Macroinvertebrate responses to insecticide application between sprayed and adjacent nonsprayed ditch sections of different sizes

Abstract

Under typical agricultural use of an insecticide, it is likely that only part of an edge-of-field drainage ditch will be directly contaminated by spray drift. The response, including recovery, of aquatic macroinvertebrates in sprayed ditch sections may be affected by immigration of organisms from adjacent nonsprayed ditch sections, but also the population dynamics in nonsprayed sections (refuges) may be affected by nearby contaminated patches (known as action at a distance). Experimental ditches were used to study the influence of the presence of nearby refuges on the responses of macroinvertebrates in ditch sections directly sprayed with the insecticide lufenuron, and vice versa. The treatment regimes differed in the proportion of the ditch (0, 33, 67, and 100% of surface area) that was sprayed to reach a lufenuron concentration of 3 microg/L in the water column of the sprayed ditch section. In sprayed ditch sections, clear treatment-related effects were observed for adult midges in the emergence traps and for aquatic arthropods (mainly juveniles) in the artificial substrate/sweep net samples. The extent in magnitude and duration of effects in sprayed ditch sections was overall larger when a larger proportion of the ditch was sprayed and/or the distance to the refuge was larger. In nonsprayed ditch sections of partially treated ditches, treatment-related effects were absent or minor for macroinvertebrates that predominantly dwell on or in the sediment compartment, particularly at a larger distance from the sprayed ditch sections. More mobile arthropods that predominantly dwell in the water column showed clear treatment-related effects in the nonsprayed ditch sections as well, but action at a distance was smaller if a smaller proportion of ditch was treated.

Rabbit Population Landscape-Scale Simulation to Investigate the Relevance of Using Rabbits in Regulatory Environmental Risk Assessment

“…& Scenario 4: identical to Scenario 2, except that the application rate was increased by a factor 10^6. & Scenario 5: identical to Scenario 2, except that the DT 50 was increased to 76 days. & Scenario 6: identical to Scenario 2, except that the DT 50 was increased to 180 days.…”

“…& Scenario 5: identical to Scenario 2, except that the DT 50 was increased to 76 days. & Scenario 6: identical to Scenario 2, except that the DT 50 was increased to 180 days. & Scenario 7: identical to Scenario 2 except that we assume the effect of the pesticide is acute and immediate mortality.…”

“…& Scenario 8: identical to Scenario 7, except that the application rate was increased by factor 10^3. & Scenario 9: identical to Scenario 7, except that the DT 50 was increased to 180 days.…”

Scientific Opinion on the effect assessment for pesticides on sediment organisms in edge‐of‐field surface water

“…To date, however, only a few studies are available that specifically address the impact of pesticide exposure to endo-and epibenthic invertebrates and rooted macrophytes (e.g. Fletcher et al, 2001;Rand, 2004;Roessink et al, 2006;Pablo and Hyne, 2009;Brock et al, 2010b). In all these outdoor micro-/mesocosm studies the pesticides were applied to the water compartment.…”

“…For example, in the experimental ditch study of Brock et al (2010b), the hydrophobic insecticide lufenuron was applied to ditch sections that covered 33 %, 67 % and 100 % of the ditch surface area. The benthic community was mainly impacted in the insecticide-treated sections and recovery of the impacted benthic population (e.g.…”