CONTACT TOXICITY OF THE ETHANOLIC EXTRACT OF THREE WEED SPECIES ON BAMBOO BORER Dinoderus minutus FABRICIUS (COLEOPTERA: BOSTRICHIDAE).

The contact toxicity of the crude ethanolic extract of leaves of three weeds species, Chromolaena odorata Linn. (Siam weed), Euphorbia heterophylla Linn. (Milk weed) and Tithonia diversifolia (Hemsl.) A,Gray, (Tree marigold) on Dinoderus minutus were investigated. Three concentrations of 2.5%, 5% and 7.5% and an increased concentration of 15%, 20% and 25% were prepared upon dilution with ethanol. Each experimental setup consists of petri dishes (9cm diameter by 2cm height), lined with a 9cm diameter filter paper (Whatman No.1) and four replicates maintained for each concentration in a completely randomized design (CRD). 1.0ml of the different concentrations of the ethanolic crude extract were spread on the filter paper in the petri dish and the control groups included a positive (+) control setup treated with the ethanol solvent alone and a negative (-) control setup without any treatment. The filter paper was allowed to air dry for 20minutes to evaporate the solvent and thereafter, ten active unsexed adults D. minutus were introduced into the petri dishes. The petri dishes were perforated and covered with muslin cloth to aid aeration and eliminate death by suffocation. The percentage mortality was recorded at 24hours interval for 96 hours and the percentage mortality calculated. The result showed low mortality using the treatment concentrations of 2.5%, 5.0% and 7.5%. The highest mean mortality of 45.00±2.89 was recorded at 25% treatment concentration in Euphorbia heterophylla, followed by Tithonia diversifolia and Chromolaena odorata with mean mortality of 37.50±8.54 and 20.00±4.08 respectively at same 25% treatment concentration while the lowest was observed in the negative (-) and positive (+) control at 2.50±2.50 and 7.50±2.50 respectively at 96hours exposure time. The application 25% E. heterophylla, and T. diversifolia can be used as an alternative to synthetic insecticide in the management of D. minutus and can be incorporated into the IPM component of the insect. [ABSTRACT FROM AUTHOR]