STUDIES ON THE MORTALITY AND REPELLENCY EFFECT OF Cymbopogoncitratus (LEMON GRASS; POACEAE)IN THE CONTROL OF Sitophilus zeamais (MAIZE WEEVILS; MOTSCHULSKY; COLEOPTERA; CURCULIONIDEA).

ABSTRACT

This study investigated the repellent and mortality activity of C. citratusleaf powder against the maize weevil, Sitophilus zeamais(Mots.) (Coleoptera:Curculioidea). Weevil infested maize were exposed to C. citratusleaf powder for 6, 12, 18, 24, 30, 36 and 42 hours after which percentage repellence and 24, 48, 72, 96, 120 and 144 hours mortality were calculated. This studyshowed that the leaf powder of C. citratussignificantly repelled S. zeamais, although therepellent and mortality activity was not really dependent of concentration (grams) and exposure time.Followinga 144-hour exposure period for mortality using 24 hours interval as inspection period, 1.5 g of C. citratus leaf powder exhibited the least (42%)mortality activity against S. zeamais. The highest mortality rate was seen in 2.5 g and 3.5 g which have the same mortality rate (47%) after 144 hours of exposure. The combine effect of repellencewas compiled using 6 hours interval as inspection period. The dose with highest effect is 3.5 g (36%) while 1.5 g and 2.5 g have the same effect (34%) after 42 hours exposure time. Mortality andrepellency ofC. citratuswas however, observed to be dependent on exposure time and but not concentration.This study demonstrates the potential of C. citratusleaf powder in the control of S. zeamais and suggests that, the use of the leaf powder of the plant may contribute to thecontrol and management of this maize weevils and lead to massive production of the plant in Nigeria.