This is from an article published thirty years ago (1983)

Killing of honey bees by insecticides has been a chronic,
severe problem in Washington for at least 60 years (Melander
1920). A basic factor in this situation is the lack
of sufficient wild pollen and nectar plants to sustain the
number of colonies required for crop pollination. Most
bees are pastured in the irrigated agricultural areas where
they are subject to killing from insecticides.

Washington commercial beekeepers are taking 83%
(67,000 in 1982) of their colonies to California during
midwinter not only to pollinate almonds, but also to
rejuvenate colonies debilitated during the previous summer's
insect control operations

For many years, Washington beekeepers have been
claiming a series of low to moderate level kills which
seriously wcaken their colonies during the summer. Such
kills are hard to document because the dead bees ejected
from the hives literally "dry up and blow away." Because
of the obvious masses of bees involved, severe
kills are normally recorded, investigated by the Pesticides
Branch, Washington State Department of Agriculture,
and the dead bees are usually analyzed for
chemical residues.

We started a honey bee monitoring program in 1979
to obtain data on the occurrence and extent of bee poisoning
in eastern Washington. We also developed technique:
s for season-long sampling, since previous studies
have mainly involved short-term experiments or investigations
of individual severe poisoning incidents.

Correlation of bee mortality with specific crop pest
control activities was usually difficult in diversified crop
areas. Figure 3 shows one exception, involving a Yakima
Valley hop yard, where repeated kills were closely
associated with insecticide applications.

Low to moderate kills of honey bees occur
periodically throughout much of the season in the 
more diversified crop areas sampled, the Yakima
Valley and the Columbia Basin. Certain regions with 
less intensive insecticide usage, the Kittitas Valley,
the Mattawa area, and the Touchet area, are much 
safer for summer bee pasture.

Occurrence of Honey Bee (Hymenoptera: Apidae)
Poisoning in Eastern Washington
DANIEL F. MAYER AND CARL A. JOHANSEN
Environ. Entomol. 12: 317-320 (1983)

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