Biology, epidemiology

• Conservation, source d'inoculum

Setophoma terrestris thought to is be preserved in soil and on plant debris for several years in the form of chlamydospores which constitute the primary inoculum. It was found up to 45 cm deep.
It can also be maintained in a plot thanks to many alternative hosts, whether or not cultivated: tomato (associated with corky roots), pepper, eggplant, cauliflower, carrot, spinach, soybean, peas, but also cereals (millet, oats , barley, wheat, corn). The fungus is also present in the rhizosphere of various herbaceous and woody plants.
The role played by pycnidia, both in the conservation and dissemination of this fungus does not seem clearly defined.

• Penetration, invasion

chlamydospores would S. terrestris germinate in the soil and mycelial hyphae would gain and penetrate the roots, gradually invading the cortex and breaking it down with various enzymes. A comparable parasitic process could take place from conidia from pycnidia.

• Sporulation, dissemination

The fungus produces tiny, globular, black structures (pycnidia) (Figure 1) in the epidermal and cortical cells of infected roots. Unicellular and hyaline conidia (figure 2) are released from them including; their role in the epidemic cycle of the disease has not been studied. Note that contaminated plants (especially onion) can ensure the spread of the disease, and infestation of new plots. It is the same for tillage implements moving from one infested plot to another healthy one. Runoffs of water and soil particles also contribute.

• Conditions favorable to its development 

This mushroom especially appreciates rather mild temperatures. It grows best around 26 ° C, but it can take place between 16 and 32 ° C.
Soil moisture does not appear to be a factor limiting its growth, since it can affect a wide range of soil moisture percentages. It would still be more damaging in heavy and poorly drained soils with low organic matter content.

The presence of other soil pests, various abiotic stresses weakening the roots, favor its parasitism on its hosts.