Biology, epidemiology

The epidemiology of Fusarium oxysporum f. sp. lactucae understood is poorly . It may be thought to have many similarities with other specialized forms of Fusarium oxysporum , vascular parasites of various cultivated plants.


- Conservation, sources d'inoculum

This soil fungus is able to stay in the soil thanks to plant debris and its thick-walled, thick-walled chlamydospores. It certainly has saprophytic life skills that allow it to colonize and survive on various organic compounds. The other plants that can house it, whether grown or not, are not known. It attacks lettuce ( Lactuca sativa ) and mash ( Valerianella locusta ). In lettuce, the butter, iceberg, oak leaf, batavia, and roman types are susceptible to this fusariosis.


- Penetration, invasion

After germination of its chlamydospores, this Fusarium must be able to penetrate lettuce either through natural wounds, such as those present at the point of emission of secondary roots, or through various alterations. Once in the plant, it reaches the vessels and invades them with its mycelium. As in the case of verticillium wilt, plants can respond to this vascular invasion by forming gum or tyloses which will prevent its progression, but which also contribute to wilting the plants.

- Sporulation, dissemination

This fungus produces chlamydospores and microconidia (Figure 1) in vessels and on colonized tissues. Its dissemination takes place through plants, agricultural equipment soiled by contaminated soil, water and plant debris. Soil dust containing chlamydospores is easily disseminated by air currents as well as by splashing water. It would also be transmitted by seeds as has been observed in Italy.


- Conditions favorable to its development

Fusarium oxysporum f. sp. lactucae prefers high temperatures instead. Its thermal optimum would be around 28 ° C. In the US, this disease is mostly seen in the fall.