Synergistic Effects Of Lecanicillium Lecanii And Insecticides Against Aphis Glycines

Aphis glycines(Matsumura)is one of the main pests of cultivated soybean.It is harmful to soybean by pricking and spreading virus.It often causes quality decline and yield loss of soybean.When serious occurs,it can cause yield reduction by more than 50%.Chemical control is the main method.As a new biological control fungus,Lecanicillium lecanii scale has stable efficacy but slow effect.In order to know the application effects of Lecanicillium lecanii mixed with new biological pesticides against the Aphis glycines,we cultured the conidia of L.lecanii BNCC336750 with PDA media,and measured the toxicity of Aphis glycines by using leaf dipping method in laboratory(108 spores/mL).The spore suspension concentration with higher toxicity based on the bioassay mixed with sub-lethal concentrations of the three pesticides.(1)The results indicated that the mortality of A.glycines increased with the increase of conidia liquid concentration of L.lecanii strain and the highest toxicity was gotten by using 108 spores/m L.(2)The results in laboratory showed that the control effect of mixture of L.lecanii and insecticides on A.glycines was better than that using single spore solution or sub-lethal pesticides solutions.Among them,nimbin mixed L.lecanii had the best control effect,the cumulate corrected mortality was 94.16%in 7 d.The Cumulate corrected mortality of matrine and imidachloprid mixed with L.Lecanii on A glycines were 86.13%and 80.29%in 7 d,respectively.(3)The control effects of three insecticides mixed with the spore suspension of L.lecanii on A.glycines at different ages were similar among different insecticides.The control effects of three insecticides mixed with the spore suspension of L.lecanii on A.glycines at 3 and 4 instars were higher,and the final corrected mortality was significantly different from that of A.glycines at 1 and 2 instars.(P<0.05);that is,the control effect of three insecticides mixed with the spore suspension of L.lecanii on the 3rd instar and adults was better than that of the younger nymphs.(4)Field experiments showed that the mixtures of L.lecanii and nimbin were had the best control effect with 89.47%after 7 days.Low concentration insecticides mixed with L.lecanii had good control effects on A.glycines.Under similar conditions,the amount of pesticides to control A.glycines could be reduced substantially by using the mixtures of L.lecanii and pesticides in soybean fields.By mixing suspensions of 108spores/mL L.Lecanii with imidacloprid,nimbin and matrine at low concertration,we can greatly reduce the use of chemical pesticides,reduce pesticide damage and residues,and solve the problem of long effective time of using L.Lecanii alone.