Nghiên cứu đặc tính sinh học và biện pháp phòng trừ bọ vòi voi diocalandra frumenti (coleoptera curculionidae) hại dừa tại đồng bằng sông cửu long tt tiếng anh

MINISTRY OF EDUCATION AND TRAINING CAN THO UNIVERSITY SUMMARY DOCTORAL DISSERTATION Major: Plant Protection Code: 9620112 NGUYEN HONG UNG STUDY ON BIOLOGICAL CHARACTERISTICS AND CONTROL METHODS ON LESSER COCONUT WEEVIL Diocalandra frumenti (COLEOPTERA: CURCULIONIDAE) IN THE MEKONG DELTA Can Tho, 2019 THE THESIS HAS BEEN COMPLETED AT THE COLLEGE OF AGRICULTURE AND APPLIED BIOLOGY, CAN THO UNIVERSITY Scientific supervisor: Assoc Prof Dr Tran Van Hai The dissertation will be defended to the University scientific committee Dissertation seminar at: ………………………… Time: …………………………………………… Reviewer 1: ……………………………………… Reviewer 2: ……………………………………… Find more information about dissertation at: Can Tho University Learning Resource Center National Library of Vietnam LIST OF PUBLISHED PAPERS Nguyen Hong Ung, Trieu Phuong Linh, Huynh Ky and Le Van Vang, 2016 Genetic diversity among Diocalandra frumenti (Coleoptera: Curculionidae) on coconut by ISSR marker, 2016 Can Tho University Journal of Science (ISSN 1859-2333), Volume 3/2016, pp 128-135 Nguyen Hong Ung, Chau Nguyen Quoc Khanh, Le Van Vang and Tran Van Hai, 2016 Damage situation and morphological characteristics of the coconut weevil, Diocalandra frumenti Fabricius (Coleoptera: Curculionidae) in Tra Vinh Province, 2016 Journal of Plant protection, No (268): 36-43 Nguyen Hong Ung, Chau Nguyen Quoc Khanh, Le Van Vang and Tran Van Hai, 2017 The results of the damage and behaviors of the coconut weevil, Diocalandra frumenti (Fabricius) (Coleoptera: Curculionidae) in Vinh Long and Ben Tre Province, 2017 Proceedings of the 9th Vietnam National Conference on Entomology, Agriculture publishing house, pp 729-736 (ISBN 978- 604-60-2511-5) Chapter 1: INTRODUCTION 1.1 The imperativeness of the dissertation Coconut (Cocos nucifera L.) is an important tree for oil extraction in the total areas of 12 millions of hectares in 90 countries of the world It has been considered a source of food, material supply for consumers’ products processing, exporting industries and a tree with economic, social and ecological significance (Vo Van Long, 2007) In addition, according to Cao Quoc Hung (2015) coconut has high economic potentials, especially suitable for poor-nutrient coastal, saline intrusion, flood and storm-effected soils Main products made from coconuts have been exported to different markets in European, Middle East, African and North American countries to bring about high profits Coconut areas of Vietnam in 2015 were approximately 160 thousands of hectares, mainly dispersed in the Mekong Delta-82.6% of the total areas It has created significant production values for the region In Ben Tre province, coconut processing is a key economic industry contributing to creating employment opportunities for numerous labor and increasing income for farmers According to Nguyen Thi Thu Cuc (2015), lesser coconut weevil is scientifically called Diocalandra frumenti Fabricius (Coleoptera: Curculionidae) This insect, which was firstly recognized in Kien Giang province in 2012, has quickly caused damages to many provinces in the Mekong Delta, Southeast and Central areas Its damages can cause fruit deformity and stunting Previously, D frumenti was recorded to cause damages on areca, nipa palm and other plants belonging to the Palmae family in many places in the world (EPPO, 2012) The damages have shown that D frumenti possibly causes serious effects on coconut productivity and quality Since coconut is significantly high; and this insect stays at places not easy to reach, preventive treatments by chemicals are extremely difficult which cause environmental pollution and affect human health At present, official studies on preventive methods, which are significantly effective to control this pest, have not been made available Therefore, the dissertation on “Study on biological characteristics and control methods on lesser coconut weevil Diocalandra frumenti Fabricius (Coleoptera: Curculionidae) in the Mekong Delta” was conducted to identify detailed information on D frumenti which sets up a foundation for developing an integrated management strategy with a focus on safe solutions to prevent from this pest 1.2 The aim and requirements of the study - Identify the damage capacity of D frumenti in three provinces: Ben Tre, Vinh Long and Tra Vinh - Survey morphological, biological and damage characteristics of D frumenti Fabricius on coconut trees - Identify the genetic diversity of D frumenti by ISSR molecular markers - Determine natural parasitic fungi of D frumenti and evaluate efficacy of bio products against D frumenti Fabricius - Establish experimental models to control D frumenti by environmentally-safety solutions 1.3 The scientific meaning of the dissertation The dissertation provides basic knowledge on lesser coconut weevil D frumenti in Ben Tre, Vinh Long and Tra Vinh provinces such as its damage status, morphological and biological characteristics etc It additionally evaluates genetic diversity of D frumenti in some provinces in the Mekong Delta and the Southeast region, which makes gene banks of insects more diverse The dissertation provides knowledge on managing lesser coconut weevil D frumenti under a sustainable direction, an important scientific basis in entomology The application of the dissertation results will contribute to ensuring coconut quality, limiting the use of insecticides, reducing environmental pollution and securing human health 1.4 The new contributions of the dissertation The dissertation results identified damage status, morphological and biological characteristics, living habits, genetic diversity, genetic relations of lesser coconut weevil D frumenti More importantly, they additionally selected some parasitic fungal strains with high effectiveness in controlling this pest Chapter 3: STUDYING METHODS 3.1 Period and location of study 3.1.1 Period The dissertation was conducted from November, 2014 to November, 2018 3.1.2 Locations The dissertation was conducted in coconut orchards in Ben Tre, Vinh Long, Tra Vinh and neighboring provinces Experiments were arranged at laboratories of Department of Plant Protection, Can Tho University and School of Agriculture and Aquaculture, Tra Vinh University 3.3 Methods 3.3.1 Content 1: Evaluate damage status of lesser coconut weevil D frumenti in Ben Tre, Vinh Long and Tra Vinh provinces - Interview farmers to obtain information on lesser coconut weevil D frumenti Interviewed households, whose areas of at least 1,000m 2, were those involved in coconut cultivation in Ben Tre, Vinh Long and Tra Vinh provinces The investigated contents included information on cultivation, damage status and D frumenti - Investigate damage status of D frumenti on coconut orchards Ten coconut trees were selected in five locations: four in peripheral and the other in central coconut orchards to record the damages caused by D frumenti on main parts of the trees The investigation were conducted on 3,300 coconut trees from 330 orchards in Ben Tre, Vinh Long and Tra Vinh provinces (based on QCVN 0138:2010/BNNPTNT) - Investigate damage progress of D frumenti on coconut orchards Damage progress of D frumenti was performed at 27 orchards in the three provinces with areas of more than 3,000m2 each The investigation was carried out once a month during 12 months 3.3.2 Content 2: Investigate the morphological, biological characteristics and damage caused by lesser coconut weevil D frumenti The investigation was carried out with 150 eggs, 29 larvae, 29 female pupae, 20 male pupae, 29 female and 20 male adults in total The study was proceeded with collecting pupal individuals from the fields for further additional investigation Living habits and damages caused by lesser coconut weevil were investigated at coconut orchards of cultivation households in Ben Tre, Vinh Long and Tra Vinh provinces, combined with laboratory investigation C B A Adults in the field laying eggs raising larvae E D pairing adults after emergence raising pupae Figure 3.5: The process of investigating the morphological and biological characteristics of D frumenti: Adults in the field (A), laying eggs (B), raising larvae and pupae (C,D) and pairing adults after emergence (E) (Nguyen Hong Ung, 2016) 3.3.3 Content 3: Evaluate genetic diversity of lesser coconut weevil D frumenti by ISSR molecular markers ISSR molecular markers were used to identify genetic relations of D frumenti strains collected respectively in eight and four provinces in the Mekong Delta and Southeast region The investigation was carried out on 40 samples of D frumenti adults which were grouped with each other based on their morphological characteristics 3.3.4 Content 4: Collect, isolate, select and evaluate effectiveness of parasitic fungi on lesser coconut weevil D frumenti Samples of lesser coconut weevil D frumenti with parasitic fungi were collected and transferred to laboratory for isolation, selection and experiment arrangements - Evaluating the effectiveness of M anisopliae on D frumenti in laboratory condition The experiment was conducted with six treatments, including five green muscardine fungus samples collected from local areas and one control with distilled water The utilized concentration of the M anisopliae treatments was 108 spores.mL-1; all treatments were added with siloxane alkoxylate as an adhesive substance The experiment was arranged in a randomized complete block design, four replications with 30 D frumenti adults for each treatment The experiment was carried out by dipping the adults into the fungal spore solution for 30 seconds Number of alive adults was recorded at the time of 1, 3, 5, 7, 9, 11, 13 and 15 days after treating - Evaluating the efficacy of green muscardine fungus M anisopliae and some insecticides on D frumenti adults in the laboratory condition This experiment was conducted with seven treatments and four replications arranged in randomized complete block design Each replication of one treatment was a petri dish small pieces of coconut ocrea and 30 adults The treatments were treated by spraying solution over the experimented treatments with three M anisopliae strains (108 spores.mL-1), three insecticides and one control with distilled water Number of alive adults was recorded at 1, 3, 5, 7, 9, 11, 13 and 15 days after treating - Evaluating the efficacy of green muscardine fungus at different concentrations on D frumenti adults in the laboratory condition The M anisopliae strain was selected for survey based on the previous results The experiment was conducted with five treatments and four replications arranged in randomized complete design Each treatment had a petri dish with coconut petiole and 30 D frumenti adults which were dipped into the fungal spore solution with concentrations of 106, 107, 108, 109 spores.mL-1 and one control (distilled water) Number of alive adults was recorded at 1, 3, 5, 7, 9, 11, 13 and 15 days after treating Figure 3.8: Arranged experiment to evaluate efficacy of M anisopliae on D frumenti adults in laboratory with coconut petioles as food supply (Nguyen Hong Ung, 2015) - Evaluate preventive efficacy of green muscardine fungus strains and some insecticides on D frumenti in the field condition Two isolates of muscardine fungi were Ma-GT-BT and Ma-LP-ST and two insecticides Emamectin benzoate and Fipronil were used The controlled treatments were treated with distilled water and adhesive substances The experienment was conducted at coconut orchards in Ben Tre province with the areas of 3,000 m2 They were in the stage of blooming and bearing young fruits which were damaged by D frumenti The experiment was arranged in randomized complete block design with five treatments and four replications Each treatment was six coconut trees with three times of application during an interval of two weeks per each time 3.3.5 Content 5: Establish experimental models to control D frumenti Fabricius by environmentally-safety solutions A model was implemented on “dua Ta” in Ben Tre province in the dry season and the other on “dua Xiem” in Tra Vinh province in the rainy season with the areas from 3,000-4,000 m2 Lesser coconut weevil D frumentri control methods which were mainly applied were orchard cleaning, periodically spraying Ma-GT-BT entomopathogenic fungus at 125gx16L-1, 2-3L per tree, once every three weeks The models in Ben Tre and Tra Vinh provinces were sprayed three and six times respectively during the implementation period 3.4 Statistical analysis Data were entered and presented by Microsoft Office Excel, collected by Duncan test and T-tested with MSTATC The investigation results on D frumenti genetic diversity were analyzed under the UPGMA method by SATISTICA 5.5 software Chapter 4: RESULTS AND DISCUSSIONS 4.1 Results on the damage capacity of D frumenti in Ben Tre, Vinh Long and Tra Vinh provinces * Farmer investigation results - D frumenti in coconut orchards recognized by farmers Average percentages of investigated households who recognized damages caused D frumenti in 2013-2014 were 32.9% 41.6% Farmers in Ben Tre province mainly realized its damage in 2013 (30.7%) while those in the other two provinces (58.9% for Tra Vinh and 43.3% for Vinh Long) knew about it in 2014 - Damage levels of D frumenti on coconut orchards in 2014 and 2015 According to the farmer investigation results, the damage in 2015 was higher than that of 2014 Its main damage in 2014 was less than 5% of fruits per orchard (38.4% households) and that of 2015 was 10 to