CropsBiology, epidemiology
Unlike Phomopsis viticola , Elsinoë ampelina performs several biological cycles per year on the plant cover of the vine. The duration of a cycle varies according to climatic conditions; in very favorable humid periods, it can be carried out in less than a week.
- Storage and sources of inoculum
Elsinoë ampelina is easily preserved from one year to the next on the vine, mainly on the twigs with canker lesions (figure 1), the branches, the pruning left on the ground, the grape berries which have fallen on the latter. ... This fungus would persist there for more than 3 to 5 years in the form of stromas developing on diseased organs. It would also persist on other species belonging to the genus Vitis , for example on V. labrusca and V. rupestris , and on Rubus fruticosus and R. idaeus .
- Penetration and invasion
In the spring, the stromas which have become spore-bearing (presence of acervuli) following wet periods are at the origin of conidia ensuring the primary contaminations on young particularly sensitive tissues. In the presence of free water on the plant, the spores germinate between 2 and 32 ° C. The filaments formed directly penetrate the cuticle. Intercellular mycelium invades the tissues and disorganizes them.
Note that contaminations could occur thanks to ascospores from ascostroma formed last season on diseased organs.
Note that contaminations could occur thanks to ascospores from ascostroma formed last season on diseased organs.
- Sporulation and dissemination
Once the tissues are invaded, conidia form on the subcuticular mycelium and subsequently in larger quantities on the formed stromas (acervuli) (Figures 2 and 3). These conidia (figure 4) ensure the dispersion of the disease following rains, splashing, during thunderstorms associated with hail, but also through unspecified “passive vectors” insects.
Asci would also be produced inside ascostromas with several compartments (multilocular). Each of them would contain 8 brown to black multicellular ascospores which are also infectious.
Asci would also be produced inside ascostromas with several compartments (multilocular). Each of them would contain 8 brown to black multicellular ascospores which are also infectious.
- Conditions favorable to its development
E. ampelina appreciates humid conditions, rains and periods of dew. Anthracnose is particularly prevalent in sheltered lowlands. On the other hand, airy, well exposed and sunny plots are less affected. Its thermal optimum is between 24 and 26 ° C. Hot and dry climatic periods are not conducive to this disease.
All the grape varieties are sensitive, some particularly: Alicante-Bouschet, Cabernet, Grenache, Malbec, Merlot. Young tissues are particularly sensitive. Older leaves seem less receptive. The bunch is sensitive from flowering to veraison.
Figure 1
Figure 2
Figure 3
Figure 4