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Oparaeke A.M. (2007): Toxicity and spraying schedules of a biopesticide prepared from Piper guineense against two cowpea pests. Plant Protect. Sci., 43: 103-108.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, Piper guineense, for managing two major post-flowering pests of cowpea, Vigna unguiculata, 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 Maruca vitrata (Lepidoptera: Pyralidae) and the cowpea coreid bug, Clavigralla tomentosicollis (Hemiptera: Coreidae). The higher concentrations (10% and 20% w/v) and more frequent applications (4 and 6/week) significantly (P < 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.

The extracts of pods of West African black pepper, Piper guineense, at 5, 10 and 20% (w/v), were applied at two, four and six weekly schedules to control the legume flower bud thrips, Megalurothrips sjostedti on flowers of cowpea, Vigna unguiculata. The trials were conducted for 2 years under rain fed conditions in the northern Guinea savanna region of Nigeria. The results showed that the M. sjostedti population was significantly controlled on treated plots compared with the untreated check in both years. The extracts at the 20 and 10% rates and with six or four weekly applications significantly (P < 0.05) reduced thrips pressure on cowpea flowers, were better than the 5% extract at all spraying schedules, and had the same efficacy as the synthetic insecticide treatment. Pod density per plant was significantly higher (P < 0.05) on plots treated with the 20% extract at six or four weekly applications compared to other extract rates and was similar to that of the synthetic insecticide treatment. Thus, the extracts could be a good alternative to the synthetic insecticides on organically managed farms as well as on farms of limited resource farmers in the tropics and subtropics.

Crude water extracts of leaves from nine plant species were tested for efficacy against three major post flowering insect pests of cowpea in Samaru, Zaria, located in the northern Guinea savanna of Nigeria. These extracts were evaluated based on the number of pests (thrips, legume pod-borers and pod-sucking bugs complex dominated by Clavigralla tomentosicollis Stals) observed after weekly spraying intervals, pod density per plant, pod damage per plant, and grain yield (Kg/ha). All the leaf extracts gave some level of protection to cowpea crops relative to the untreated control. Pod density per plant was increased on plots sprayed with extracts of African marigold (Tagetes sp.), African Goat weed (Chromolaena odorata) and African curry (Ocimum gratissimum L.) in that order. Extracts of African curry, African bush tea (Hyptis suaveolens Poit), African marigold significantly (p 5 0.05) reduced pod damage and ensured relatively higher grain yield compared with other extracts and the untreated control. However, none of the extracts were comparable to the synthetic insecticide (Cypermethrin + Dimethoate) used in the two years of study.

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