The effect of aqueous extracts of neem (Azadirachta indica A. Juss), clove (Syzigium aromaticum L.) and chinaberry (Melia azedarach L.) on survival of eggs, larvae, nymphs and adults females of the cassava green mite, Mononychellus tanajoa (Bondar), was studied. Egg treatment consisted of dipping cassava leaf discs with 30 eggs into each plant extract concentration. Leaf discs dipped into destilled water were used as control. The treated and control leaf discs were dried for 30 minutes under environmental conditions. The effect of the several plant extracts on immature stages and females was studied by exposing 40 individuals to each plant extract concentration. Neem extract at concentrations 0.5, 2.5 and 5% w/v caused mortality of 16.8, 59.2 and 60% of the eggs, while the clove 5% w/v and the control treatment caused mortality of 10.8 and 4.2%, respectively. Larvae, protonymphs and deutonymphs treated with neem extracts at 2.5 and 5% had mortality ranging from 57.5 to 100% and from 85 to 100%, respectively, but they were not killed by neem extract at 0.5%. Clove extract at 5.0% did not cause any significant mortality of larvae and nymphs. Neem extracts at 2.5 and 5% caused 97.5 and 100% mortality of M. tanajoa females, while, at the same concentrations, chinaberry extracts caused only 5 and 7.5% mortality and clove extracts caused 5 and 12.5% mortality of females, respectively. These results suggest that neem extracts at concentrations higher than 2.5% are promising for M. tanajoa control.
Mite; cassava; plant extract; natural mitecide
