STUDY OF THE EFFECT OF TWO SURFACTANTS ON SPRAY RETENTION BY BARLEY LEAVES

Poster (2013, February 08)

Surfactants are nowadays very useful additives to improve the effectiveness of phytosanitary treatments. They contribute to change the types of impact and thus the amount of spray retained by the leaves ... [more ▼]

Surfactants are nowadays very useful additives to improve the effectiveness of phytosanitary treatments. They contribute to change the types of impact and thus the amount of spray retained by the leaves of the treated plant. We performed tests of retention on whole barley plants on BBCH 12 stage and small pieces of barley leaves at the same stage of growth. Spraying was done in three ways: water without surfactant, water with Break-Thru S240 and water with Li700. The three slurries of fluorescein contained in an amount of 0.2 g / l. Fluorescein retained by the leaves in both cases is then measured by a spectrofluoremeter. The retention tests on whole plants show that it is tripled by the first surfactant and doubled by the second. By cons on small pieces of barley leaves, the amount was increased by the use of surfactants but not to the same scale. This study concluded that the use of surfactants in spray pesticides may increase the amount of retention as a function of leaf area and the surfactant used. [less ▲]

THE EFFECT OF LEAF ORIENTATION ON SPRAY RETENTION ON BLACKGRASS

Conference (2012, July)

Spray application efficiency depends on the pesticide application method as well as target properties. A wide range of drop impact angles exists during the spray application process because of drop ... [more ▼]

Spray application efficiency depends on the pesticide application method as well as target properties. A wide range of drop impact angles exists during the spray application process because of drop trajectory and the variability of the leaf orientation. As the effect of impact angle on retention is still poorly documented, laboratory studies were conducted to highlight the effect of leaf orientation on drop impact outcomes. Measurements were performed with a high-speed camera coupled with a retro-LED lighting. Size and velocity of the drop were extracted by image analysis. Drop impact types were determined by the operator. Drops were produced with a flat-fan nozzle mounted on a movable ramp. Excised blackgrass [Alopecurus myosuroides HUDS. (ALOMY)] leaves were stretched between two parts of a U-shaped support. A surfactant (Break-Thru® S240) was sprayed to highlight the effect of mixture surface tension. The whole device was tilted from 0 to 90°. Relative volume proportions were computed within of an energy scale divided into 11 classes. These proportions have been weighted by an average volume distribution and the results were summed for all energy classes to obtain the total volume proportions for each impact outcomes and for all leaf angles. For distilled water (high surface tension) the increase of rebound proportion with the increase of drop impact angle is highlighted. For surfactant (lower surface tension), it results in an increase of drop fragmentation in Cassie-Baxter wetting regime. To be statistically representative, bigger drop samples should be used. [less ▲]

Effets de la variation de pression sur la qualité des jets de pulvérisation et leur contribution aux risques de pollution environnementale.

Conference (2011, November 16)

Un traitement phytosanitaire s’effectue en visant un triple objectif: être efficace, ne pas mettre en danger l’opérateur et protéger l’environnement. (MOREAU et al., 1997). La quantité de pesticides ... [more ▼]

Un traitement phytosanitaire s’effectue en visant un triple objectif: être efficace, ne pas mettre en danger l’opérateur et protéger l’environnement. (MOREAU et al., 1997). La quantité de pesticides appliquée chaque année est estimée à 2.5 millions de tonnes mais la part de cette quantité qui entre en contact avec les organismes indésirables est très faible. La plupart des chercheurs l’évaluent à moins de 1% (ELAISSAOUI et al., 2004), ce qui veut dire que 99% des substances chimiques entre en contact avec le milieu environnant d’une manière non ciblé et sont potentiellement dangereux pour les écosystèmes entiers. D'après FAGOT et LARRAT (2002), la pression a un effet direct sur la répartition du produit et le volume de bouillie appliqué par son action sur la taille des gouttelettes et sur l'angle du jet de pulvérisation. Dans le but d’accroître l’efficacité de pulvérisation de pesticides et de réduire les pertes diverses de bouillie qui en résultent, nous avons étudie l’influence de la variation de pression sur la forme et la composition d’un jet de pulvérisation à l’aide d’un pulvérisateur à pression de liquide à jet projeté avec une buse à turbulence. Le travail a été effectue avec 5 valeurs de pression 0.5 bar, 1 bar, 1.5 bar, 2 bar et 2.5 bar. Les résultats obtenus nous ont permit d'en déduire que la pression de 1bar donne la meilleure couverture et répartition du jet de pulvérisation. A partir de la pression de 1.5 bar commence la dérive, et des pressions plus élevées rendent le jet irrégulier et hors cible. L'augmentation de pression augmente les pertes en bouillie et la quantité de fines gouttelettes. [less ▲]