In June a commercial landscape manager in Oregon made an off label application of dinotefuran to flowering linden trees resulting in the death of more than 25,000 bumblebees and immediate action by the Oregon Department of Agriculture to implement a six month ban on all dinotefuran products labeled for landscape use http://www.oregon.gov/ODA/docs/pdf/news/130627dinotefuran.pdf
The labels on dinotefuran products and all other neonicotinoid products marketed for turf and landscape use (imidacloprid, thiamethoxam and clothianidin; see table 1 below) contain clear and concise statements warning of the potential environmental hazards associated with applications to flowering plants. One example of a potential environmental hazard is the potential negative effects of these insecticides on bee populations which have declined in recent years.
This unfortunate incident should serve to remind us all about the potential costs of ignoring label directions. One mistake can cost an entire industry the use of critically important tools and, as we’ve seen in the Oregon case, State agencies can and will ban these insecticides in order to protect human and environmental health.
As many folks start to think this time of year about making insecticide applications to protect their lawns from white grubs, it may be prudent to keep a few things in mind.
In any given year only about 20% of home lawns will be afflicted by damaging white grub populations in this part of the country.
The likelihood of a given lawn being afflicted with damaging white grub populations 2 years in a row is only about 50%
Some of our most common lawn weeds, such as white clover, provide excellent forage for bees and other beneficial insects, so proper weed control is a must if neonicotinoid insecticides will be used to control insect pests. In other words, if the lawn is weed free then an application of one of these insecticides should not pose a hazard to bees, but if the lawn has high populations of flowering clover these insecticides should not be applied.
Since neonicotinoids are systemic compounds that are readily taken up by plant roots, it may be advisable to maintain a reasonable buffer area between treated areas of the lawn and landscape beds where flowering plants that are likely to attract pollinators are less likely to take these products up through their roots.
When possible, it may be prudent to wait until after flowering to apply systemic insecticides to trees or other flowering plants to allow nearly a year between the application and the production of new flowers.
At the very least, use common sense and do your part by following the label.
Table 1. Trade names of turf insecticides containing a neonicotinoid as one of the active ingredients.
Common Name/Active Ingredient
Merit, Allectus and many post-patent products
Doug Richmond, Turfgrass Entomologist
Cliff Sadof, Landscape Entomologist
Aaron Patton, Turfgrass Extension Specialist