Study On The Field Survival Potential Of Beauveria Bassiana And The Compatibility With Common Insecticides

Vegetables play an important role in dietetic culture, chemicals are used extensivelyto control diseases and pests on vegetables, which will cause exceeded pesticides residueand hinder the rapid development of vegetable industry. So studying on microbialpesticide can completely replace or mix with sublethal chemicals has great significanceto improve control effect, reduce pest resistance, improve the quality of vegetables andpromote the sustainable development of agriculture.Beauveria bassiana BD-B015has the highest germination rate, sporulation,Protea-Bse activity level, UV radiation viability, and extensive insecticidal spectrum andpersistent control effect. So the technique of obtaining quickly high spores indoor, thefield survival potential of conidia, the high efficient insecticide against Brevicorynebrassicae and Plutella xylostella and the compatibility of insecticides with this strainwere studied to provide a scientific basis for green prevention and control. The resultswere as follows.1. Beauveria bassiana BD-B015conidia were isolated from liquid-solid two-phasefermentation in order to research and use this strain in laboratory, and the conditions ofpreparing quickly and efficiently were as follows: Beauveria bassiana BD-B015wascultured in liquid fermentation broth for24hours, inoculated20%to solid fermentedmaterial (wheat bran/wheat husk is5:1), sealed the culture vessel by plastic film, thendried and separated the spores after6days, therefore the high spores had low moisturecontent of5.63%, high germination rate of97.22%and high sporulation of2.05×1011/g.2. The germination rate of Beauveria bassiana BD-B015indoor and in field atdifferent months showed that the conidial germination rate indoor had been maintainedmore than90%; the germination rate of field direct sunlight dropped respectively to14.25%,4.88%,7.84%, and19.77%in May, June, July, and September; the germinationrate of shade field had been maintained more than50%; and the germination rateovernight was high than illuminated spores and lower than initial level. So Beauveriabassiana BD-B015had different field survival abilities in different months, and thespores could self-healing in dark after sunlight damage. 3. The toxicities and field control effects of nine insecticides were studied to screenhigh efficient insecticides against Brevicoryne brassicae and Plutella xylostella. Theresults showed that chlorantraniliprole thiamethoxam40%WG had the highest toxicityto B. brassicae with LC50of1.9355mg/L, the selective toxicity ratio (STR, Harmoniaaxyridis LC50/B. brassicae LC50and Propylaea japonica LC50/B. brassicae LC50) was16.34and18.28, and it had fast and residual effect to B. brassicae with the efficacy morethan90%during3to14days; chlorantraniliprole5%SC had the highest toxicity toPlutella xylostella with LC50of0.9774mg/L, and its field control had fast and residualeffect, so it was the optimal insecticide against Plutella xylostella.4. The influence of nine common insecticides with vegetables on conidialgermination, mycelial growth and sporulation of Beauveria bassiana BD-B015had beentested. The results show that all insecticides had inhibition to this strain in differentdegree, chlorantraniliprole5%SC and chlorantraniliprole thiamethoxam40%WG hadhigher compatibility with Beauveria bassiana BD-B015, imidacloprid10%WP andacetamiprid20%WP had high compatibility at1/10recommended concentration, sothese four insecticides could mix with this strain in corresponding concentration, butabamectin2%EC had poor compatibility with this strain agents, so they must be usedalone or alternately.