Evaluation of Insecticides for Control of Cassava Mealybug (Phenacoccus manihoti)

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Abstract
A field trial on a moderately infested four-month old cassava plot was initiated at Ugwuoba field station of National Root Crops Research Institute, to determine the efficacy of five insecticides for control of cassava mealybug (CMB), Phenacoccus manihoti Mat-Ferr. The insecticides were Rogor 40 (dimethoate), Supracide 40 (methidathion), Basudin 60 (diazinon), Nuvacron 40 (monocrotophos) and Dimecron (phosphamidon) and were applied at the rate of 0.05 percent active ingredient (500 ppm). A CP3 type sprayer was used to discharge the insecticides. The treatments were replicated five times. Knock-down effect on the crawlers (nymphs) and adult mealybugs was recorded 24 hours after insecticide application. Mean percentage knock-down figures were Dimecron, 25; Nuvacron, 37; Basudin, 40; Rogor, 20 and Supracide, 45. Although the highest knock-down was recorded in Superacide, there were no significant differences between Superacide, Basudin and Nuvacron. At five weeks after insecticide application, mean plant vigour (improvement) based on the mealybug infestation on new plant growths were rated on a scale of 1–5 as follows: Basudin, 4.9; Superacide, 4.6; Dimecron, 4.5; Nuvacron, 4.4; and Rogor, 3.6.

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