are essential to modern agriculture. These industrious social insects
produce over $100 million worth of honey and beeswax each year in
the United States. Their service as pollinators of agricultural
crops adds another $10 billion to their overall value. Due to the
destruction of native habitat, native pollinators such as bumblebees
and leafcutter bees are in short supply, further magnifying the
impact of the honey bee and the work of our beekeeping industry.
The honey bee
is about 12 mm (1/2 inch) long and usually yellow, with 3 or 5 dark
brown abdominal bands. They carry two pairs of wings and lack the
constricted abdomen (wasp waist) of the wasp and hornet. Honey bees
can sting, but are much less aggressive than wasps and hornets.
bee (R.A. Casagrande)
It takes 21
days for the honey bee to develop into a "hive bee" upon hatching
from the egg. The "hive bee" spends the next 21 days doing hive
chores and feeding larvae. After the "hive bee" period, the bee
passes into the category of "field bee," or forager. These are the
bees who leave the hive to return with nectar, pollen and water.
In the height of nectar flow, these bees wear their wings out from
flying and die within three weeks.
When a colony
becomes overcrowded, the "field bees" gorge on honey and leave the
hive with the queen bee to establish a new colony. Because they
are gorged on honey, they are not generally aggressive and pose
no threat to humans if left alone. A typical swarm may contain thirty
to fifty thousand bees and will constitute a definite loss to the
beekeeper whose apiary they have left.
is a general term used for a chemical designed to kill target pests
such as insects (insecticide), mites (miticide), weeds (herbicide)
and organisms which cause plant diseases such as bacteria (bactericide)
and fungi (fungicide). Unfortunately, many agricultural pesticides
may be toxic to bees. Each year many honey bee colonies are damaged
or destroyed by pesticides, primarily insecticides. Such losses
have a devastating impact on the beekeeper, who may have to relocate
damaged hives or perhaps even be forced out of business. Growers
of most insect-pollinated crops (apples, raspberries, cucurbits,
alfalfa seed and many others) experience lower yields, and ultimately
the consumer must pay higher food prices.
involving insecticide application affect the potential for honey
bee losses. The most important factors are outlined below.
Growth Stage: Severe bee poisoning most often results from spraying
insecticides directly on flowering plants. Insecticide applications
are generally not recommended on blooming crops.
Toxicity of the Chemical: Pesticides vary in their toxicity
to honey bees. Most fungicides, herbicides and miticides are relatively
nontoxic to honey bees and can generally be used around them without
serious harm. The biological insecticide Bacillus thuringiensis
exhibits very low toxicity to bees. One group of insecticides which
is highly toxic to honey bees cannot be applied to blooming crops
when bees are present without causing serious injury to colonies.
Among the materials in this high-risk category are diazinon, Imidan,
malathion and Sevin.
of Formulation: Different formulations, even of the same pesticide,
often vary considerably in their toxicity to bees. Dust formulations
are typically more hazardous than sprays because they are picked
up on bee hairs. A wettable powder such as Sevin 80S would usually
remain toxic in the field for longer time than Sevin XLR Plus, an
emulsifiable concentrate. However, granular insecticides are less
hazardous to honey bees. Microencapsulated materials such as Penncap-M
are particularly dangerous to use around bees because the capsules
have a special tendency to adhere to bees due to their size and
electrostatic charge, and because the contaminated pollen collected
by bees in the treated fields is stored in the hive and remains
toxic for an extended period.
Action: Residual activity of an insecticide is an important
factor in determining its safety to pollinators. An insecticide
which degrades within a few hours can generally be applied with
minimum risk when bees are not actively foraging.
Drift of spray applications can cause significant bee poisoning
problems, particularly when drift reaches colonies or adjacent flowering
weeds. In general, sprays should not be applied if wind speed exceeds
10 mph and favors drift towards colonies.
Temperature can have a substantial effect on the bee poisoning hazard.
If temperatures following treatment are unusually low, insecticide
residues can remain toxic to bees many times longer than if higher
from Treated Fields: The most severely damaged colonies are
usually those closest to fields where insecticides are being applied.
However, during periods of pollen or nectar shortage, hives within
five miles of the treated area can be injured.
of Application: Evening application of a short residual insecticide
can greatly reduce any potential for bee damage.
injury to honey bees requires communication and cooperation between
beekeepers, farmers and applicators. It is important that beekeepers
understand cropping practices and pest management practices used
by farmers in the vicinity of their apiaries. Likewise, insecticide
applicators should be sensitive to locations of apiaries, obtain
a basic understanding of honey bee behavior, and learn which materials
and application practices are the most hazardous to bees. While
it is unlikely that all poisonings can be avoided, a balance must
be struck between the effective use of insecticides, the preservation
of pollinators and the rights of all--the beekeeper, farmer and
applicator. In most cases, bee poisonings can be avoided by observing
the following practices.
1. Do not treat
fields in bloom. Be especially careful when spraying crops such
as alfalfa, soybeans, and other legumes and pollinating crops. The
label of certain insecticides expressly prohibits their application
to flowering crops.
fields and field margins before spraying to determine if bees are
foraging on flowering weeds such as milkweeds, smartweed or dandelions.
Where feasible, eliminate weeds by mowing or tillage.
3. Choose short
residual materials and low-hazard formulations if insecticides absolutely
must be applied during the flowering period to save the crop. Notify
local beekeepers as far in advance as possible.
4. Avoid spray
drift. Give careful attention to position of bee colonies relative
to wind speed and direction. Changing spray nozzles or reducing
pressure can increase droplet size and reduce spray drift.
5. Apply insecticides
when bees are not foraging. Some insecticides can be applied in
late evening or early morning with relative safety. In the case
of corn, where bees collect pollen which is shed by tassels in the
early morning, short residual materials could be applied from late
afternoon until midnight to reduce the bee hazard.
6. Adjust spray
programs in relation to weather conditions. Reconsider the timing
of insecticide application if unusually low temperatures are expected
that night because residues can remain toxic to bees which enter
the field the following day. Cease applications when temperatures
rise and bees re-enter the field in early morning. Avoid treating
during hot evenings if beehives are very close to the target field
and honey bees are clustered on the outside of the hives. Be especially
careful that spray does not contact hives.
7. Read the
pesticide label. Carefully follow listed precautions with regard
to bee safety.
from Ralph T. Vale, RI Beekeepers Association; Steven R. Alm, URI
and the University of Nebraska Cooperative Extension, 1999