Sublethal Effects Of Two Botanical Pesticides On Cotton Aphids And Applied Technology Research

Due to the outstanding natural conditions such as water,soil,light and heat,Xinjiang has become the largest high-quality cotton production base in China.However,in recent years,investigations have shown that with the long-term large-scale continuous cropping and the changes of management mode in the cotton planting areas in southern Xinjiang,the frequent occurrence of Aphis gossypii has become more and more serious,which has become an important constraint to the sustainable development for Xinjiang cotton industry.In recent years,the control measures relying on chemical pesticides have caused the reinfestation of A.gossypii in cotton fields to become more and more serious,and the resistance has continued to increase,making control more difficult.Therefore,it is urgent to seek green,efficient and safe alternative pesticides.In this study,the sensitivity of two plant-derived insecticides to A.gossypii and ladybirds and their effects on the development and reproduction of A.gossypii were measured and compared.The field test of synergy reduction in the hope of providing a basis for the search for alternative agents to delay the development of pest’s resistance,scientifically using botanical pesticides to control cotton field aphids.Combining the content of this study,results are as follows:1.The influence of different management models on the dynamic population of cotton field aphidsThe biological control field（9 regiments）was not sprayed with any pesticides,and the chemical field（12 regiments）was sprayed pesticdes 9 times（including 7 times of imidacloprid and acetamiprid sprayde）.The population of A.gossypii of the fiele reached its peak in late June and early July,and the population density was 40031 heads/100 plants and 53742 heads/100 plants,respectively.Among them,the occurrence of Acyrthosiphon gossypii and Aphis atrata in chemical control fields（12 regiments）was small;In the biological control fields（9 regiments）the peak of Ac.gossypii was slightly earlier than that of A.gossypii,and the insect population reached its peak in mid-late June,with 39762 heads/100 plants.A.gossypii was dominant populations in the middle and late stages under different management models in the two places,and the cotton plants were more harmful.The early application of pesticide had obvious effects on Ac.gossypii and A.atrata.2.Examination of virulence of two botanical pesticides on cotton field aphids and ladybirdsThe sensitivity of the three aphids to the two botanical pesticides（0.3%matrine,0.5%veratrine）was Ac.gossypii>A.atrata>A.gossypii.The relative virulence index of 0.5%veratrine to A.gossypii and A.atrata was 2.23 times and 1.15 times that of A.gossypii.The LC₅₀ of 0.3%matrine on the Coccinella undecimpunctata,Propylaea japonica,and Harmonia axyridis were 2.79,1.40,and 1.56 ml/L,respectively.The LC₅₀ of 0.5%veratrine to C.undecimpunctata was 31.60 ml/L,and its relative virulence index was the highest at 3.09.The sensitivity of the three natural enemy ladybugs to the two botanical pesticides was P.japonica>H.axyridis>C.undecimpunctata,and the relative safety factors were all C.undecimpunctata>H.axyridis>P.japonica.3.Sublethal effects of two botanical pesticides on cotton field aphidsAfter 0.3%matrine LC₃₀ treatment compared with CK,the average fecundity of F₀ Ac.gossypii decreased by 15.8 heads,and the average life and average population of adult Ac.gossypii decreased by5.55d and 13.22 heads;the life cycle of A.gossypii generation was shortened 3.21 d,the net reproduction rate of Ac.gossypii decreased by 13.22.Compared with CK.After 0.5%veratrine dose LC₃₀ treatment,the average fecundity of the A.gossypii,A.atratas,and Ac.gossypii adults populations of F₁ generation decreased by 16.49,17.31,and 19.85 heads,and the generation period was shortened by 4.99 d,5.20 d,6.35 d.with the increase of sublethal dose of the two botanical pesticides increased,the average generation period of the three aphid populations was shortened,the population doubling time decreased,and the intrinsic growth rate increased.4.Field control effects of two botanical pesticides mixed at reduced dose on A.gossypiiThe does of two botanical pesticides（0.3%matrine,0.5%veratrine）were reduced by 10%-30%in combination use with 8 different auxiliaries.The order of effectiveness of the auxiliaries were as follows:JI JIAN>SI RUN>FENG ZHAN>MAI FEI>AI GE FU>Agricultural Silicone>Orange Peel Oil>Green Peel Orange Oil and JI JIAN>FENG ZHAN>SI RUN>MAI FEI>AI GE FU>Agricultural Silicone>Orange Peel Oil>Green Peel Orange Oil.The combination of the two botanical pesticides（10%and 20%reductions）and the JI JIAN,SI RUN,and FENG ZHAN aids on A.gossypii,the control effects were not significantly different from the normal dosage,showing a significant synergistic effect.It can be seen that when appropriate additives were added within a reasonable range of the reduction of the agent,the insecticidal effects could be improved.