Cercospora longissima

Cercospora leaf spot

- Distribution and damage

This fungus is rampant not serious in many countries of the world (USA, India, Iran ...); it is especially damaging in tropical areas , particularly in a few countries in Africa (Somalia), Asia (Japan, Hong Kong, etc.) and in Central America. To our knowledge, it has never been reported in France in recent decades. On the other hand, it seems to be present in Italy.


- Symptoms

Small, spots damp, brown surrounded by a pale green to yellow halo (Figures 1 and 2). They extend and form brown alterations circumscribed by the veins (figures 3 and 4); the tissues are gradually necrotic. They can merge (Figures 5 and 6); under these conditions, portions of leaves are completely necrotic (figure 7). They are sometimes covered with a greyish to buff down consisting of conidiophores and hyaline conidia (figures 8 and 9), cylindrical, with 1 to 18 partitions.

These spots are found especially on old leaves, it is also possible to observe them on the main vein (figure 10).

- Elements of biology

This fungus is maintained in the soil on plant debris . It would also be preserved on seeds and on a number of hosts, in particular wild lettuce : Lactuca serriola . It develops during humid periods, in the presence of free water on the leaves. Conidia (Figures 6 and 7) present on the surface of the leaf blade germinate and enter through the stomata. He appreciates temperatures close to 25 ° C. Under these conditions, it quickly invades the tissues: symptoms are already visible after 3 days and it sporulates 5 days after contamination. The spores formed are released as soon as the humidity drops. They are also disseminated by splashing after rains or irrigation.


- Protection

In the tropical and subtropical countries particularly affected, preventive or stopping treatments can be carried out with approved fungicides. In the French overseas departments and territories, as in France, no product is approved for this use .

Care will be taken to remove plant debris and carry out crop rotations . Future crops should be planted in disease-free, well-drained plots, limiting plant density. We will use the healthy seeds . There are no resistant varieties .


NB: The legislation on pesticides evolving 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.