Effects of biopesticides on developmental stages and longevity of Callosobruchus maculatus in some leguminous grains

Abstract

The study deals with the effects of biopesticides or botanical treatments and a synthetic chemical
(pirimiphos methyl) on the developmental stages and longevity of Callosobruchus maculatus in Vegan
unguiculata, V. subterranea and Cajanus cajan and to suppress or delay the development of this pest.
The biopesticide concentrations were 0, 0.2, 0.4, 0.6, 0.8 and1.0 g per 20 g of each grain and that of
synthetic chemical was 0.1 g per 20 g of each grain. The result revealed that the highest delay in
development of C. maculatus was recorded with pirimiphos methyl, also development, was observed
only at egg stage where it took 40 days for the C. maculatus egg to emerge on V. unguiculata , 38 days
for its emergence on C. cajan and 37 days for the egg to emerge on V. subterranea while all other
stages of development viz larva, pupa and adult could not emerge with pirimiphos methyl. The
botanicals used were all effective when compared with the control. In C. cajan, A. sativum caused
highest delay in C. maculatus development viz egg 15.00 days, larva 22.00 days, pupa 33.00 days and
adult 38.00 days. Also, in V. subterranea, A. sativum delayed development of C. maculatus at the
highest dose rate viz egg 13.00 days, larva 19.00 days, pupa 33.00 days and adult 37.00 days. Capsicum
nigrum treatment was the 2nd best in delaying or reducing development of C. maculatus at the highest
dosage rate in all the grains. All other treatments behaved alike. The efficacy and performance of these
treatments also showed that A. sativum and C. nigrum delayed development of C. maculatus more than
all other treatments. From the findings of this study it is evident that A. sativum and C. nigrum are very
effective in delaying C. maculatus development and longevity and therefore could be recommended in
development and longevity studies.