TOXICITY OF Piper guineense SCHUM AND THONN AND Chlorpyrifos POWDERS FOR THE CONTROL OF Callosobruchus subinnotatus (Pic.) ON STORED Vigna subterranea (L.) Verdcourt IN GOMBE STATE, NIGERIA

A study was conducted with aim of determining toxicity effects of Piper guineense and chlorpyrifos powders on adult mortality of Callosobruchus subinnotatus, progeny emergence (F1), damage and weight loss, germination of Bambara nuts. Study was carried out at Botany laboratory, Gombe State University, Gombe State, Nigeria. P. guineense and chlorpyrifos were mixed at 0.0g and 0.8g concentration with 20g Bambara nuts inside 1000ml plastic containers. Experiment was conducted in randomized complete block design in three replicates. Ten pairs of adult C. subinnotatus unsexed were introduced into treatments nuts and stored for 7days. Bruchid mortality, progeny emergence, nut damage and weight loss, and germination were assessed. Data obtained were subjected to analyses of variance, significant differences of treatment mean were separated using New Duncan’s multiple range test at 5% probability level. Piper guineense and chlorpyrifos powders had comparable toxicity effects, causing 100% C. subinnotatus adult mortality between 5-7 days of treatment. P. guineense and chlorpyrifos powders proved effective as lower C. subinnotatus progeny emergence was observed compared with control. Progeny emergence under control was 93.42% and 100% higher than nuts treated with P. guineense and chlorpyrifos, respectively. P. guineense and chlorpyrifos did not cause significant reduction in seed germination. Study recommends P. guineense is a reliable organic material that could offer protection to Bambara nuts against C. subinnotatus

Comparative Efficacy of Jatropha curcas L. Seed Powder for the Control of Callosobruchus subinnotatus (Pic) on Stored Bambaranut, Vigna subterranea (L.) Verdcourt

The study was to assess insecticidal effectiveness of Jatropha curcas L. seed powder on Callosobruchus subinnotatus (Pic) infesting stored bambaranut, Vigna subterranea (L.) Verdcourt. The experiment was laid out in a factorial design of 4×2 levels (seed powder at the rates of 0.0, 0.5. 1.0 and 1.5 g, with and without addition of the synthetic insecticide at 0.01 g/20 g bambaranut seed) and laid out in a completely randomized design, in three replicates. Results obtained showed lowest oviposition, progeny emergence and seed damage (5.33, 1.58 and 1.83, respectively) in bambaranut seeds admixed with 1.0 g of the seed. Although, statistically similar to all other treatments, it was significantly (P≤0.001) better than the control treatment in which 33.83 eggs were laid and 24.08 adults emerged from 22.92 emergence holes. In addition, at six (6) days after treatment, highest adult mortality rate (99.17%) similar to that (99.17%) obtained in the synthetic insecticide was also recorded in seeds treated with 1.0 g seed powder. However, all other treatments were also significantly better than the control, in which 72.50% of the introduced bruchids died. Comparatively, lowest rate of seed damage (6.68%) and lasting effect was also obtained with the addition 1.0 g seed powder. In conclusion, appreciable level of protection on bambaranut seeds was achieved using seed powder of J. curcas. Therefore, it is recommended that for effective management of C. subinnotatus infesting bambaranut, farmers could use 5 Kg seed powder on 100 Kg bambaranut seeds.

Bioactive effect of Jatropha curcas L. leaf product on Callosobruchus subinnotatus (Pic) infesting stored bambara nut, Vigna subterranea (L.) Verdcourt

The research was conducted in the year 2016 at the Entomology laboratory of the Department of Crop Protection, Bayero University Kano to assessed the bioactive effect of physic nut, Jatropha curcas L. leaf powder on Callosobruchus subinnotatus (Pic) infesting stored bambara nut, Vigna subterranea (L.) Verdcourt. The study was also aimed at comparing the effectiveness of the leaf powder with conventional chemical insecticide (pirimiphos-methyl). In a 2×2 factorial experiment, the leaf powder and pirimiphos-methyl were admixed with bambara nut seeds. The first factor (leaves) had two (2) levels (0.0 and 0.5 g/20 g seed) while the second factor (pirimipos-methyl) also had two levels, with and without the standard rate of application (0.00 and 0.01 g/20 g). These were laid out in a Completely Randomized Design and repeated three times. Results showed fumigant, repellant and contact effects were best exhibited in seeds treated with the leaf powder admixed at the rate of 0.5g, but was not significantly different from seeds treated with pirimiphos- methyl. In conclusion, appreciable level of protection on bambara nut seeds was achieved using the leaf powder of J. curcas applied at 0.5 g/20 g bambara nut seeds during storage.Keywords: Bioactive, Callosobruchus subinnotatus, bambara nut, Jatropha, fumugant

Comparative efficacy of Jatropha curcas L. leaf powder for the control of Callosobruchus subinnotatus (Pic) on stored bambara nut Vigna subterranea (L.) Verdcourt

The research was conducted in the year 2016 at the Entomology laboratory of the Department of Crop Protection, Bayero University Kano to assess the biocidal and damage reduction effect of leaf powder from physic nut, Jatropha curcas L. caused by Callosobruchus subinnotatus (Pic) on stored bambara nut, Vigna subterranea (L.) Verdcourt. Also, the study aimed at comparing the effectiveness of the plant product with conventional chemical insecticide (pirimiphos-methyl). Factorial experiment of 4×2 levels (leaf powder at the rates of 0, 0.5. 1.0 and 1.5 g, with and without addition of the synthetic chemical at 0.01 g/20 g bambara nut seed) were laid out in a Completely Randomized Design and repeated three times. Results showed that, admixture of 0.5g leaf powder proved effective in causing high biocidal effect and reduced seed damage. However, this was statistically same with seeds treated with 1.0g leaf powder. Comparatively, all treatments were statistically different from the untreated control seeds but similar with the check treatment. Highly significant (p<0.001) persistent effect was observed in seeds treated with 1.5g leaf powder mixed with 0.5g seed powder at 60 days after treatment (DAT) without any negative effect on seed viability. This was also statistically similar in all other treatments apart from the untreated control. In conclusion, appreciable level of protection on bambara nut seeds was achieved using leaf and seed powder of J. curcas applied at different mixture rates and singly. Therefore, it is recommended that for effective management of C. subinnotatus infesting bambara nut, farmers could use 1.5 g leaf powder or 1.0 g seed powder per 20 g bambara nut seeds singly each. Alternatively, 0.5:1.0, 1.0:1.0 or 1.5:0.5 leaf/seed combinations could be used for safe bambara nut storage.Keywords: Biocidal, Callosobruchus subinnotatus, bambara nut, Jatropha, damage, insecticide

Postmating sexual selection and the enigmatic jawed genitalia ofCallosobruchus subinnotatus

SummaryInsect genitalia exhibit rapid divergent evolution. Truly extraordinary structures have evolved in some groups, presumably as a result of post-mating sexual selection. To increase our understanding of this phenomenon, we studied the function of one such structure. The male genitalia ofCallosobruchus subinnotatus(Coleoptera: Bruchinae) contain a pair of jaw-like structures with unknown function. Here, we used phenotypic engineering to ablate the teeth on these jaws. We then experimentally assessed the effects of ablation of the genital jaws on mating duration, ejaculate weight, male fertilization success and female fecundity, using a double-mating experimental design. We predicted that copulatory wounding in females should be positively related to male fertilization success. However, we found no significant correlation between genital tract scarring in females and male fertilization success. Male fertilization success was, however, positively related to the amount of ejaculate transferred by males and negatively related to female ejaculate dumping. Ablation of male genital jaws did not affect male relative fertilization success but resulted in a reduction in female egg production. Our results suggest that postmating sexual selection in males indeed favors these genital jaws, but not primarily through an elevated relative success in sperm competition but by increasing female egg production.

Conspecific sperm precedence in Callosobruchus subinnotatus (Coleoptera: Bruchidae): mechanisms and consequences

Conspecific sperm precedence (CSP) has been identified as an important post-copulatory, pre-zygotic mechanism that can act to reduce gene flow between populations. The evolution of CSP is thought to have arisen as a by-product of male and female coevolution in response to intraspecific post-copulatory sexual selection. However, little is known about the mechanisms that generate CSP. When Callosobruchus subinnotatus females copulate with both C. subinnotatus and Callosobruchus maculatus males, regardless of mating order, the majority of eggs are fertilized by conspecific sperm. The low number of heterospecific fertilizations does not result from general differences in the viability of sperm in the female reproductive tract, as heterospecific sperm fertilized equivalent numbers of eggs as conspecific sperm in the absence of sperm competition. Instead, CSP results from disadvantages to heterospecific sperm that are manifest only when in competition with conspecific sperm. CSP in C. subinnotatus appears to result from two, not mutually exclusive, mechanisms. First, conspecific sperm are better able to displace heterospecific sperm from female storage. Second, conspecific sperm achieve disproportionately higher numbers of fertilizations relative to their proportional representation in the fertilization set. Thus, we provide evidence of differential sperm use from the female spermatheca.