Efficacy and acceptability of neem (Azadirachta indica A.!Juss) seed oil and pirimiphos-methyl applied in three storage devices for the control of Callosobruchus maculatus (F.) (Coleoptera: Bruchidae)

The efficacy of four dosages (25, 50, 75 and 100 mg) of neem seed oil applied separately in 0.2 mi of analytical grade of acetone to four replicates of 20 g of cowpea seeds in reducing the reproductive potential of Callosobruchus maculatus was evaluated in th ree storage devices (two unventilated and one ventilated) over a 3-month period. These were compared with untreated cowpea seeds and seeds created with pirimiphos-methyl (Actellic 25 EC) applied at the recommended race of 175 mg a. i./kg (3.5 mg a. i./20 g seed). There was no significant difference in the efficacy of neem seed oil (NSO) and pirimiphos-methyl (PMM) in reducing oviposition, adult emergence or seed damage in treated cowpeas stored in the three devices. The dosages of NSO significantly reduced oviposition and adult emergence. No adult emerged in PMM-treated seeds. At the dosages of 75 and 100 mg/20 g seed, NSO completely suppressed adult emergence in the second and third generations of C. maculatus. Percentage of damaged seeds ranged from 0.6 % in the first month of storage to 3.4 % in the third month in NSO-treated seeds and from 8.3 % in the first month to 100 % in the third month in untreated seeds. No damage occurred in PMM-treated seeds. Treatment with NSO or PMM imparted strong objectionable flavour and aroma to cooked cowpea seeds.