Non Technical Summary
This project originated with reports of dead honey bees in Indiana at corn planting time. Our initial experiments to find the cause of these observations highlighted a previously unknown route of exposure for honey bees to neonicotinoid insecticides used in seed treatments - the talc exhaust produced by planters. The magnitude of corn and other annual cropping systems using treated seed (over 200 million acres each year), combined with the mobility of this exhaust and the extremely high toxicity and persistence of neonicotinoids create a situation where the margin for error in terms of honey bee exposure is very low. Using field experiments combined with existing land use, weather and apiary location data we will quantify the area potentially affected by talc exhaust and provide stakeholders across 4 states with this information via the Driftwatch.org platform. This site is already familiar to both crop producers and beekeepers.
Animal Health Component
Research Effort Categories
Goals / Objectives
Most annual crops planted in the United States are coated with neonicotinoid seed treatments, including virtually all corn. Corn alone accounts for over 90 million acres of cropland annually, the vast majority of which is in the North Central region. Neonicotinoid insecticides are highly toxic to honey bees and recent research investigating honey bee kills near corn fields at planting time has demonstrated several potential routes of exposure for honey bees near agricultural plantings. We plan to build on published work by focusing directly on a key mechanism for honey bee exposure - the movement of waste talc produced during planting. We will accomplish this using field experiments in production fields that will enable us to quantify the spread of exhaust talc beyond the planting field. We will then combine this information with data that are currently available online or published that reflect land use patterns (NASS-USDA website, includes high-resolution data describing where crops are planted annually), where honey bees are found (www.driftwatch.org), and published estimates of honey bee foraging distances. These data will then be used to determine the level of risk to honey bees in areas near plantings of treated seed, across four midwestern states
OBJECTIVE 1: QUANTIFICATION OF PESTICIDE LEVELS SURROUNDING FIELDS AT PLANTING Our previous research indicates that talc exhaust from planting equipment is highly toxic. To put the figures in Table 2 in perspective, the levels of clothianidin found in the talc produced during planting of "Commercially treated seed 4" are equivalent to 700 000 times the contact LD50 for honeybees. It is unlikely that any forager passing behind this planter would survive long enough to return to the hive. The more relevant question is how these concentrations change as a function of distance from the point source (i.e. the planter). To quantify this, it is useful to think of the talc plume as a form of spray drift. Pesticide drift is a long-standing concern for agriculture, but this topic has not been a concern with seed treatments. In fact, the lack of drift is often cited as a benefit of this method of insecticide application (15). To characterize the rate of drift of talc exhaust during corn planting, we will work in production fields, using commercially-treated seed. The grower/cooperators we will be working with use air planters to plant seed. We will use four fields in each year of the study. These fields are all located within 20 miles of Purdue campus, in Tippecanoe and Benton counties, Indiana. The field dimensions will vary, but all fields will be at least 10 acres in size. Along each edge of the field, we will place passive dosimeters to measure deposition of material. These dosimeters have been used in other published studies of liquid spray deposition, and consist of a 17 X 11 cm plastic lid that is screwed onto 2 cm diameter wooden dowel that is 30 cm in length. Four standard microscope slides (approx. 7 x 2 cm) are placed on top of each plastic lid. Because we are working with dust and not liquid, we will modify the methods used by other researchers slightly by treating our microscope slides with a light coating of Tangle-Trap sticky coating (Contech Industries, Grand Rapids, MI) applied using an aerosol can. This material is inert and can be used with the chemical analyses. These horizontally-oriented dosimeters will serve as a proxy for surfaces that honey bees may contact, including flower heads or the surface of their hive. We will place four dosimeters at the midpoint of each edge of the field (i.e. N, S, W, E border), moving steadily away from the field edge. One dosimeter will be placed at each field margin, with subsequent dosimeters located at 10, 50, and 100 m beyond the field edge. Dosimeters will be stored horizontally in Styrofoam "racks" and placed in a cooler for transport to the lab, where they will be frozen until analysis. Dosimeter and planter talc samples will be sent to an analytical chemist. The procedure used is a modified version of the protocol used to quantify pesticide levels in food and feed. This allows the various pesticides (incl. herbicides and fungicides) to be unambiguously identified at the parts per billion (i.e. nanograms/gram) concentration level.