Dew from Warm-Season Turfgrasses as a Possible Route for Pollinator Exposure to Lawn-Applied Imidacloprid
- James D. McCurdy *a,
- David W. Heldb,
- Jonathan M. Gunnc and
- T. Casey Barickmand
- a Assistant Professor, Dep. of Plant and Soil Sciences, Mississippi State Univ., 117 Dorman Hall, Starkville, MS 39762
b Associate Professor, Dep. of Entomology and Plant Pathology, Auburn Univ., 301 Funchess Hall, Auburn, AL 36849
c Undergraduate Research Scholar, Dep. of Animal and Dairy Sciences, Mississippi State Univ., Dep. of Plant and Soil Sciences, Mississippi State Univ., 117 Dorman Hall, Starkville, MS 39762
d Assistant Professor, Dep. of Plant and Soil Sciences, Mississippi State Univ., Northeast Mississippi Research and Extension Center, Verona, MS 38879
- This is the first study to report warm-season turfgrass dew as a potential source for pollinator contact with imidacloprid.
- Observed imidacloprid concentrations were similar to those reported in creeping bentgrass guttation droplets but less than those typically found in agronomic crops grown from treated seed.
- Foliar-treated bermudagrass contained more than 10 times the imidacloprid residue of the isolated soil-only treatment.
Imidacloprid is a neonicotinoid insecticide used for the control of turfgrass insect pests. It can be translocated into guttation fluid, thus potentially creating an exposure avenue for beneficial insects. Our research objectives were to investigate the fate of soil- and foliar-applied imidacloprid in dew forming on bermudagrass (Cynodon spp.) and St. Augustinegrass [Stenotaphrum secundatum (Walter) Kuntze] turf. Imidacloprid was applied at standard use rates (443 g a.i. ha−1; 6.32 oz a.i. acre−1) to soil only via sub-irrigation (Years 1 and 2) or by foliar treatment (Year 2), which is representative of standard home lawn application. Dew fluid, which includes guttation, was collected 48 h after treatment and was analyzed for imidacloprid. During Year 1, dew collected from the soil-only treatment of bermudagrass and St. Augustinegrass contained 15.8 and 9.2 ng imidacloprid mL−1, respectively. During Year 2, foliar treated bermudagrass contained more than 10 times the amount of imidacloprid as found in the soil-only treatment (59.8 versus 5.2 ng mL−1, respectively). Observed imidacloprid concentrations were similar to those reported in creeping bentgrass guttation droplets but were less than those typically found in agronomic crops grown from treated seed. Levels were less than those reported to be acutely lethal to the European honeybee. However, depending on the amount of contaminated dew or guttation transported into hives, similarly low concentrations could be associated with sublethal effects (reportedly >10 ng mL−1). This is the first study to report warm-season turfgrass dew as a potential source for pollinator contact with imidacloprid and suggests that post-application irrigation is perhaps the best way to avoid pollinator exposure.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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