Combined Application Of Beauveria Bassiana Granules And Soild-welling Predatory Mites Stratiolaelaps Scimitus For Control Of Western Flower Thrips,Frankliniella Occidentalis

Western flower thrips?WFT?,Frankliniella occidentalis?Pergande??Thysanoptera:Thripidae?,is one of the most important pests of horticultural crops worldwide.Damage is caused directly through oviposition?aesthetic damage to fruiting crops?and feeding?damage scars on foliage,flowers and fruits?.Indirectly,WFT act as an important vector of several plant viruses,which may cause over 90%yield loss in some instances.The majority of current pest management strategies focus on control of adults and larvae with a substantial portion of the soil-dwelling stages being neglected.Ninety-eight percent of the WFT that pupate enter the soil although this is dependent on the host plant species.The use of chemical insecticides remains commonplace for managing WFT.Frequent applications of chemicals may leave excessive pesticide residues on the plant,result in high levels of insecticide resistance,and are particularly expensiveTo overcome the limited effectiveness of using a single natural enemy,a variety of biological control agents may be combined to suppress pest populations and improve the efficacy of biological control.The objective of our study was to investigate the influence of individual applications of Stratiolaelaps scimitus?Berlese?and Beauveria bassiana?Balsamo?granules,as well as combined releases of mites and B.bassiana for control of soil-dwelling stages of F.occidentalis under greenhouse conditions.In this study,we investigate the feasibility of the individual and combined use of soil-dwelling predator,S.scimitus and entomopathogenic fungi,B.bassiana to control F.occidentalis which provides a way forward for biological control in protected crops.1.Laboratory and greenhouse evaluation of a granular formulation of Beauveria bassiana for the western flower thrips,Frankliniella occidentalis controlThe efficacy of Beauveria bassiana granules was investigated against WFT pre-pupae by pathogenicity assay under laboratory conditions.The highest level of WFT mortality?83.33±3.33%?was obtained from the treatment where 100 g of B.bassiana-containing granules was mixed with 1 kg of soil.Based on our micromorphological observations of fungal conidia,during the infection process after treatment of WFT with a B.bassiana suspension,fungal conidia complete the process of surface attachment,germination,and penetration of the body wall of the WFT pupa and enter the host within 60h of treatment.When the survival and growth of B.bassiana on granules under different soil moisture conditions were measured and the soil moisture content was kept at 20%,survival was the highest.From these results,we have conducted a controlled greenhouse experiment and B.bassiana granules were applied to soil on eggplant cultivation.After 8 weeks,F.occidentalis populations on eggplants grown in treated soil were lower than those on plants grown in the untreated soil.These results suggest that the application of B.bassiana-impregnated granules could be an effective biological control strategy for use against F.occidentalis under greenhouse conditions.2.Indirect effects of Beauveria bassiana on S.scimitusThe life table population parameters of S.scimitus were accessed,such as,developmental duration,survival rate,reproductive capacity,which were slightly affected when fed on B.bassiana-infected F.occidentalis pupae.Compared to the control group,the treatment group prolonged its developmental duration,shortened its life span,decreased the average egg production of females,and increased the intrinsic rate of growth?r?,finite rate of increase???,and net reproduction rate?R₀?becomes smaller or shorter,and the average generation period?T?was prolonged.It indicates that the B.bassiana has an indirect effect on the S.scimitus.3.Simultaneous application of entomopathogenic fungus B.bassiana granules and predatory mites S.scimitus for control of western flower thrips,F.occidentalis.Effects of the B.bassiana granules on the predatory mite S.scimitus individually and in combined for the management of F.occidentalis were investigated on eggplants under greenhouse conditions.For the first and second experiments in 2018,there were significant differences among the treatments,times and in the interaction of treatments and time duration for larval and adult.Combined use of S.scimitus and B.bassiana could provide an effective IPM program for the control of F.occidentalis.Thus,we have displayed the feasibility of the individual and combined use of soil-dwelling predators and entomopathogenic fungi to manage F.occidentalis through biological control in protected crops.