THE CONTROL OF RED SPIDER MITES ON TOMATOES USING

THE CONTROL OF RED SPIDER MITES ON TOMATOES USING NEEM AND SYRINGA EXTRACTS by NEPHIOUS JAMES KAMALENJE MWANDILA Submitted in accordance with the requirements for the degree of DOCTOR OF

THE CONTROL OF RED SPIDER MITES ON TOMATOES USING NEEM AND

SYRINGA EXTRACTS

by

NEPHIOUS JAMES KAMALENJE MWANDILA

Submitted in accordance with the requirements

for the degree of

DOCTOR OF PHILOSOPHY

in the subject

ENVIRONMENTAL MANAGEMENT

at the

UNIVERSITY OF SOUTH AFRICA

SUPERVISOR: PROF J OLIVIER

Co - SUPERVISORS: DR D VISSER PROF D.C MUNTHALI

NOVEMBER 2009

Abstract

The efficacy of Neem (Azadirachta indica A Juss) and Syringa (Melia azedarach L.)

against red spider mites (RSM) life phases (adult, nymphs and eggs) was assessed at different concentrations (0.1%, 1%, 10%, 20%, 50%, 75%, 100%) and at exposure time

of 24, 48 and 72 hours using tomato leaf dip assays on water agar in plastic Petri dishes Tomato plants were grown in the greenhouse as a source of leaves and for the greenhouse trial A Greenhouse trial was carried out to simulate field conditions Neem seeds were sourced from Botswana, India, and Zambia Syringa seeds were sourced from Botswana and South Africa Laboratory and Greenhouse trials were carried out at the Agriculture Research Council, in the Vegetable and Ornamental Institute laboratories and green houses in Pretoria South Africa

Data was analysed by using the GenStat statistical program Overall results of both Neem and Syringa assays indicated that all levels of concentrations and time of exposure had significant effects on mortalities of adult RSM and compared significantly with commercial acaricides (Abamectin-plus, Hunter and Selecron) Both Neem and Syringa caused significant mortalities at low concentration of 0.1% as early as 24 hours of exposure Both Neem and Syringa assays had significant mortalities on RSM nymphs as early as 24 hours and with longer periods of exposure Both Neem and Syringa had significant effects on the hatching of RSM eggs at 48 hours and 72 hours of exposure In general, effects occurred in a dose (concentration) dependent manner Based on the findings and evidence in the literature, Neem and Syringa extracts could be useful as

Key terms:

Neem (Azadirachta indica); Syringa (Melia azedarach); Azadirachtin compound;

Azadirachtin standard; High Performance Liquid Chromatography (HPLC); Samples; homogenous; Analysis of Variance; Randomized Designs; Abamectin-plus; Hunter; Selecron; liquid–cooling agar; red spider mites; life cycle; heterogeneous; antifungal; antibacterial; antifeedant; larva; protonymph; deutonymph.; Globalisation; food production; food consumption; cereals; vegetables; pests; pesticides; limonoids

Dedication

This thesis is dedicated to:

• the memory of my mother Elinala and my father James Kamalenje Mwandila two individuals who made a lasting impact on my life by bringing me up and affording me an opportunity to attend school

• my late son Daniel who kept encouraging me till he met his death by a robber’s bullet

• my eldest son Harvesto Malombo and his siblings- Elizabeth, Tiyezye, Bangala, Newton, Esnart, Kasimba and Khumbo

Acknowledgements

I am grateful to members of my family for their unstinting support throughout the duration of this study Special thanks are due to my children Harvest-Malombo, Daniel (late), Elizabeth, Tiyezye, Esnart, Bangala, Newton, Kasimba, Khumbo and my nephew Conerlius who always kept me smiling and feeling lighthearted in those anxious moments

of thesis-writing when I was very sick I also wish to thank, most profoundly, my promoter, Professor Jana Olivier, for her encouragement, her intelligence, her care, and above all, her nurturing approach to the whole process of supervision For me, working with her was always a source of much immense joy even when I was seriously sick and quitting seemed to be the only option especially after losing my son Daniel

I want to thank

• Dr Diedrich Visser my co-promoter, for his support and advice throughout the time when I carried out the Laboratory bioassays at the Vegetable and Ornamental Plant Institute (VOPI) and his valuable comments during the process of supervision

• Professor David Munthali my co-promoter, for his advice while in Botswana

• The staff at the Agricultural Research Council’s (ARC) Vegetable and Ornamental Plant Institute, Roodeplaat in particular Dr Nolwazi Mkize and Sakki Sambo for their support and help in purchasing several useful materials that were used in the bioassays during my research experiments

• Nanga Irrigation Research Station - Zambia for harvesting and providing me with Neem seeds

• Mrs Jeyasseeli Michael for sourcing me Neem seeds from India

• My heart goes to all the VOPI staff for welcoming me as part of their team

• Dr Gerhard Prinsloo for providing me with much advice on research activities, especially in the handling of High Performance Liquid Chromatography (HPLC)

• Subject Librarian, Mrs Leanne Tracy Brown for her efficiency, integrity and charm

• Marie Smith, Elise Robbertse and Poloko Chepete for helping with statistics

• Charnie Creamer ARC - Plant Protection Research Institute, for the identification

of the mites used in the bioassays

• Dr Fetson Kalua of UNISA for making my life easier while in South Africa by providing accommodation and valuable advice and encouragement

• G.N Mthombeni for financial assistance during the time I desperately needed to pay my fees at UNISA

• Letsholo Bongalo for helping me with statistical graphs during my write up

• Not forgetting other friends and individuals too many to mention who stood by

me when getting the thesis done

Finally, I wish to acknowledge the Department of Agriculture and Environmental Sciences and the Agricultural Research Council (ARC) for funding part of this project

Yebo/ Thank you

1.1.1.1 Food production and consumption patterns 2

1.2 Summary and problem statement 20

2.4.1 Neem (Azadirachta indica A Juss) as a botanical pesticide 36

2.4.2.1 Origin and distribution of Neem (Azadirachta indica A Juss) 38

2.4.3 Syringa (Melia azedarach L) as a botanical pesticide 41

3.3 2 Determination of azadrachtin content of seeds 50

3.3.4.4 Testing the effect of neem and syringa extracts on red spider mite eggs 55

Chapter 4 Comparison of azadirachtin composition in Neem

and Syringa from different parts and regions of the world 59

4.2.1 Extraction of the active constituents from Neem and Syringa seeds 60 4.2.2 Determination of Azadirachtin content in Neem and Syringa 60

4.3.1 Peaks for azadirachtin standard at three concentrations 62

Chapter 5 Results of Neem and Syringa extract treatments

5.2.1 Effect of Neem and Syringa extracts on adult mites 68

5.4 Effect of Neem and Syringa extracts on eggs 81

Chapter 6 Overview summary, conclusions and recommendations 88

6.1.1 High Performance Liquid Chromatography (HPLC) 88

6.1.3 Syringa seed extracts (SSE) and crushed Syringa leaves: Results 91 6.1.3.1 Adult red spider mites: SSE and crushed Syringa leaves results 91

Abbreviations and short forms used for primary texts

Red Spider Mites – RSM

Neem Seed Extracts – NSE

Syringa Seed Extracts – SSE

Integrated Pest Management – IPM

Neem Seed Kernel Extracts – NSKE

Neem Oil – NO

Northern American Free Trade Agreement – NAFTA

Tetranychus – T

Safety and Quality Assurance – SQA

Commercial farmers, providing food for the population and beyond – Globalisation Dusting powder – DP

List of Tables

Table 1 Percentage world cereal crop production in 2000 20

Table 3 Production and yield of vegetables in Africa and globally as

compared to those of other food commodities (1990) 24

Table 4 Vegetable production by SADC countries (in 1000 tonnes 27

and as percentage of world vegetable production)

Table 5 A few vegetable chemical pesticides used in South Africa and 47

the world

Table 6 Mean percentage mortalities of adult red spider mites 80

(untransformed means) that died using Neem seed extracts at

Table 7 Mean percentage mortalities of red spider mite adults 83

(untransformed means) for Syringa Seed Extracts (SSE) at

Table 8 Mean percentage mortalities of red spider mite adults 87

(untransformed means) feeding on tomato leaves treated with

Syringa leaf extracts at 24, 48 & 72 hours

Table 9 Mean percentage mortalities of red spider mite nymphs 89

(untransformed means) feeding on tomato leaves treated with Neem seed extracts at 24, 48 & 72 hours

Table 10 Mean percentage mortalities of red spider mite nymphs 90

(untransformed means) feeding on tomato leaves treated

with Syringa seed extracts at 24, 48 & 72 hours

Table 11 Mean percentage red spider mite eggs that hatched after 48 91

& 72 hours exposure to Neem seed extracts

Table 12 Mean percentage red spider mite eggs that hatched after 48 98

& 72 hours exposure to Syringa seed extracts Table 13 Mean percentage mortalities of red spider mite adults 99

(untransformed means) feeding on tomato leaves treated with

Neem and Syringa seed extracts at 24, 48 & 72 hours in the

greenhouse trial

APPENDICES

APPENDIX 1

1 A Dead adult mites on Neem seed extracts

1 B Dead adult mites on Syringa seed extracts

1 C Dead adult mites on Syringa leaf extracts

1 D Dead mite nymph on Neem seed extracts

1 E Dead mite nymph on Syringa seed extracts

1 F Number of hatched eggs on Neem seed extracts

1 G Number of hatched eggs on Syringa seed extracts

1 H The greenhouse trial

CHAPTER 1: GENERAL INTRODUCTION

1.1 Background to the study

1.1.1 Introduction

This chapter presents the background of the study which includes an overview of global food production and consumption, the problem statement, the aim and objectives of the study and the significance of study

1.1.1.1 Overview on food production

Low agriculture productivity and declining production efficiencies pose a threat to global food production According to FAO (2006a), in 2006, world food production rose by less than 1% As a consequence, per capita food production was estimated to have fallen by about 0.2%, representing the first decline since 1993 (WTO, 2201) The food production levels in SADC are in no way different from the crisis in the rest of the World (SADC, 2002) Declining agricultural output is part of a wider pattern whereby governments have continuously failed to recognize the role of small farmers in increasing agricultural production In SADC, over 80% of the population is engaged in subsistence farming Yet the thrust of governments and donors to improve agricultural output has largely been toward the more powerful and politically organized modern commercial farming sector, leading in general to low levels of food production

In Botswana, as a result of some good rains received during the 2007/08 growing season, cereal production increased by 26%, from 29,000 tonnes in 2007 to 37,000 tonnes in 2008

Maize production alone increased from 1,000 tonnes in 2007 to about 8,000 tonnes in

2008, while the combined production of sorghum/millet increased only slightly, from 28,100 tonnes to 28,500 tonnes The overall food supply/demand assessment indicated a revised cereal deficit of about 253,000 tonnes By the end of July 2008, the country had already imported 119,000 tonnes of cereals or 41% of its planned imports for the marketing year Thus Botswana food production is very low and the country meets its food requirements from imports This chapter will include a discussion on world cereal and vegetable production and their patterns

1.1.1.2 Food production and consumption patterns

Food is vital for survival Food production changed gradually from subsistence agriculture to the development of commercial farming to provide food for the local populations and beyond With trade extending over borders, the consumer base expanded from one region to another (Duncan, 1997) However, subsistence or barter farming is still practiced in poorer communities and in developing countries Cereals together with vegetables are the most consumed crops in many parts of the world (United Nations, 1993) Trends in food production can thus be represented by patterns of cereal production and consumption

1.1.1.3 World cereal production

Since the 1950s, the growth of world cereal production has exceeded that of World

population growth

World output of cereals, the main food source for the majority of consumers, increased by 2.7% per year while the population grew by about 1.9% per year (Duncan, 1997)

This increased production has led to an increase in per capita calorie consumption in the world, especially in developing countries, where the increase was by about 27% (United Nations 1993; Duncan, 1997) The globalisation of food production implies that a set of pronounced extended linkages exists between the sites of production and consumption (Goodman, 1999) (Figure 1.1 & 1.2) Oosterveer (2007) has observed that the transition towards globalising food production increased the choices for food consumers in the world Consumers are now demanding greater variety For example, consumers who a decade ago consumed most of their food cereals such as rice or maize, now demand meat, fruits and vegetables (Pamplona-Roger, 2004)

s

Figure 1.1 Linkages showing the sites of production and consumption Adapted from Oosterveer (2007)

Decreasing Distance Places of

production

Places of consumption

Figure 1.2 World Map showing the movement of cereal grains moving from its country

of production to country of consumption as shown by the direction of arrows

cereal crop totals are taken into account

Source: FAO Statistical year book (2005)

Despite these impressive figures and the global character of food trade in general, only a very limited number of countries dominate the international trade in food products This state of affairs brings about price distortions because trade is monopolised by the few countries which are able to produce both for the local market and for world trade McMichael (2000) and Einarsson (2000) claim that most (roughly 90%) of the world’s food consumption occurs in the country where it is produced The production of cereals has been declining since 2000, and continues to do so According to the FAO (2006a), cereal production growth slowed down since 1990 In 2003 the world cereal production declined even further (Table 1.2) Table 1.2 shows the decline in the selected world countries total cereal production as compared to that of 2000 (Table 1.1)

Source: FAO Statistical year book (2005)

When one compares the years 2000 and 2003 (Table 1.1 and Table 1.2) in terms of cereal production, a decline in total world cereal production is noticeable (in percentage terms) What could have caused this decline in world cereal production? A number of factors are plausible and some of these include:

1 Drought

Inadequate rainfall, especially where countries experience early-season dry spells, result in delayed planting (SADC, 2002) This effectively shortens the duration of the growing

2 Bio-fuels

The other reason is the new trend where crops are produced for bio-fuels rather than for

food (WRR, 2007) In an article entitled “The world’s choice: food or bio-fuels” which

appeared in The Sunday Times of March 9 2008 page 6, Beddington (2008) pointed out that the world today is concentrating on the production of crops for bio-fuels rather than for food supply, thereby contributing to the decline in cereal production In the 2006 annual assessment of the global agriculture, it was noted that increased use of grains for biofuels would affect food production and that food prices would be kept higher than average Among many cereals, maize is noted to be the main cereal used for the production of ethanol, one of the byproducts of bio-fuels (FAO, 2006b)

1.1.1.3 World vegetable Production

Vegetables contribute about 40% of the world food trade (Okigbo, 1990) Vegetables are generally herbaceous (non-woody) plants that are cultivated in farms as well as backyard gardens for home use Usually all the botanical parts of these plants (leaves, buds, flowers, fruits, stalks, roots or tubers), can be consumed fresh, steamed or boiled separately or in combination with other foodstuffs (Okigbo, 1990; Pamplona-Roger, 2004) The growing

of vegetables plays a major role in providing food for people, creating employment, and acting as a source of income in many parts of the world including the Southern African Development Community (SADC) region (Bandeke, 1996) Vegetables are the main source of micronutrients which are essential in preventing malnutrition, and are also becoming increasingly important with respect to preventive medicine, as a source of fibre, for their special proteins and oils, and other nutritive qualities (McDonald & Low, (1990)

Pamplona-Roger (2004) has commented that vegetables should no longer be considered a mere side dish to the “main course”; quite the contrary Vegetables, together with grains and fruits, should be principal elements of a truly healthy and nutritious diet The World Health Organisation is also advocating an increase in the consumption of fruits and vegetables (WHO, 1999) According to FAO (1989) (cited in Okigbo 1990), vegetables constitute the fourth largest agricultural commodity group produced worldwide, and the fifth largest in the African region (Table 1.3) Vegetables have been grown in such climatic diversity Consequently, plant species adapted to specific climate and soil conditions have evolved and a wide array of annual and perennial crops are used as vegetables (Shanmugasundaram, 1990) Okigbo (1990) defines vegetable as inclusive of separated roots, tubers and pulses (Table 1.3) Thus vegetable production in Africa and globally is now greater than cereals (Okigbo, 1990)

Yield (t/ha)

% production

of all commodities

Production (million t)

Yield (t/ha)

% production

of all commodities

World Vegetable Production

in millions of tons per year (2006)

13.4 13.3 6.8 5.8

27.9

9.1 29.4

37.2 69.3

131.7 157.7

Fig.1.3 Selected World Vegetable produced in millions of tonnes (2004)

Source: ENCYCLOPEDIA of Foods

Most of the trade in fruits and vegetables occurs within three geographic regions namely, the European Union (EU), the North American Free Trade Agreement (NAFTA) countries and East Asia (China and Japan) However, this trend where trade was concentrated within the mentioned countries has changed over the past few years, with greater imports of fruits and vegetables coming from SADC countries (Table 1.4) and other developing countries in the southern hemisphere

1.1.1.4 Vegetable production in the SADC region

Until recently, vegetable production was an ignored and little-known industry in the SADC region (Mnzava, 1990) For a long time, the production of vegetables was restricted to areas with favourable climate, and invariably where the major consumers had established themselves

This has now changed Critically important for Africa and SADC countries is the fact that the produce is harvested when the crop is off-season in countries in the Northern hemisphere (Mnzava, 1990) Within Africa and the SADC region, however, only a few countries contribute to the world’s vegetable production and trade According to FAO (2006b) Production Yearbook, South Africa is the highest contributor to the world vegetable production and trade in the SADC region, while most of the SADC countries produce only for their domestic consumption (Table 1.4)

Table 1.4 Vegetable Production by SADC Countries (in 1000 tonnes and as percentage of world vegetable production)

_

Angola 661 0.1 663 0.08 669 0.06 721 0.05 721 0.05 Botswana 26 0.00 28 0.00 27 0.00 27 0.00 27 0.00 DRCongo 3 094 0.49 3 833 0.47 2 867 0.24 2 962 0.22 2 893 0.21

Madagascar 1 002 0.16 1 118 0.14 1 231 0.1 1 234 0.09 1 234 0.09 Malawi 588 0.09 732 0.09 778 0.06 918 0.07 1188 0.09 Mozambique 513 0.08 558 0.07 461 0.04 451 0.03 451 0.03

South Africa 4 662 0.74 5 801 0.71 7 141 0.59 7 897 0.59 7769 0.56 Swaziland 133 0.02 153 0.02 113 0.01 122 0.01 122 0 Tanzania 2 227 0.35 2 505 0.31 2 482 0.21 2 522 0.19 2528 0.18 Zambia 285 0.05 378 0.05 366 0.03 369 0.03 369 0.03 Zimbabwe 244 0.04 325 0.04 373 0.03 378 0.03 378 0.03 Total 13 488 2.13 16 159 1.99 16 607 1.37 17 686 1.31 17 765 1.3 Source: FAO production Yearbook 2006b

According to FAO Production Yearbook (2006b), Namibia, the Seychelles and Botswana

do not contribute significantly to the world vegetable trade (Table 1.4)

1.1.1.5 Vegetable production in Botswana

In Botswana, most of the vegetables are produced by small scale farmers, and these vegetables are consumed locally It is estimated that this production (by small scale

farmers) accounts for only between 20% to 30% of the national demand (Bok et al.,

The most widely grown vegetable crops in Botswana are cabbages, potatoes, tomatoes, onion, rape, spinach, kale (choumolier) and green mealies Out of these vegetable crops,

spinach and tomatoes top the list (Bandeke, 1996; Bok et al., 2006) For purpose of this

study, a brief review of tomatoes will be given

1.1.1.5.1 Tomato production in Botswana

Tomato (Lycoperiscon esculentum L.) is a vegetable crop that is grown worldwide Its

selection and preference as a crop is due to its nutritional value and economic importance Records reveal that tomato is the second most important vegetable crop next to potato

(Solanum tuberosum L.) (Pamplona-Roger, 2004), (Figure.1.3) According to FAO

(2005), 125 million tonnes of tomatoes were produced in the world in 2005 The largest producers of tomatoes (in tonnes) were: China, accounting for about one-fourth of the global output; the United States is second, with Turkey third In South Africa, tomatoes are among the most important and highly valued horticultural products (Louw, 2005) Louw (2005), has observed that in 2004 tomato production in South Africa was worth R1.6 billion (an equivalent of US $246 million) per year

In Botswana, (one of the SADC member countries), most of its tomatoes are produced by local farmers and a few commercial farmers in the ‘Tuli block’ along the Limpopo River,

bordering with South Africa (Bok et al., 2006) Poor performance in the production of

tomatoes and other vegetables in Botswana is attributed to a number of factors, including unreliable and inadequate rainfall as well as pests Pests are the most important factors or determinants in the production of vegetable crops (Bandeke, 1996; Molefi, 1996)

1.1.2 Factors affecting food production

There are a number of factors that affect food production However, pests are among the most contributing factors that affect food production Pests affect harvests in all cereals and other food plants However, pest problems are mostly experienced in Africa due to the high importation costs (and therefore unavailability) of pesticides (FAO, 2006b)

1.1.2.1 Crop pests

In nature, pest densities tend to fluctuate and the environment plays a major role in this trend Changes in environmental conditions lead to changes in the pest population levels that attack and affect yields of cultivated crops and in particular tomatoes (Molefi, 1996;

Bok et al., 2006) Crop losses due to pests have a great impact on the decline of food

production There have been major pest infestations leading to total crop failure Crop

production losses to pests are estimated to exceed 35% annually (Henneberry et al., 1991)

The damage caused by pests to crops increase with the increase in pest population Pest damage to crops causes loss in crop yields and affects the quality of the produce which

results in loss of revenue to the farmer (Kasozi et al., 1999) In many cases, the pest

attacks the final product such as the leaves or fruits and this drastically reduces the market value of the crop For example, buyers are reluctant to buy spinach, cabbage or other leafy vegetables with holes in them Tomatoes which have larvae in them or are covered with red spider mites are equally unacceptable

of other pests that cause damage to tomatoes and reduce yields These include pests like

tomato semi-looper (Chrysodeixis acuta), and nematodes (Meloidogyne species) (Kasozi

et al., 1999) However, one of the most common pests of tomato is the red spider mite (Wikipedia, 2007) Bok et al., (2006) reported that various species of red spider mites

attack the tomato crop in Botswana reducing the yield to very low levels This may be one

of the reasons why Botswana is not included among the world and SADC tomato

producing countries (FAO, 2005) Red spider mites (Tetranychus species) are a

polyphagous, parenchyma cell feeding pest on over 200 host plant species and have a serious economic impact on many crops, especially tomatoes (Spencer, 1990; Flaherty &

Wilson, 1999; Van den Boom et al., 2003) These phytophagus mites attack mainly the

mature and old leaves of the tomato plant by sucking cell sap and damaging the chlorophyll-producing organs, thus reducing photosynthesis, causing a great deal of yield

loss (Biswas et al., 2004) One of the methods of limiting damage to these crops is by

applying chemical pesticides

1.1.2.3 Pesticides and their problems

Although the use of insecticides in the production of these crops has become unavoidable, chemical insecticides have their own problems and may have severe environmental consequences They also appear to follow a pattern of initially being very successful, resulting in high yields After a number of years the target insect develops some degree of tolerance A series of events then occurs: more frequent application of pesticides and higher dosages are needed to obtain effective control; insect population often increase rapidly after treatments and the pest population gradually becomes increasingly tolerant to the pesticide and its efficacy decreases (Ellis & Mellor, 1995) As a result, another pesticide is substituted and the cycle is repeated Resistance to more than one pesticide is then usually the end result It is estimated that only 1% of the applied insecticide actually reaches the target (Daka, 2003) A large proportion of the insecticides end up in the environment where they may affect non-target species Insecticides may also have adverse effects on wildlife and may pollute soil and water (Fig 1.4) Other disadvantages include the presence of pesticide residues in foods and animal feed which is causing health concerns among consumers (Dent, 1991; Ellis & Mellor, 1995; Daka, 2003) Figure 1.4 illustrates the numerous ways in which pesticides can contaminate the environment via drainage water, dust and aerial drift

Figure 1.4 Different pathways through which insecticides may reach the environment

Source: Adapted from Daka (2003)

As the world population increases, so does the demand for food This leads to the use of more pesticides in order to eradicate pests on ever increasing areas of food production However, this draws a substantial amount of foreign currency resources for the

importation of insecticides (Bok et al., 2006) Most farmers, especially the resource poor

farmers, do not have the knowledge to use pesticides correctly The reality is that pesticide abuse leads to fatalities The World Health Organisation attributes about 20,000 deaths and more than a million illnesses each year to pesticides being mishandled or used in excess (USOIA, 1992) In addition, chemical pesticides are usually very expensive and beyond the ability or reach of resource poor farmers

It is clear that some solution must be found to assist such farmers in fighting the effects of crop pests One way to rectify this would be to select crop varieties that are naturally resistant to pests and that do not need pesticides The other way would be to identify botanical pesticides that are not harmful to animals or humans (Rembold, 1993)

1.1.2.3 Possible solutions: Botanical pesticides

Most farmers in sub-Saharan Africa are resource poor in terms of access to natural resources, credit, information and external inputs (van Huis & Meerman, 1997) These farmers rely on low-input traditional farming and cultural control techniques These farming and control techniques that contribute either directly or indirectly to pest management, include sanitation, seed selection, rotation, weeding, multiple cropping, tillage, fire, flooding and natural pesticides (van Huis & Meerman, 1997) One option, therefore, is to use locally available pesticides, which can be obtained and applied by local farmers themselves It is also important that the pesticides are not harmful to humans or animals Thus botanical pesticides which are mostly found within easy reach and in most cases do not interfere with parasitoid foraging (Charleston, 2004) can be a good alternative for the resource poor farmers It is documented that several substances of plant origin have been tried in the control of insect pests For example, secondary metabolites

present in Amoora ruhituka (Meliaceae), Annona reticulata and Annona squamosa

(Annonaceae), act as insect feeding deterrents and growth regulators Anti ovipositional properties of extracts from custard apple oil were found to reduce the egg–laying of the female pulse beetle (Völlinger, 1995; Charleston, 2004)

Plants form the basis for many medicines and have been used for centuries to protect humans and animals Plants synthesize secondary plant compounds which can partly be considered as weapons to defend themselves against pests and diseases that have competed with them since time immemorial (Schmutterer, 1995) Since the manufacture

of chemical pesticides require chemicals and laboratory facilities, the use of plant materials may offer a solution Extracts from plants contain numerous compounds in comparison to synthetic pesticides and therefore delay the build up in resistance (Rice, 1993; Völlinger, 1995; Charleston, 2004) Research showed that the seed kernel extracts

of Neem (Azadirachtin indica) have anti-feedant effects (feeding inhibition) and growth

inhibition properties and cause abnormal development in many insects (Hedge, 1996; Juan

& Sans, 2000) Melia azedarach (L.) (also known as the Syringa tree) has anti-feedant properties (Ascher et al., 1995; Singh et al., 1998; Nathan, et al., 2006) According to

Schmutterer (1995), and Charleston (2004), triterpenoids and tetranortriterpenoids are the main active ingredients found in these two plants Azadirachtin, a tetraterpenoid, is found

in the Neem tree, while two other tetraterpenoids, meliacin and meliacarpin besides azadirachtin, are found in the Syringa fruits The growth inhibition and anti-feedant effects

of these two tetraterpenoids from Syringa compare favourably with that of azadirachtin

(Lee et al., 1991; Juan & Sans, 2000) The advantage of using botanicals is that they are

easily available; Syringa for example grows easily in many parts of the SADC region In

South Africa it is even considered a weed (Ascher et al., 1995; Charleston, 2004)

1.1.2 Summary and problem statement

In 1998, the world population increased at a historically high annual average rate of 1.8%

(since 1950) (Gretchen et al., 1998) Cereal production more than kept pace (accounting

for more than 50% of the energy intake of the world’s poor at that time) (Duncan, 1997;

Gretchen, et al., 1998) Cereal production in the world has declined to an alarming level,

resulting in unrest and furious debates in the media on these shortages of food Recently, the United Nations warned that 82 countries, including China, face food emergencies, as stock piles of wheat drop to the lowest level since 1980, resulting in food prices rising to a

record high (Gretchen et al., 1998; McMichael, 2000) The prospect of food shortages

over the next 20 years is so acute that urgent attention is required to increase food production However, growing enough food is getting more difficult because of:

1 climate change, which leads to shortage of water in many regions

2 the new policy of changing from growing crops for food to that of bio–fuels

3 pests, which reduce the yield of many crops

The first two factors are important in helping to bring about an understanding of the problem of food shortage, and deserve merit However, it is the third factor for which intervention strategies can be implemented, some aspects of which are dealt with in this study

In summary, the importance of the need to increase food production and the impact of pests, especially red spider mites, in tomato crop production needs attention The application of insecticides as a solution has revealed numerous problems

Botswana farmers are mostly resource poor who cannot afford the expensive and intricate usage of conventional pesticides and most of the food that they produce is consumed locally One of the main vegetable food crops produced in Botswana and in the world is

tomato However, this crop is heavily attacked by red spider mites (Bok et al., 2006) It is

important therefore that a solution be sought A solution could be the development of a botanical pesticide against red spider mites that can be produced cost-effectively by the small scale farmers themselves The question is, can effective pesticides be developed against red spider mites on tomatoes for use by resource-poor farmers in Botswana?

Research has shown that Neem (Azadirachta indica A Juss) and Syringa (Melia azedarach L) are effective insecticides These plants are readily available to farmers in

Botswana as they are found in large parts of the country Little or no research has been

done to determine whether Neem and Syringa are effective acaricides

Research Questions:

• Neem and Syringa are effective insecticides but are they effective as acaricides?

• Can Neem and Syringa extracts be used to control red spider mites in tomatoes?

1.3 Aim:

To explore the potential of Neem (Azadirachta indica) and Syringa (Melia azedarach) extracts to control red spider mites (Tetranychus spp.) on tomatoes

1.3.1 Objectives of the study:

The objectives of the study were to:

• investigate the possible geographical variations in the chemical composition of Neem and Syringa

• to determine whether Neem and Syringa extracts are as effective against red spider mites on tomato plants as the conventional acaricides

• to establish the optimum concentrations of Neem and Syringa extracts (which does not cause phytotoxicity) for red spider mite control

1.4 Chapter layout

Chapter 1 is a general introduction of the study Chapter 2 provides an overview of the literature related to red spider mites as well as Neem and Syringa as botanical pesticides and Chapter 3 deals with the Research Design and the Methodology used Chapter 4 gives

a comparison of azadirachtin composition in Neem and Syringa samples Chapter 5 deals with the analysis and discussion of the results, and Chapter 6 gives an overview, summary, conclusions and recommendations This is followed by a section on appendix then References

CHAPTER 2: Literature Review

2.1 Introduction

Cultivated tomatoes, Lycoperiscon esculentum L., have a variety of pests, the most serious

being the red spider mite This has resulted in dependence on intensive use of pesticides, especially when the crop is grown in open fields (Engindeniz, 2005) The overwhelming nature of red spider mites attack often prompts desperate farmers to apply any available pesticide in a bid to bring the infestation under control (Luchen & Mingochi, 1994) Such indiscriminate application of chemical measures has limited effect on red spider mites and often leads to loss of the crop (Messiaen, 1992) However, the introduction of pest management strategies in the form of Integrated Pest Management (IPM) has helped in controlling red spider mites and other tomato pests such as African bollworm

(Helicoverpa armigera) (Reganold, et al., 1990) The idea of Integrated Pest Management

took root in the 1960s in response to the pesticides dilemma The principle behind IPM was to use a variety of insect controls instead of relying solely on chemical insecticides These methods may include the use of cultural practices, natural enemies, and selective

pesticides (Reganold et al., 1990; Bohmont, 1997) Cultural practices are simple

techniques such as vacuuming out insects, the introduction of certain plants to ward off pests that attack a particular crop or dislodging insects with strong jets of water However,

a successful IPM program depends on a thorough understanding of pest populations, the associated ecosystems, and the available management tactics IPM is based on proper pest identification, periodic scouting, and the application of pest management practices during the precise stage of the crop’s development where no control actions would result in

significant economic losses (Bues et al., 2003)

The following section gives an overview of the characteristics of the red spider mites

2.2 Red spider mites (RSM)

2.2.1 Taxonomy

Red spider mites belong to the class Arachnida and genus Tetranychus Both the class and genus include at least three well known species which are Tetranychus cinnabarinus (Boisduval), also called the carmine mite; Tetranychus urticae Koch, also called the two spotted red spider mite (Bok et al., 2006); and the tobacco spider mite, Tetranychus evansi

Baker & Prichard (Visser, 2005) Differentiating these three red spider mite species is not

easy Wang (1987) tried to differentiate between T urticae Koch and T cinnabarinus

Boisduval by using morphological characters This proved difficult because they are both polymorphic and there was a significant variation in morphology among populations found on different host plants and in different geographic locations (Wang, 1987) Meyer

(1987), considered T cinnabarinus and T urticae to be one and the same organism This

was subsequently accepted by specialists of the Tetranychidae (Ehara, 1993; Baker &

Tuttle, 1994; Bolland et al., 1998) However, Kuang & Cheng (1990), using

morphological, biological and molecular data, showed that there were in fact marked

differences between T urticae and T cinnabarinus in that T urticae females have 10 setae

on tibia I whereas T cinnabarinus has 10-13 setae (an addition of up to three solenidia) on

tibia I Zhi-qiang & Jacobson (2000), in their study on greenhouse tomato plants in the

UK, confirmed that the colour of the mite cannot be reliably used to separate T.urticae and

T cinnabarinus

The lack of clarity in terms of classification has now resulted in the green form of these

complex species being referred to as T.urticae while the red form is called T cinnabarinus (Baker & Tuttle, 1994; Bok et al., 2006) In this study, no differentiation is made between

the different mite species This is because normally more than one type of mite occur within a single infestation and the eventual goal of the research is to develop an effective acaricide against all red spider mites

2.2.2 Life cycle

The spider mite’s life cycle starts with a small, round egg (Figure 2.1) There are three active immature stages (larva, protonymph and deutonymph), each separated by a resting

stage before a final moult to the adult (Klubertanz et al., 1991) The life cycle of spider

mites is temperature-regulated and occurs rapidly at warmer temperatures (Mau &

Kessing, 1992) Both T cinnabarinus and T urticae complete their life cycle from egg to

adult in about a week or two when temperatures are favourable (Mau & Kessing, 1992; Bolland & Valla, 2000) Spherical shiny eggs are laid singly by the adult on the underside

of the leaf surface or are attached to the silken web span (Figure 2.2.)

Larvae

Protonymph Deutonymph

Adult

Eggs