Risk to Pollinators from the Use of Chlorpyrifos in the United States - Reviews of Environmental Contamination and Toxicology - page 240

rhopalosiphi and Aphidius pyri to fresh dried residues of product applied on glass
plates to generate LR 50 values (rate of application of the pesticide causing 50%
mortality of the test organisms) (Candolfi et al. 2001 ). This test is meant to represent
a case worse than that experienced on a natural substrate such as a leaf. No reports
of toxicity data for CPY to A. rhopalosiphi and T. pyri using the glass plate tech-
nique were found, but data for Bracon hebetor (Braconidae) and A. ervi , which are
related species of wasps were found. The LR 50 value for B. hebetor was 62 g CPY
ha −1 (Ahmed and Ahmad 2006 ) and that for adult female A. ervi was 0.047 g CPY
ha −1 (Desneux et al. 2004 ). These results were obtained with the active ingredient
coated on the inside of a 2.3 cm diameter by 9.3 cm glass vial in which the wasp was
contained, leading to a greater potential uptake of the dose from the surface than
would occur under field conditions. Thus, the results may be useful for comparison
of toxicity but are not an indication of toxicity in the field. At present, too few data
obtained using this method are available to permit comparisons to be made among
species. In addition, the small size (and large surface area to volume ratio) of these
wasps suggests that they may experience greater exposures via contact with treated
surfaces than the larger pollinators and thus would be poor surrogates.

4.2 Tier-2 Tests of Effects

Semi - ield studies . The following semi-field (tunnel tests) studies were conducted in
Europe and with formulations not currently registered in the U.S. Nonetheless,
these studies were conducted using standard methods with formulations containing
amounts of active ingredient similar to that in current US formulations and therefore
provide data that are relevant in the assessment of risk of CPY to pollinators.
A semi-field experiment with mini-beehives (approximately 2,000 individuals)
in field cages large enough to allow foraging behavior to be assessed in a contained
colony was conducted to test effects of exposure of honey bees to CPY and other
pesticides at a series of times after application (Bakker and Calis 2003 ). When pot-
ted Phacelia plants treated with Dursban 75WG (76.3% CPY) at 1 kg CPY ha −1
were added to the cages at night, the number of dead bees collected outside hives
was significantly greater compared to control hives on the first day of exposure, but
not on subsequent days. Foraging activity of bees was also reduced for up to 4 d
following the exposure phase (Bakker and Calis 2003 ).
In another tunnel test, the effects of aged Dursban 75WG foliar residues on
behavior and mortality of foragers, and brood development of A. mellifera was
examined (Bakker 2000 ). Dursban 75WG was applied at 1 kg CPY ha −1 to potted
Phacelia tanacetifolia under outdoor conditions at 14, 7, 5, and 3 d before exposure,
and the evening before exposure. During the aging process, plants were placed
under UV-transparent synthetic foil to protect them from rain. Exposure to aged
CPY did not result in a statistically significant increase in the number of dead bees.
However, reduced foraging activity was observed in all treatments. Exposure to 1 or
3 d-old CPY residues resulted in an immediate reduction of foraging activity that