Effect of the entomopathogenic fungus, Lecanicillium lecanii, on the biology and predation rate of the anthocorid predatory bug, Blaptostethus pallescens, feeding on the flower thrips, Frankliniella schultzei Trybom (Thysanoptera: Thripidae)

Abstract

Abstract Background The flower thrips, Frankliniella schultzei Trybom (Thysanoptera: Thripidae) is a notorious pest that attacks the plants of economic importance. The anthocorid bug Blaptostethus pallescens Poppius (Heteroptera: Anthocoridae) is a predator of thrips in field crops and greenhouses. Another biocontrol agent, the entomopathogenic fungi (EPF) Lecanicillium lecanii (Zimm.) (Hypocreales: Cordycipitaceae), has been effectively used in management of various insect pests. With the aim to develop an effective combination of biocontrol agents like microbial and insect predator for the management of the serious pest F. schultzei, the present studies were carried out on development, predation rate and prey preferences of the predator B. pallescens provided with the EPF (ICAR-NBAIR Vl-8)-treated thrips under laboratory conditions. Results The predator, B. pallescens, could complete its life cycle on treated thrips. The nymphal duration of bugs fed on treated thrips was higher (25.25 ± 0.13 days). The Vl-8 strain did not show any negative effect on hatchability of eggs (83% hatchability in treatment; 86% in control). However, the longevity was comparatively less in bugs fed on treated thrips than that of control group The fecundity of the treated group was found to be reduced to one half of the control group. The rate of daily feeding potential of bugs on treated thrips was less (7.29 ± 0.15) than the untreated thrips (12.54 ± 0.1) throughout their lifetime. Moreover, when the F1 generation from both parents line fed on treated and untreated thrips allowed to feed on Corcyra cephalonica eggs, it did not show any difference in terms of nymphal duration which revealed that the fungi did not affect the F1 generation. When choice was given between treated and untreated thrips to different instars of this predatory bug, all the instars including adult significantly preferred the untreated thrips. However, nymphs and adult bugs were found to encounter both the treated and untreated thrips. No mortality was observed in any stage of the predator. Conclusion This study shows that the effect of L. lecanii (ICAR-NBAIR Vl-8) on B. pallescens is not harmful. However, further field studies are required to evaluate their combined effect against this pest.