The effect of insecticides against the root mealybug (Cataenococcus ensete) of ensete ventricosum in Southern Ethiopia.

The effect of six commercially available insecticides was evaluated for the control of the enset root mealybug, Cataenococcus ensete (Williams and Matile-Ferrero) (Hemoptera: Pseudococcidae) under greenhouse and farmers’ field conditions. In the greenhouse study, pared and boiled water treated seedlings of E. ventricosum were planted in 10 L pots and infested at 2 months after planting with 25 thirdinstar C. ensete per plant. Each insecticide was diluted to a 1/500 concentration and applied at a rate of 660 ml of diluted solution per pot. In the farmers’ field study, the number of adult C. ensete before insecticide application was estimated by sampling a 20 × 20 × 20 cm soil volume at one side of the plant. Each plant was drenched with 1.7 L of diluted insecticide solution. The results showed a significant difference (p<0.05) in C. ensete mortality amongst the treatments. Diazinon 60% EC and Chlorpyrifos 48% EC caused at least 98% mortality both under field and greenhouse conditions. Applications of Endosulfan, Dimethoate, Fenitrothion and Malathion resulted in a 74, 65, 77 and 83% mortality in the greenhouse experiment and a 51, 65, 51 and 50% mortality in the field trials, respectively. The efficacy of a double application of Malathion, Fenitrothion, Endosulfan and Dimetohate was inferior to a single application of either Chlorpyrifos or Diazinon. Therefore a single application of Diazinion or Chlorpyrifos is recommended. However, it is advisable/imperative that farmers continuously monitor infestation levels in their enset plots by assessing adult root mealybug numbers in soil samples dug out adjacent to the corms and repeat insecticide applications when a mealybug population build up is observed. _____________________________________________________________________________________________________________