Chemical control : how to be successful in herbicide spraying

• Choose the best product according to the weed species to be controlled and the cultural operations.
• Respect the application dose; often, farmers have the tendency to reduce the amount of the products so as to reduce the costs and the risks of phytotoxicity ; the treatments are not always done in a regular way on the crop rows, creating zones where the product is under-rated, therefore inefficient, and zones where the product is over-rated, therefore phytotoxic.
• Intervene at the recommended period; for example, pre-emergent products are not to be applied on plants already germinated; herbicides for already grown up plants are spread according to the development stage of the weeds, in particular if they have a contact action, they will be more efficient particularly when the targeted plants are young ; in rice cultivation, the propanil which acts by contact, must be applied on very young plants (3-4 leaves stage) to be efficient on Poaceae.
• Use equipment adapted for herbicide spraying, equipped with flat jet nozzles (flatfan or mirror nozzles), while we often see people using equipment for insecticide spraying, equipped with conical jet nozzles, or motorised atomizers; furthermore, a particular follow-up must be done by spraying supervisors for the maintenance after use (rinsing, cleaning, ...).
• Check regularly the calibration of the equipment, so as to correct the defects (nozzles wearing) or the operators’ failings ; the quantity of mixture spread per hectare must be determined so as to calculate the dilution.
• Prepare conveniently the mixture so as to avoid blocking the nozzles , it is essential to use water of good quality, to use a filter and to make sure the mixture is homogeneous.
• Have a good mastery of the application technique : the distribution over the treated surface must be perfectly homogeneous, imposing therefore a regular debit of the equipment and of the travel speed.
• Do not neglect the instructions for use and the toxicity risks.
• The use of pre-emergent herbicides has consequences on the rest of the cultural practices ; for example, it is impossible to work the soil after spreading such an herbicide.

In the case of mixed or associated cropping, the selectivity of the herbicides with respect to the crops in association is essential. It will then be necessary, among herbicides that can be used on one or another culture to check if at least one is very selective on each of the crops to the dosage used according to the period of application and the stage of development of the cultivated crops.

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