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Potential of sorghum and physic nut (Jatropha curcas) for management of plant bugs (Hemiptera: Miridae) and cotton bollworm (Helicoverpa armigera) on cotton in an assisted trap-cropping strategy

Ratnadass A., Togola M., Cissé B., Vassal J.M.. 2009. Journal of Semi Arid Tropical Agricultural Research, 7 : 7 p..

The cotton bollworm (CBW) Helicoverpa armigera and to a lesser extent plant bugs (PB) (Hemiptera: Miridae) are important pests of cotton in Africa. For sustainability reasons, it is necessary to reduce use of chemical control measures for these pests. A promising alternative to chemical control of both CBW and PB is trap cropping, assisted with botanical pesticides sprays, if needed. We report studies conducted from 1995-98 on sorghum attractiveness to PB and CBW, on the potential of physic nut (Jatropha curcas) extracts [particularly the phorbol ester (PE) fraction of the oil] for sorghum protection from PB damage, and on the insecticidal activity of Jatropha extracts on CBW. At the ICRISAT research station (Samanko, Mali), infestation by the five main species of PB (accounting for 96% of total) was much higher on sorghum than on cotton. In the Kolokani region, CBW infestation was negligible on the Guinea loose-panicled sorghum cultivar Bibalawili, while it was significant on both compact-panicled PB susceptible ICSH 89002 and PB resistant Malisor 84-7. At Samanko, Jatropha oil application on sorghum panicles showed some effect on PB when damage level was high, better than Jatropha and neem aqueous extracts. However, it did not compete with pyrethroid protection level. PE contact toxicity on CBW larvae was too low to determine a LC 50. An ingestion insecticidal activity of PE was found on all tested larval instars. Contact toxicity LC 50 of PE on eggs was 1.66 g ml-1. Development of larvae and reproductive ability of adults derived from new-laid eggs treated with solutions of 0.35 g ml-1 PE and above were considerably affected. Prospects for using sorghum and Jatropha extracts for cotton protection against insect pests in an assisted trap-cropping strategy are discussed. (Résumé d'auteur)

Mots-clés : pesticide d'origine végétale; lutte biologique; système de culture; miridae; helicoverpa armigera; sorghum bicolor; jatropha curcas; gossypium; mali; plante piège

Thématique : Ravageurs des plantes

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