Management of Pulse Beetle, Callosobruchus chinensis L. in Stored Chickpea using Entomopathogenic Fungi and Bacteria

Abstract

Chickpea ranks 2nd in area under cultivation & 3rd in production among pulses in the world and faces severe insect pest infestations in storages. Callosobruchus chinensis is an economic insect pest and renders grains unfit for human consumption. For its management, grain protectants, fumigants and ethno-botanicals have been used since long. Being unsafe, control trends have to be replaced with safer ones particularly biopesticides. In current studies, entomopathogenic fungi (EPF), Metarhizium anisopliae, Beauveria bassiana, entomopathogenic bacteria (EPB), Photorhabdus temperata and Xenorhabdus nematophila were used as effective bio-control agents against this pest and proven good alternatives to chemicals. Destruxins are produced by EPF that cause paralysis and death whereas EPB cause septicemia. The core objective of the research encompassed to determine the aptness of aforementioned EPF and EPB against C. chinensis. In addition, the synergistic aptness and effectiveness for long storages were also studied. C. chinensis culture was maintained as ‘Pulse Beetle Rearing Cell’. Chickpea cultivar Noor-2009 was arranged from NARC to conduct bioassays. EPF and EPB were imported from the Korean Agricultural Culture Collection (KACC), Korea. Five concentrations of every fungus and bacterium were prepared, each replicated thrice for bioassays to determine their effectiveness against C. chinensis and parameters of study included eggs number, holes number, number of new progeny appeared, number of days to hundred percent death of new progeny, percent weight loss, percent inhibition rate and percent damage. In addition, mortality bioassays of C. chinensis were also conducted for both EPF and EPB. Synergistic effects of EPF and EPB were also determined against C. chinensis. For longer grain storages, bags and grains were also treated. The data were analyzed using SPSS 22, DMRT and Excel programs. The LC50 values viz., 3.4×107, 1.5×105 and 0.4×104 of B. bassiana and 1.2 ×106, 1.1×106 and 0.7×105 of M. anisopliae were recommended after 24, 48 and 72 hours, respectively. Similarly, LC50 values viz., 0.2×106, 0.7×106 and 0.1×106 of P. temperata and 0.6×105, 0.1×106and0.1×105 of X. nematophila were recommended after 24, 48 and 72 hours respectively. Synergistic concentrations (1 ×108) of best entomopathogenic fungi and bacteria gave the best results against C. chinensis as compared to application of individual treatments. The maximum percent conidial germination of B. bassiana and mortality were observed when DE (Diatomaceous earth) was used with BBM (Bitterbarkomycin, Chinese plant extract) after seven, fourteen and twenty one days. In the end, best treatments of these entomopathogenic fungi and bacteria were used in bags stored for six months concluding good results in minimizing the damage of this insect pest. Number of alive insects in grains after storage of six months in the control ranged from zero to seventy whereas in all other treatments it remained between ten and twenty and it went below ten in best bacteria applied on both grains and bags. Number of damaged grains ranged from zero to 350 in the control whereas it ranged below 50 in all other treatments. Inert material was more than 4% in control whereas it decreased to 2% in all other treatments. Percent germination in grains after storage of six months was almost more than 80% in all treatments whereas it went below 20% in the control. Acceptance for consumption and detection of off flavors in grains after storage of six months was higher and lower in all treatments respectively as compared to permethrin and control where it went vice versa. The present research has significant contribution towards development of microbial formulations of B. bassiana, M. anisopliae, P. temperata and X. nematophila to manage C. chinensis in chickpea grains for shorter and longer storages.