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1984). The base for pesticide granules is usually clay, gypsum, silica, crushed
corn cobs, or coal. All are attractive to birds, although coal possibly less so.
When they are readily available, birds will consume large quantities of granules
(Kenaga 1974).
The problem of ingestion is primarily a result of the limitation of agricultural
engineering. At planting time, pesticide granules are frequently incorporated
into the soil over the seed or actually in the seed furrow. Unfortunately, even
the best modern machinery cannot adequately cover the granules so that none
remains on the surface (Erbach and Tbllefson 1983; Hummel 1983; Maze et al.
1991). In rice cultivation, the granules are simply applied to shallow water or
to fields about to be flooded, giving rise to severe effects on waterfowl
(Flickinger et al. 1980; Littrel 1988). As a result of an EPA proposal to prohibit
all uses of granular carbofuran, the manufacturer voluntarily withdrew the
substance for all but a few minor uses in the USA. This product is also under
regulatory review in Canada. Manufacturer-conducted field tests have shown
that the material cannot be used safely, at least for corn, and kills are being
recorded world wide (Mineau 1988).
As little as one granule of carbofuran is usually sufficient to kill a small
songbird. Eagles and other raptors have been killed as a result of consuming
birds killed by granular carbofuran. However, carbofuran is not the only
hazardous granular product (Table 3). The rating scheme outlined in Table 3
was derived from concentration and toxicity values of the pesticide as well as
on the basis of available field evidence. The ranking is tentative as evidence
varies greatly from one product to the next. The manner in which these
products are used in various countries may differ; therefore, a use pattern
cannot easily be incorporated into the rating. The physical integrity of these
products has also not been considered. It is reasonable to expect that, all else
being equal, granules that are more friable and break down quickly (e.g., clay
High hazard
Table 3. Tentative ranking of the hazard to wildlife
of common granular insecticides.
Moderate hazard
Low hazard
Parathion Fensulfothion
Carbofuran
EpNa
Fenamiphos
Phorate
Aldicarb
Diazinon Oxamil
Ethoprop Disulfoton
Fonophos Ethion
Chiorpyrifos Terbufos
Very low hazard Tefluthrin
a 0-ethyl o-4-nitrophenyl phenyl phosphonothionate.
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