Survey of vegetable pests and associated predators with emphasis on onion thrips control at South Darfur State

This study was conducted in South Darfur State, Sudan during seasons 2007/2008 and 2008/2009 in order to identify and estimate the population densities of insect pests and their predators on vegetable crops, and to assess the awareness and knowledge of farmers regarding vegetable pests and the current management practices through questionnaires. Moreover, field experiments were conducted to evaluate the efficacy of Neem Azadirachta indica seed kernel, Handal Citrullus colocynthis fruit and Gafal gum Commiphora Africana water extracts against onion thrips on onion. Onion leaves were found attacked heavily by Thrips tabaci. Tomato and snake cucumber leaves were found attacked by whitefly, Bemisia tabaci and leaf miners, Liriomyza spp., while 6.5% and 9.6% of tomato fruits were infested by African bollworm Helicoverpa armigera during the two seasons, respectively. High population density of whitefly was found on okra while jassid, Jacobiasca lybica was present at low density contrary to what was found on eggplant. High numbers of aphid, Aphis gossypii were recorded on okra, eggplant and snake cucumber. Regarding the predators, spiders were found on tomato, and ladybird beetles, spiders and lacewing were detected on okra, whereas, ladybird beetles and spiders were reported on eggplant and snake cucumber in low densities. The questionnaire revealed that all vegetable farmers considered whitefly to be the most important insect pest of tomato, followed by African bollworm and leaf miners. Similarly, all farmers determined onion thrips to be the major insect pest of onion. They mentioned whitefly, aphid and jassid as the most important insect pests attacking okra and eggplant. However, aphid, whitefly, leaf miners, fruit fly and red melon beetles were reported as major insect pests of snake cucumber. Nearly 50% of the farmers were experienced onion pink root caused by Pyrenochaeta terrestris in their onion fields however, 28% of the farmers were experienced tomato leaf curl. On the other hand, Cynodon dactylon, Cyperus rotundus and Orobanche ramosa were known to be the most problematic weeds. All interviewed farmers used insecticides to control insect pests of vegetables, whereas 30% of them used fungicides to control vegetable diseases and 40% of the farmers used the herbicide (Goal) to control weeds in onion. The results of field trials at Nyala area using water extracts of Neem seed kernel, Handal fruit and Gafal gum against Thrips tabaci on onion, showed that all extracts induced slight reduction in thrips and insignificant increase in yield, compared withe control and the standard insecticide. However, the standard insecticide significantly increased onion yield compared with plant extracts