Biology, epidemiology

• Conservation, sources d'inoculum
  

Alternaria tomatophila peut se conserver period plusieurs années à la surface des graines de tomate, in sol et les debris waste, grâce à son mycélium mélanisé , ses conidies and her chlamydospores . In some parts of the world, it would also be able to sustain itself from season to season on other nightshades * such as potatoes, eggplant, peppers, black morel ( Solanum nigrum ), S. carolinense , S. pseudocapsicum .

• Penetration and invasion

Once multicellular spores come into contact with the cells of tomato, their germination can occur in 2 hours in water at temperatures between 6 and 34 ° C . This fungus enters the tissues either directly through the cuticle, or through the stomata or various wounds. It quickly invades the tissues, and lesions begin to be visible 2 to 3 days after the first contaminations.
 

• Sporulation and dissemination

On colonized tissues, if the climatic conditions are humid , A. tomatophila does not take long to produce short conidiophores (figure 1) surmounted by long conidia multicellular club-shaped (figure 2). These are disseminated by the wind , but also by rain and as a result of sprinkling. The presence of water is necessary for sporulation to take place. Seeds, workers, especially through their tools, also contribute to the spread of early blight. The conidia produced ensure secondary contaminations and subsequently several parasitic cycles may take place in the culture.

• Conditions favorable to its development

This blight is favored by high humidities and temperatures between 18 ° C and 30 ° C . Dews, continuous low rainfall (5 mm) or sprinkler irrigations are sufficient for its extension, but they must be repeated for the disease to progress rapidly. Plants that are stressed, poorly smoked or heavily loaded with fruit would be more sensitive. The disease never takes on an explosive character, but gradually increases over time as the plants age, and becomes serious at the end of the season. Under favorable conditions, symptoms are quite noticeable within 5-7 days .

* It may be worth reconsidering potential hosts of A. tomatophila which are not necessarily those of A. solani. It is indeed possible that these two species have somewhat different host spectra.