Crops
Classic symptoms of Rhizoctonia on Cucurbitaceae
- Organs attacked :
| Fruits | Rod | Collar | Roots |
- Symptoms :
- Damping off , occurring both pre- and post-emergence of seedlings, yellowish to more or less dark brown lesions on the roots and hypocotyl. Eventually, a canker can encircle more or less the part of the stem located at ground or substrate level (figure 1), causing the seedlings to collapse and die.
- Root alterations on adult plants, with yellowing, browning and disappearance of small feeder roots, and yellowing, browning of the cortex which may become soft or superficially cortex. Possible root rot (Figures 1 and 2).
- The lower part of the stem present in the ground or nearby can also be affected, the tissues of the cortex taking on a grey-green to brown color, and progressively rotting (figures 3 and 4).
- Cankered lesions on certain portions of stems, but especially the part of fruit in contact with the ground. More or less superficial and circular lesions on fruits, tawny to brownish in color, showing small bursts (figures 5 and 6).
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- Signs : several fungal structures make it possible to confirm the presence of R. solani on or near the altered tissues:
- often discrete whitish to brown filaments running on the germinated seeds, the roots, along the stem and on the fruits (figures 7 and 8);
- more rarely ill-defined, brown masses, visible locally on the damaged tissues (pseudo-sclerotia).
- Confusions possibles : Oomycètes ( Pythium et Phytophthora spp.), Sclerotium rolfsii , etc.
- Affected production areas :
| Mayotte | Reunion | Guadeloupe | New Caledonia |
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7
Figure 8