Integrated Control Of Rhinoncus Sibiricus And Frankliniella Occidentalis In Buckwheat

Buckwheat is one of the main cereal crops in China.Buckwheat is very suitable to be cultivated in Inner Mongolia area because of its geographical characteristics and climatic conditions.Therefore,buckwheat is widely distributed in Inner Mongolia and the planting area of common buckwheat accounted for 80%?90%of the cultivated area in China.Rhinoncus sibiricus is an important pest of buckwheat which was discovered in 2013,and Frankliniella occidentalis is also very harmful to buckwheat.These two pests have to be controlled effectively because of their huge damage to buckwheat production.This thesis focused on integrative control to the two pests on buckwheat.The results are as follows:1.Effects of different sowing dates on the stem-damaged rate of R.sibiricus and yield of buckwheat.The stem-damaged rate of R.sibiricus on common buckwheat and tartary buckwheat showed a downward trend from May 27 to July 11.The yield of common buckwheat increased with the delay of sowing date,however,the yield of tartary buckwheat did not change significantly with the delayed sowing date.Therefore,it is recommended that the best sowing time of buckwheat is before June 20 in Baotou and after June 20 in Chifeng areas.2.Influence on stem-damaged rate of R.sibiricus in different varieties of buckwheat.The stem-damaged rate of R.sibiricus to tartary buckwheat is higher than that of common buckwheat.The stem-damaged rate of R.sibiricus to Hushi-Qingshuihe buckwheat was the highest,and that of ShaanxiYulinsaf flower buckwheat was the lowest among common buckwheat.The stem-damaged rate of R.sibiricus to Diku 2 was the highest,and that of Yunku 3 was the lowest among tartary buckwheat.3.Effects of different regions and previous crops on stem-damaged rates of R.sibiricus.Field research showed that the stem-damaged rate of R.sibiricus in buckwheat is higher when the previous crop is wheat than that of potato.The stem-damaged rate of R.sibiricus is higher in Chifeng than that in Ulanqab and Baotou.The results about the stem-damaged rate of R.sibiricus showed a gradually decreasing trend from east to west in Inner Mongolia district,and also showed a gradually spreading trend in Inner Mongolia.4.Toxicity and mechanism of different insecticides to R.sibiricus and F.occidentalis.The toxicity of pyrethroids to R.sibiricus was higher than that of organophosphorus,carbamate insecticides and nicotine insecticides.The toxicity of beta-cypermethrin was the highest one among the tested pyrethroids,its LC50 was 17.367mg/L.Carbosulfan contained highest toxicity to R.sibiricus among carbamate insecticides,its LC50 was 29.556 mg/L.LC50 of thiamethoxam and imidacloprid to R.sibiricus were 42.140mg/Land 46.191mg/L respectively.Methomyl contained highest toxicity to F.occidentalis,its LC50 was 6.659 mg/L.Bifenthrin contained highest toxicity in pyrethroids while lambda-cyhalothrin contained lowest toxicity,its LC50 was 17.144 mg/L 37.284 mg/L respectively.According to our research,Acetylcholinesterase and carboxylesterase could be inhibited by organophosphorus and carbamate insecticides,and ATPase activity could be inhibited by pyrethroids.5.Effects and mechanism of seed coating with thiamethoxam on F occidentalis controlling and physiological and biochemical characteristics on growth of buckwheat.The results showed that control effect of 70%thiamethoxam ZF to F.occidentalis was 35,59?62.50%.The seed coating reduced the germination percentage of buckwheat seed,but there was no significant difference compared to the control.The germination energy and germination index of buckwheat seeds increased significantly with the coating dosage of 5.0 g/kg.The growth of buckwheat was affected when buckwheat seed was treated with 70%thiamethoxam ZF.Two weeks after emergence,the plant height,root length,fresh weight and dry weight of buckwheat increased obviously,and the effect was dose-dependent.The CAT activity of buckwheat leaf was significantly increased when the seed was treated with 70%thiamethazine ZF(5.0 g/kg).The SOD activity of buckwheat leaf was significantly inhibited at the dose of 7.5 g/kg during the first two weeks after emergence.The SOD activity of buckwheat leaf was significantly increased during the first 3 weeks after emergence at the treated dose of 5.0 g/kg,but there was no significant effect on SOD activity at the dose of 2.5 g/kg.The content of MDA in buckwheat was significantly increased when the seed was coated with 70%thiamethoxam ZF.The MDA content increased while the thiamethoxam dose increased.There was no significant difference in MDA content between treatments and control in the 5th week.