Insecticidal activities of three weed varieties against the Bamboo Powder Post Beetle Dinoderus minutus Fabricius (Coleoptera: Bostrichidae)
The insecticidal activities of crude ethanol extracts of leaves of three weed species, Siam weed, Chromolaena odorata Linn., Milk weed, Euphorbia heterophylla Linn. and Tree Marigold Tithonia diversifolia (Hemsl.) A, Gray on the insect, Dinoderus minutus Fabricius, were investigated on bamboo as substrate. Bamboo blocks were treated with different concentrations: control (positive), control (negative), 20% and 25% of each plant extracts. Twenty-five active adult D. minutus insects were introduced into each setup of five bamboo blocks in 0.32 L jars for 60 days and were replicated four times in a Completely Randomized design in the laboratory. Data were collected on mortality of D. minutus at 5, 10 and 15 days after introduction. The number of holes bored by D. minutus on bamboo blocks after 60 days of storage were counted and the percentage weight loss of bamboo block was calculated using standard procedure. The result showed that the highest and the lowest percentage mortality of D. minutus were recorded in 25% T. diversifolia (94.67±2.67) and control (–) respectively at 15 days after treatment. The number of holes bored by D. minutus on bamboo blocks in the control treatments was higher than the number of holes bored on bamboo blocks treated with different concentrations of the three extracts. The mean percentage weight loss of bamboo blocks obtained at 20% and 25% concentrations of each extract was lower than that of the two control treatments. The maximum wood protection (1.33±0.22) against D. minutes was recorded at 25% concentration of T. diversifolia. The number of D. minutus holes on bamboo block correlated positively (R2 = 0.538; p<0.0001) with the percentage weight loss of bamboo. The three weeds at 20% and 25% concentrations could be used in the management of D. minutus on bamboo.
Keywords: Plant extract; Dinoderus minutus; bamboo pest; mortality; weight loss.