The following was sent to me by an anonymous contributor with a degree in forensics:
I have been thinking about soybean pesticide treatments and soy-based bee feed supplements.
I understand that in June 2004 Gustafson LLC (Bayer CropScience) petitioned the United States Environmental Protection Agency (EPA) that 40 CFR 180.472 be amended by establishing tolerances for residues of the insecticide imidacloprid in or on soybean seed at 1.0 ppm and soybean meal at 2.5 ppm. The proposed tolerance for soybean meal was subsequently revised by the petitioner to a proposed tolerance of 4.0 ppm.
The eventual changes to Sec. 180.472 were reported by the US EPA as follows:
- The time limited tolerance for soybean, seed at 1.0 ppm is removed from Sec. 180.472(b).
- Tolerances for soybean seed at 1.0 ppm and soybean meal at 4.0 ppm are added to Sec. 180.472(a).
This increase in tolerances for soybean meal could be significant as I understand some bee feed supplements are soy-based. Some use organic soybean meal in thier mix but some use off the shelf soybean meal.
I came upon a translated Swiss research report on imidacloprid which cites J.M. Bonmatin's investigation concluding that a LD50 was reached after 8 days by feeding individual bees an imidacloprid/sugar solution of just 0.1 ppb.
I have not been able to verify the cited investigation but have found other references stating toxicity can be found at low concentrations of imidacloprid fed with sucrose syrup (Suchail et al. 2000; Decourtye et al. 2003; Dechaume-Moncharmont et al. 2003).
My question to the beekeeping community is if bee feed supplements are soy-based and an established tolerance for soybean meal is 4.0 ppm when feed overtime could soy-based bee feed supplements affect bee behavior?
For example, 10% soybean meal at 4000 ppb (4 ppm) imidacloprid would result in a 400 ppb exposure level that may cause long term irreversibble damage to the consuming bees.