Lutte, gestion et protection intégrée : cas du sorgho et de ses ravageurs

There are several definitions of Integrated Pest Management (IPM), which emphasize either the " management " or the " integration " aspect, the former being knowledge-intensive, while the second is more empirical. As for sorghum pests, midge can be " managed " by imposing a planting date or by using a resistant cultivar alone, namely without integrating several techniques. As soon as several methods are combined, one should study their interactions, positive or negative. Host plant resistance (HPR) is generally considered as perfectly compatible with other control options, while chemical control is considered to adversely interact with biological control (BC). Prospects for " classical " BC of sorghum pests in West Africa are limited, because on the one hand, both the crop and its pests are indigenous, and that the cereal is cultivated annually, in small scattered fields. However, conservation of beneficial arthropods by rational pesticide use, should be a constant concern. Actually, although several lists of beneficials were established, some of them being considered as promising candidates, particularly for stem borer control, no BC program per se was ever implemented in practice on sorghum pests. There is theoretically a positive synergy between HPR and BC (or rational chemical control), since insect pest development is affected by feeding on resistant plants, which make them more susceptible to natural enemies or moderate pesticide applications. In sorghum, fast internode elongation, hard stems, or presence of a superficial wax layer (or its chemical composition), are factors which adversely affect stem borer larvae by extending the periods during which they are exposed. All the same for the leaf surface wetness, which when low, hampers sorghum shootfly larva migration to the host plant growing point. Similarly, rapid ovary growth in some sorghum cultivars literally " pushes " midge larvae outside the glumes, exposing them both to adverse climatic factors and natural enemies. However, in case of chemical-based antibiosis, ingestion of plant toxins by the pest could also affect its predators or parasitoids. This should not be overlooked in the case of transgenic sorghums. The possibility of "dire straits " semio-chemicals being released when the plant is attacked by herbivores, and of those being used by natural enemies to locate their prey, should be further investigated in the case of sorghum. On the other hand, inter-cropping sorghum with cowpea increases parasitism of sorghum midge. Lastly, although it is not " rational pesticide use " per se, targeted preventive application of a systemic insecticide at sowing can be considered as an " integrated protection " measure, as it results in the direct or indirect control of a broad spectrum of pests.

Bibliographic Details

Main Author:	Ratnadass, Alain
Format:	conference_item biblioteca
Language:	fre
Published:	CIRAD
Subjects:	H10 - Ravageurs des plantes, Sorghum, lutte antiravageur, lutte intégrée, lutte biologique, résistance aux organismes nuisibles, http://aims.fao.org/aos/agrovoc/c_7244, http://aims.fao.org/aos/agrovoc/c_5726, http://aims.fao.org/aos/agrovoc/c_16187, http://aims.fao.org/aos/agrovoc/c_918, http://aims.fao.org/aos/agrovoc/c_5731,
Online Access:	http://agritrop.cirad.fr/478745/ http://agritrop.cirad.fr/478745/1/ID478745.pdf
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