Crops
Symptoms on roots and collar
In tropical and equatorial zones, Oomycetes are likely to cause symptoms on several vegetables throughout their development cycle and on several of their telluric organs, whether roots or crowns, with of course leaf repercussions.
- Organs attacked :
| Leaves | Rod | Vessels |
| Collar | Roots |
- Symptoms :
- Damping -off (absence of germination, moist and brown lesions on the roots and/or collar (figure 1); wilting, collapse and death of the seedlings.
- Browning and root rot in soil and above ground ( root rot ) (figures 1 to 5) sometimes localized at the end of the roots. Browning, decomposition and disappearance of rootlets and small diameter roots. The cortex of the main roots and taproot also ends up rotting more or less locally. The vascular tissues facing the altered areas end up turning brown.
- Moist lesions gradually encircling the neck (figures 6 to 9)
- Leaf yellowing and wilting more or less marked and reversible (figures 10 to 13).
- Sometimes poor plant growth and reduced fruit size.
- Apical necrosis ( blossom end rot ) on the fruits of certain bouquets.
- Signs : fluffy white and airy mycelial felt covering more or less the lesions in humid conditions. Sporangia, oospores, chlamydospores can be observed using a light microscope in degraded tissues.
- Confusions possibles : Rhizoctonia solani , Sclerotium rolfsii , etc.
- Affected production areas :
| Mayotte | Reunion | Guyana |
| Guadeloupe | New Caledonia |
Figure 1
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Figure 5
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Figure 9
Figure 10
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Figure 13