- Animal Products: honey
- Pest Management: general pest management
This study determined the effects of higher amounts of imidacloprid aplied to soil on residue in canola pollen, and the effects of imidacloprid in sugar syrup on honey bee and bumblebee colony health.
Since 1990 the neonicotinyl insecticides, imidacloprid, thiamethoxam, clothianidin, and dinotefuran, were implicated in the decline of bees as they accumulate in pollen and nectar, are systemic, and are expressed for years from a single application (Doering 2004, 2005, EPA 2007, Blacquiere et al. 2012). Neonicotinyls are applied in various ways (seed treatments, soil drenches, foliar sprays, irrigation systems, tree injections) on agricultural and landscape plants. Most genetically modified crops (corn, canola, and soybeans) use seed treatments of imidacloprid (Gaucho), clothianidin (Poncho), or thiamethoxam (Crusier) (Farm Press 2003). The annual market for neonicotinyl insecticides is in the billions of dollars due to their low mammalian toxicity, systemic nature, and extended efficacy (Aliouane et al. 2009). In the U.S., at least 143 million acres of the total 442 million acres of cropland are treated with over 2 million pounds of imidacloprid, clothianidin, and thiamethoxam (Pilatic 2012). In 2009 in Minnesota, where most crops use seed treatments, corn, soybeans, potatoes and canola used 46,766 pounds of imidacloprid and 19,347 pounds of clothianidin (MDA 2012). Most research focused on the effects of <10 ppb of imidacloprid that was found in nectar and pollen of neonicotinyl-seed treated crops, such as canola, cotton, corn, soybean, and sunflower, on bee foraging, memory, and colony health. However, new residue data found 50-5,000 ppb in flowers of landscape plants and some flowering crops.
Residue levels of neonicotinoids in pollen and nectar differ depending on application method in crops and landscapes. Gaucho, an imidacloprid seed treatment of ?1.0 mg AI/seed, depending on the crop (Bonmatin et al. 2005, Girolami et al. 2009), resulted in 4.4-7.6 ppb imidacloprid residue in canola pollen, 3 ppb in sunflower pollen, and 3.3 ppb in maize pollen (Scott-Dupree and Spivak 2001, Bonmatin et al. 2005, EFSA 2012).
Landscape applications of imidacloprid result in much higher levels of residue in nectar and pollen. A homeowners’ formulation of imidacloprid, Bayer Advanced Tree and Shrub, or professional Marathon 1% G permits 270-300 mg AI to be applied to a 3 gallon pot, resulting in a 400 times higher application rate compared to Gaucho treated corn of 0.675 mg AI/seed. Doering et al. (2005) found 1,038–2,816 ppb in Cornus spp., dogwood flowers, at 17 months after application. A soil injection around Eucalyptus trees resulted in 660 ppb imidacloprid in nectar (Paine et al. 2011).
Field and cage studies that exposed bees to higher amounts of neonicotinyl-treated sugar syrup have been repeatedly shown to reduce colony health and bee foraging. Foraging was reduced at 10 ppb imidacloprid for B. terrestris (Mommaerts et al. 2010, Gill et al. 2012) and 30 ppb imidacloprid for B. impatiens (Morandin and Winston 2003). Honeybee foraging was reduced at 15 ppb imidacloprid (Schenider et al. 2012), 5 ppb clothianidin (Schenider et al. 2012), and 67 ppb thiamethoxam (Henry et al. 2012).
Our research objectives were:
Objective 1. Determine thru residue analysis how much imidacloprid (Admire Pro) is translocated to pollen of canola from a soil treatment and seed treatment. We studied 8 treatments: 1)non-seed treated canola , 2)imidacloprid-seed treated canola, 3)clothianidin seed-treated canola, 4)controls, 5)1X label rate applied to soil (4mg/sgft), 6)2X label rate applied to soil (8mg/sgft), 7)20X field rate or 25% landscape rate applied to soil or (80mg), and 8)40X field rate or 50% landscape rate applied to soil (160mg).
Objective 2. Determine the effects imidacloprid in sugar syrup on the behavior and colony health of bumble bees in a greenhouse at 10, 20, 50, and 100 ppb imidacloprid and clothianidin.
Objective 3. Determine the effects imidacloprid in sugar syrup on the behavior and colony health of honeybees on the St. Paul campus of the University of Minnesota at 0, 50, 100, and 200 ppb imidacloprid.
Objective 4. Implement research results through an outreach website and write publications on landscape management to increase foraging habitat for bees, nectar plants available for bees and, effects of insecticides on bees. See CUES website on Pollinator Conservation http://www.entomology.umn.edu/cues/pollinators/index.html