Biology, epidemiology

Xylophilus ampelinus  is a gram - bacterium which primarily attacks the vine, affecting its aerial organs and invading its vascular system.

• Conservation, sources d'inoculum

 It can be stored during the winter on and in the vines, at the base of infected shoots, and on and in pruning left in or near plots. It is on and in this plant material that the bacteria multiply during winter and spring, thus generating various sources of potential inoculum. It should be noted that the "tears" in spring can harbor a large number of bacterial cells which are the source of contamination of buds, for example, but also of other aerial organs of the vine.

• Penetration, invasion

This bacteria can infect vines in several ways:
- by the stomata of the leaves which constitute natural openings;
- by recent pruning wounds and wounds produced in particular during cultivation operations carried out with one or more soiled tools;
- via the buds;
- more rarely by the roots in the absence of rootstock.

• Multiplication, dissemination

Once in place in the tissues, X. ampelinus colonizes and multiplies there, locally resulting in their destruction. It gains the vascular system of this vitaceae, in particular the xylem in which the raw sap circulates.

Considering that the bacterium can be epiphytic and present in the vines, its dissemination can take place in several ways:
- by contaminated plant material: plants, rootstocks and scions;
- by the tools used for pre-pruning, pruning, topping, mechanically harvesting the vine;
- during rains or sprinkler irrigation causing splashing, mist, micro-droplets harboring many bacterial cells. These present in weeping, exuded from cankers or leaf spots are dispersed by the wind sometimes over long distances, and by runoff;
- inside the vines by the sap flow ...

• Conditions favorable to its development

Like the majority of phytopathogenic bacteria, X. ampelinus likes humid and rainy periods occurring in spring and summer. On the other hand, bacterial necrosis is greatly reduced in times of drought. Temperature does not seem to be a limiting factor in the development of this bacterium, except when it exceeds 30 ° C. The immersion of the vineyard plots would be rather conducive to its parasitism.

It should be remembered that it is favored by the most diverse injuries, linked to cultivation operations, frost and hail, but also to parasitic attacks. Excess nitrogenous and organic manures, the use of vigorous rootstocks would influence it favorably.

In addition, the vine is particularly sensitive to this bacteriosis at the beginning of its vegetative cycle, from bud break up to the 5-6 leaf stage. The grape varieties do not have the same sensitivity to bacterial necrosis, some of them seem particularly sensitive such as alicante, bouschet, clairette rose and clairette blanche, colombard, gamay N, grenache, sémillon, ugni blanc ... are much less like aramon, merlot, syrah.