Crops
Pyrenochaeta lycopercisi (Corky roots)
Pyrenochaeta lycopersici , fungus responsible for the disease of corky roots of tomatoes (c orky root; Pyrenochaeta corky root ), also attacks other Solanaceae, as well as various cucurbits, salads ... It is very present in market garden soils and affects both field crops and under cover. In the latter, it necessitates disinfection of the soil or the use of resistant rootstocks. Found in the past in certain soilless crops grown on pozzolana or peat, in greenhouses with uncovered soil, it has now almost disappeared from these crops.
As with all of its hosts, P. lycopersici causes rotting and the disappearance of many rootlets (Figure 1). Brown changes are also visible on young roots (brown root rot) (figure 2). The roots of larger section show corky and rather dry lesions (Figure 3). Of limited extension at first, they spread gradually and eventually surround the roots and form sleeves over several centimeters (Figure 4). These sometimes have the appearance of the bark of a tree. They can be very corky and have cracks. Remember that this fungus can produce fairly characteristic pycnidia adorned with black bristles around the ostiole (figures 5 and 6).
Its impact on tomatoes can be considerable in heavily contaminated soils. The limitation of the root system, as well as the numerous lesions present, have the consequence of reducing the vigor of the plants. Reversible wilting during the night can be recorded during hot periods and at the approach of harvest, possibly preceded or accompanied by chlorosis of the leaflets as well as premature leaf drop.
Note that there are resistant varieties and rootstocks.
P. lycopersici is reported in many countries under rather cold growing conditions; it is found in France in all production areas, in intensive crops as well as in the plots of amateur gardeners. It is not uncommon for it to be associated with other pests of the root such as Colletotrichum coccodes , Rhizoctonia solani , root-knot nematodes ... R. solani is sometimes associated with weakly suberized root systems on the surface: beware of confusion! (see chapter Yellowing of roots ).
It should be noted that another fungus, Rhizopycnis vagum spoiled DF Farr, was recently isolated from the roots of tomatoes grown in the open field in several plots in central and southern Italy. The diseased roots showed symptoms quite comparable to those caused by P. lycopersici , in particular suberization of the cortex. Previously, R. vagum was rather known to cause quite considerable damage to the roots of cucurbits, especially on melon and watermelon in the United States, Mexico, Guatemala, Honduras and more recently in Spain. Note that microsclerotia can be observed on the secondary roots of diseased plants. To our knowledge, it has never been observed on tomatoes and these other plants in France.
For further information on this fungus, you can consult the sheet Pyrenochaeta lycopersici fact .
As with all of its hosts, P. lycopersici causes rotting and the disappearance of many rootlets (Figure 1). Brown changes are also visible on young roots (brown root rot) (figure 2). The roots of larger section show corky and rather dry lesions (Figure 3). Of limited extension at first, they spread gradually and eventually surround the roots and form sleeves over several centimeters (Figure 4). These sometimes have the appearance of the bark of a tree. They can be very corky and have cracks. Remember that this fungus can produce fairly characteristic pycnidia adorned with black bristles around the ostiole (figures 5 and 6).
Its impact on tomatoes can be considerable in heavily contaminated soils. The limitation of the root system, as well as the numerous lesions present, have the consequence of reducing the vigor of the plants. Reversible wilting during the night can be recorded during hot periods and at the approach of harvest, possibly preceded or accompanied by chlorosis of the leaflets as well as premature leaf drop.
Note that there are resistant varieties and rootstocks.
P. lycopersici is reported in many countries under rather cold growing conditions; it is found in France in all production areas, in intensive crops as well as in the plots of amateur gardeners. It is not uncommon for it to be associated with other pests of the root such as Colletotrichum coccodes , Rhizoctonia solani , root-knot nematodes ... R. solani is sometimes associated with weakly suberized root systems on the surface: beware of confusion! (see chapter Yellowing of roots ).
It should be noted that another fungus, Rhizopycnis vagum spoiled DF Farr, was recently isolated from the roots of tomatoes grown in the open field in several plots in central and southern Italy. The diseased roots showed symptoms quite comparable to those caused by P. lycopersici , in particular suberization of the cortex. Previously, R. vagum was rather known to cause quite considerable damage to the roots of cucurbits, especially on melon and watermelon in the United States, Mexico, Guatemala, Honduras and more recently in Spain. Note that microsclerotia can be observed on the secondary roots of diseased plants. To our knowledge, it has never been observed on tomatoes and these other plants in France.
For further information on this fungus, you can consult the sheet Pyrenochaeta lycopersici fact .
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