Pathogenic Mechanism And Application Of Lecanicillium Lecanii JMC-01 Against The Nymphs Of Bemisia Tabaci

Bemisia tabacii is an important pest that harms many crops including vegetables and cotton.In this paper,B.tabaci and Lecanicillium lecanii JMC-01 were used as research objects,and the process of infection of L.lecanii JMC-01 against the nymph of B.tabaci was observed by stereo microscope and scanning electron microscope,and then measured some physiological and biochemical indication of L.lecanii JMC-01 against the nymph of B.tabaci.The result explored pathogenic mechanism of L.lecanii JMC-01.The optimal culture conditions for liquid medium were selected by optimizing the liquid culture medium of L.lecanii JMC-01.Compatibility of 8 common pesticides with L.lecanii JMC-01 and their toxicities against the nymph of B.tabaci,screened the best insecticide with the compatibility of L.lecanii JMC-01.It is compounded with L.lecanii JMC-01 to control greenhouse vegetable pests.The major tests in this paper are listed as follows:1?Infested procession and ectoenzyme activities of L.lecanii JMC-01 on the nymphs of B.tabaciThe process and ectoenzyme activities of L.lecanii JMC-0 1 infestation the nymphs of B.tabaci is studied.While L.lecanii JMC-01 was inoculated at 12 h,conidia became attached to the cuticle;and the conidia began to germinate,and a few hyphae formed the surface at 24 h.Production of a network of hyphae on the insect epidermis after 48 h.By 72 h,hyphae had covered the host surface and had colonized the body cavity.At 94 h of inoculation,the internal structure of the nymph was destroyed.It was cultured for 6 days in a PDA medium,and it was found that the protease activity had been increased in the first three days,and then slightly decreased.Chitinase began to increase on the 3rd day and reached a maximum of 0.38 U/104 Cell on the 4'h day;lipase began to increase on the 4th day.It indicated that protease was activated firstly when L.lecanii JMC-01 infestation the nymphs of B.tabaci,and then exposing the chitin on the body wall,chitinase was activated,and finally entering the body wall,and the lipase took part in this work.2?Response of some physiological and biochemical indication of the nymphs of B.tabaci to the infection of L.lecanii JMC-01Study the changes of enzymes of B.tabaci infested by L.lecanii JMC-01.The 3rd-instar nymph of B.tabaci are treated by dipping method,and the detoxifying and protective enzymes,and weight increment,fat content and water content are determined by spectrophotometry.The results showed that the activities of detoxifying and protective enzymes increased firstly,then decreased.The highest activity of carboxylesterase(CarE),acetylcholinesterase(AchE),peroxidase(POD)and catalase(CAT)was respectively observed 10.5 U/mg prot,0.32 U/mg prot,20 U/mg prot,and 6.3 U/mg prot on the 3rd day,reaching 2.2-fold,4.3-fold,2.5-fold and 1.4-fold the control level,respectively.The highest activity of glutathione-S transferase(GSTs)and superoxide dismutase(SOD)was respectively observed 64 U/mg prot and 43.5 U/mg prot on the 2nd day,reaching 4.5-fold and 1.1-fold the control level,respectively.Water content and fat content had been always decreasing,which was significantly different from the control level.At 72 h,the infection level was 66%and 20.5%.It was found the weight increment was increased continuously in the first 24 h and then decreased.At 72 h,the infection level was about 0.78-fold of the control level.3?Optimization of liquid culture conditions of L.lecanii JMC-01 based on response surface methodologyLiquid culture conditions are opitimized by taking chitinase activity as response indicator for L.lecanii JMC-01 using response surface method(RSM).Firstly,a liquid medium optimized for L.lecanii JMC-01 is screened from five media.Then,three factors that effecting chitinase activity are screened out optimal time and pH,and inoculum size by single factor test.The optimum conditions of culture and their interaction of the three factors were determined through Box-Behnken design and regression analysis using design expert software.The results showed that the glucose yeast extract medium was the best liquid medium for L.lecanii JMC-01.The chitinase activity was the highest when the inoculum size was 1%,the opitimal pH was 6.5,and the inoculation time was 5 days.4?Compatibility of 8 pesticides with L.lecanii JMC-01 and their toxicities against the nymph of B.tabaciTo test the mycelial growth,spore germination and sporulation of L.lecanii JMC-01,and LC50,co-toxicity co-efficient and mortality of nymph of B.tabaci by the coating and dipping method.The results showed that the mycelial growth inhibition rate,spore germination inhibition rate and sporulation inhibition rate of L.lecanii JMC-01 was decreasing with the increase of the dilution times of the insecticides.The inhibition rates of spinetoram,veratrine and azadirachtin at concentrations of 2 mg/L,1.25 mg/L,and 0.06 mg/L to the spore germination were 20.02%,16.41%,and 15.38%,respectively;the sporulation inhibition rate was 17.77%,15.90%,and 14.96%,respectively,and the mycelial growth inhibition rates were 9.96%,8.87%,and 9.74%,respectively.The Co-toxicity co-efficient of 8 common insecticides and L.lecanii JMC-01 were all greater than 120,indicating that 8 insecticides have synergistic effect with L.leanii JMC-01.The synergistic effect of azadirachtin and veratrine with L.lecanii were the best.The maximum CTCs were 302 and 315,respectively.The corrected cumulative mortality of veratrine?azadirachtin and spinetoram reached 95%,97%,and 94%,respectively.