TOXICITY OF AQUEOUS EXTRACT OF NEEM (AZADIRACHTA INDICA A. JUSS) SEEDS ON GIANT POD SUCKING BUG (ANOPLOCNEMISCURVIPES) OF COWPEA (VIGNAUNGUICULATA(L.) WALP)

Cowpea ( Vignaunguiculata) is the major source of protein supplement in Nige rian diet, which is attacked by many insects pests in farm and storage conditions. Studies were carried out to determine the efficacy of water extract of neem ( Azadirachtaindica A. juss) kernel against Anoplocnemiscurvipesadults and nymphs. Neem kernel extract at 5%, 10% a nd 15% w/v were evaluated using 0% as control under field condition s. The extracts were sprayed once weekly for three (3) weeks. The extract reduced the population of in sects in both nymphs and adults stages. 10% and 15% of extract were found more effective than the 5 % for both the stages of insect. Toxicity of neem kernel was time and dose dependent on tested insect s.Nymphs of A. curvipes were more susceptible than the adults. After third spray of 10% and 15% o f neem extract showed 100% reduction in nymph population of A. curvipes, while same spray caused 66.67% reduction in adult population of A. curvipes. Singh K. , J. Harmoniz. Res. Appl. Sci. 2014, 2(4), 359-364 www.johronline. com 360 | P a g e in cowpea fields, though this depends on a number of ecological and agronomic factors such as climatic conditions, susceptibility to pests and diseases. It is now realized that the use of synthetic pesticides are posing serious environmental hazards. Plant products have played an important role as herbal traditional medicine for treatment of human ailment and also served other roles including protection of crop against pests and disease vectors in Africa (Delobel and Trans, 1993). Plants are known to produce a range of secondary metabolites which possess multiple mode of action including acute toxicity, repellency, antifeedent, and inhibition of oviposition, growth, development and reproduction (Uko and Kamalu, 2001). Large numbers of plant families possess pesticidal properties (Oparaekeet al. 2006). It has been observed that oil of neem ( Azadirachtaindica) possess leathal property against molluscs (Singh and Singh 1997). The active moiety responsible for insecticidal activity in neem is azadirachtin. In the present study we have evaluated the toxicity of aqueous extract of neem against A. curvipes with broader objective to control different species of cowpea pests. Materials and Methods The investigations were conducted under rain fed conditions in UsmanuDanfodiyo University, Sokoto, Nigeria at Dry Land Research Farm. Treatments consists of 5%, 10% and 15% of neem kernel extract w/v. Neem fruits were collected locally, depulped, dried and crushed. 250gm. 500gm. and 750gm. of crushed neem seeds were soaked in plastic buckets containing 3L. of water, stirred and kept overnight and labelled as 5%, 10% and 15% of neem extract respectively. Each extract was filtered with an additional of 2 L. of water, using muslin cloth making the total valum of extract to 5 L. The field layout was a randomized complete block design (RCBD). Plot size was 6.0m × 5.0m and each plot had five (5) ridges (three inner rides and two discarded). The ridges were spaced 0.75m apart. There were three treatments and one untreated control. All replicated three times. The seed of cowpea variety Ba’dare (a local variety of cowpea which attracts most of the pests) was used for the experiment and 3-4 seeds were sown per hole, using the dibbling method of sowing. The seedlings were thinned to two plants per planting hill two to three weeks after sowing. A compound fertilizer (NPK 15:15:15) was topdressed at the rate of 37.5 kg/ha. Field application of neem extract commenced at 7 (seven) weeks after planting. This was the time of flower bud formation and onset of flowers in the cowpea variety used. Spraying was done between 8.00 a . m to 10.00 a. m each day using a pressurized low-volume knapsack (CP 3) at the discharge rate of 150L/ha. A single row of cowpea was sprayed per pass or trip. All the concentrations of spray were applied once every week for three weeks and if there was rain within two hours of application, spraying was repeated the next day. Anoplocnemis curvipes, adults and nymphs were counted and sampled separately, before each spraying from 6.30 to 8.30 a. m. and 24 hours after the spraying of neem seed extract counting of insects was repeated and recorded. All the data were subjected to Analysis of Variance (ANOVA) and means were separated using LSD at 5% treatment level (SAS), 1989. Results Table 1 showed that the treatments (5%) did not reduce insect count significantly after first spray , but there was 72.73% reduction in the nymph population after first spray of 10% and 15% of neem extract. Counting after second spray Singh K. , J. Harmoniz. Res. Appl. Sci. 2014, 2(4), 359-364 www.johronline. com 361 | P a g e showed that there is significant reduction in the population of A. curvipes nymph treated with 5%, 10% and 15% of aqueous extract of neem seed, but there were no difference between sprayed plots. Treatments 10% and 15% showed similar effect against nymphs. After third spray 100% reduction in A. curvipes nymph population, but there is significant difference between the 10% and 15% treatments as compared to 5%, as well as there was significant difference between 5% treatment and the control. Table 1: population of A. curvipes (nymph) as affected by neem seed extracts on cowpea , aft r first, second and third spray. Treatments (conc. %) Mean population (survival) of A. curvipes (nymph) after 1 spray 2 nd spray 3 spray