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 threatened.

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 fully appreciated.

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 non-specialists.

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 generation.

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.

Nicola Bradbear