Interaction insectes-maladies : cas du sorgho

This paper reviews sorghum insect pests whose damage symptoms can be mistaken for those of pathogen infection, and those who are responsible for transmitting diseases to sorghum. Late shoot fly damage provokes a leaf symptom similar to that of a bacterial disease. Stem borer tunneling may prevent grain filling, resulting in panicle chaffiness which on the other hand can also be due to a disease like anthracnose. More than 800 viruses pathogenic to plants have been recorded worldwide, most of them being insect-borne. Most viral disease-transmitting insects are Homoptera (Hemiptera) with sucking mouth parts. There are two modes of transmission. In the circulating mode, the virus crosses the insect gut cell barrier and enters into the hemolymph, then migrates to the salivary glands. In the non circulating mode, which is the most common, viruses are confined to the stylets or the esophagus. Several leafhopper and planthopper species are to be found in West and Central Africa, but they are not responsible for significant damage to the sorghum crop (unlike in India), although they might be associated with viruses (e.g. Peregrinus maidis). Aphids do not pose problem except during dry spells. In West and Central Africa, Melanaphis sacchari attacks old leaves, while Rhopalosiphum maidis and Schizaphis graminum prefer young leaves. All three species can serve as disease transmitting agents. Leaf-feeding punctures by spittle-bug (Locris spp. ou Poophilus spp.) adults and nymphs result in leaf blotching, due to the transmission of a bacterium. It might also be the case for the leafhopper species Neolimnus aegypticus. Panicle attack by the sorghum midge can also result in total abortion. However, such chaffiness can be distinguished from those due to other causes (e.g. stem borers or panicle anthracnose). Feeding and egg-laying punctures by sorghum panicle-feeding bugs (particularly Eurystylus oldi), facilitate secondary infection by grain molds.

Bibliographic Details

Main Author:	Ratnadass, Alain
Format:	conference_item biblioteca
Language:	fre
Published:	CIRAD
Subjects:	H10 - Ravageurs des plantes, Sorghum, insecte nuisible, dégât, transmission des maladies, vecteur de maladie, maladie transmise par vecteur, http://aims.fao.org/aos/agrovoc/c_7244, http://aims.fao.org/aos/agrovoc/c_5729, http://aims.fao.org/aos/agrovoc/c_26768, http://aims.fao.org/aos/agrovoc/c_2329, http://aims.fao.org/aos/agrovoc/c_8164, http://aims.fao.org/aos/agrovoc/c_34142,
Online Access:	http://agritrop.cirad.fr/478739/ http://agritrop.cirad.fr/478739/1/ID478739.pdf
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