Estimating buffer zone widths for pesticide applications

Abstract

A technique for estimating the width of buffer zones required around sensitive areas during pesticide applications has been devised and tested. The technique has been used to estimate the buffer width required around water bodies during ground‐based permethrin applications in Canadian forests to prevent significant impact on fish and their food populations. A worst‐ case scenario was developed for environmental impact in water bodies result ing from ground‐based permethrin applications, and a spray application was made under these worst‐case conditions. Permethrin deposit on ground sheets was measured downwind of overlaid crosswind swaths. From these measurements the deposit at various downwind distances from a single crosswind swath was calculated, and a curvilinear regression line fitted to these values. Permethrin deposit downwind of multiple‐swath applications was computed by adding the contributions from individual swaths. Mortality resulting from various permethrin concentrations was measured for Aedes aegypti larvae. Although these larvae are not an important food species for the fish species of interest, salmon and trout, they are more sensitive to permethrin than most aquatic invertebrates. Predicted mortality in populations of this species and Salmo gairdneri, rainbow trout, at various downwind distances from the permethrin application was calculated from the toxicological and spray‐cloud dispersal data. Buffer width was estimated by choosing an acceptably low mortality, and determining the downwind distance at which this value was obtained. For example, a 20 m swath width was found to be adequate to limit mortality in A. aegypti andS. gairdneri populations to 10 and 0.1% during ground‐based permethrin applications.

Best Management Practices for Silvicultural Chemicals and the Science Behind Them

“…We can come very close, with simple mathmatical calculations, to determining how far a droplet of known mass will travel under specific conditions of speed and height of application and therefore how wide an SMZ will be required to minimize contamination of streams. There are some very sophisticated models like AgDRIFT, FSCBG, and AGDISP (FEMVTF, 2002), which give an even better estimate of required SMZ width (Teske and Ice, 2002;Payne et al, 1988). These models take into consideration spray nozzle drop distribution patterns which describe the mass of any spray pattern that occurs in drops of various particle sizes, wind speed and direction, height of application and SMZ porosity to estimate the amount of contamination that may occur from specific applications.…”

“…others (1988, 1990) have used the modeling approach to calculate SMZ width. Payne et al, (1988) determined that 65.6 ft (20 m) was sufficient to protect streams and limit mortality of Aedes aegypti (yellow fever mosquito) to less than 10% from an application of permethrin at the rate of 0.035 kg ha −1 . The species they were most interested in protecting was trout, a species relatively tolerant of permethrin.…”

Aerial application

“…As with ground applications, (see Chapters 1 and 12), a buffer zone around sensitive areas during pesticide application needs to be determined (Payne et al, 1988). In the UK, the Environment Agency approved a 50 m buffer zone when helicopters fitted with Raindrop nozzles were spraying bracken (Robinson et al, 2000).…”

“…Detailed studies have been carried out in Scotland Bevan 1979, 1981) and in Canada (e.g. Payne et al (1988) used a motorised mistblower with spinning disc to apply a synthetic pyrethroid as a fine spray to assess a worst-case scenario. The trials in Scotland provided an interesting comparison between LV and ULV applications, the latter doubling the recovery on pine needles and the pine beauty moth larvae with a much higher work rate (Table 11.9) (Spillman, 1987).…”

The Characteristics of Riparian Buffer Studies

“…Riparian buffers are vegetated areas along water bodies that serve an array of functions (Hairston-Strang and Adams, 2000;Swanson et al, 1982), ranging from water quality protection (Carpenter et al, 1998), soil erosion control (Bilby, 1984), wildlife preservation (Boulet et al, 2003), to regulatory setbacks between certain human activities and a water body (Payne et al, 1988). The establishment and maintenance of riparian buffers have been an important environmental management practice in the United States since the 1970's (Xiang, 1993a,b).…”