Toxicity and spraying schedules of a biopesticide prepared from Piper guineense against two cowpea pests

Abstract

The toxicity of three concentrations (5%, 10% and 20% w/v) and spraying schedules (2, 4 and 6 weekly applications) of an extract from West African black pepper, <i>Piper guineense</i>, for managing two major post-flowering pests of cowpea, <i>Vigna unguiculata</i>, was investigated in two cropping seasons at the Research Farm of the Institute for Agricultural Research, Ahmadu Bello University, Zaria, Nigeria. The insect pests were the larvae of <i>Maruca vitrata</i> (Lepidoptera: Pyralidae) and the cowpea coreid bug, <i>Clavigralla tomentosicollis</i> (Hemiptera: Coreidae). The higher concentrations (10% and 20% w/v) and more frequent applications (4 and 6/week) significantly (<i>P</i> < 0.05) reduced the numbers of the two insect pests compared to the untreated control in both years. Pod damage was significantly reduced and grain yields consequently increased in treated plots compared with the other extract treatments and the untreated control. West African black pepper extract applied at higher concentrations and more frequently could play an important role in integrated management of pests’ infestations on field cowpea managed by limited resource farmers in third world countries.