Crops
Phytotoxicities
( phytotoxicity )
- Mainly affected organs : leaves, stems, fruits.
- Symptoms :
- Slow development of plants, total cessation of growth;
- Leaves slightly serrated, or more irregularly cut, filiform, blistered, more or less curled, corkscrews, crumpled etc., strongly thickened tissues (figures 1 to 3);
- Marbling, leaf yellowing (in spots, veins, periphery of leaf blade, interveinal veins; bleaching; greenish to livid tint, dull and / or tan appearance of 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, crowns, roots: swelling of their crown, rough roots on stems, etc. (figure 12);
- Fruits: oily lesions, more or less raised and / or corky, bursts (figure 13).
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- Cause (s) : Many pesticides used in agriculture can cause phytotoxicity to vegetables *. If more or less significant damage is sometimes associated with the use of insecticides or fungicides overdosed or used in mixture, it is those caused by herbicides which are the most frequent and the most damaging on vegetables, as on many species. cultivated.
- Diagnostic clues :
- Time to onset of symptoms : very short (almost immediate cause and effect relationship) (after the application of a pesticide on or near the crop - in the form of spray -; rather long (example of a poor previous crop, an annual or perennial crop weeded by a residual herbicide or poorly leached following a dry winter; perennial crop weeded for several years (this situation leading to an accumulation of product in the soil); addition of straw from 'a crop of weeded cereal or manure made from straw of the same type).
- Distribution of plants in the crop : product applied to the foliage (foliar herbicide, insecticide or fungicide overdosed or applied in bad conditions ...) (generalized and homogeneous distribution; at the beginning of the line; on one side of the plants); compound present in the soil (root herbicide, etc.) (generalized 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 ( at the right doses )?
- Did you follow the recommendations for use indicated on the packaging?
- Did you rinse your treatment equipment well?
- Do you take good care of your spraying equipment (cleaning, calibration)?
- Have you mixed incompatible products or too many products together?
- Did the applications take place under good conditions, particularly wind and temperature?
- Was the previous crop weeded with residual herbicides?
- Have herbicide treatments been carried out near your crop?
- Has straw 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 : the answer to one or more of the questions proposed above should allow you to implement the necessary measures and corrections.
* Remember that the use of a herbicide on or near a crop is never a completely trivial operation. The risks of causing phytotoxicity are by no means totally ruled out. Inhibitors of cell division, synthesis of fatty acids and amino acids as well as phytohormones are the most involved in leaf and root malformations in vegetables. Other pesticides, for example insecticides and fungicides, used alone or in mixture, substances such as fertilizers, can also be the source of phytotoxicity on these crops.
Differences in sensitivity between vegetables, and between varieties for the same species can appear in vegetables.
In addition, we also advise you to look at all the weeds still present in the crop or other plants cultivated nearby which may have suffered the same phytotoxicity and therefore express the same symptoms. If so, this partially confirms the hypothesis of a non-parasitic disease, and probably phytotoxicity if other information confirms this possibility.
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