Neem combats cowpea pests

Cowpea is an important component in several cropping systems prevalent in Africa. It is attacked by numerous insect pests, some of which have proved intractable in research so far. Efforts to control them have included host plant resistance and cultural practices, as well as agrochemicals. Biological control offers another possibility and neem, a plant that is often grown in backyards and along borders of crop fields offers considerable promise as an easily available source of natural chemical compounds to be harnessed for pest control. In Nigeria, where much of the world's cowpea is grown, aqueous extracts of neem are used to keep grasshoppers off the crop in the dry season. Neem leaves are soaked overnight and the solution sprinkled on cowpea plants using a shaped tree branch or broom. Despite this use, and the fact that it is known for its efficacy in controlling pests of stored products, neem has been little used as a control measure for other pests of cowpea. The International Institute of Tropical Agriculture (IITA) has conducted field trials on two major pests of cowpea, the pod borer Maruca testulalis and the pod sucking bug Clavigralla tomentosicollis. Solutions made from ground neem seed or kernel were sprayed onto cowpea flowers and pods. The resulting low survival rates of both nymphal and adult pests were encouraging. Trials using neem oil derived formulations were also evaluated. Fears are sometimes expressed that neem could adversely affect pest predators, but evidence so far suggests that these fears are unjustified. Workers with long experience of neem have not found any serious impact on the beneficial fauna associated with most crops, nor should there be any adverse effects on users of neem as it is already used medicinally in some countries to combat various ailments. L E N Jackai, IITA PMB 5320 Ibadan, NIGERIACowpea is an important component in several cropping systems prevalent in Africa. It is attacked by numerous insect pests, some of which have proved intractable in research so far. Efforts to control them have included host plant resistance and..