| Flower thrips(Frankliniella intonsa Trybom)is an omnivorous pest that exists in many parts of the world and feeds on crops,vegetables,flowers and other plants.Chemical control is one of the most common methods used to control this pest,but due to its small size,stealthiness,and rapid breeding,the thrips pest easily develops resistance to insecticides,resulting in lower insecticides utilization,higher insecticides application,and higher residue levels in agricultural products.In this paper,we studied the spatial distribution and occurrence of flower thrips in daylily fields,aiming to lay the foundation for insecticides the effective application period and seizing the critical period for control.In addition,the toxicity of 18 insecticides against flower thrips was measured,and field efficacy tests were carried out on this basis;conducted a study on the reducing and increasing effect of abamectin mixed with 10 insecticides and different spray adjuvants mixed with 2 insecticides,finally measured and analyzed the changes of detoxifying enzymes and acetylcho esterase(AChE)activities of thrips at sublethal concentrations of 2 insecticides.The main experimental results were as follows:1.Spatial distribution and occurrence pattern of flower thrips in daylily fields in Yanchi County.Flower thrips had an aggregated distribution in daylily fields,and there was mutual attraction between individuals,the most suitable field sampling method was the parallel line method.Flower thrips started to occur in late May and reached the peak on July 15,with the number of thrips up to 53.4 per plant,and declined rapidly after August 6 as the number of daylily decreased.It is recommended to control flower thrips at the tillering stage or pre-bud stage of daylily.2.Toxicity and field efficacy of 18 insecticides on flower thrips.The indoor toxicity bioassay of different insecticides was determined by the leaf-tube membrane method,and the results showed that spinetoram was the most effective against flower thrips,the LC50 was 0.05 mg/L,while ambda-cyhalothrin had the lowest toxicity,the LC50 was 236.26 mg/L.The toxicity of the 18 insecticides against thrips in descending order was:spinetoram,spinosad,chlorfenapyr,cyantraniliprole,abamectin,emamectin bencoate,matrine,sulfoxaflor,ciprofloxacin,thiamethoxam,flupyradifurone,imidacloprid,spirotetramat,metarhizium anisopliae,dinotefuran,tetraniliprole,flonicamid,ambda-cyhalothrin.Based on toxicity bioassay,11 insecticides were selected for the field efficacy test,and the results showed that the best control effect was achieved at 3 d after the treatment with different insecticides.Among them,spinetoram,chlorfenapyr,thiamethoxam and cyantraniliprole had excellent efficacy and could be used for the control of flower thrips in actual production.3.Reduction and synergistic effect of different spray adjuvants mixed with two kinds of insecticides against flower thrips.The synergistic effect of four spray adjuvants on indoor toxicity bioassay and field efficacy of the two insecticides were compared by the leaf-tube membrane method and spray method.Result of toxicity showed that the LC50 values of spinetoram was 0.05 mg/L,the synergistic effects of four spray adjuvants to spinetoram were as follows:Qiangliyuan>Chuandao>Jijian>Huainongte and the synergistic ratios ranged between 20.41%-61.22%.The LC50 values of imidacloprid was 43.33 mg/L,the synergistic effects of four spray adjuvants to imidacloprid were as follows:Qiangliyuan>Huainongte>Chuandao>Jijian and the synergistic ratios ranged between 20.36%-47.95%.Field efficacy triais showed the preparation dosage of spinetoram decreased by 30%after adding Qiangliyuan,the preparation dosage of imidacloprid decreased by 30%after adding Qiangliyuan and Huainongte.The control effects of spinetoram reduced by 20%mixed with Qiangliyuan was 90.11%after three days application,compared with single insecticide the control effect significantly increased by 14.97%,the synergistic ratio was 19.92%.4.Synergistic effect and field efficacy of insecticide combinations on flower thrips.The indoor synergistic effects of abamectin in combination with 10 insecticides to flower thrips were tested using the leaf-tube membrane method.The preliminary screening results showed the mixture of abamectin with cyantraniliprole,spinetoram and thiamethoxam 1:1 indicated a synergism on flower thrips,co-toxic factors were 20.98,27.41,21.30,respectively.Results of the optimal mixture ratio showed that the mixture of abamectin with cyantraniliprole 1:2,spinetoram 1:1 and thiamethoxam 5:1 show the most significant synergistic effect,and coefficients of co-toxicity were 629.16,192.06,250.20,respectively.Results of field efficacy test showed that the combination of abamectin and cyantraniliprole 1:2 had a significant synergistic effect on flower thrips,compared with single insecticide the control effect increased by 13.27%after one day application,reduce the dosage of cyantraniliprole active ingredient 33.33%,the control efficacy was as high as 82.07%after three days application.5.Effects of sublethal concentrations of two insecticides on detoxifying enzymes and acetylcho esterase(AChE)activity in flower thrips.The LC25 values of spinetoram and chlorfenapyr were obtained under indoor conditions;and the changes of detoxifying enzymes and acetylcho esterase(AChE)activities were studied by biochemical methods at 6 h,12 h,24 h and 48 h after flower thrips had been treated with LC25 doses of spinetoram and chlorfenapyr.The results showed that flower thrips was sensitive to both spinetoram and chlorfenapyr,with LC25 values of 0.02 mg/L and 0.12 mg/L.AChE,CarE and MFOs activity were inhibited and then induced,GSTs activity showed an activated state at 6 h,12 h,24 h,and showed an inhibitory trend at 48 h after treatment with spinetoram of LC25 concentration.After the treatment of sublethal concentration of chlorfenapyr,AChE activity were induced and then inhibited;the activity of CarE was induced at any time;GSTs activity was inhibited;MFOs activity was inhibited at 6h and 24h and induced at 12h and 48h.Overall,the detoxifying enzymes and acetylcho esterase(AChE)activity were different after the treatment of sublethal concentrations of the 2 insecticides,the time effect was different too. |
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