Golf Course Management

OCT 2014

Golf Course Management magazine is dedicated to advancing the golf course superintendent profession and helping GCSAA members achieve career success.

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10.14 GOLF COURSE MANAGEMENT 87 that honey bees readily foraged on contami- nated corn pollen, taking it back to the hive for storage. Similar troubling situations can be observed with canola production in the northern U.S. and Canada, and an increasing majority of soybean seeds are now coated with a mixture of neonicotinoids and fungicides. The rationale for these seed treatments is that they "protect against a suite of yield-limiting pests," but little evidence supports this asser - tion, and many of the key annual crop pests across the Corn Belt are relatively unaffected by these treatments. Green industry use Based on these fndings, it would be easy to place the blame for increased public scru - tiny of neonicotinoid use squarely on the shoulders of large-scale production agricul - ture, but this would be a mistake. Neonicoti- noids are by far the most widely used insecti- cides in the green industry, and the usage data presented in Figure 2 do not include neonic - otinoids used on turf and ornamental crops. For our purposes, this group includes several excellent white grub insecticides, which, de - pending on the particular active ingredient, can provide very effective control of many sur - face-feeding turfgrass insects. They are also commonly used to protect perennials, woody plants and landscape trees against a variety of sucking and wood-boring insects, including the emerald ash borer (Agrilus planipennis). To say the least, neonicotinoids represent a valu - able set of insect management tools that are much safer (for people and other mammals) than the older generation of insecticides they replaced. However, their breadth of use in the green industry does carry with it the risk of pollinator exposure. Honey bees are complex social animals, and it is important to remember that acute poisoning is only the tip of the iceberg when it comes to understanding how neonicotinoids could impact their well-being. We should be wary of studies that make conclusions about the hazard of neonicotinoid exposure based on acute toxicity (that is, brief exposures fol - lowed by death in short order). Such studies only lend insight into the amount of material required to kill honey bees over an exposure period that is relatively brief. These studies provide an important starting point, but they do not come close to capturing the complexi - ties of exposure in nature, where bees may be exposed to low, but variable levels of these ner - Insecticide (trade name/ company) Toxicity † Mammal LD 50 (mg/kg) ‡ Bird LD 50 (mg/kg) ‡ Fish LC 50 (mg/liter) § Honey bee LD 50 (µg/bee) // Clothianidin (Aloft/ArystaLifeScience; Arena/Nufarm) >500 430 104 0.004 Dinotefuran (Zylam/PBI-Gordon) >2,000 >2,000 >100 >0.023 Imidacloprid (Merit/Bayer; others) 424 152 211 0.0037 Thiamethoxam (Meridian/Syngenta) >1,563 576 >125 0.005 † Toxicity only refers to active ingredient and does not take into account formulation. Data from IUPAC (5). ‡ LD 50 for mammals and birds represents acute oral toxicity. § LC 50 for fsh represents acute 96-hour toxicity. // LD 50 for honey bees may represent either acute contact or oral toxicity. Table 1. Ecotoxicology of several neonicotinoid insecticides in several different animal species. LD 50 represents the amount of material (per unit body mass or individual) required to kill 50% of a test population. LC 50 represents the con- centration of material in water required to kill 50% of the test population. Ecotoxicology of several neonicotinoid insecticides Figure 2. Usage of three common neonicotinoid insecticides on agricultural crops in 2011 (most recent data available) expressed in pounds of active ingredient per square mile. A, imidacloprid ( http://water.usgs.gov/nawqa/pnsp/usage/ maps/graphics/H_IMIDACLOPRID_2011.png ); B, clothianidin ( http://water.usgs.gov/nawqa/pnsp/usage/maps/ graphics/H_CLOTHIANIDIN_2011.png ); C, thiamethoxam ( http://water.usgs.gov/nawqa/pnsp/usage/maps/graphics/H_ THIAMETHOXAM_2011.png ). Usage data for nonagricultural crops (turf and ornamentals) not included. Source: United States Geological Survey, Water Quality Assessment Program

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