Impacts of carbofuran on birds in Canada and the United State - Carbofuran and Wildlife Poisoning: Global Perspectives and Forensic Approaches - page 213

Before FMC conducted the Texas study and the Iowa and Illinois studies (see above), there were
numerous reports of bird of prey deaths due to secondary exposure to carbofuran. Therefore, in
these studies, FMC tried to examine the effects of granular carbofuran on bird of prey populations.
However, EPA largely discredited these portions of the studies on the basis of poor methodology
(US EPA 1989).
8.2.1.5 Balcomb 1983, Balcomb et al. 1984b: corn, Maryland,
in-furrow application
Balcomb, Bowen, Wright et al. (1984b) estimated an uncorrected kill rate of 0.13 to 0.2 birds per
hectare in cornfi elds in Maryland after an in-furrow application of carbofuran at 1.1 kg ai/ha.
However, one cannot readily compare the kill rate reported by Balcomb, Bowen, Wright et al.
(1984b) with the rates from the FMC studies reviewed above. In Maryland, the total search effort
was very low. Furthermore, Balcomb (1986) later reported that the rate of carcass removal by scav-
engers was very high at this location. Balcomb (1983) documented secondary poisoning in this
study. Finally, this study provided information to assess the hazard of eating contaminated earth-
worms. It further showed that common grackle ( Quiscalus quiscula ) nestlings taken from a nest on
the edge of a treated cornfi eld had carbofuran residues in their gastrointestinal tracts, presumably
because their parents fed them contaminated invertebrates.
8.2.1.6 Overgaard et al. 1983, Cerezke and Holmes 1986; Pine seed orchards
In a study conducted in the United States, Overgaard, Walsh, Hertel et al. (1983) used a deep-
injection mechanism (POWR-TILL TM ) to incorporate the granules and reported soil incorporation
rates of 99.1, 99.5, 99.9, and 100% on four treated sites. The investigators used a fl uorescent tracer
dye applied to the granules to estimate incorporation rates. Yet, over a 5-day period post-treatment,
Overgaard and colleagues recovered 96 dead and 30 moribund birds from around the treated trees.
Many species died, including wood warblers (Family Parulidae ), largely insectivorous species.
Even on a study site where investigators stated that the incorporation rate was at 100%, personnel
recovered three moribund birds and 12 carcasses. The species included a loggerhead shrike ( Lanius
ludovicianus ), a bird of prey, that likely died of secondary poisoning.
Canadian forestry entomologists (Cerezke and Holmes 1986) also conducted research in pine
seed orchards, attempting to place a very high rate (up to 30 kg ai/ha) of granules into the tree root
zones. Despite the (assumed) complete incorporation of the insecticide, the investigators reported
having found 15 bird carcasses from an unspecifi ed search area.
In both studies, it is likely that the casualties uncovered granules through their foraging activi-
ties, but Overgaard, Walsh, Hertel et al. (1983) suggested they may have been poisoned by ingesting
contaminated invertebrates.
8.2.1.7 The State of Virginia test of FMC's 'Avian Risk Reduction Plan'
(Stinson 1991, Stinson et al. 1994)
In 1990, the Virginia Department of Game and Inland Fisheries conducted a monitoring exercise
to look for bird carcasses in fi elds following operational use of granular carbofuran (15G) applied
in-furrow following a strict series of risk mitigation measures proposed by the manufacturer. FMC
personnel conducted intensive training of the applicators, provided devices to cut off the supply
of granules at row ends, and designated 18 to 23 metre wide no-pesticide zones along the edges