Biology and Epidemiology

- Survival and sources of inoculum

                                                                   

Botrytis cinerea is a highly ubiquitous and polyphagous fungus able to remain in soil on most diverse vegetal debris and in several forms : conidia, mycelium, sclerotia. These saprophytic potentials allow it to survive easily on the organic matter. Botrytis cinerea is likely to attack and colonise many cultivated plants or weeds that contribute to its conservation and form its potential sources of inoculum.


- Penetration into the plant and invasion

Contaminations are often aerial involving conidia. They take place either directly through the cuticle, or through various injuries from senescent tissues, which are the ideal nutritive "bases" for the fungus development. This is particularly true for the corollas of flowers, which, when falling on the leaves provide a number of foliar contaminations ("dead-blossom leaf spot"). The fungus rapidly invades the tissues that rot in a few days.


- Sporulation and dissemination of the fungus (figure 1)

On all these hosts, like on the vegetal debris it produces mycelium, small flat sclerotia and many long, branched conidiophores producing spherical conidial ovoids thus ensuring its dissemination. The dissimination is done by the wind, rain and water splashes, and also by workers during the farming practices.


- Favourable conditions for the fungus development (figure 2)

Like many airborne fungi, Botrytis cinerea is particularly fond of humid environments. Relative humidity around 95 % and temperatures between 17 and 23°C are very favourable conditions commonly found in sheltered nurseries, but also in field during rainy periods or during sprinkler irrigation. Etiolated plants have many injuries and/or senescent tissues that are particularly vulnerable.