Measuring and preliminary modeling of drift interception by plant species

Currently, the concept of plant capture efficiency is not quantitatively considered in the evaluation of off-target drift for the purposes of pesticide risk assessment in the United States. For on-target pesticide applications, canopy capture efficiency is managed by optimizing formulations or tank-mixing with adjuvants to maximize retention of spray droplets. These efforts take into consideration the fact that plant species have diverse morphology and surface characteristics, and as such will retain varying levels of applied pesticides. This work aims to combine plant surface wettability potential, spray droplet characteristics, and plant morphology into describing the plant capture efficiency of drifted spray droplets. In this study, we used wind tunnel experiments and individual plants grown to 10–20 cm to show that at two downwind distances and with two distinct nozzles capture efficiency for sunflower (Helianthus annuus L.), lettuce (Lactuca sativa L.), and tomato (Solanum lycopersicum L.) is consistently higher than rice (Oryza sativa L.), peas (Pisum sativum L). and onions (Allium cepa L.), with carrots (Daucus carota L.) showing high variability and falling between the two groups. We also present a novel method for three-dimensional modeling of plants from photogrammetric scanning and use the results in the first known computational fluid dynamics simulations of drift capture efficiency on plants. The mean simulated drift capture efficiency rates were within the same order of magnitude of the mean observed rates of sunflower and lettuce, and differed by one to two orders for rice and onion. We identify simulating the effects of surface roughness on droplet behavior, and the effects of wind flow on plant movement as potential model improvements requiring further species-specific data collection

The Effect of Adjuvants, Pesticide Formulation, and Spray Nozzle Tips on Spray Droplet Size

Many factors, including adjuvants, pesticide formulations, and nozzle tips, affect spray droplet size. It is important to understand these factors as spray droplet size affects both drift and efficacy of pesticides, which is a main concern with pesticide application. A laser particle analyzer was used to determine the spray droplet size and distributions of a range of formulations sprayed through several types of nozzle tips. Nozzles included were extended range flat fan sizes 11003 and 11005 (Spraying Systems XR), air induction flat fan sizes 11005 and 11004 (AI) air induction extended range flat fan size 11005 (AIXR), preorifice flat fan size 11005 (TT), and a second preorifice flat fan size 2.5 (TF). Several deposition/ retention adjuvants were studied, including Array, Interlock, In-Place, and Thrust. Another study looked at diflufenzopyr + dicamba (Status, BASF) in combination with several adjuvants. Also, three fungicides were evaluated at differing spray volumes. Results indicated that the droplet size of some nozzle tips is more affected than others by changes in the contents of the spray solution

Dicamba off‐target movement from applications on soybeans at two growth stages

Abstract The objective of this study was to evaluate dicamba off‐target movement during and after applications over soybean at two growth stages. Dicamba‐tolerant soybean [Glycine max (L.) Merr.] at V3 and R1 growth stages in Nebraska and Mississippi fields were treated with diglycolamine salt of dicamba (560 g ae ha−1), potassium salt of glyphosate (1260 g ae ha−1), and a drift‐reducing adjuvant (0.5% v v−1). Filter papers positioned outside the sprayed area were used to determine primary movement and air samplers positioned at the center of sprayed area were used to calculate dicamba flux from 0.5 up to 68 hours after application (HAA). Flux was calculated using the aerodynamic method. Soybean growth stage did not affect dicamba deposition on filter papers from 8 to 45 m downwind from the sprayed areas. At 33 m downwind (i.e., distance of the labeled buffer zone), a spray drift of less than 0.0091% (0.05 g ae ha−1) of applied rate is estimated. Dicamba secondary movement may not be affected by soybean growth stage during the application. Although dicamba was detected in air samples collected at 68 HAA, the majority of the secondary movement was observed in the first 24 HAA. Dicamba cumulative loss was lower than 0.77% of applied rate. Results suggest the more stable the atmospheric conditions, the higher the dicamba flux. Thus, meteorological conditions after applications must be considered, and tools to predict the occurrence of temperature inversion are needed to minimize secondary movement of dicamba

Dicamba off-target movement from applications on soybeans at two growth stages

The objective of this study was to evaluate dicamba off-target movement during and after applications over soybean at two growth stages. Dicamba-tolerant soybean [Glycine max (L.) Merr.] at V3 and R1 growth stages in Nebraska and Mississippi fields were treated with diglycolamine salt of dicamba (560 g ae ha−1), potassium salt of glyphosate (1260 g ae ha−1), and a drift-reducing adjuvant (0.5% v v−1). Filter papers positioned outside the sprayed area were used to determine primary movement and air samplers positioned at the center of sprayed area were used to calculate dicamba flux from 0.5 up to 68 hours after application (HAA). Flux was calculated using the aerodynamic method. Soybean growth stage did not affect dicamba deposition on filter papers from 8 to 45 m downwind from the sprayed areas. At 33 m downwind (i.e., distance of the labeled buffer zone), a spray drift of less than 0.0091% (0.05 g ae ha−1) of applied rate is estimated. Dicamba secondary movement may not be affected by soybean growth stage during the application. Although dicamba was detected in air samples collected at 68 HAA, the majority of the secondary movement was observed in the first 24 HAA. Dicamba cumulative loss was lower than 0.77% of applied rate. Results suggest the more stable the atmospheric conditions, the higher the dicamba flux. Thus, meteorological conditions after applications must be considered, and tools to predict the occurrence of temperature inversion are needed to minimize secondary movement of dicamba