier in this publication you learned how to calculate the area and volume of a pond Now it’s time to use those calculations All aquatic herbicides are applied in dosages that are based on either the surface area of the pond (in acres) or the volume of pond water (in acre-feet) It is imperative that you carefully calculate these pond parameters to ensure that you apply the proper amount of herbicide Measurements should be made immediately before you intend to apply the herbicide since pond depth can change dramatically in a short period of time in some ponds Overestimating the pond size or volume will result in overapplying an herbicide that could kill pond fish and other aquatic life Underestimating the pond size or volume will result in an underapplying an herbicide that may result in little or no control of the target plant Do not estimate your pond area or depth—calculate it carefully Now let’s assume the pond above has nearly the entire pond bottom covered with elodea After consulting information on the Penn State Pond Management Web site (water.cas.psu.edu/ponds.htm), the pond owner determines that diquat dibromide is the most effective active ingredient to control elodea in a pond with a healthy fish population The label for Reward® (one of the diquat dibromide products) recommends to gallons per acre of pond area to be treated (for typical application rates of commonly used aquatic herbicides, see the information in Appendix 1) Given the 1- to 2-gallon-peracre recommended dose, the pond owner uses the average of 1.5 gallons per acre.The total amount of herbicide that would be needed in this case would be as follows: 1.5 gallons per acre x 0.69 acres of pond area = about gallon of Reward® Given the heavy growth of elodea, the herbicide should be applied in two separate treatments—half of the pond each time— to prevent a lethal loss of dissolved oxygen from the pond due to the death of too much aquatic vegetation Splitting herbicide applications into two or three treatments separated by to 10 days is always a good idea when abundant plant and algae growth is being treated Obtain state permit for herbicide application Many pond owners are unaware that a state permit is necessary before making any herbicide application to a private pond or lake The permit, officially known as the Application and Permit for Use of an Algaecide, Herbicide, or Fish Control Chemical in Waters of the Commonwealth, is a simple, two-page permit that is jointly reviewed by the Pennsylvania Fish and Boat Commission and the Pennsylvania Department of Environmental Protection The permit must be submitted and approved by both agencies before the herbicide is used It is available online at water.cas.psu.edu or from any local PFBC or DEP office The permit application requires the following information: • Name and location of the water body, including a topographic map or latitude and longitude of the pond • Specific uses of the water body • Types of fish present in the water body • Total area of the water body and the size of the area to be treated • Average depth of the water body • Name of plant to be controlled • Commercial and manufacturer’s name of the chemical to be applied (Note: Only herbicides that are registered with the U.S Environmental Protection Agency, registered with the Pennsylvania Department of Agriculture, and labeled specifically for aquatic use can be listed on the permit application.) • Dosage of each chemical to be applied • Number of treatments to be made throughout the year Effects of the chemical in and downstream from the pond are considered in the approval process The permit may be denied or limited if the pond overflows into a stream where downstream aquatic life may be affected In an impoundment with a wet weather discharge, avoid problems by treating when little or no overflow is occurring Keep in mind that herbicides are more likely to be effective in ponds with little or no outflow where the chemical stays in the water for a longer period of time Apply herbicide Once you have received the state permit to apply the aquatic herbicide, you can purchase it at many local farm and home supply stores or through numerous online outlets Simply type the herbicide name into any Web search engine to find online suppliers Make sure you purchase the correct herbicide for your problem—using the wrong herbicide will result in failure to control the target plant and may damage other nontarget plants or aquatic life in the pond After obtaining the herbicide, read and follow the product label very carefully All aquatic herbicides are potentially dangerous and should be handled carefully The information on the label of the herbicide comes from years of testing and research required by the U.S Environmental Protection Agency as part of the herbicide registration process Keep in mind that the label is the law Applicators are legally obligated to follow all label instructions, including the following: • Protective clothing The label will give specific information on the types of protective clothing recommended for each herbicide Protective clothing such as coveralls, boots, rubber gloves, eye protection, and a mask or respirator are often needed • Mixing instructions Herbicides should be mixed in an approved container or sprayer in a well-ventilated area If using a hose to provide water for mixing, not allow the hose to be submerged in the container as this might allow back-siphoning of the herbicide into the water line • Proper dosage Herbicide doses will usually be given in pounds or gallons of herbicide per surface acre of pond or per acre-foot of pond water Double-check your pond area or volume calculations as described earlier in this publication to make sure you are applying the proper dosage Overdosing the herbicide may lead to damage to nontarget plants and aquatic life, while underdosing may lead to no control at all • Water use restrictions Most aquatic herbicides have restrictions on how the pond water can be used for some time period after the herbicide treatment These restrictions are summarized for each herbicide in Appendix Be careful not to use water in violation of these restrictions • Timing of application Applications should be made on calm days to prevent drifting of the chemical off site Herbi- Use protective clothing when applying an aquatic herbicide In this example, the pond owner has eye protection, rubber gloves, long sleeves, and leg protection as listed on the herbicide label Remember! A state permit is required to apply an aquatic herbicide to your pond Aquatic herbicides should be applied when plants are actively growing To avoid impacts to fish, avoid applying herbicides during fish spawning and incubation periods 19 Always read and follow the label of the aquatic herbicide very carefully Failure to so may cause personal injury or damage to aquatic life Professional herbicide applicators can be hired to apply herbicides to ponds or lakes 20 cides should also be applied when the target plant is actively growing but not when the plant has already reached a nuisance level (see the “Cautions about Using Aquatic Herbicides” section below) Most aquatic herbicides work best when applied to warmer water above 60ºF Avoid applying herbicides when fish are spawning in the pond (usually during May and early June) • Application method The method used to apply an herbicide varies between liquid and granular products They range from use of a backpack sprayer to hand application of granules from the shoreline In general, when applying herbicides along shorelines or spot-treating weed beds, start applications along the shoreline or in the shallowest area and apply out to the deeper water This will enable fish to move into deeper water to escape the chemical • Cleanup Once the herbicide application is complete, all equipment should be cleaned The wastewater produced from cleaning the spraying container can be added to the pond as long as it does not exceed the dosage allowed for the herbicide Other wastes from the cleanup should be disposed of according to the herbicide label Be sure to wash hands and any other exposed body areas after completing the herbicide application • Storage Unused herbicide should be stored in the original container with the label intact in a cool, dry, and ventilated location Make follow-up herbicide applications Completely eradicating a nuisance plant through the use of aquatic herbicides is rarely accomplished and unrealistic More often, the herbicide treatment will reduce the growth below a nuisance level Aquatic herbicides often must be reapplied every year or every few years to keep a problem plant under control Multiple applications during a year, however, should be done with great caution This can be damaging to both the pond ecosystem and the pond owner’s wallet Herbicide applications that are made too frequently may result in high concentrations of the chemical in the water that result from one application overlapping on the residual chemical from a previous application Frequent treatments can also cause accumulation of chemicals in the pond sediments and the possibility of plants or algae becoming resistant to the herbicide active ingredient The problems associated with frequent reapplications of chemicals can best be avoided by treating the plant or algae early in the growing season before it becomes a major problem or through combining the nonchemical plant control strategies discussed earlier in this publication Professional Herbicide Applicators Keep in mind that many professional consultants are available to apply herbicides to a pond or lake These consultants must be state certified to make herbicide applications They can take care of all aspects of an herbicide application, including choice of herbicide, permit acquisition, and application of the chemical A complete list of state-certified aquatic herbicide applicators is available at the Penn State Pond Management Web site at water.cas.psu edu/ponds.htm Cautions about Using Aquatic Herbicides Each year many pond owners experience problems when using aquatic herbicides for plant control in ponds These problems often can be traced to the following mistakes: • Failure to acquire state permit The state permit is not only required by law but also provides a valuable service to prevent the use of incorrect or inappropriate aquatic herbicides The permit process allows an aquatic herbicide expert to review the target plant to ensure that the correct herbicide and dose are being used to minimize the chances of an accidental fish kill • Overdose of herbicide An overdose of herbicide can cause direct toxicity to fish and other aquatic life, along with death of nontarget plants in the pond Herbicide overdoses may be caused by inaccurate estimates of pond area or volume or incorrect measurement of the amount of herbicide • Failure to follow the herbicide label Problems may arise if the herbicide is not used according to the label These problems might include application at the wrong time of year, incorrect herbicide for target plant, using water in violation of the water use restrictions, wrong application method, or incorrect dose In short, read the herbicide label carefully to avoid these problems • Treatment of too much vegetation A very common problem associated with aquatic herbicide use is indirect death of fish due to oxygen depletion This occurs when too many aquatic plants are killed quickly The resulting decay of large amounts of plants or algae will consume oxygen from the pond water, causing fish mortality To reduce this danger, treat only one-third to onehalf of the pond at a time when controlling abundant plant or algae growth Summary and Sources of More Information Nuisance growth of aquatic algae and plants is the most common problem reported by pond owners in Pennsylvania Excessive addition of nutrients into the pond through natural processes and landuse activities around the pond are usually to blame for this growth Pond owners frequently rely on aquatic herbicides for a quick fix—sometimes with disastrous results Proper management of aquatic plants and algae usually requires a comprehensive plan that includes reduction in nutrient loads and a combination of physical, biological, and/or chemical control strategies Explore all the control options before taking action Where aquatic herbicides are found to be a suitable part of the management plan, be sure to obtain the proper state permit, choose the least damaging chemical possible, and follow the label carefully to maximize the chance of success and minimize the chance of detrimental impacts For more information on all aspects of pond management, consult the Penn State Cooperative Extension Water Resources Web site (water.cas.psu.edu) and choose “Pond Management” from the menu Improper use of aquatic herbicides may result in fish kills 21 Appendix Herbicide Descriptions Aquashade • Active ingredient: Various dyes (acid blue dye, acid yellow dye, etc.) • Mode of action: Designed to shade portions of the light spectrum required by underwater aquatic plant and algae growth • Uses: Normally used to control planktonic algae, but also can inhibit photosynthesis in filamentous algae and submerged aquatic vegetation if applied early during the growing season • Dose: Usually applied at a rate of quart per acre-foot early in the growing season before plants or algae reach a nuisance level • Cautions: Dyes should not be used and will not be permitted for ponds with a significant outflow to a surface stream; dyes should also be used early in the season while algae and plants are confined to the bottom of the pond • Approximate cost: $30 per acre-foot of pond volume • Water use restrictions: None Aquathol-K • Active ingredient: Dipotassium salt of endothall • Mode of action: Contact herbicide that inhibits photosynthesis • Uses: Effective on most submerged pondweeds, milfoil, coontail, and naiad • Dose: Normally applied at a rate of 0.6 to 1.9 gallons per acre-foot • Cautions: Breaks down rapidly but still very toxic to trout • Approximate cost: $200 per acre-foot of pond volume • Water use restrictions: Irrigation and watering livestock should be prohibited for to 25 days 22 Copper Sulfate • Active ingredient: Copper sulfate • Mode of action: Usually applied as a blue crystal, it disrupts the cell membrane, which inhibits the cell growth • Uses: Effective on all types of algae, although the long-term use of this product has led to algae that are now resistant to it • Dose: Normally applied at a rate of 0.68 to 1.36 pounds per acre-foot • Cautions: Water hardness should be measured in the pond prior to application because hardness directly affects the dosage and toxicity of copper sulfate; copper sulfate should not be used where trout, grass carp, koi, channel catfish, or other sensitive fish exist; slight overdoses of coppers sulfate can kill even more tolerant fish species; a state permit will not be granted for the use of copper sulfate if the pond overflows into a surface stream with fish • Approximate cost: Less than $10 per acre-foot of pond volume • Water use restrictions: None Cutrine Plus, Cutrine Ultra, Earthtec, K-Tea • Active ingredient: Various percentages of elemental copper • Mode of action: Similar to copper sulfate except these are chelated copper compounds that prevent the copper from precipitating out of solution in hard water; most are available as a granular (for bottom-dwelling algae) or liquid (for floating or suspended algae) formulation; Cutrine Ultra was recently developed for algae that are resistant to other copper algaecides • Uses: Effective on all types of algae • Dose: Cutrine-Plus liquid = 0.6 to 1.2 gallons per acre-foot, Cutrine-Plus granular = 60 pounds per acre, Cutrine Ultra = 0.6 to 3.0 gallons per acre-foot, Earthtec = 0.22 gallons per acre-foot, K-Tea = 0.7 to 1.7 gallons per acrefoot for planktonic or filamentous algae and 1.7 to 3.4 gallons per acre-foot for branched algae • Cautions: Similar to copper sulfate— these products should not be used in ponds with trout, carp, koi, channel catfish, or other sensitive fish species; treat one-third to one-half of the pond at a time • Approximate costs: Less than $50 per acre-foot for filamentous and planktonic algae, $100 to $150 per acre-foot for branched algae • Water use restrictions: None GreenClean • Active ingredient: Sodium carbonate peroxyhydrate • Mode of action: Granular product first sold in 2004 for algae control; works rapidly through direct contact and oxidation • Uses: Used on filamentous or planktonic algae, especially where copperresistant algae occur or where fish species sensitive to copper are present • Dose: Normal application rates are to 17 pounds per acre-foot depending on the amount of algae growth • Cautions: None • Approximate cost: $50 to $200 per acrefoot depending on severity of problem • Water use restrictions: None Komeen • Active ingredient: Elemental copper • Mode of action: See information above for Cutrine Plus • Uses: Although this is a copper-based herbicide, it is not used to control algae; instead, it provides broad control of submerged aquatic plants like pondweeds, elodea, coontail, and milfoil • Dose: 1.7 to 3.3 gallons per acre-foot • Cautions: As with other copper herbicides, it should not be used in ponds with sensitive fish species like trout, grass carp, koi, or channel catfish; since it is a chelated copper compound, it is not affected by water hardness • Approximate cost: $70 to $150 per acrefoot • Water use restriction: Ponds used for human drinking water should not contain more than part per million of copper after application Navigate/AquaKleen/Aquacide • Active ingredient: 2,4–D • Mode of action: These are systemic herbicides that cause the plant cells to divide rapidly and respiration to increase while photosynthesis decreases causing exhaustion of the plants food supply • Uses: Mostly used for floating plants like water lily, spatterdock, and watershield; some use for a few submerged plants like milfoil and bladderwort • Dose: 100 to 200 pounds per acre (lower dose for submerged plants, higher for floating plants) • Cautions: Not used frequently because of water use restrictions listed below • Approximate cost: $300 per acre (submerged plants) to $600 per acre (floating plants) • Water use restrictions: Should not be used on water bodies that are used for irrigation, animal watering, or human consumption Reward/Weedtrine-D • Active ingredient: Diquat dibromide • Mode of action: Systemic herbicide that is quickly absorbed by plant tissues and interferes with photosynthesis • Uses: Broad control of nearly all submerged aquatic plants • Dose: Reward = to gallons per acre, Weedtrine-D = to 10 gallons per acre • Cautions: Few because diquat decomposes in aquatic environments through microbial degradation and exposure to light • Approximate cost: $150 to $400 per acre • Water use restriction: One to five days (Reward); 14 days (Weedtrine) for irrigation and animal drinking water Rodeo • Active ingredient: Glyphosate • Mode of action: Glyphosate is a systemic herbicide that moves through the plant from the point of foliage contact into the root system; this results in a cessation of growth, cellular disruption, and eventually plant death • Uses: Used for many emergent plants like cattail, arrowhead, purple loosestrife, and common reed; also can be used for some floating plants like water lily, spatterdock, and watershield • Dose: 0.75 gallons per acre for emergent plants; 0.5 to 0.9 gallons per acre for floating plants • Cautions: Rodeo should be applied during the active growing season until later summer • Approximate cost: $30 to $70 per acre • Water use restrictions: None Sonar SRP and Sonar A.S • Active ingredient: Fluridone • Mode of action: A systemic herbicide that is absorbed through leaves and roots; absorbed fluridone inhibits carotene formation; the absence of carotene pigment causes unprotected chlorophyll to photodegrade, causing plant death • Uses: Sonar SRP can be used on many submerged aquatic plants; Sonar A.S is useful for many floating plants and a few submerged plant species • Dose: 3.2 to pounds per acre-foot (Sonar SRP), 0.16 to 1.5 quarts per acre-foot (Sonar A.S.) • Cautions: This product needs a long contact time to work effectively; it is best used on ponds with little or no overflow; split treatments may be beneficial to maintain a more constant concentration • Approximate cost: $500 to $1,000 per acre • Water use restriction: Seven to thirtyday restriction on irrigation use of water 23 Table Effectiveness of various aquatic herbicides on common aquatic plants and algae in Pennsylvania ponds.1 Filamentous algae Aquashade Aquathol-K Copper2 GreenClean Komeen Navigate/ AquaKleen/ Aquacide +++ — +++ +++ — — Reward/ Weedtrine-D Rodeo Sonar + — — Planktonic algae ++ — +++ +++ — — ++ — — Branched algae (Chara, Nitella) +++ — +++ ++ — — ++ — — Bladderwort — — + — — +++ +++ — +++ Coontail ++ +++ + — +++ ++ +++ — +++ Elodea ++ + + — +++ ++ +++ — +++ Eurasian milfoil ++ +++ + — +++ +++ +++ — +++ Hydrilla ++ ++ ++ — ++ — ++ — +++ Naiad ++ +++ + — +++ — +++ — +++ Parrotfeather ++ +++ + — ++ — +++ — +++ Pondweeds ++ +++ + — +++ — +++ — +++ Duckweed — — — — — — ++ — +++ Spatterdock — — — — — +++ — +++ +++ Water lily — — — — — +++ — +++ +++ Watermeal — — — — — — — — ++ Watershield — — — — — +++ — +++ +++ Yellow floating heart — — — — — ++ — +++ +++ Arrowhead — + — — — — ++ +++ — Bulrush — — — — — ++ — +++ — Cattail — — — — — — +++3 +++ + Common reed — — — — — — — ++ — Pickerelweed — — — — — — ++ ++ — Purple loosestrife — — — — — — — +++ — +++ = excellent control; ++ = good control; + = some control; — = little or no control All ratings assume that the product is used early in the growing season to suppress growth Mid- to late-summer use not recommended Includes copper sulfate, Cutrine Plus, Cutrine Ultra, Earthtec, and K-Tea Surfactant use recommended 24 Prepared by Bryan Swistock, senior extension associate, School of Forest Resources; and Mark Hartle, chief, Aquatic Resources Section, Division of Environmental Services, Pennsylvania Fish and Boat Commission This publication was supported, in part, with funding from the U.S Environmental Protection Agency, Region 3, Pesticide Misuse Initiative, under Grant Agreement 97337101 Based on Pond Management and Aquatic Plant Control (The Pennsylvania State University, 1998) by Daniel Angelo, Penn State Pesticide Education Program; Mark Hartle, Pennsylvania Fish and Boat Commission; and Winand Hock, professor of plant pathology and director of Pesticide Education Program The authors wish to thank the following individuals who served as reviewers for versions of this publication: Thomas McCarty, senior extension educator, Penn State Cooperative Extension, Cumberland County Heather Smiles, fisheries biologist, Pennsylvania Fish and Boat Commission Ed Molesky, owner, Aqua Link, Inc and Hydro Logic Products, Doylestown, Pennsylvania Eric Lorenz, senior extension associate, Pesticide Education Program, Penn State Photo Credits Cover; pages 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 17, 18, 19, 20: Bryan Swistock Inside cover; pages 4, 8, 15: Ed Molesky, Aqua Link, Inc and Hydro Logic Products Page 3: Dr Richard Soderberg, Mansfield University of Pennsylvania Page 5: Louis Cunfer Pages 8, 10, 16, 21: Mark Hartle, Pennsylvania Fish and Boat Commission Page 9: Susan Boser, Penn State Cooperative Extension, Beaver County Pages 9, 11: Amy Smagula, New Hampshire Department of Environmental Services Page 11: Nadine Barrie Smith Pages 14, 15: Heather Smiles, Pennsylvania Fish and Boat Commission Page 18: Adam Kaeser Visit Penn State’s College of Agricultural Sciences on the Web: www.cas.psu.edu Penn State College of Agricultural Sciences research, extension, and resident education programs are funded in part by Pennsylvania counties, the Commonwealth of Pennsylvania, and the U.S Department of Agriculture This publication is available from the Publications Distribution Center, The Pennsylvania State University, 112 Agricultural Administration Building, University Park, PA 16802 For information telephone 814-865-6713 Where trade names appear, no discrimination is intended, and no endorsement by Penn State Cooperative Extension is implied This publication is available in alternative media on request The Pennsylvania State University is committed to the policy that all persons shall have equal access to programs, facilities, admission, and employment without regard to personal characteristics not related to ability, performance, or qualifications as determined by University policy or by state or federal authorities It is the policy of the University to maintain an academic and work environment free of discrimination, including harassment The Pennsylvania State University prohibits discrimination and harassment against any person because of age, ancestry, color, disability or handicap, national origin, race, religious creed, sex, sexual orientation, gender identity, or veteran status Discrimination or harassment against faculty, staff, or students will not be tolerated at The Pennsylvania State University Direct all inquiries regarding the nondiscrimination policy to the Affirmative Action Director, The Pennsylvania State University, 328 Boucke Building, University Park, PA 16802-5901; Tel 814-865-4700/V, 814863-1150/TTY Produced by Ag Communications and Marketing © The Pennsylvania State University 2008 CODE # AGRS-102 5M5/08graphtech 4867 ... to water lily, but its leaves are slightly more heart shaped and the flowers are yellow This plant will grow more quickly than water lily and can reach nuisance levels Hydrilla Curly leaf pondweed... increasingly becoming a problem in private ponds and lakes throughout Pennsylvania Some of these plants have occurred in the state for many years and are slowly spreading, while others have only recently... imperative that you carefully calculate these pond parameters to ensure that you apply the proper amount of herbicide Measurements should be made immediately before you intend to apply the herbicide since