Honey bees are vulnerable to many of the insecticides used to control damaging pest species by

fruit, vegetable, nut, and seed growers. Growers dependent on honey bees for the pollination of

their crop(s) must constantly maintain a delicate balance between protecting their crops from

pests and pathogens, and protecting the insects that are necessary to pollinate these crops.

The recent dramatic die-off of tens-of-thousands of honey bee colonies has left many beekeepers

devastated and possibly many growers without the quantity and quality of bees needed to

pollinate crops this spring and summer. A research group; the Colony Collapse Disorder

Working group (see MAAREC.org) is trying to determine what factors are responsible for these

unprecedented colony losses. Chemical contamination is one of the possible contributing factors

that is being investigated. These include chemicals being used within the hive for mite and

disease control as well as chemicals pesticides used on crops that may inadvertently find their

way into hives. Until we have more documented information, it is advisable to use pesticides

with care, erring on the precautionary side.

The neonicotinioids are a relatively new class of insecticides that impact the central nervous

system of insects. They act either as contact insecticides or applied to plants, they are

translocated throughout the plant tissue, making all parts of the plant toxic to pests that ingest

them. While imidacloprid registered in 1992, is the best-known insecticide in this class, there

thiamethoxam, etc.). Their use has increased dramatically over the past few years and they are

now the most widely used group of insecticides in the US. Their many uses include: seed

treatments for corn, cotton, canola and sunflowers; foliar sprays of fruit, nut and coffee crops;

granular, and liquid drench applications in turf, ornamentals, fruit crops and in forests; and in

California the number one use of imidacloprid is for the control of structural pests.

There is conflicting information about the affects of neonicotinoids on honey bees, and different

chemicals in this class are known to vary in their toxicity to bees, however the EPA identifies

both imidacloprid and colthianidin as highly toxic to honey bees. For example: "Clothianidin is

highly toxic to honey bees on an acute basis (LD50>0.0439 mg/bee). It has the potential for toxic

chronic exposure to honey bees, as well as other non-target pollinators through the translocation

of clothianidin resides in nectar and pollen. In honey bees, the affects of this toxic chronic

exposure may include lethal and/or sub-lethal effects in the larvae and reproductive effects on the

queen". [EPA Fact Sheet on Clothianidin]. Documented sub-lethal affects of neonicotinoids

include physiological affects that impact enzyme activity leading to impairment of olfaction

memory. Behavioral affects are reported on motor activity that impact navigation and orientation

and feeding behavior. Additional research has found that imidacloprid impairs the memory and

brain metabolism of bees, particularly the area of the brain that is used for making new

memories. Decourtye et al. (2004). Recent research done on imidacloprid looked at crops where

imidacloprid was used as a seed treatment. The chemical was present, by systemic uptake, in

corn and sunflowers in levels high enough to pose a threat to honey bees. Bonmatin et al. (2003

and 2005). In 2002 a broad survey for pesticide residues in pollen was conducted across France.

Imidacloprid was the most frequently found insecticide and was found in 49% of the 81 samples.

Chauzat et al. (2006).

In addition, there is concern about the practice of combining certain insecticides and fungicides.

A North Carolina University study found that some neonictinoids in combination with certain

fungicides, synergized to increase the toxicity of the neonicotinoid to honey bees over 1,000 fold

in lab studies. Iwasa et al. (2004). Both the neonicotinoids and the fungicides (Terraguard and

Procure) are widely used. This synergistic effect needs to be looked at more carefully.

Below is a summary of the chemical and brand names of the commonly used neonicotinoids and

• Know the pesticides you are using and their toxicity to bees (do not depend on third party to

provide this information).

• READ the LABEL AND FOLLOW THE LABEL DIRECTIONS

are present.

apples), select a material that has a lower toxicity to bees (acetamiprid or thiacloprid) and apply

only when bees are not foraging, preferably late evening.

• Do not apply these materials post bloom (example petal fall) until after the bees have been

removed from the crop.

• Blooming time varies depending on varieties. Bees pollinating one variety or crop may be at

risk while another post-bloom crop or variety is being treated. Also while crops may have

completed blooming, bees may be visiting blooming weeds in an around crops. Be aware of

these situations and avoid the application of pesticides on a non-blooming crop if there is risk of

drift onto blooming crops and weeds if bees are present. If a spray must be applied, use the least

toxic material and apply when bees are not foraging.

• Protect water sources from contamination by pesticides. If necessary, provide a clean source of

water close to colony locations prior to their arrival in the orchard or crop.

(http://extension.oregonstate.edu/catalog/pdf/pnw/pnw591.pdf)

EPA Pesticide Fact Sheet on Clothianidin

EPA Pesticide Fact Sheet on Dinotefuran

Decourtye, A., C. Armengaud, M. Renou, J. Devillers, S. Cluzeau et al.(2004). Imidacloprid

78:83-92

Bonmatin, J. M., P. A. Marchand, R. Charvet, I. Moineau, E. R. Bengsch and M. E. Colin. 2005.

Bonmatin, J. M., I. Moineau, R. Charvet, M. E. Colin, C. Fleche, E. R. Bengsch. 2003. Fate of

Chauzat, M. P., J. P. Faucon, A. C. Martel, J. Lachaize, N. Cougoule and M. Aubert. (2006).

Iwasa, T. N. Motoyama, J. T. Ambrose and R. M. Roe. (2004). Mechanism for the differential

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