Effects of Ten Plant Materials in the Preservation of Stored Cowpea Against Callosobruchus maculatus F
The potentials of the pulverized parts of ten locally available plant products compared to a conventional storage insecticide (Actellic 2% dust) as protectants of stored cowpea, Vigna unguiculata (L.) Walp were evaluated under laboratory conditions. Each of the plant materials was tested at four rates (2.5g, 5.0g and 10.0g/100g seed including a control, i.e., 0.0g. Actellic dust was applied at the rate of 1.0g, 2.0g and 3.0g/100g seed. Fifty (50) seeds from each of the treatments were infested with 5 pairs of adult weevils. Assessment was based on the emergence of the F generation and seed damage (mean number of seeds with holes and the number of holes per seed). The seed damage data were used to estimate the weevil perforation index (WPI).All data were analyzed for variance at P=0.05.Although most of the plant materials afforded some measure of control of the insects in this experiment, only three of them, Piper guineense, Moringa oleifera and Ocimum gratissimum in that order, performed comparably well with Actellic dust. Actellic dust treated seeds had the least number of emerged adults (26.2-75.0) over the 7-month storage period, and a WPI of between 0.0 - 26.7%. The cumulative number of emerged adults were also significantly reduced (40.5 86.8 insects) with WPI of between 12.2 and 44.4% and 35.4 90.3 insects with WPI of 16.4 47.8% in seeds treated with Piper guineense and Moringa oleifera, respectivelly. For Ocimum gratissimum, the cumulative number of emerged insects were between 85.6 and 195.0 with only the highest rate (10.0g/100g seed) having protection ability with WPI ranging between 31.7 48.5%. The untreated control had between 104 272.7 emerged insects and an average of 100.0%WPI.
Key words: Piper guineense, Moringa oleifera, Ocimum gratissimum,actellic dust, cowpea, bruchids