Ralstonia solanacearum (Smith, 1896) Yabuuchi et al., 1996
Bacterial wilt
General
bacterium present mainly in tropical, semi-tropical and warm temperate regions, is severe in many countries of Asia (China, Japan, Malaysia, Phillipines, Pakistan, Thailand, Vietnam, India), America (States States, Mexico, Brazil, Argentina…) and Africa (both in the north and in the south). It is now installed in Europe.
Very polyphagous, capable of infecting many plants, more than 250 plant species belonging to at least 50 botanical families.
Several strains are known allowing to consider the existence of a complex of species belonging to 4 phylotypes of different geographical origins.
Observed in the open field as well as under shelters.
Sensitive botanical family (s):
Solanacées
Cucurbits
Biology
Conservation : remains in the soil in a saprophytic state on organic matter for several years up to 30 cm deep, and in irrigation water from canals (Holland), rivers (Scotland), ponds or various water supplies. Infects and multiplies on various cultivated plants (sunflower, groundnut, tobacco, pepper, cassava, potato, banana) or weeds ( Amaranthus spinosus, Chenopodium album, Cyperus rotundus, Erechtites valerianaefolia, Euphorbia hirta, Hydrocotyle ranunculoides, Malva sp., Physalis minima, Polygonum pensylvanicum, Rumex dentatus, Solanum nigrum, S. dulcamara, Vicia sp., etc.) not always showing wilting.
Infection : penetrates the roots either at the level of the emergence point of the lateral secondary roots, or through various injuries caused by tools, punctures and alterations caused by root-knot nematodes, insect bites, etc.
Development - Dissemination : once in the cortex, the bacterium rapidly reaches the vessels which it invades by multiplying; found in the xylem and in the final phase in the phloem. Dispersed in the soil by reaching the roots of neighboring plants, but also through runoff water, contaminated plants and agricultural tools, workers during disbudding and leaf stripping.
Favorable conditions :
likes tropical temperatures, between 25 and 35°C, moist and heavy soils, with a moderate pH,
the contribution of a highly nitrogenous manure would contribute to sensitize the plants,
parasitism favored by attacks of root-knot nematodes.
Protection
Build nurseries in plots that have not grown susceptible crops . Preferably produce the seedlings in soil , with a healthy substrate. The plants purchased must have been produced under conditions avoiding any risk of contamination.
No method of protection can effectively control Ralstonia solanacearum during cultivation.
Carry out crop rotations , even if this measure is not always easy to manage given its very many potential hosts. Sugar cane, two years of Digitaria grassland, green manure sorghum, etc. make it possible to sanitize the soil more or less.
Think about integrating in the rotation plants that are not very sensitive, even resistant (fescue, cotton, soya, grasses, maize, rice, etc.).
Soil disinfection does not seem very effective, regardless of the technical option chosen.
Crops
