Chapter 7 Pesticides and beekeeping

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A. Bee-poisoning symptoms
B. Relative toxicity of pesticides

For its essential role in crop pollination, beekeeping is an essential component of agriculture today. Pesticides are evidently another. Without either of the two, global food production would be seriously impaired. Yet beekeeping has been sustaining heavy losses through pesticide use since the advent of synthetic pesticides several decades ago. Pesticides, and especially herbicides, reduce the foraging areas available to the bees; the application of toxic pesticides on farmlands and in forests often makes it impossible for the bees to utilize potential forages; and, worst of all, the pesticides frequently kill bees, reduce colony strength and contaminate hive products.

While beekeepers have no direct way of controlling the application of pesticides near their apiaries or within the flight range of their bees, some lines of action are still available to them to prevent damage: they can ask for help from extension agents, for understanding and cooperation on the part of the growers (whose crops often in fact depend on the bees' work), and finally for legal protection. At the same time, they must be fully alert to the potential damage that certain toxic pesticides can inflict on their colonies.

When bees are kept in or near areas where such pesticides are occasionally used, the beekeeper must be in a position to know in advance the pesticides used and their residual effect, what damage they can cause to the bees, and the time of application. Moving the colonies out of range of pesticide application temporarily is often one approach available to the beekeeper; in some circumstances he can prevent the bees from flying for several days, until the residual effect of the pesticide has subsided.

The recent development of new "micro-encapsulated" insecticide formulations, specifically designed for the controlled release of the product over time, has created a new tree-poisoning problem. When such pesticides have been dusted on blooming crops, worker bees collect the particles, return them to the hive and store them in pollen cells. The consequence is the poisoning of the entire colony.

A. Bee-poisoning symptoms

Honeybees react differently to different pesticides, and most herbicides and fungicides are less toxic to bees than are insecticides. To the beekeeper, the most obvious sign of pesticide poisoning is the presence of an exceptional number of dead bees in front of the hives. The following figures have been established as guidelines for assessing the extent of pesticide poisoning: 100 dead bees per day is the colony's normal death rate; 200-400 dead bees indicate a low level of pesticide poisoning; 500-1000 dead bees indicate a medium level of pesticide poisoning; over 1000 dead bees indicate a high level of pesticide poisoning.

B. Relative toxicity of pesticides

As indicated above, pesticide application is one of the most important inputs to agriculture. Understanding and cooperation among growers and beekeepers are essential to prevent, or at least to minimize, the loss of honeybees due to the toxic effects of pesticides. The following table lists the most common pesticides, indicating their relative toxicity to honeybees.

Table 7/1. Relative Toxicity of Pesticides to the Common Honeybee

Group 1 - Highly Toxic

The application of these pesticides to foraging areas when bees are active may cause severe damage. Beekeepers must know in advance when they are to be used and take special precautions; moving colonies out of the area temporarily is perhaps the safest approach.

Group 2 - Moderately Toxic

These products should not he applied directly on fields when bees are actively foraging or when hives are exposed. Dose, timing and application methods are among factors determining whether the pesticides can he used with minimum risk to bees.

Table 7/1. Relative Toxicity of Pesticides to the Common Honeybee (contd.)

Group 3 - Relatively Non-Toxic

These products can be used on fields or near hives with minimum damage to bees; in fact, a few of the listed acaricides can he used to control bee mites within the hive.

A. INSECTICIDES AND ACARICIDES

B. FUNGICIDES

C. HERBICIDES

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