The efficacy of plant-derived insecticides was compared with a synthetic insecticide, Lambda-cyhalothrin over two cropping seasons (2015 and 2016) against Leucinodes orbonalis, the eggplant fruit and shoot borer (EFSB) infesting eggplant, Solanum gilo. The plant materials included oil palm (Elaeis guineensis) bunch ash, soursop (Annona muricata) seeds, and goat weed (Ageratum conyzoides) leaves. These plant materials were formulated into aqueous extracts of 150 g/L (w/v), while Lambda-cyhalothrin was applied at the rate of 5 mL/L (v/v). The experimental design was a Randomized Complete Block Design (RCBD). There were 5 treatments with 3 replications applied on 2 cultivars of eggplants (Afufa Ukwu and Ngwa Large). Percentage fruit damage varied significantly (P< 0.05) with various treatments. The lowest mean percentage fruit damage was observed in the plot treated with Lambda-cyhalothrin (20.38%), followed by goat weed (29.03%), soursop (40.69%), palm bunch ash (43.30%) and the control (67.08%) for 2015 and 2016. Other parameters measured followed the same trend. Mean yield was significantly affected by the treatments. The highest mean yield was obtained from the plots treated with Lambda-cyhalothrin (12,346.6 g), followed by plots treated with goat weed (11,295.0 g), soursop (9877.2 g), palm bunch ash (8729.4 g) and control was the least (6583.0 g). Among the plant extracts, A. conyzoides that recorded low mean percentage damage had very high yield. Therefore, it can be used as insecticides in the control of EFSB.
Post-harvest losses due to insect pest infestation in storage constitute a challenge to sustainable food security and economic losses to farmers throughout the world. Use of synthetic chemicals have been the most effective means of reducing losses in storage. Unfortunately, these toxicants have adverse effects in humans and the environment. There is renewed search for safer plant products as alternatives. In this study, we assessed the potential use of Piper guineense seed oil in the control of cowpea bruchid, Callosobruchus maculatus (F.) infestation on stored cowpea seeds. Adult mortality, oviposition rate, F1 progeny emergence, cowpea seed damage and seed germinability were the indices considered in the assessment under laboratory conditions. The setup of the experiment was completely randomized design (CRD). Statistical analysis of the data was by analysis of variance (ANOVA). Adult C. maculatus mortality was dose-dependent with higher dosages inducing 100% mortality. The number of eggs laid on the treated seeds were significantly (P<0.001) reduced. Progeny emergence and feeding damage were completely inhibited at higher dosages. The seed oil has no adverse effect on cowpea seed viability. The results indicated that P. guineense seed oil has protectant potential against insect pest damage in storage and a good alternative to synthetic insecticides in the control of insect pest of stored products.
A study was carried out to determine the efficacy of three plant materials; pawpaw (Carica papaya) seed powder, kapok tree (Ceiba pentandra) leaf powder, soursop (Annona muricata) leaf powder as well as clay and Permethrin dust against Sitophilus zeamais (Mots.) under laboratory conditions. The experiment was laid out in 5×4 factorial with 5 replicates in Completely Randomized Design in the laboratory. Maize grains weighing 50 g were treated with the plant powders, clay and the synthetic Permethrin at the rate of 0.00 g, 1.5 g, 3.5 g and 5.0 g by weight and then infested with 10 adult weevils in each vial for assessments of adult mortality, F1 emergence and damage. The comparative effectiveness of each of the treatments were assessed by counting weevils’ mortality at 14 days, 28 days, 42 days and 56 days post treatment and progeny emergence at 28 days, 42 days and 56 days post-treatment. The results were subjected to statistical analysis after transforming the data using mean percentage method and the ANOVA, the significant means were separated using the least significant differences test at 5% level. The Permethrin, a synthetic insecticide proved to be very effective followed by clay among all the treatments. Among the botanicals, C. papaya was the most effective followed by A. muricata, but were concentration dependent while C. pentandra was the least or not effective. In all trials, percentage mortality among adult S. zeamais reared on maize treated with Permethrin powders was observed to be the highest (100%) followed by those treated with C. papaya seed powder (56.6%), clay (55.5%) and A. muricata seed powder (38.8%). However, grains treated with powdered leaves of C. pentandra exhibited a low mean percentage mortality of 0.00, 0.20, 0.57 and 0.63, respectively, at different intervals post treatment which was not significantly different when compared with the untreated (control). These percentage mortality among adults were significantly (P<0.05) different from the untreated (control). Thus, all the treatments were found to significantly affect the survival of the S. zeamais at different concentration except in C. pentandra. Effect of plant powder on the emergence of adult S. zeamais was significantly (P< 0.05) different and reduced the F1 progeny emergence. The result indicated that C. pentandra had no significant effect on mortality and F1 emergence of adult S. zeamais (P< 0.05) resulting in severe damage of the grains and weight loss.
<p>Weevil<em> </em>(<em>Sitophilus zeamais</em> Motsch.) is a vital arthropod pest of maize (<em>Zea mays </em>L.) grains and flours in traditional storage systems. The pest bore holes into stored grains reducing their nutrient contents germination potentials and contaminating produce with frass. Its control using synthetic insecticides such as permethrin is being downplayed due to eco-mammalian toxicity from pesticide residues. Therefore, this study evaluates the toxicities of some indigenous plants <em>Ageratum conyzoides </em>L., <em>Cymbopogon nardus </em>L.<em>,</em> clay and permethrin, under laboratory conditions to the insect pest. Maize grains weighing 50 g were treated with the plant powders and the synthetic insecticide at five different levels 0.00; 1.25; 2.50; 3.75 and 5.00 g. Subsequently, 10 adult weevils in each vial were used to infest the 50 g maize grains. Each plant powder and permethrin's effectiveness was assessed by recording weevil mortality at 5, 7, 14, 21 and 28 days post-treatment. The damage indices recorded by the weevil perforation index (WPI), percentage of perforated and unperforated grains, and weight loss percentage were also considered. Permethrin proved most toxic, followed by clay at 5.00 g among all the treatments. <em>A. conyzoides </em>and <em>C. nardus</em> were less effective in controlling <em>S. zeamais</em>. In conclusion, clay can be used in the integrated management of <em>S. zeamais</em> to minimize synthetic insecticides.</p>
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