Effect of Some Plant Oils and Biological Factors on the Control of Southern Cowpea Beetle, Callosobruchus maculatusPages 230-236

Abstract

This study was conducted to determine the effect of treating cowpea seeds with four vegetable oils: cinnamon oil, Cinnamomum verum, peppermint oil, Mentha piperita, harmal oil, Peganum harmala and camphor oil, Cinnamomum camphora. These oils were used at concentrations of 2, 4 and 6%, and the exudates of two fungi Trichoderma longibrachiatum, Trichoderma harzianum, and the bacteria Pseudomonas flourescns suspension were added in volumes of 1.5, 1.0 and 0.5 ml to control the southern cowpea beetle Callosobruchus maculatus. The mortality rate of the southern cowpea beetle adults reached 100% for laboratory-treated cowpea seeds with harmal and camphor at a concentration of 6%, 5 days after treatment. Results also showed that the mortality rate increased with increasing concentration and time of exposure to the oils. The mortality rate of the insect adults reached 59.78, 37.57 and 67.39% when treated with exudate of T. longibrachiatum and T. harzianum and the bacteria P. fluorescens, respectively. The germination rate of seeds treated with oils was 98.88,92.22,93.33 and 96.66% for each of cinnamon, caramel, mint and eucalyptus oils, whereas the germination rate of seeds treated with fungal exudates and bacterial suspension reached 82.20,70.00 and 80.00%.

Keywords:

C. maculatus, vegetable oils, P. fluorescens, southern cowpea beetle.