Management of Callosobruchus maculatus Fab. (Coleoptera: Chrysomelidae) in Stored Cowpea Using Varietal Resistance and Diatomaceous Earth
NJE Vol. 35: 7-18, 2019
Kabir, B.G. J.* and Gaya, S. S.
The cowpea seed beetle, Callosobruchus maculatus (Fab.) is among the most important insect pest of stored cowpea, Vigna unguiculata (L.) Walp. Synthetic insecticides are heavily relied upon for the control of this pest. However, the problem of insecticide resistance and environmental hazards associated with synthetic grain protectants underscore the need to explore reduced risk control measures. Laboratory studies were conducted to evaluate the efficacy of varietal resistance and diatomaceous earth (DE) against C. maculatus in stored cowpea, under ambient laboratory conditions (27-32°C and 48-55% R.H.). Six improved cowpea varieties (IT89KD-288, UAM09-1046-6 -1, UAM09-1051-1, UAM573-1-1, UAM573-2-1 and ITI79K-499-35) and one local cultivar (Borno Brown) were evaluated for their resistance to infestation by C. maculatus, then treated with DE and bio-assayed. The results showed significant variations among the tested varieties in their susceptibility to C. maculatus infestation. According to susceptibility indices the varieties were ranked: UAM573-2-1, IT89KD288 and UAM09-1046-6-1 (moderately resistant), Borno Brown, IT97K499-35 andUAM1051-1 (susceptible) and UAM573-1-1 (highly susceptible). Efficacy of DE increased with increase in dosage. Diatomaceous earth applied at the rates of 750 -1000 mg/kg of seed consistently resulted in very few eggs laid in the moderately resistant varieties compared to the susceptible ones and which also prevented seed damage and weight loss. These results indicate that DE could be combined with varietal resistance for use against C. maculatus in stored cowpea.
Keywords: Stored cowpea, C. maculatus, Varietal resistance, Diatomaceous earth.