Crops
Phytotoxicities
(phytotoxicity)
- Susceptible botanical family(s)
| All families |
- Production areas affected :
| Mayotte | Reunion | Guyana |
| Guadeloupe | Martinique | New Caledonia |
| French Polynesia |
- Mainly affected organs :
| Leaves | Fruits |
| rods | Snares |
- Symptoms :
- slowed development of plants, total cessation of growth;
- leaves slightly serrated, or more irregularly cut, filiform, blistered, more or less rolled up, corkscrew, crumpled etc., tissues strongly thickened (figures 1 to 3);
- mottling, leaf yellowing (in spots, veins, on the periphery of the blade, interveinals; whitening; greenish to livid tint, dull and/or bronzed appearance of the leaf blade) (figures 4 to 8); lesions, more or less extensive chlorotic spots, rapidly becoming necrotic (figure 9); wilting and drying out (figures 10 and 11);
- twigs, collar, roots: swelling of their collar, root outlines on stems, etc. (Figure 12);
- fruits: oily lesions, more or less raised and/or corky, bursting (figure 13).
- Cause(s) : Many of the pesticides used in agriculture can cause phytotoxicity on vegetables*. If more or less significant damage is sometimes associated with the use of insecticides or fungicides over-dosed or used in mixture, it is those caused by herbicides that are the most frequent and the most damaging on vegetables, as on many cultivated species.
- Diagnostic clues :
- Time to onset of symptoms : very short (almost immediate causal relationship) (after the application of a pesticide on the crop or nearby - in the form of spray -); quite long (example of a bad previous crop, an annual or perennial crop weeded with a persistent or poorly leached herbicide following a dry winter; perennial crop weeded for several years (this situation leading to an accumulation of product in the soil); straw from a crop of weeded cereal or manure made from straw of the same nature).
- Distribution of plants in the crop : product applied to the foliage (foliar herbicide, insecticide or fungicide over-dosed or applied in bad conditions...) (generalized and homogeneous distribution; at the start of the line; on one side of the plants) ; compound present in the soil (root herbicide, etc.) (widespread and more or less homogeneous distribution; randomly over the entire plot).
- Possible confusion :
- Ask the right questions :
- Have you used pesticides during cultivation and especially recently?
- Did you use the right product(s), at the right doses ?
- Did you follow the recommendations for use indicated on the packaging?
- Have you rinsed your treatment equipment well?
- Do you properly maintain your spraying equipment (cleaning, calibration)?
- Have you mixed incompatible products with each other or too many products together?
- Did the applications take place in good conditions, wind and temperature in particular?
- Was the previous crop weeded with residual herbicides?
- Have herbicide treatments been carried out near your crop?
- Has straw-based manure been added to the crop?
- Are you sure of the quality of the irrigation water? Could it not have been polluted by a herbicide in particular?
- Remedies :
* Remember that the use of a herbicide on or near a crop is never a completely harmless operation. The risks of causing phytotoxicity are by no means completely ruled out. Inhibitors of cell division, fatty acid and amino acid synthesis as well as phytohormones are the most implicated in leaf and root malformations in vegetables. Other pesticides, for example insecticides and fungicides, used alone or in combination, substances such as fertilizers, can also be the cause of phytotoxicity on these crops.
Differences in susceptibility between vegetables, and between varieties for the same species can occur in vegetables.
In addition, we also advise you to look at all the weeds still present in the crop or other plants grown nearby that may have suffered the same phytotoxicity and therefore expressed the same symptoms. If so, this partially confirms the hypothesis of a non-parasitic disease, and probably of phytotoxicity if other information confirms this possibility.
Figure 1
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Figure 12
Figure 13