Comparaison de la dérive pour deux types de pulvérisateurs utilisés en production cotonnière au Bénin

Description of the subject. Increasing use of plant protection products and a continuous change in their active substances during recent years raise crucial questions regarding environmental pollution, particularly for aquatic ecosystems in the cotton production area. Objectives. Field trials were carried out (in Batran, province of Banikoara) in conditions close to those of local practices. The objective was to quantify and compare the drift generated during spraying both with a centrifugal cane and a backpack sprayer, which are the two most popular types of sprayer used in the cotton area of Benin. Method. A mixture of water and tartrazine (a food grade dye) was prepared for spraying at 20 g.l ^-1 . Ten spraying trials were conducted, at two heights (1 m and 1.5 m), according to a pre-established protocol validated by an initial trial carried out with water-sensitive paper. Fifty-four white cotton patches were placed at the predetermined heights and distances from the emission point. After each trial, the patches were collected and the tartrazine concentrations (in µg.cm ^-2 ) were determined after extraction in water with a colorimeter. The percentages of drift were then calculated from the quantities of tartrazine recovered. Results. Results showed that, in the same weather conditions (35° ± 1 °C; R.H.: 64 + 4%; wind speed stable around 3 m.s ^-1 ), spraying at the height of 1.5 m with the centrifugal cane generated drift percentages significantly higher than those generated by spraying at the height of 1 m with the backpack sprayer. Conclusions. Droplets of mixture were observed at up to 16 m, whichever sprayer was used.