Omnivorous Phymatotrichopsis

(Duggar) Hennebert (1973)

 Texas root rot

- Distribution and damage

This fungus is rather subservient to semi-desert regions . It was detected fairly recently in avocado and mango orchards in semi-tropical areas. It is very polyphagous , affecting approximately 2,000 cultivated dicotyledons (cotton, alfalfa, vines, apple trees, etc.) or not. It is very rare on salad ; it has been reported primarily in the southern United States where it is considered a minor pathogen of lettuce.


- Symptoms

There is a rotting of the root system linked to its colonization by the mycelium of this fungus. It disrupts the sap currents; the leaves soon turn yellow and take on a bronze tint . The plants suddenly wither and die. Cottony mycelium and mycelial cords are present on the roots and in the soil around them and near the soil surface. There are also small sclerotia isolated or aggregated , more or less spherical, 1 to 2 mm in diameter, reddish brown when mature.


- Elements of biology

Phymatotrichopsis omnivora can be kept for several years in the soil thanks to its sclerotia which can be found up to more than 2 meters deep. It is also maintained on many other cultivated plants (vine, cotton, alfalfa, apple tree ...) or not. It settles first at the level of the cortex of the root then gains the vessels. It appreciates alkaline, calcareous soils containing low levels of organic matter. Its optimum temperature ranges between 28 and 30 ° C .


- Protection

It is a soil fungus that does not normally require special control methods in the context of growing lettuce. We can always increase the rate of organic matter in the soil and carry out crop rotations involving monocots. In addition, we can draw inspiration from the measures recommended to control the 2 Sclerotinia spp. .


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.