Biology, epidemiology

The biology of Ilyonectria liriodendri understood associated with Blackfoot disease is not yet well in grapevine. On the other hand, it has been studied a little more on other plants such as various fruit trees and several herbaceous plants on which these fungi are sometimes damaging.

• Conservation, sources d'inoculum

 It is assumed that these fungal species live in the latent state in the soil and maintain themselves there without difficulty, thanks in particular to their chlamydospores which are conservation structures. They are also capable of maintaining themselves on numerous cultivated or non-cultivated hosts which ensure their perenniality in or near the plots. 

• Penetration, inv asion

 The infections certainly take place via the rootstock, via the heel or various wounds present on the roots. Once in place, the mycelial filaments progress through the woody tissue causing characteristic brown to black necrosis.

• Sporulation, dissemination

Once the root tissues are invaded, they probably produce their conidia and chlamydospores in greater or lesser quantities. The former will largely contribute to the spread of this disease. It should be noted that contaminated plants, recycled substrates, equipment and tillage machinery carrying soil particles can also contribute.

• Conditions favorable to their development

These different fungi, considered to be weak parasites, seem well adapted to asphyxiating, poorly structured, compacted soils, often resulting from insufficient soil preparation before planting, a lack of land development work ... Rainfall in winter or in early spring contributes to the water saturation of compacted soils, especially in the lower parts of plots and in wetlands. Young plants placed in such conditions are weakened and therefore more susceptible to attack by these fungi. It is certainly the same in hot climates and in compacted soils, when localized irrigation is used continuously, causing a humid and asphyxiating bulb at the foot of young vine plants.

The high heat of summer can play an important role in the manifestation of symptoms on herbaceous vegetation. Indeed, the strong evaporation generated by the high temperatures would not be compensated by a sufficient influx of water, this because of a deficient root system. It follows quite quickly a partial or total drying out of the plant.

It should be noted that the surveys carried out in particular in Champagne (Descottes et al. , 1994) did not show any difference in sensitivity to black foot between rootstocks.