Evaluation of Toxicity of Crude Extracts of Some Botanicals on Different Castes of Macrotermes Termites

Abstract

The effects of water extracts of seed powder of Milletia ferruginea and Azadirachta indica, fresh stem bark and leaf of Croton macrostachys, and fresh leaf and fruit of Datura stramonium were evaluated at three concentration levels (10, 25, and 40% w/v) against different castes of adult Macrotermes termites. The study was conducted under laboratory and field conditions at
Melkassa Agricultural Research Center and Ziway, respectively. One conventional synthetic insecticide, chlorpyrifos, was used as a standard check. Extracts of seed powder of M. ferrugina and A. indica and stem bark of C. macrostachys that showed higher toxic effects in filter paper bioassays were used to treat termite castes placed in a mixture of soil and sawdust in plastic boxes. M. ferruginea and C. macrostachys were further tested in the field to poison mounds. In filter paper bioassays, water extract of M. ferruginea caused higher toxicity to all castes in which 93-100% mortality of alate termites was recorded at all concentration levels.
The effect of the extract was equal to chlorpyrifos which caused 100% mortality to all castes. Croton stem bark extract at 40% concentration caused relatively higher (> 83%) mortality of workers, alates and minor soldiers than the control. Neem seed powder extract caused low mortality (0-10%) of alates and major soldiers at all levels of concentration; whereas, the toxicity of the extract on other castes was high. The toxic effects of datura leaf and datura fruit extracts were relatively low (0-20%) on all castes, except that datura leaf extract at 25 and 40% concentration showed relatively higher mortality (37% and 68%, respectively) on minor soldiers and workers. In mound poisoning, cheesecloth filtered water extract of croton stem bark at 40% concentration showed no effect, and there was no significant difference from with that of the control (p > 0.05). Milletia seed powder extract at 10% concentration caused low mean percentage mortality of major soldiers, minor soldiers and worker termites; the toxic effect of the extract was significantly lower than that of chlorpyrifos, but higher than that of the control.