Crops
Yellowing, browning, blackening of the roots, sometimes with an alteration of the crown
The root system of the tomato can show various alterations when attacked or placed in poor conditions. Figures 1 to 4 provide a better understanding of the observation of an altered root system.
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| Figure 1 | Figure 2 |
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| Figure 3 | Figure 4 |
In the presence of such symptoms and many others, one can make many assumptions:
- either parasitic
- Colletotrichum coccodes
- Fusarium oxysporum f. sp. root-lycopersici
- Phytophthora spp.
- Pyrenochaeta lycopersici
- Pythium spp.
- Rhizoctonia solani
- Sclerotium rolfsii ( Athelia rolsii )
- either non-parasitic
- Root asphyxia
The majority of parasitic and non-parasitic diseases affecting tomato roots first cause their diffuse yellowing, then their browning (localized or generalized), and finally necrosis and the disappearance of numerous rootlets and roots. In the most severe cases, the root system is totally damaged and the vessels located at the taproot may turn yellow and brown slightly (Figure 4). The alterations sometimes evolve towards the neck and the base of the stem, causing more or less substantial cankers (see the section Various alterations of the neck and the portion of the stem close to the ground ). These symptoms can be observed both on seedlings in the nursery and on adult plants during cultivation. In the first case, they will be the cause of damping off.
In addition to the symptoms described above, a certain number of root pests induce other relatively characteristic alterations or form structures (signs) which make their identification easier. In many cases, laboratory tests will be essential to define their exact nature.