Ecofriendly management of Lepidiota mansueta Burmeister in potato

Abstract

Laboratory and field experiments were carried out at Soil Arthropod Pest Laboratory, Department of Entomology, Assam Agricultural University, Jorhat and in the farmer s field at Maharichuk, Majuli, Assam to study ecofriendly management of Lepidiota mansueta Burmeister (Coleoptera: Scarabaeidae) in potato during 2019-21. Efforts were also made to test the pathogenicity of different entomopathogens and to know their effects on haemocytes in L. mansueta as well to evaluate some newer insecticides against the grubs. newlineWhile studying the pathogenicity of different entomopathogens for their virulence against third instar L. mansueta grubs, Beauveria bassiana (formulation: KR855715) recorded highest mortality (76%) of grubs followed by 72 per cent mortality in B. brongniartii (formulation: BbUASB16) and 70.67 per cent in Bacillus thuringiensis (formulation: Bio-Bt) at 30 days after treatment (DAT). The Metarhizium anisopliae based formulation (Bio-Meta) registered the highest LT50 value (23.05 days) (FL 19.24-30.33) whereas the lowest LT50 value was 12.15 days (FL 11.15-13.11) in case of B. bassiana (KR855715). Five different haemocytes were identified based on differences in size, shape, morphology and dye-staining properties of cell and nucleus and were functionally categorized as Prohaemocytes (PRs), Plasmatocytes (PLs), Granulocytes (GRs), Spherulocytes (SPs) and Oenocytes (OEs). The Total Haemocyte Count (THC) and the population of PRs, GRs, PLs, OEs and SPs were affected in response to B. bassiana (KR855715). The application of B. bassiana (KR855715) in addition to abnormal haemocyte counts also caused great abnormalities to the haemocytes by distortion of the plasma membrane, cytoplasmic extension, rupturing of cell wall, oozing out of cell contents, degranulation of the cells, vacuolation, enlargement of cells and abnormal staining of the haemocytes...