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Pesticide toxicity to bees

Further information: Colony Collapse Disorder

Pesticides vary in their effect on bees. Contact insecticides, those which kill by touching the organism, affect the worker bee that is directly sprayed. Systemic insecticides, those that are incorporated by treated plants, can contaminate nectar or pollen, and kill bees in the hive.

Dusts and wettable powders tend to be more hazardous to bees than solutions or emulsifiable concentrates.

Actual damage to bee populations is a function of the degree of toxicity of the compound, in combination with the mode of application; a highly potent insecticide applied only to the soil, for instance, would be expected to kill mainly soil-dwelling insects, such as grubs or mole crickets, and not bees.


Classification of pesticide toxicity

Insecticide toxicity is generally measured using LD50 - the exposure level that causes 50% of the population exposed to die. Toxicity thresholds are generally set at

  • highly toxic (acute LD50 less than 2μg/bee)
  • moderately toxic (acute LD50 2ug/bee to 10.99μg/bee)
  • slightly toxic (acute LD50 11ug/bee to 100μg/bee)
  • practically non-toxic (acute LD50 more than 100μg/bee) to adult bees.

[1] [2]

LD50 is an incomplete measure of toxicity to bees and other social insects because it is a measure of individual toxicity, not colony toxicity. It does not account for the ways in which bee behavior can mitigate or exacerbate the effects of the pesticide on the colony. For example, a moderate to low toxicity pesticide (by LD50 measurement) which is used in granular form and is collected and concentrated along with pollen can be highly lethal to the colony. On the other hand, a pesticide which is so toxic that the exposed bees die in the field can be less dangerous to the colony than a less toxic pesticide which allows the exposed bees to return to the hive and contaminate their fellows. Likewise, a highly toxic pesticide (according to LD50 measures) is "safe" for bees if it is applied on a grass lawn or other location without blooming flowers which would attract the bees. Furthermore, LD50 studies are conducted against adult bees and do not measure the effects on larvae, etc.

Bee kill rate per hive

The kill rate of bees in a single bee hive can be classified as:

< 100 bees per day - normal die off rate
200-400 bees per day - low kill
500-900 bees per day - moderate kill
> 1000 bees per day - high kill

Bee Toxic Pesticides

Highly toxic and banned in the US

  • Aldrin banned by US EPA in 1974
  • carbofuran (banned in granular form)
  • dieldrin banned by US EPA in 1974
  • heptachlor
  • lindane, BHC (banned in California)

Pesticide Class Brand name Generic name length of residual toxicity Comments Bee toxicity
Carbamate Baygon propoxur highly toxic
Carbamate Furadan carbofuran 7 - 14 days highly toxic
Carbamate Lannate methomyl highly toxic
Carbamate Lannate LS 2 hours + highly toxic
Carbamate Mesurol methiocarb highly toxic
Carbamate Nudrin methomy highly toxic
Carbamate Sevin carbaryl 3 - 7 days highly toxic
Carbamate Sevin XLR Carbaryl 8 hours @ 1.5 lb/acre (168 kg/km²) or less. Bees poisoned with carbaryl can take 2-3 days to die, appearing inactive as if cold. It allows them time to take contaminated nectar and pollen back to the colony. Some crops treated with Sevin® under the wrong conditions (in bloom, using a dust formulation, with large numbers of bees in the field) have been responsible for disastrous kills. Sevin® is one of the United States' most widely used insecticides for a wide variety of insect pests. It is also one of the most toxic to honey bees, in certain formulations. There are formulations, however, which are determined to be less toxic (see tables). Usually, applicator-beekeeper communication can effectively be used to adequately protect bees from Sevin® poisoning. highly toxic
Organophosphate Afugan pyrazophos highly toxic
Organophosphate Azodrin monocrotophos highly toxic
Organophosphate Baytex fenthion highly toxic
Organophosphate Bidrin dicrotophos highly toxic
Organophosphate Cygon dimethoate 3 days banned in the US highly toxic
Organophosphate Cythion malathion highly toxic
Organophosphate Dasanit fensulfothion highly toxic
Organophosphate DDVP dichlorvos highly toxic
Organophosphate De-Fend dimethoate highly toxic
Organophosphate Dibrom naled 16 hours highly toxic
Organophosphate Dursban chlorpyrifos banned in the US for home and garden use highly toxic
Organophosphate Dyfonate EC fonofos 3 hours highly toxic
Organophosphate Gardona tetrachlorvinphos highly toxic
Organophosphate Guthion azinphos-methyl 2.5 days highly toxic
Organophosphate Imidan phosmet highly toxic
Organophosphate Lorsban chlorpyrifos [2] 4 - 6 days banned in the US for home and garden use highly toxic
Organophosphate Malathion USB >8 fl oz/acre (58 L/km²) ⇒ 5.5 days highly toxic
Organophosphate Malathion EC 2-6 hours highly toxic
Organophosphate Metasystox-R oxydemetonmethy <2 hours highly toxic
Organophosphate Methyl-Guthion azinphos-methyl highly toxic
Organophosphate Monitor methamidophos highly toxic
Organophosphate parathion Penncap-M methyl parathion 5-8 days By far the most potentially damaging pesticides for honey bees are those packaged in tiny capsules (microencapsulated). Microencapsulated methyl parathion (PennCap M®), for example, is a liquid formulation containing capsules approximately the size of pollen grains which contain the active ingredient. When bees are out in the field, these capsules can become attached electrostatically to the pollen-collecting hairs of the insects, and at times are collected by design. When stored in pollen, the slow-release feature of the capsules allows the methyl parathion to be a potential killer for several months. At the present time, there is no way to detect whether bees are indeed poisoned by micro-encapsulated methyl parathion, so a beekeeper potentially could lose replacement bees for those already poisoned by the pesticide. It is, therefore, strongly recommended by experts that this formulation be used only when honey bee exposure is not a possibility. highly toxic
Organophosphate Spectracide diazinon highly toxic
Organophosphate Sumithion fenitrothion highly toxic
Organophosphate Supracide methidathion highly toxic
Organophosphate Tameron methamidophos highly toxic
Organophosphate Thimet EC phorate 5 hours highly toxic
Organophosphate Vapona dichlorvos highly toxic
Synthetic pyrethroid Ambush permethrin 1 - 2 days safened by repellency under arid conditions. Permethrin is also the active ingredient in insecticides used against the Small hive beetle, which is a parasite of the beehive in the temperate climate regions. highly toxic
Synthetic pyrethroid Ammo cypermethrin Less than 2 hours highly toxic
Synthetic pyrethroid Asana esfenvalerate 1 day safened by repellency under arid conditions highly toxic
Synthetic pyrethroid Pounce permethrin 1 - 2 days safened by repellency under arid conditions highly toxic
Synthetic pyrethroid Pydrin esfenvalerate 6 hours highly toxic
Synthetic pyrethroid resmethrin highly toxic
Chlorinated cyclodiene DMDT, Marlate methoxychlor 2 hours highly toxic
Chlorinated cyclodiene Thiodan endosulfan 8 hours highly toxic
Chloronicotines Imidacloprid (see also Imidacloprid effects on bee population) highly toxic
Dimecron phosphamidon highly toxic
Famophos famphur highly toxic
Phosdrin mevinphos highly toxic
phosphamidon Dimecron highly toxic
Systox demeton <2 hours highly toxic
Tepp most toxic to bees LD50 0.001 micrograms per bee but short residual activity highly toxic
Zectran mexacarbate highly toxic
Orthene acephate 3 days Moderately toxic
demeton-s-methyl Moderately toxic
Checkmite coumaphos This is an organo phosphate insecticide that is used inside the beehive to combat varroa mites and small hive beetles, which are parasites of the honey bee. Overdoses can lead to bee poisoning. Relatively non-toxic
Endosulfan Relatively non-toxic
dicofol Relatively non-toxic
pirimicarb Relatively non-toxic
petroleum oils Relatively non-toxic
most pyrethroid chemicals Relatively non-toxic
Temik aldicarb apply 4 weeks before bloom Relatively non-toxic
Dylox trichlorfon 3 - 6 hours Relatively non-toxic
2,4-D herbicide [3] Relatively non-toxic

Source: Protecting Bees When Using Insecticides University of Nebraska Lincoln, Extension, May 1998

Common insecticides toxic to bees and used on soybeans

Many insecticides used against soybean aphids are highly toxic to bees.

  • Orthene 75S (acephate)
  • Address 75 WSP (acephate)
  • Sevin (Carbaryl)
  • Lorsban 4E (Chlorpyrifos)
  • Dimate (Dimethoate)
  • Steward 1.25 SC (Indoxacarb)
  • Lannate (Methomyl)
  • Cheminova Methyl 4EC (Methyl Parathion)
  • Penncap M (microencapsulated Methyl Parathion)
  • Tracer (Spinosad)

See also


  1. ^ [1] Pollinator protection requirements for Section 18 Emergency Exemptions and Section 24(c) special local need registration in Washington State; Registration Services Program Pesticide Management Division Washington State Dept of Agriculture, Dec 2006
  2. ^ Hunt, G.J.; Using honey bees in pollination Purdue University, May 2000


  • Commonly Used Insecticides for Soybeans Kansas State University Extension, Aug 2004

External links

  • Honey Bees and Pesticides, 1978, Mid-Atlantic Apiculture Research and Extension Consortium
  • Mayer, D.F., Johansen, C.A. & Baird, C.R.; How to Reduce Bee Poisoning from Pesticides, PNW518, A Pacific Northwest Extension Publication, Washington, Oregon, Idaho, Copyright 1999 Washington State University. Includes an extensive list of toxic chemicals such as pesticides that affect bees.
  • McBride, Dean k.; Protecting Honeybees From Pesticides, 1997 North Dakota State University
  • Sanford, Malcolm T.; Protecting Honey Bees From Pesticides, University of Florida Institute of Food and Agricultural Sciences Extension, April 1993
  • US EPA Pesticide Registration (PR) Notice 2001-5
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Pesticide_toxicity_to_bees". A list of authors is available in Wikipedia.
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