Impact assessment of spray drift from silvicultural aerial applications of permethrin on aquatic invertebrates using mosquito bioassays

Abstract

Permethrin (Pounce®) was applied at 70 g active ingredient per hectare by fixed‐wing aircraft to a 16‐ha jack and red pine plantation under application and meteorological conditions that were highly conducive for insecticide drift. Mortalities of an indicator aquatic insect species, Aedes aegypti mosquito larvae, and corresponding permethrin residues in shallow, artificial aquatic habitats, along with droplet densities on ground Kromekote® cards, were measured along five lines downwind and crosswind of the spray block. At 30, 60, 120, 180, and 240 m downwind, larval mortalities averaged 40, 39, 51, 18, and 34%; permethrin residues averaged 1.4, 1.1, 1.2, 0.6, and 0.8 μg/L; and droplet densities averaged 25, 22, 17, 14, and 10 droplets per centimeter squared, respectively. At similar distances crosswind of the block, mortalities were 60, 53, 11, 1, and 0%; residues to 180 m were 1.6, 2.6, 1.1, and 0.3 μg/L; and droplet densities were 30, 22, 12, 2, and 0.1 droplets per centimeter squared, respectively. Mortalities and residues were not high for such shallow water (6.7 cm depth), particularly beyond 120 m, and were less than or similar to the values predicted from a swath‐superposition model. Impact on sensitive aquatic arthropods and stream insects in deeper water (≥25 cm), more representative of natural habitats, is predicted to be insignificant at such distances. A buffer zone of 150 m around productive water bodies (depth ≥25 cm) is suggested for aerial permethrin applications to such plantations.

Assessing coral stress responses using molecular biomarkers of gene transcription

“…Whereas permethrin was not identified in these previous studies, this pesticide is used in the Florida Keys for mosquito control. Permethrin concentrations of 1 μg/L have been measured in spray drift from aerial applications [33]. The low concentration used in this study (1 μg/L) is, therefore, within the range detected from aerial spray drift.…”

Spray Deposition of Two Insecticides into Surface Waters in a South African Orchard Area

“…For both endpoints, the effects decreased with increasing distances from the sprayed orchard, which is in accordance with the measured concentration levels, as well as with the results of other studies employing aquatic or terrestrial test species (Davis et al, 1994; Helson et al, 1993).…”

Buffer zone and windbreak effects on spray drift deposition in a simulated wetland

“…Plants in the field, predominantly alfalfa, were about 150–200 mm tall when the tests were conducted. A procedure to collect spray drift deposits in a simulated wetland, similar to the approach taken by Helson et al ,5 was developed. Aluminium pie pans 200 mm in diameter were filled with water to collect drift deposits, and these were placed along a sampling line downwind and perpendicular to the direction of sprayer travel in the field (Fig 1).…”

“…Much larger buffer zones have also been recommended in several studies. For example, a buffer zone of 150 m around bodies of water >250 mm deep was recommended from a study of an insecticide (permethrin) applied by a fixed‐wing aircraft to a forestry nursery block in Ontario 5. A study with a herbicide applied by helicopter in Derbyshire, UK showed that drift of large droplets decreased rapidly, with most deposition occurring within 35 m downwind 6.…”