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 91 tious. In this instance, it seems prudent to be proactive and implement simple practices that may serve us — and the bees — well in the long term since how and where we are able to use these products is sure to change. Minimizing the potential hazard to bees from neonicotinoids Weed control. Pollinators in general and honey bees in particular forage for nectar and pollen on a wide range of fowering plants, including some of the most common weeds. Bird's-foot trefoil (Lotus corniculatus), dande - lion (Taraxacum offcinale), ground ivy (Gle- om ederacea), heal-all (Prunella vulgaris), speedwells (Veronica species), white clover (Trifolium repens) and other weeds provide for - age for a variety of pollinators in mowed turf. In unmowed native areas of the golf course, an even wider variety of fowering weeds provide such forage. If any of these weeds are present and fow - ering at noticeable levels, it may be wise to do one of the following: • Avoid treating weedy areas (fowering weeds) with neonicotinoids. This is consis - tent with many insecticide labels that ad- vise not to treat blooming nectar-producing plants with neonicotinoid insecticides if bees may visit the treatment area. • Mow the turf immediately before spray - ing an insecticide. Mowing should remove 90% or more of the fowers and reduce bee foraging. Research at the University of Ken - tucky has shown this strategy to be effective in protecting bees (7). • Remove weeds with an herbicide in areas you plan on treating with an insecticide. Turf that is relatively weed free should not pose a substantial risk to pollinators should Mowing white clover and other weeds before applying insecticide will remove 90% of the fowers, which reduces bee foraging in these areas and thus reduces the impact of an insecticide application on bees. Before mowing (left); after mowing (right). Controlling patches of weeds adjacent to areas treated with insecticide, like this patch of clover next to a fairway, will reduce the risk of bees being affected by the insecticide application. a neonicotinoid be applied. Effective weed control should be a prerequisite for using neonicotinoid insecticides. Treat areas where you plan on using a neonicotinoid insecticide as well as areas adjacent to these sites. It is not known how much of the neo - nicotinoid insecticide ends up in the pollen and nectar of our most common weeds, but if no weeds are available to take up the in - secticide, the risk to pollinators can be sig- nifcantly reduced. Although there are some reports of the herbicide 2,4-D causing injury to bees (8), these reports are specifc to formulations of 2,4-D no longer used in the U.S., such as isopropyl ester (11). The dimethylamine salt formulation and the isocytyl ester formula - tion of 2,4-D are currently the most com- monly used 2,4-D formulations in turf. Their safety has not been tested on all bee species, but both are nontoxic to honey bees at labeled rates (9). Other commonly used broadleaf herbicides are also relatively safe on honey bees as the LD 50 for these products is as follows: 94 µg/bee for 2,4-D and >100 µg/bee for dicamba, mecoprop (MCPP), fu - roxypyr and triclopyr (5). Time of day. Bees are most actively forag - ing during the middle of the day, so making

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