Socio-economic implications of cashew nut shell liquid and cypermethrin in protecting cowpea, Vigna unguiculata (L.) Walpers against field insect pests

摘要

Cowpea is an important crop in tropical regions particularly in West and Central Africa. The green parts of the plant are used as a vegetable or as fodder for cattle. The seeds contain a high amount of protein and B-vitamins and help to prevent starvation among low resource farmers and the poor urban population. Cowpea is a crop that is vulnerable to insect pests at almost every stage of its development. Insect infestation causes a change in protein quality, a reduction in the contents of vitamins ofthe B-complex, starch, energy and non-reducing sugars while contents of crude fibre, cellulose, hemicellulose, lignin and uric acid increase. On this basis, several approaches have been adopted in its control. Research had centred primarily on the use of synthetic insecticides but in recent years it has been turning more towards selective natural pesticides, including plant extracts that are generally perceived to be safer than synthetic pesticides. The use of cashew nut shell liquid (CNSL) has been gaining more attention due to its active phenolic compounds, anacardic acid and cardol which also have corrosive and abrasive properties. It has been demonstrated that low concentrations of about 0.5% ethanolic extract of CNSL could be effective in preventing oviposition in Callosobruchus maculatus, Ofuya & Fayape (1999) as well as in the protection of okra Abelmoschus esculentus L. against Podagrica beetles (Olotuah, 2003). This paper reports the results of two field trials at Adekunle Ajasin University, Akungba-Akoko on the comparative control of cowpea using a protectant of plant origin, CNSL and a synthetic insecticide, Cymbush 10EC (lOOg cypermethrin per litre).