Deterrent effects of some botanical products on oviposition of the cowpea bruchid Callosobruchus maculatus (F.) (Coleoptera: Bruchidae)

Extracts from nine plant materials were tested in choice and no-choice tests as oviposition deterrents for cowpea bruchid, Callosobruchus maculatus (F.) on chickpea, Cicer arietinum L. Seed treatment with 0.1% crude extract of materials resulted in a significant reduction in ovipositional preference of the bruchid. The highest repellency was found in Rhazya stricta leaves (82%), Azadirachta indica seeds (76.8%), Heliotropium bacciferum aerial parts (59.2%) and citrus peels (58.6%). Progeny production was significantly reduced: only 11.5, 11.9, 12.4, 13.4 and 14.8% of the eggs deposited reached adulthood in R. stricta, neem seeds, Piper nigrum, citrus peels and H. bacciferum, respectively. F1 females laid significantly fewer eggs in response to R. stricta, neem seeds, Eugenia caryophyllata cloves, H. bacciferum, citrus peels and P. nigrum. Percentage reduction in F₂ progeny ranged between 71.4% with R. stricta-treated seeds and 24.5% in the P. nigrum treatment.     

Role of chemical characteristics of the seed coat in the resistance of selected cowpea varieties to Callosobruchus maculatus (F.) (Coleoptera: Bruchidae) in Nigeria

The role of seed coat chemical factors in the resistance of the cowpea varieties, Kanannado, IT89KD-391 and Borno brown, to the cowpea seed bruchid Callosobruchus maculatus (F.), was investigated under laboratory conditions (30-35C and 65-67% RH) in Maiduguri, Nigeria. Significantly higher numbers of eggs were laid on de-coated than on intact Kanannado seeds whereas significantly smaller numbers of eggs were laid on de-coated than on intact IT89KD-391 or Borno brown seeds. Susceptibility was higher in de-coated than in intact Kanannado seeds (susceptibility indices [SI] 3.4 and 0.0, respectively). Egg-hatch was significantly reduced in seeds with intact seed coats by 88.6%, while the proportion of eggs that failed to hatch in de-coated seeds was 31.9%. Treatment of Borno brown seeds especially with 32 and 64 mg of extracts from Kanannado and IT89KD-391 seed coats, reduced oviposition by 61.9% and 95.2%, respectively. Treatment with 32 mg of the seed coat extracts reduced egg-hatch by 49.2%. Identical dosages (32 and 64 mg) of these seed coat extracts also significantly reduced susceptibility ofBorno brown to C. maculatus (SI values 6.7 and 1.5, respectively). Comparable SI values for Borno brown treated with 16 mg of the seed coat extracts or extract-free acetone were 14.9 and 14.0, respectively.     

Effects of Hyptis spicigera Lam. (Labiatae) on the behaviour and development of Callosobruchus maculatus F. (Coleoptera: Bruchidae), a pest of stored cowpeas

Abstract

The use of beni seed, Hyptis spicigera Lam. (Labiatae), to protect stored cowpeas from bruchid attacks is a widespread practice in West Africa. More knowledge about its actual effects on storage pests is needed to enhance its effectiveness. In this laboratory study, repellent and lethal effects of powder and essential oil from H. spicigera on Callosobruchus maculatus, the main pest of stored cowpeas, were studied. Repellency tests undertaken with a Y-tube olfactometer showed that powder was repulsive for C. maculatus adults. On the other hand, this product had no insecticidal activity. Essential oil had a dose-dependent insecticidal effect while sublethal doses repelled the adults. Both products reduced oviposition by 15 – 19 and 7 – 78% according to the doses of powder and essential oil, respectively, tested. Similarly, egg viability decreased with increasing doses of powder and essential oil used in a range of 40 – 75 and 24 – 86%, respectively. Only essential oil was lethal to C. maculatus larvae developing within cowpea seeds; however, oil activity was age-dependent, younger instars being more susceptible. These results are discussed with a view of controlling C. maculatus populations in stored cowpeas.     

Evaluation of powdered fruits of four peppers (Capsicum spp.) for the control of Callosobruchus maculatus (F) on stored cowpea seed

Abstract

The efficacy of two application rates of powdered fruits of four types of peppers (Capsicum spp.) was evaluated for the control of Callosobruchus maculatus (F). The various pepper powders at 2.5 g‐5.0 g per 250 g of seed were effective in reducing oviposition and damage to cowpea seeds. The pepper type Capsicum frutescens var. yarmunchi was the most effective in discouraging oviposition and minimizing damage to the seed, as indicated by the significantly lower number of emergence holes. The seed quality and viability were not affected by the powdered pepper fruit treatment. The result is indicative of the potential for the use of powdered fruits of some peppertypes in protecting stored cowpea seeds against C. maculatus.     

Influence of carrier solvent on the efficacy of neem (Azadirachta indica A. Juss) seed oil applied for the control of Callosobruchus maculatus (F.) (Coleoptera: Bruchidae)

Journal of Plant Diseases and Protection - The influence of four carrier-solvents (acetone, ethanol, petroleum ether and hexane) on the efficacy of neem (Azadirachta indica A. Juss) seed oil...