Biology, epidemiology

Let us recall in the preamble that the epidemiology of Botryosphaeriaceae on vines is still relatively poorly understood.

• Storage and source of inoculum

 The various fungi of this botanical family are conserved on and in vine wood, mainly in the form of pycnidia and / or perithecia when the teleomorph is formed. Indeed, these structures are present on bark, diseased parts of wood, as well as on cut wood debris left on the ground. It should be noted that these fungi have very significant saprophytic potentials allowing them to easily survive on many substrates and various hosts.

Vine plants can be sources of inoculum.
Remember that some of these ascomycetes are also opportunistic pathogens on a good number of woody species such as apple, peach, pistachio, kiwi ... vineyard plots. Although the role of these “alternative” hosts as sources of primary inoculum cannot be ruled out, it will need to be clarified and quantified.

• Sporulation, dissemination

During humid and rainy periods, spores are produced in the pycnidia and expelled in the form of gelatinous cirrhia; they come after polluting the aerial organs of the vine following water projection over short distances. For example in the case of Neofusicoccum spp., This distance would not exceed 2 meters. These pycniospores (Figure 1) therefore constitute the primary inoculum.

Remember that these fungi can be disseminated by vine plants following contamination in nurseries, several species have thus been isolated from this material or from mother plants: D. seriata , N. parvum , B. dothidea , L. theobromae , N. mediterraneum , N. vitifusiforme

• Plant penetration and host invasion

Botryosphaeriaceae mainly penetrate the vine through wounds made during pruning or grafting. Pruning wounds are receptive to these fungi for many days, or even months, depending on the time of year and the geographic area of ​​production. Subsequently they colonize the wood. They remain there in the state of endophyte or latent pathogens, or develop their parasitism as a result of biotic or abiotic stresses which are still poorly understood.

• Favorable conditions

Climatic conditions clearly affect the incidence, distribution and epidemiology of these fungi.

Sporulation, and in particular spore dispersal, is strongly influenced by relative humidity, but especially by rain and sprinkler irrigation. These components of the Botryosphaeriaceae life cycle are less influenced by temperature. Sporulation can occur both during winter and during periods. It would be reduced or even zero at 0 ° C and below. The receptivity of sizing wounds would decrease with increasing temperature, the latter favorably influencing wound healing. In addition, temperature seems to play a positive role on the geographical distribution of the different species, as well as on their pathogenicity.