Ralstonia solanacearum , bacterium responsible for bacterial wilt , polyphagous and better known by its synonym Pseudomonas solanacearum , is particularly feared in hot production areas, especially tropical to sub-tropical, both in open fields and under cover. In this latter context, it seems to be able to appear in more northern production areas, as was the case occasionally in a few European tomato greenhouses, especially after it had developed on potatoes.

 

Symptoms can appear very early on in tomato seedlings. Young leaves wither more or less completely (Figure 1), and the leaflets tend to curve upward (epinasty, Figure 2). Brownish interveinal necrotic lesions are sometimes visible on some leaflets. Vascular tissue also turns yellow and brown quite early (Figures 3 and 4).
 

Quite comparable symptoms are observed in adult plants. Here again, sudden wilting and vascular browning characterize this bacteriosis. The pith and cortex of the stem show more or less extensive brown lesions when conditions are particularly favorable for the development of Ralstonia solanacearum .
 

A relatively simple test to carry out is often recommended to differentiate this bacteriosis from vascular diseases caused by fungi. It consists of cutting transversely the stem of an infected plant and immersing it in water: if, in the following minutes, a milky trickle, made up of innumerable bacteria, begins to exude from the vessels, it is well of a bacterial disease.

For further information on this fungus, you can consult the sheet Ralstonia solanacearum fact .