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Alternaria cichorii Nattrass (1937)

Alternaria leaf spot

- classification : Fungi, Ascomycota, Dothideomycetes, Pleosporomycetidae, Pleosporales, Pleosporaceae
- English name: Alternaria leaf spot

- Distribution and damage

This fungus is not currently considered a pathogen serious on salad , except perhaps on endive. It is reported in the USA, Japan, Argentina, Slovenia, Germany, Italy In France , although previously reported on escarole in the Pyrénées Orientales, it no longer seems to affect lettuce and chicory (figure 1).

- Symptoms

At spots first small and moist , gradually taking on a circular to oval shape. Concentric patterns are visible on the spots confusing with stemphyliosis (Figure 2). The central tissues, once necrotic, thin out (Figure 3).

- Elements of biology

This fungus has potential saprophytic significant . It is able to survive on plant debris in its mycelial form or through its conidia (figure 4). It would also remain on seeds . The contaminations occur mainly during climatic periods wet accompanied temperatures of between 20 and 25 ° C . The spores germinate on the leaf surface and enter the leaf blade directly through the cuticle, occasionally through the stomata. Subsequently, the fungus quickly colonizes the tissues. It sporulates on injured tissue, producing large, conidia isolated at the tip of club-shaped conidiophores. These are dispersed by the wind and the projections following a rain or an irrigation. Morning dews also favor its development, as well as humid climatic periods.

- Protection

The control of this fungus requires the use of healthy seeds . It is easily maintained on plant debris, so it will be essential to remove it after harvest. Some authors recommend weeding and crushing them quickly and rotating them with green manure. Sprinkler irrigations should be avoided or they will be carried out during the day in order to allow the vegetation to dry quickly. No fungicide is registered for this use on salads in France .

NB: As legislation on pesticides evolves very quickly, we advise you to consult the
e-phy site of the Ministry of Agriculture and Fisheries which is an online catalog of plant protection products and their uses, fertilizers and culture media approved in France . This also applies to all biological products based on microorganisms or natural substances.

Last change : 04/29/21
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Figure 4