BIOACTIVITY OF CITRUS AURANTIFOLIA, CITRUS LIMON AND PIPER NIGRUM ESSENTIAL OILS ON CALLOSOBRUCHUS MACULATUS (F.) (COLEOPTERA:BRUCHIDAE)

Abstract

ABSTRACT In the current study Callosobruchus maculatus adults were exposed to essential oils of Citrus limon, Citrus aurantifolia and Piper nigrum and the contact mortality, repellency, fumigation effects and oviposition deterrent activities of each oil were determined over a 72h period. After 72h, 50% mortality of C. maculatus adults was observed for C. limon at a concentration of < 1.56 µL/mL, for C. aurantifolia at a concentration between 12.5–25.0 µL/mL and for P. nigrum the concentration causing 50% mortality was 1.56 µL/mL. All oils tested displayed some level of repellency to C. maculatus after 12h and 24h. C. aurantifolia essential oil at concentrations above 6.25µL/mLwere classified as a Class IV repellent, while P. nigrum was classified as a Class IV repellent at 25.0 and 50.0 µL/mL at 24h post application and a Class V repellent only at 50.0 µL/mL at 12h. The results of the 50% fumigant mortality (FC50) indicated that P. nigrum essential oil was the most toxic fumigant (FC50 = 0.140µL/L air) among the three oils tested. Black pepper oil also took the shortest time (FT50 = 7.71h) to cause 50% mortality to a population of C. maculatus.The anti-oviposition effects reveals that both C. limon and C. aurantifolia gave relatively low DQ values at all concentrations. At 25.0 and 50.0 µL/mL, C. aurantifolia had higher values (0.62 and 0.64 respectively). However, apart from the lowest concentration, P. nigrum essential oil consistently gave high DQ values indicating its potential in preventing egg laying on Cajanus cajan seeds. Thus, the use of these essential oils can be considered as alternatives to the use of synthetic insecticides for management of C. maculatus