Prevention of food losses during postharvest storage is of paramount economic importance. Integrated pest management is now a widely accepted strategy in pest control including postharvest infestation control which involves the use of chemical (contact/residual) insecticides along with fumigants. The use of synthetic chemical insecticides is either not permitted or used restrictively because of the residue problem and health risks to consumers. In view of the above, there is a need for plants that may provide potential alternatives to the currently used insect control agents as they constitute a rich source of bioactive molecules. Available literature indicates that plant could be source for new insecticides. Therefore, there is a great potential for a plant-derived insecticidal compounds. This paper focuses on the current state of the botanical insecticides as grain protectants and its mode of action.

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Botanicals as Grain Protectants

Antifeedant, larvicidal and growth inhibitory effects of ononitol monohydrate isolated from Cassia tora L. against Helicoverpa armigera (Hub.) and Spodoptera litura (Fab.) (Lepidoptera: Noctuidae)

Essential oils from four species of the genus Tagetes L. (Asteraceae, Helenieae) collected in Tucuman province, Argentina, were evaluated for their chemical composition, toxicity, and olfactory activity on Mediterranean fruit fly Ceratitis capitata Wiedemann adults and for repellent properties on Triatoma infestans (Klug) (Chagas disease vector). Yields of essential oils range from 0.2 to 0.8% (v/w). The same main constituents among Tagetes minuta L., Tagestes rupestris Cabrera, and Tagetes terniflora Kunth, (cis–trans)-ocimenes, (cis–trans)-tagetones, and (cis–trans)-ocimenones showed important differences in their relative compositions. Tagetes filifolia Lag. was characterized by the recognized phenylpropanoids methylchavicol and trans-anethole as the main components. LD50 was ≤20 μg/insect in topical bioassays. T. rupestris was the most toxic to C. capitata females, whereas the other oils presented similar toxicities against males and females. Tagetes rupestris oil attracted both sexes of C. capitata a...

Composition and Anti-insect Activity of Essential Oils from Tagetes L. Species (Asteraceae, Helenieae) on Ceratitis capitata Wiedemann and Triatoma infestans Klug

The insecticidal and repellent properties of Lantana camara and Tephrosia vogelii were evaluated against Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae) in stored maize grain. Five treatment rates (1.0, 2.5,5.0,7.5 and 10.0% w/w) of each powdered plant material, an untreated control and a synthetic insecticide (Actellic Super™ 2% dust) were used to investigate treatment efficacy on mortality of the adult insect (five to eight days old), F1 progeny emergence and repellency against S. zeamais adults. After 21 days, L. camara and T. vogelii caused 82.7–90.0% and 85.0–93.7% insect mortality, respectively. The mean lethal exposure times (LT50) to achieve 50% mortality varied from five to six days (7.5–10.0% w/w) to seven to eight days (2.5–5.0% w/w) for both plants. Probit regression analysis showed a significant relationship between plant powder concentration and insect mortality. The plant powders and synthetic insecticide reduced adult F1 insects by more than 75% compared to the untreated control. Tephrosia vogelii was most repellent to S. zeamais at 7.5–10.0% (w/ w), repelling 87.5% of the insects, followed by T. vogelii at 2.5% w/w and L. camara at 10% w/w which repelled 65.0 and 62.5% of insects respectively. The implications of these results are discussed in the context of smallscale farmer usage of these plants for stored product protection.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S1742758400020348

Comparison of Toxic and Repellent Effects of Lantana Camara L. with Tephrosia Vogelii Hook and a Synthetic Pesticide Against Sitophilus Zeamais Motschulsky (Coleoptera: Curculionidae) in Stored Maize Grain

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Leaf Extracts of Shiyalmutra (Blumea lacera Dc.) as Botanical Insecticides Against Lesser Grain Borer and Rice Weevil

Crude seed extracts of pithraj, Aphanamixis polystachya were evaluated fortheir repellency, feeding deterrency, contact toxicity and oviposition deterrency to rice weevils. The extracts had strong repellent and feeding deterrent effects on rice weevils. Pithraj seed extracts were moderately toxic to rice weevils. An ethanol extract was the most toxic of four extracts tested and showed the lowest LD50 and LT50 values. The ground leaves, bark and seeds at a 2.5% ratio provided good protection for rice grains by reducing the F1 progeny emergence and the grain infestation rates.

P.E. Howse

Papers

Laboratory evaluation of toxic and repellent properties of the pithraj tree, Aphanamixis polystachya Wall & Parker, against Sitophilus oryzae (L.)