MINISTRY OF EDUCATION MINISTRY OF AGRICULTURE AND TRAINING AND RURAL DEVELOPMENT VIETNAM ACADEMY OF AGRICULTURAL SCIENCES **************************** NGUYEN MINH DUC STUDY ON ACARICIDES RESISTANCE OF THE RED SPIDER MITE Oligonychus coffeae Nietner (Acarina: Tetranychidae) ON TEA AND THEIR MANAGEMENT IN THE NORTHERN MOUNTAINOUS AREA OF VIETNAM Specialization: Plant protection Specialization code: 962 01 12 SUMMARY OF AGRICULTURAL DOCTORATE THESIS HANOI – 2019 The thesis was completed at: Vietnam Academy of Agricultural Sciences Supervisors: Ass Prof Dr Le Van Trinh Dr Nguyen Thi Nhung Peer reviewer 1: Peer reviewer 2: Peer reviewer 3: The thesis will be defended for the doctoral degree of PhD and evaluated by defense committee at Vietnam Academy of Agricultural Sciences At … hour, day… month … year 2019 This thesis can be accessed at: Vietnam National Library Library of Vietnam Academy of Agricultural Sciences Library of Plant Protection Research Institute INTRODUCTION Urgency of the thesis Red spider mite (Oligonychus coffeae Nietner) is a popular insect which caused yield and quality lost on tea Nowaday, insecticides have been used as the first choice of tea growers There was number of insecticides which used to have high effective in controlling red spider mite, however, their effectiveness has reduced rapidly recently The determination of insecticide utilization’s status and the evaluation of resitance ability of red spider mite are the basic for constructing effective management of resistance Consequently, the research namely “Study on acaricides resistance of red spider mite Oligonychus coffeae Nietner (Acarina: Tetranychidae) on tea and their management in the northern mountainous area of Vietnam” has been conducted because of its urgency Objectives and requirement of the thesis 2.1 Objective: To determine resistance level and formation rate of resistance of red spider mite against common groups of insecticide Based on results of the research, propose some solutions to manage resistance of red spider mite in tea cultivated area in the northern mountainous region of Vietnam 2.2 Requirement To evaluate actual situation of pesticide utilisation in controlling insect pests in general and red spider mite in particular on tea in Thai Nguyen province and Phu Tho province To determine resistance level and formation rate of resistance of red spider mite against popular chemical acaricides that used to manage red spider mite in tea cultivated area in Thai Nguyen province and Phu Tho province To evaluate effectiveness of intergrated red spider mite management based on the rational use of pesticides The scientific and practical significance of the thesis 3.1 The scientific significancen of the thesis: Providing information, latest update of scientific references on the extent of damage, resistant index and formation rate of resistance groups of pesticides which have been using popularly to control pests in Thai Nguyen province and Phu Tho province 3.2 The practical significance of the thesis: The result of this research is to determine scientific basis in construction of resistance management solutions against red spider mite in IPM on tea contributing to safe and sustainable utilization of pesticides in tea production Object and scope of the thesis 4.1 Object of the thesis:Resistance of red spider mite (O coffeae Nietner) on tea 4.2 Scope of the thesis: The research focuses on evaluatation of pesticide utilization state on tea in Thai Nguyen province and Phu Tho province Susceptibility level and resistance formation rate of red spider mite against some groups of chemical and solutions for reduction in chemical resistance in Thai Nguyen province are researched as well New research findings of the thesis: The research firstly provides scientific references in a systematic way the resistance level and resistance formation rate of red spider mite against 11 active ingredients (Abamectin, Azadirachtin, Dimethoate, Emamectin benzoate, Fenpyroximate, Fenpropathin, Hexythiazox, Matrine, Propargite, Pyridaben, Rotenone) which have been using popularly in controlling pests on tea in mountainous region of northen Vietnam Adding some references on the efficacy of technical measures to restric the development of red spider mite and propose resistance management of red spider mite as well Thesis structure: The thesis has 119 pages includes introduction, content (3 chapters), conclusion and suggestion with 36 tables, figures The references has 125 individuals with 41 Vietnamese references, 82 English references and references downloaded on the Internet CHAPTER I SCIENTIFIC BASIS AND LITERATURE REVIEWS 1.1 Scienfific basis The utilization of pesticides on tea are not the same in different countries lead to the variation in rresistance formation in tea plantation area Resistance management solutions of red spider mite are also different Consequently, research on insecticide resistance of red spider mite is needed to conduct in particular condition 1.2 Oversea studies 1.2.1 Biological, ecological characteristics and development regulation of red spider mite In South India, under laboratory condition with the average temparature is 25±2oC, relative humidity is 85±5% and on UPASI-10 variety, the average duration from 1st instar to instar was 8.10±1.65 days Lifespan of male and female adults are 12.60±2.15 days and 24.20±3.50 days in average, respectively Gender ratio was 1:2.25 (male:female) Egg laid ability was 120.8 ± 13,80 eggs/ female (Sudarmani, 2004) Red spider mite prefer sunlight, thus tea plants which are cultivated in area without shade will be damaged more severely than that with shade (Das, 1959b) In southern India, red spider mite has successive generations and appears on tea plants throughout the year and the density reaches a peak from March to April Low temparature, high humidity and heavy rain has detrimental influence to the development of red spider mite (Sudarmani, 2004) 1.2.2 Actual situation of insecticide utilization to control red spider mite on tea In Shizuoka (Japan), tea growners spray 16.9-21.6 times per year and 4.1-8.1 times per year in average to control insect pest and disiease pest, respectively (Takafuji and Amano, 2001) Recently, there are number of new insecticides such as Propagite, Fenpyroximate, Hexythiazox, Bifenthrin, Fenazaquin and Spiromesifen has been used to manage red spider mite (Anomyous, 2012; Babu and Muraleedharan, 2010; …) 1.2.3 Resistance of red spider mite The repeated use of acaricide leads to the increase in serious damage of red spider mite to tea production The decline of susceptibility of red spider mite against insecticide groups is one of the reasons for increasing number of populations (Sarker and Mukhopadhyay, 2008; Roy et al., 2008; Shahoo et al., 2003) According to Roy (2009), among chemicals which have been tested on red spider mite populations in Terai and Dooars - India, LC50 of Ethion and Dicofol were higher than 300ppm LC50 of Propagite were 46.246 and 97.110 in average in Terai and Dooars, respectively That of Fenazaquin and Fenpropathrin were less than 10ppm In northern of Bengal, India, the resistance against chemicals namely Ethion, Dicofol, Propargite, Fenazaquin and Fenpropathrin of red spider mite have observed and the results showed that Terai popupation had lowest susceptibility to all of them in comparision with Dooars pupolation Susceptibility level corresponds to number of acaricides in regions indicated selective population pressure caused by acaricide (Roy et al 2010a) In laboratory, LC50 value of Ethion, Dicofol, Profenofos, Propargite, Fenpropathrin, Ferazaquin and Abamectin of populations in the northern of India were 687.18ppm, 534.04ppm, 241.684ppm, 90.256ppm, 12.549ppm, 4.319ppm, 2.405ppm, respectively Among number of acaricide, Abamectin has highest toxic and Ethion is opposite LC50 values went down corresponding to egg-killed insecticides namely Fenazaquin, Profenofos, Propagite, Fenpropathrin, Ethion, Dicofol and Abamectin, respectively (Roy et al., 2012) In Terai, India, population in which Ethion group were used frequently, LC50 value was 79-100 times higher in comparision with others where acaricide was not used The result was similar with Fenpropathrin in which LC50 value was 73-108 times higher than others without using acaricides (Soma et al., 2017) 1.2.4 Management of the resistance of red spider mite According to Sudarmani (2004), in north India, the proportion of tea leave which is infected by red spider mite in tea field without shaded trees was high because of high temperature and long lighting time on leave Tea plant with shaded trees develops well and reduces number of red spider mite According to Roy et al (2010a), egg-killed insecticide utilization is one of the strategic solution for red spider mite management Roy et al (2010b) also said that at egg stage, Fenazaquin had lowest value of LC50, followed by Profenofos, Propargite, Fenpropathrin, Ethion, Dicofol, Abamectin and Azadiractin, respectively The process of red spider mite management includes: 1) Measures should be taken (Two rounds of spray at 15 days interval) during December and January in young and unpruned tea; skiffed tea – February; pruned tea – early March; 2) after severe attack of mite impose two rounds of applications must be followed at an interval of -10 days (April – October: days and Nov-March: 10 days); 3) avoiding an application of sulfur formulation during hot sunshine and dry spell; 4) collecting tea leaves on the surface; 5) during full cropping seasons spraying should be undertaken as spot treatment only; 6) for pruned tea monitoring is necessary soon after tipping; 7) avoid spraying at noon in sunny weather; 8) mixing of acaricides with foliar nutrients, insecticides and others should be avoided for retaining the toxicity of the acaricides and better control in red spider prone sections; 9) remove serious infected tea plants; and 10) thorough drenching of top, middle and bottom hamper of bushes with pray fluid spray fluid is mandatory to kill the residual population (Das, 1960; Gurusubramanian Borthakur, 2005) 1.3 Studies in Vietnam 1.3.1 Biological, ecological characteristics and development regulation of red spider mite Nguyen Van Dinh (1994) reported that there were spider mite spicies on tea: false spider mite, red spider mite and broad mite The red spider mite is the most dangerous one among them Adult has pair of legs, segmented leg with a lot of scattered sharp hairs The body is separated into parts, the head and chest + abdomen with the size are 0,06 – 0,09mm x 0,05 – 0,07mm, 0,25 – 0,31mm x 0,17 – 0,24mm, respectively One to two days after hatching, female starts laying eggs which have flat sphere shape and the size is around 0,09-0,12mm There is a curve and small hair in the middle of the egg New egg laid has light pink color, then turn to red-brown and getting dark brown before hatching New hatching red spider mite has light pink body, the size is 0,13-0,15mm x 0,100,12mm with pair of legs (Nguyen Van Hung and Nguyen Van Tao 2006) In the laboratory condition with the temperature and relative humidity (RH) are 27,5oC and 81,6%, respectively, lifetimes of red spider mite on Trung Du Xanh and PH1 varieties are 10,70 days and 10,86 days, respectively (Pham Thi Mai, 2010) Depend on environmental conditions, particularly temperature, red spider mite’s lifespan vary from 11,2 to 12,8 days Each female is able to lay up to 79 eggs, oviposition rate is highest at the date of 5th – 10th from the first day of laying egg Female can lay egg during 20 days The most favourite temperature for the development of red spider mite is 30 oC, number of egg laid increase to 88 eggs/each and lifetime is only 11,2 days compared to 12,8 days at 25oC (Nguyen Thai Thang, 2000) According to Nguyen Khac Tien (1994), red spider mite is the most dangerous insect pests on tea There are two peak of density per year, the 1st is from Ferbruary to May and the 2nd is from September to November 1.3.2 Actual situation of insecticide utilization to control red spider mite on tea The number of spraying varied from to 16 times per year in key points of tea plantation in Ba Vi district, periodic spraying rate is still high, up to 75% and most of farmers spraied without “4 right regulation” (Nguyen Thi Bich Thuy, 2009) According to the investigation in Thai Nguyen province from 2005 to 2006, 28.8% to 33.3% of interviewed farmers admitted that they spraied insecticide less than 16 times per year while 60.0%-66.7% of interviewers did 16 to 20 times per year (Nguyen Van Toan and Pham Van Lam, 2014) 1.3.3 Resistance of red spider mite Although insecticides which have been spraied on tea plant, have broad spectrum effects, however, not work well with red spider mite and they even promote the development of this pest Otherwise, those chemicals destroy natural enemies, thus red spider mite is able to develop much more than before spraying (Nguyen Van Hung and Nguyen Van Tao, 2006) 1.3.4 Management of the resistance of red spider mite There is not any deeply research on resistance of red spider mite against chemical in Vietnam There are some researches on management of red spider mite on tea (Nguyen Van Dinh, 1994; Luong Thi Huyen, 2017; Nguyen Tran Oanh, 2012; Nguyen Thai Thang, 2000; Nguyen Thi Thu et al., 2016; Vu Thi Thuong et al., 2015) CHAPTER II MATERIAL, CONTENTS AND METHODOLOGY 2.1 Location and schedule The research has been conducted in the laboratory and greenhouse in Plant Protection Research Institute (PPRI), in the field in Thai Nguyen province and Phu Tho province from 2014 to 2018 2.2 Materials and equipments Pesticies, tea varieties, equipments in lab and on tea fields 2.3 Contents - Investigation and evaluation of actual situation of insecticide utilization in controlling red spider mite in Thai Nguyen province and Phu Tho province - Determination of resistance formation of red spider mite against common acaricides - Evaluation of resistance development and across-resistance ability of red spider mite against common acaricides - Research on some solutions to manage resistance of red spider mite in IPM method - Building model and propose technical measures to control resistance of red spider mite in IPM method 2.4 Methodology Investigation of pesticide utilization on tea in Thai Nguyen province and Phu Tho province accroding to general method (Dao Trong Anh, 2002) Rearing susceptible red spider mite strains which were collected from the field accoring to the method of Helle and Sabelis (1985) Determine resistance level of red spider mite according to the method of IRAC (2009) and Sato et al (2005) Investigate population dynamic of red spider mite according to QCVN 01-118 issued by MARD (2012), Sudarmani (2004), Nguyen Van Hung and Nguyen Van Tao (2006) Investigate natural enemies on tea according to the method of Pham Van Lam (1997) Evaluatie effectiveness of acaricides according to the method of Kumari et al (2012), Knight et al (1990) Evaluate the effectiveness of alternative utilization of management resistance of red spider mite against insecticides according to Le Truong et al (2005) and Nguyen Tran Oanh (2012) Building model and propose technical measures to control resistance of red spider mite in IPM method based on the research’s results and Intergrated Tea Management Process (Nguyen Van Hung and Nguyen Van Tao, 2006) 2.5 Analysis The efficacy of insecticides was canculated by Abbott formula (1925) ; Sarmah (1999) and Henderson-Tilton (1995) LC50 was calculated by Finney's 1971 Probit program Resistance indices (Ri) was determined according to FAO (1980) Data was processed by IRRISTAT 5.0 program CHAPTER III RESULTS AND DISCUSSION 3.1 Field investigation of pesticide utiliation’s status in red spider mite management in Phu Tho province and Thai Nguyen province 3.1.1 Insects and spider mites on tea in Thai Nguyen province and Phu Tho province 3.1.1.1 Insects and spider mites on tea through interview with farmers In two research area, green hopper and mosquito bug are two major insects on tea The ratio of farmers who consider that green hopper is the most popular one in Thai Nguyen province and Phu Tho province were 99.8% and 97.1%, respectively In term of posquito bug, those were 77.1% and 70.9%, respectively In Thai Nguyen province, the percentage of farmers who believe that red spider mite is serious threat to tea production was 81.0% in average meanwhile it was 67.3% in average in Phu Tho province 3.1.1.2 Insects and spider mites on tea through field investigation In 2004, we found 13 spieces on tea including insects and spider mite in Thai Nguyen province and Phu Tho province The common spicies (with frequency encounter is over 50%) were green hopper, mosquito bug, and red spider mite in Thai Nguyen province and mosquito bug and red spider mite in Phu Tho province 3.1.2 Pesticie utilization status in pest management on tea 3.1.2.1 Number of pesticide application on tea in one year According to an interview in Hoa Binh commune, La Bang commune, and Phan Me commune (Thai Nguyen province) in 2014, tea growners spraied 14.4 times/year in average (vary feom 12.37 to 16.89 times) In Phu Tho province, the interview was conducted in Phu Ho commune, Tien Phu commune, and Vo Mieu commune, the result illustrated that tea growners applied pesticides with lower quantity than that in Thai Nguyen province and the average application was 12.0 times per year (vary from 9.82 to 14.16 times) 3.1.2.2 Concentration and doze Table 3.4 Concentration of insecticides and acaricides were used in 2014 Increase in comparison with Percentage of applicant (%) recommendation (times) Thai Nguyen1 Phu Tho2 Recommendation 71,27 78,15 > to 19,38 15,74 > to 8,39 5,68 >3 0,96 0,43 Notice: Investigation sites: Hoa Binh commune (Dong Hy district); La Bang commune (Dai Tu district); Phan Me commune (Phu Luong district) Investigation sites: Phu Ho commune (Phu Tho district); Tien Phu commune (Phu Ninh district); Vo Mieu commune (Thanh Son district) The percentage of tea growners who applied accurate concentratin and doze according to recommendation of producers were quite high with 71.27% in Thai Nguyen province and 78.15% in Phu Tho province In Thai Nguyen province, 8.39% of interviewers said they applied pesticides with 2-3 times in comparision with the recommendation from producers In term of Phu Tho province, it was 5.68% The number of farmer who increased concentration and doze of pesticide in Thai Nguyen province was higher than that in Phu Tho province (Table 3.4) 3.1.2.3 Sort of pesticide The active ingredients namely Abamectin and Emamectin benzoate (Avermectin group) were used popularly to control insect pests on tea The percentage of farmer households who applied abamectin were 31.32% and 26.93% in Thai Nguyen province and Phu Tho province, respectively Otherwise, the ratio of farmer households who spraied Emamectin benzoate were 10.19% and 18.15%, respectively In term of other active ingredients, the numbers varied from 0.14% to 6.34% in Thai Nguyen province and from 0.02% to 5.16% in Phu Tho province The mixture of pesticides applying to control insect pests on tea was a combination between abamectin and emamectin benzoate (3.67% farmer households used/ highest) and mixture of Fenitrothinon and Trichlorfon (5.16% farmer households used/ highest) in Thai Nguyen province and Phu Tho province, respectively Table 3.7 Single active ingredients were used to manage red spider mite in 2014 Proportion of households Toxic using (%) Groups Active ingredients group* Thai Nguyen1 Phu Tho2 Abamectin II 19.16 26.37 Avermectin Emamectin benzoate II 8.45 15.02 Điều hòa sinh Hexythiazox III 3.67 2.78 trưởng Este sulfite Propargite III 10.18 8.67 Focmamidin Diafenthiuron III 4.49 Lân hữu Dimethoate II 4.24 Pyrazol Fenpyroximate II 6.30 9.47 Pyrethroid Acrinathrin III 1.16 5.54 Pyridazinon Pyridaben III 5.41 3.28 Azadirachtin IV 3.51 7.27 Botanical insecticide Matrine III 3.39 4.41 B thuringiensis var III 0.13 kurstaki Biopesticide B thuringiensis III 0.25 var T36 Triazapentadiene Amitraz III 2.78 Notice: Toxic group *: according to WHO -: Do not use Investigation sites: Hoa Binh commune (Dong Hy district); La Bang commune (Dai Tu district); Phan Me commune (Phu Luong district) Investigation sites: Phu Ho commune (Phu Tho district); Tien Phu commune (Phu Ninh district); Vo Mieu commune (Thanh Son district) Table 3.8 Mixtural pesticides used for management of red spider mite on tea in 2014 Toxic Proportion of * group households using (%) Groups Ingredients Thai Nguyen1 Phu Tho2 Avermectin, Abamectin + Chlorfluazuron II+II 0,35 Benzoylurea Avermectin, Abamectin + II+III 0,37 Diamide Chlorantraniliprole Avermectin, Abamectin + Acetamiprid II+II 3,78 2,36 Neonicotinoid Abamectin + Imidacloprid II+III 2,39 Avermectin, Dầu khoáng Avermectin, Phenylpyrazole Avermectin, Pyrethroid Avermectin, Botanical insecticide Avermectin, microbial insecticide Botanica insecticide Abamectin + Petroleum oil Emamectin benzoate + Petroleum oil II+III 1,07 4,07 II+III 0,42 - Abamectin + Fipronil II+II 0,96 2,43 4,85 1,48 2,91 - 2,46 3,58 0,27 - 0,88 - 3,54 3,27 Abamectin + AlphaII+II cypermethrin Abamectin + LambdaII+II cyhalothrin Abamectin + Matrine II+III Abamectin+ Azadirachtin+ II+IV+I Emamectin benzoate I Emamectin benzoate + II+IV Azadirachtin Emamectin benzoate + Matrine II+III Abamectin + Bacillus thuringiensis var kurstaki II+III 1,29 - Azadirachtin + Matrine IV+III 1,34 - Noitice: *: Toxic group: according to WHO , - :do not use Investigation sites: Hoa Binh commune (Dong Hy); La bang commune (Dai Tu); Phan Me commune (Phu Luong) Investigation sites: Phu Ho commune (Phu Tho); Tien Phu commune (Phu Ninh); Vo Mieu commune (Thanh Son) Abamectin was the most popular active ingredient which applied to control re spider mite on tea Proportion of households used above chemical were 19.16% and 26.37% in Thai Nguyen province and Phu Tho province, respectively Follow by Abamectin, Propargite was the 2nd popular active ingredient which was chosen by 11 Table 3.12 Resistance level of red spider mite against some common chemicals in investigation site (PPRI, 2014) Ingredient name Commercial name Fenpyroximate Ortus 5SC Propargite Comite 73EC Abamectin Catex 1.8EC Azadirachtin Matrine Trutat 0.32EC Sokupi 0.36SL LC50 (ppm) and limit value of 95% Populations collected in Phu Ho-Phu Tho 39,5301 (35,1267 - 44,6843) 183,8344 (160,2341 -203,8748) 0,7084 (0,6538-0,8861) 3,3562 (2,8794-3,7653) 3,4262 (2,6583-4,0285) Susceptible population 3,8755 (3,2794 - 4,4561) 15,9856 (13,3480 -17,3285) 0,06269 (0,0579-0,07156) 0,7296 (0,6128-0,8463) 0,7138 (0,5166-0,8041) Ri 10,2 11,5 11,3 4,6 4,8 Notice: Target was adult re spider mite Collected in Oct and Nov 2014 3.3 Resistance development speed and across-resistance ability of red spider mite 3.3.1 The increase of resistance speed of red spider mite After 12 generations continuously exposed to an active ingredient, LC50 of experimental active ingredients increased remarkably LC50 of Abamectin against red spider mite went up to 15.4 times In term of Hexythiazox, LC50 increased only 4.6 times Otherwise, Pyridaben, Propargite and Fenpyroximate had an increase in LC50 7.0; 7.3; and 11.5, respectively (table 3.13) Table 3.13 LC50 of some active ingredients against red spider mite after 12 generation exposed (PPRI, 2014 - 2016) LC50 (ppm) Active Increase of Commercial names Before ingredients After treatment LC50 (times) treatment 0,0696 1,0712 15,4 Abamectin Catex 1.8EC Fenpyroximate Ortus 5SC 4,0907 46,8385 11,5 3,0596 14,0742 4,6 Hexythiazox Nissorun 5EC 16,0317 117,0314 7,3 Propargite Comite 73EC 2,9038 20,3266 7,0 Pyridaben Alfamite 15EC 3.3.2 Reduction of resistance without chemical exposure After generations without exposition to chemical, LC50 of Abamectin was reduced the most by 9.3 times Meanwhile, LC50 of Pyridaben, Fenpyroximate, Hexythiazox decreased 6.7; 5.7; 5.3 times, respectively In contrast, LC50 of Propargite reduced at least, only 4.6 times (table 3.14) That means the resistance of red spider mite against Propargite was more stable than others 12 Bảng 3.14 LC50 of some active ingredients after generations without exposure to chemical (PPRI, 2015 - 2016) Active ingredients LC50 (ppm) Commercial Reduction of Before After names LC50 (times) treatment treatment Abamectin Catex 1.8EC 0,7865 0,0845 9,3 Fenpyroximate Ortus 5SC 42,1342 7,3920 5,7 Hexythiazox Nissorun 5EC 14,0742 2,6555 5,3 Propargite Comite 73EC 181,1582 39,3822 4,6 Pyridaben Alfamite 15EC 30,1995 4,5074 6,7 3.3.3 Development of across-resistance of red spider mite against some active ingredients 3.3.3.1 Across - resistance ability of population has been resistant against Abamectin Red spider mite population (after 12 generation of exposure to Abamectin) resisted this active ingredient with quite high Ri (24.4%) and it was 16.4% with Emamectin benzoate (same group of Avermectin) This population did not show across-resistance phenomenon against active ingredients belong to different groups Azadirachtin, Matrine, Rotenone, Hexythiazox, Fenpyroximate, Propargite, Pyridaben, Fenpropthrin, and Dimethoate Ri value of red spider mite to other groups was low and varied from 0.9 to 2.9 (Table 3.15) Table 3.15 Across-resistance ability of populations at 12th generation who has been resistant Abamectin against some other acaricides (PPRI, 2016) LC50 (ppm) Commercial Population has Active ingredients Ri Susceptible names been resistant population Abamectin Abamectin Catex 1.8EC 1,6300 0,0668 24,4 Azadirachtin Trutat 0,32EC 0,7782 0,7705 1,0 Dimethoate Bini-58 40EC 238,4909 82,5228 2,9 Emamectin benzoate Tasieu 1.9EC 1,2890 0,0786 16,4 Fenpropthrin Danitol 10EC 35,6579 13,3052 2,7 Fenpyroximate Ortus 5SC 5,9532 3,9688 1,5 Hexythiazox Nissorun 5EC 3,3246 2,9684 1,1 Matrine Sokupi 0,36SL 0,7599 0,6440 1,2 Propargite Comite 73EC 20,2202 15,5540 1,3 Pyridaben Alfamite 15EC 8,2544 2,8172 2,9 Rotenone Trusach 2,5EC 0,5767 0,6785 0,9 Population (after 18 generations of exposure to Abamectin) which has been resistant against this active ingredient, has been evaluated across-resistance against other active ingredients which have been applied to control red spider mite The result illustrated that population which has been sresistant Abamectin, also showed high 13 resistant against this active ingredient itself and others in the same group Ri of above population to Abamectin was highest and it was 31.4 To Emamectin benzoate (same group of Avermectin), it was 24.4 In term of active ingredients belong to other groups (Pyridaben, Fenpyroximate, Propargite), Ri of this population were low and varied from 1.3 to 2.9 (table 3.16) Table 3.16 Across-resistance ability of 18th generation of red spider mite who has been resistant Abamectin against some other acaricides (PPRI, 2016) LC50 (ppm) Commercial Active ingredients Ri Resistance against Susceptible names Abamectin population Abamectin Catex 1.8EC 2,1352 0,0680 31,4 Emamectin benzoate Tasieu 1.9EC 1,66408 0,0682 24,4 Fenpyroximate Ortus 5SC 6,0861 4,0574 1,5 Propargite Comite 73EC 20,67156 15,9012 1,3 Pyridaben Dandy 15EC 8,456859 2,8863 2,9 Consequently, population which has been resistant Abamectin did not show across-resistance against other active ingredients belong to different groups Pyridaben, Fenpyroximate, and Propargite Its shown that population which has been resistant abamectin from 12th to 18th generation (after generations of exposure to Abamectin), Ri has increased significantly from 24.4 to 31.4 In term of Emamectin benzoate, it went up from 16.4 to 24.4 (Table 3.15 and table 3.16) 3.3.3.2 Across-resistance ability of population which has been resistant against Propargite Table 3.17 Across-resistance ability of 23th generation of red spider mite which has been resistant Propargite against some other acaricides (PPRI, 2016) LC50 (ppm) Commercial Active ingredients Ri Resistance against names Susceptible Abamectin Abamectin Catex 1.8EC 0,0922 0,0668 1,4 Azadirachtin Trutat 0,32EC 0,7089 0,7705 0,9 Dimethoate Bini- 58 40EC 208,7827 82,5228 2,5 Emamectin benzoate Tasieu 1.9EC 0,0967 0,0786 1,2 Fenpropathrin Danitol 10EC 0,0967 0,0786 1,2 Fenpyroximate Ortus 5SC 5,3579 3,9688 1,4 Hexythiazox Nissorun 5EC 3,3246 2,9684 1,1 Matrine Sokupi 0.36SA 0,5732 0,6440 0,9 Propargite Comite 73EC 205,0017 15,5540 13,2 Pyridaben Alfamite 15EC 0,0922 0,0668 1,4 Rotenone Trusach 2.5EC 0,4546 0,6785 0,7 14 Population (after 23 generations of exposure to Propargite) which has been resistant Propargite, showed high resistance against Propargite itself Ri of this population reached a peak at 13.2 There was not any report of the resistance of this population against other active ingresients belong to different groups Ri of above population to other active ingredients varied from 0.7 to 2.5 They have not shown across - resistance phenomenon against Dimethoate, Ri was 2.5 only (table 3.17) 3.4 Solutions in management of resistance of red spider mite in IPM method 3.4.1 Variety Red spider mite usually arises and reaches a peak of density twice per year in May and October Trung Du variety has highest density of 6.43 individuals/ leave at the peak in the end of May At the same time, the density of red spider mite on other varieties LDP1, TRI 777, PH8 was lower than that of Trung Du variety and they were 6.29; 5.61; and 5.02 individuals/ leave, respectively In term of Kim Tuyen, Phuc Van Tien variety, red spider mite’s density were significant lower at 4.37 and 4.06 individuals/ leave, respectively Farmer should choose tea varieties which are less infected by red spider mite when they cultivate new plants 3.4.2 Cultivation measures 3.4.2.1 Cultivation shaded tree The density of red spider mite on tea field with shaded tree is always higher than that without shaded tree At the peak of density, there were 6.15 and 9.29 individuals/leave in plantation area with and without shaded tree, respectively Consequently, planting shaded tree leads to the reduction in using acaricide Fifure 3.2 The effectiveness of shaded tree on density of red spider mite on Trung Du variety (La Bang, Dai Tu, Thai Nguyen, 2015) Notice: Treatment 1: Density of red spider mite on tea field with sahded tree Treatment 2: Density of red spider mite on tea field without sahded tree 3.4.2.2.The effect of branch cutting method The density of red spider mite reached a peak at the end of May 2015 in Treatment and it was 5.14 individuals/leave, meanwhile it was 8.07 head/leave in term of Treatment In conclusion, the density in former was significant lower than that of the latter It was extremely consistent with previous researches conducted by Das (1960) and Nguyen Van Dinh (1994) In addition, application of the former method helps to reduce pressure of using acaricide 15 Figure 3.3 The impact of branch cutting method on red spider mite on Trung Du variety (La Bang, Dai Tu, Thai Nguyen, 2015) Notice: Treatment 1: Pruning (40cm from the ground) Treatment 2: Pruning (60cm from the ground) 3.4.2.3 Fertilizer application on tea Density of red spider mite on tea in different treatments of using fertilizer were all over prevention threshold (6 individuals/leave) In the tea field where was applied inorganic fertilizers (treatment no.1) density reached a peak at 9.2 – 11.2 individuals/leave in May On the contrary, in the tea field where organic fertilizer “Song Gianh” and inorganic fertilizers were applied (treatment no.2 and treatment no.3), density was lower than in the treatment where only inorganic fertilizers were applied (density reached a peak at 7.3-9.1 individuals/leave in May) In treatment no.2 and treatment no.3, the utilization of organic fertilizer helps tea plant develops well leads to the reduction of red spider mite’s density Density of red spider mite, however, was not significant different among treatments 3.4.3 Natural enemies’ protection 3.4.3.1 Component of spider mite’s natural enemies Table 3.18 Component of spider mite’s natural enemies on tea (La Bang, Dai Tu, Thai Nguyen, 2015) Frequency of Scientific names Family Class encounter Oligota sp Staphylinidae Coleoptera + Stethorus sp Chrysopa sp Scolothrips sexmacultus Pergrande Amblyseius sp Coccinellidae Chrysopydae Thripidae Phytoseiidae Coleoptera Neuroptera Thysanoptera Acarina ++ + + + Notice: - : very rare, Frequency of encounter 0,3 13,41a 50,20a 63,64a 71,79a 71,91a 59,51a 12 L Motoring 0,2 - 0,3 12,93a 62,69ab 77,42ab 83,86b 85,14b 68,27a knapsack 25L High pressure < 0,2 12,50a 67,29b 83,87b 85,94b 87,73b 70,16a knapsack 12,21a Control LSD0.05 CV (%) 2,50 10,4 13,35 11,1 17,02 11,5 10,53 6,5 7,81 4,8 14,92 11,3 Notice: DAT: Day after treatment Mean values followed by the different letters within a column are significant difference at P