Protecting bees from pesticides
Pollinator protection: a bee and pesticide hand book, by Carl A.
Johansen and Daniel F. Mayer, Wicwas Press, 1991.
When farmers lose live-stock in large numbers to some deadly
disease, the emergency is usually reported in the press, and readers sympathize
with the loss of years of work in stock selection, and whose livelihood is
But the same thing happens to beekeepers every year: they too
lose their livestock - often as a result of the deadly activities of other
farmers. Perhaps it is because of the generally low status of mere insects or
the fact that bees are not highly visible livestock that the problem is not more
Yet, as Johansen and Mayer point out, in a single year in the
United States losses due to poisoning of honey bee colonies and consequent
reduction in pollination are estimated at US$135 million. And not only honey
bees are killed. An attempt to control aphids on alfalfa hay fields when the
plants were in partial bloom caused a 95 per cent reduction in alkali bee larvae
in three nearby soil nesting sites. Losses in seed production and pollination
totalled US$287000. Even after two years the alkali bees had only regained 25
per cent of their original population.
It is in no one's interest for bees to be harmed. Their
pollinating activity is a vital part of food production. Without it, many of our
everyday foods would not be on the menu. Nor would there be viable seed for
future crops. If a fruit orchard is optimally pollinated, the trees will bear to
their maximum; each fruit will be well-formed, and all fruit will be ready at
the same time - the best possible harvest.
Of course, farmers growing crops which are improved by insect
pollination often understand the need to have bees nearby at the time of
flowering, and know enough not to spray when bees are working the flowers.
However, bees can be harmed at any time by chemical sprays present on any plants
where bees might forage, even the flowering weeds along the sides of fields.
Clearly, pesticides have many implications and anyone who must
use them needs good information. Unfortunately, books containing long lists of
chemical names, and data on toxicity, tend to be off-putting for
There is an evident need for a handbook accessible to laymen,
and this volume meets it. Split into 15 compact chapters, with essential data
grouped into six appendixes, it is quite readable. Information can be obtained
quickly via the two indexes, which work well. The first index lists chemical
names and leads the reader to specific data on each substance. The second leads
to more general information. The writing style of the book is informal, with
minimum references, and much of the contents are obviously based on the authors'
own field experience.
Many points not widely grasped are explained simply. One is how
a substance applied to a plant can poison not just the bee that visits the
plant, but a whole colony of honey bees. Pollinating bees have hairy bodies. The
branched hairs covering them have evolved to allow bees to pick up minute pollen
grains from flowers - the method by which cross-pollination between plants is
achieved. But plants produce pollen in abundance and only a minute amount is
needed to pollinate other flowers. The rest eventually reaches the bees' nest,
where it serves as a protein food source for developing young.
If, rather than pollen, the bees pick up pesticide, the results
can be catastrophic. The amount of pesticide pickup will depend on the pesticide
formulation, but micro-encapsulated pesticides are about the same size as pollen
grains. These tiny capsules adhere readily to foraging bees and are brushed or
combed by the bee into the pollen-carrying "baskets" on its legs. When the bee
returns to the hive, the poisonous load may bring death to the hive's next
It is not only the toxicity of a pesticide, but also its
formulation that counts. Least hazardous for bees are pesticides in granular
form. The large particles are applied to the soil, and bees don't normally come
in contact with them. Insecticides can also be made less dangerous to bees by
adding solvents or oily substances to the spray. This either causes the
insecticide to adsorb more strongly to plant tissues, or hinders uptake of the
poison into the bees' body fluids.
Johansen and Mayer take a pragmatic approach to pesticide use,
emphasizing the benefits they've brought to food production and storage.
(Ironically, they note that DDT - so widely known as an environmental nemesis -
is actually among the pesticides that are less toxic to bees.)
If widely used, this handbook could help minimize some of the
unnecessary harm done by pesticides. It can help beekeepers protect their
colonies, as well as to recognize the symptoms and signs of poisoning and to
know what to do if the worst happens. The book will also be helpful to crop
growers, fostering understanding of the value of local bee populations to their
own operations. It will also help pesticide users to select substances least
poisonous to bees, to use them in the least harmful formulations and apply them
in the least harmful way.
The authors write primarily for North America, but their
information is widely applicable elsewhere.