Spray Drift and Pest Control From Aerial Applications on Soybeans

Abstract

ABSTRACT:Pesticide drift is an issue in modern farming, mainly for crops under constant spraying as soybeans. This study aimed at assessing drift and pest control for aerial applications in soybean crops. Hydraulic nozzles and rotary atomizers, regulated to a wide spectrum of droplet sizes, sprayed thiamethoxam plus lambda-cyhalothrin using an agricultural aircraft Ipanema 202A at volume rate of 20 L ha -1 . Treatments consisted of testing two devices: a rotary cage atomizer (Micronair AU 5000) with blade angles of 65° for larger droplets, and with angle of 55° for smaller ones; and a set of adjustable nozzles (Stol model) with deflector angle of 90° for smaller droplets, and with angle of 30° for larger ones. Drift was evaluated through quantification of active ingredient, by means of liquid chromatography, on nylon strings set 20, 40, 80, 160 and 320 m downwind from the applied area. Control efficiency was measured by counting caterpillars and stinkbugs found five days after spray. Rotary atomizers produced lesser drift compared to adjustable nozzles at the designed setting. Furthermore, drift can be reduced through a suitable regulation of the devices, keeping an effective pest control.

Factors affecting aerial spray drift in the Brazilian Cerrado

“…Drift depositions at the shortest distance from the field border account for most of the total drift. Some research likewise measured aerial spray drift deposition at distances of 320 m [31] up to 2,000 m [6] from the field border, measuring 0.10% and 0.05% of the dose applied, respectively. Analyzing the amount of spray drift found at 2000 m from the applied field, it can be discussed that a small portion of the spray syrup can be deposited even in a higher distance.…”

Initial stability loss of insecticide solution mixed with fungicides and adjuvants

“…The dispersants may be steric and/or electrostatic. Steric dispersants have a large molecular weight which stabilizes the system using molecule-liquid and molecule-particle a nities, in which the molecules bind to the particles through regions that highly resemble the surface, and the unbound regions of the molecules protect the solution, remaining totally dissolved in the liquid and imparting stability 11 . In electrostatic dispersants, the molecules adhere to the particles, increasing the electrical potential of the surface and its diffuse layer.…”

“…As the attraction force is low, the diffusion force is greater, and the diffuse layer moves further away from the surface. The larger the layer, the greater the interaction resulting in greater repulsion 11 .…”