Abstract

Fruit yield loss in cucumber(Cucumis sativus L.) to leaf feedingby Epilachna chrysomelina Fabricius (Coleoptera: Coccinellidae) at six population densities (0, 1-,2-,3-,4- and 5-pairs per cage) was studied in screen house and field experiments. Increased beetle density, resulted into a significant reduction (P < 0.05) in the number of fruit, fruit length, fruit width and fresh fruit yield produced in both experiments. At 1-pair and 2-pairs infestation level yield reduction was not statistically different from the control. However, over 54% fruit yield reduction was recorded when beetle density was increased beyond 3-pairs infestation level. The damage threshold of the beetle at which significant reduction (P < 0.05) occurred in fresh fruit yield per cage, when compared with the control, was 3-pair level. At this infestation level, initiation of control measures is justified. Regression analysis in both experiments indicated that Epilachna chrysomelina density was positively related to fruit damage and negatively associated with fresh fruit yield. Results of the chi-squared analysis further revealed that the screen cage and field cage experiment models were similar and either model could be used for predicting damage and yield with respect infestation by the beetle.

Key Words: Epilachna chrysomelina, Yield response, Infestation level, Cucumber, Damage