Killing bees with pesticides

Every beekeeper tries to avoid killing bees.  We usually as a group are supportive of efforts to control widespread use of pesticides.  Homeowners at times need to control honeybees that have invited themselves into their home.  So what are we to do?

In the past it seems that information about pesticides and bees was hard to come by.  Today, the information is more available, but with knowledge there requires a sharing of information.  The following list can be used both to save bees and to also kill them.  I leave the information for your personal use.  Print the list and take it with you next time you need to buy pesticides.

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)
• non-toxic (acute LD50 more than 100μg/bee) to adult bees.

Bee kill rate per hive

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

• Less than 100 bees per day - normal die off rate
• 200-400 bees per day - low kill
• 500-900 bees per day - moderate kill
• More than 1000 bees per day - high kill 

Toxicity of Pesticides to Bees

Common name (ISO)	Examples of Brand names	Pesticide Class	length of residual toxicity	Comments	Bee toxicity
Aldicarb	Temik	Carbamate		apply 4 weeks before bloom	Relatively non-toxic
Carbaryl	Sevin, (b) Sevin XLR	Carbamate	High risk to bees foraging even 10 hours after spraying; 3 – 7 days (b) 8 hours @ 1.5 lb/acre (168 g/Ha) 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. These should never be sprayed on flowering crops especially if bees are active and the crop requires pollination. 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
Carbofuran	Furadan	Carbamate	7 – 14 days	US-EPA ban on use on crops grown for human consumption (2009)carbofuran (banned in granular form)	highly toxic
Fipronil	Various Roach & Ant Baits			Fipronil is a slow acting poison. Should not be applied to vegetation when bees are foraging. See here for damage to crayfish.	highly toxic
Methomyl	Lannate, Nudrin	Carbamate	2 hours +	Should never be sprayed on flowering crops especially if bees are active and the crop requires pollination.	highly toxic
Methiocarb	Mesurol	Carbamate			highly toxic
mexacarbate	Zectran	Carbamate			highly toxic
Pirimicarb	Pirimor, Aphox	Carbamate			Relatively non-toxic
Propoxur	Baygon	Carbamate			highly toxic
Acephate	Orthene	Organophosphate	3 days		Moderately toxic
Azinphos-methyl	Guthion, Methyl-Guthion	Organophosphate	2.5 days	banned in the European Union since 2006.	highly toxic
Chlorpyrifos	Dursban, Lorsban	Organophosphate		banned in the US for home and garden use Should never be sprayed on flowering crops especially if bees are active and the crop requires pollination.	highly toxic
Coumaphos	Checkmite	Organophosphate		This is an insecticide that is used inside the beehive to combat varroa mites andsmall hive beetles, which are parasites of the honey bee. Overdoses can lead to bee poisoning.	Relatively non-toxic
Demeton	Systox	Organophosphate	less than 2 hours		highly toxic
Demeton-S-methyl	Meta-systox	Organophosphate			Moderately toxic
Diazinon	Spectracide	Organophosphate		Residential uses of diazinon were outlawed in the U.S. in 2004. Should never be sprayed on flowering crops especially if bees are active and the crop requires pollination.	highly toxic
dicrotophos	Bidrin	Organophosphate			highly toxic
Dichlorvos	DDVP, Vapona	Organophosphate			highly toxic
Dimethoate	Cygon, De-Fend	Organophosphate	3 days	Should never be sprayed on flowering crops especially if bees are active and the crop requires pollination.	highly toxic
Fenthion	Entex, Baytex, Baycid, Dalf, DMPT, Mercaptophos, Prentox, Fenthion 4E, Queletox,Lebaycid	Organophosphate		Should never be sprayed on flowering crops especially if bees are active and the crop requires pollination.	highly toxic
Fenitrothion	Sumithion	Organophosphate			highly toxic
fensulfothion	Dasanit	Organophosphate			highly toxic
fonofos	Dyfonate EC	Organophosphate	3 hours	List of Schedule 2 substances (CWC)	highly toxic
Malathion	Malathion USB, ~ EC, Cythion, maldison, mercaptothion	Organophosphate	>8 fl oz/acre (58 L/km²) ⇒ 5.5 days		highly toxic
Methamidophos	Monitor, Tameron	Organophosphate		Should never be sprayed on flowering crops especially if bees are active and the crop requires pollination.	highly toxic
Methidathion	Supracide	Organophosphate		Should never be sprayed on flowering crops especially if bees are active and the crop requires pollination.	highly toxic
methyl parathion	parathion Penncap-M	Organophosphate	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. It is classified as a UNEP Persistent Organic Pollutant and WHO Toxicity Class, "Ia, Extremely Hazardous".	highly toxic
mevinphos	Phosdrin	Organophosphate			highly toxic
Monocrotophos	Azodrin	Organophosphate		Should never be sprayed on flowering crops especially if bees are active and the crop requires pollination.	highly toxic
naled	Dibrom	Organophosphate	16 hours		highly toxic
Omethoate		Organophosphate		Should never be sprayed on flowering crops especially if bees are active and the crop requires pollination.	highly toxic
oxydemeton-methyl	Metasystox-R	Organophosphate	<2 hours		highly toxic
phorate	Thimet EC	Organophosphate	5 hours		highly toxic
Phosmet	Imidan	Organophosphate			highly toxic
phosphamidon	Dimecron	Organophosphate			highly toxic
pyrazophos	Afugan	Organophosphate	fungicide		highly toxic
tetrachlorvinphos	Rabon, Stirofos, Gardona, Gardcide	Organophosphate			highly toxic
Trichlorfon, Metrifonate	Dylox, Dipterex	Organophosphate		3 – 6 hours	Relatively non-toxic
Permethrin	Ambush, Pounce	Synthetic pyrethroid	1 – 2 days	safened by repellency under arid conditions. Permethrin is also the active ingredient in insecticides used against theSmall hive beetle, which is a parasite of the beehive in the temperate climate regions.	highly toxic
Cypermethrin	Ammo, Raid	Synthetic pyrethroid	Less than 2 hours	Cypermethrin is found in many household ant andcockroach killers, includingRaid and ant chalk.	highly toxic
Fenvalerate	Asana, Pydrin	Synthetic pyrethroid	1 day	safened by repellency under arid conditions	highly toxic
Resmethrin	Chrysron, Crossfire, Pynosect, Raid Flying Insect Killer, Scourge, Sun-Bugger #4, SPB-1382, Synthrin, Syntox, Vectrin, Whitmire PT-110	Synthetic pyrethroid			highly toxic
Methoxychlor	DMDT, Marlate	Chlorinated cyclodiene	2 hours	available as a General Use Pesticide	highly toxic
Endosulfan	Thiodan	Chlorinated cyclodiene	8 hours	banned in European Union (2007?), New Zealand (2009)	moderately toxic
Clothianidin		Neonicotinoid		Banned in Germany In June 2008, the Federal Ministry of Food, Agriculture and Consumer Protection (Germany) suspended the registration of eight neonicotinoid pesticide seed treatment products used in oilseed rape and sweetcorn, a few weeks after honey bee keepers in the southern state of Baden Württemberg reported a wave of honey bee deaths linked to one of the pesticides,clothianidin.
Imidacloprid	Confidor, Gaucho, acetamiprid, clothianidin, nitenpyram, thiacloprid, thiamethoxam, Kohinor, Admire, Advantage, Merit, Confidor, Hachikusan, Premise, Prothor, and Winner	Neonicotinoid		(see also Imidacloprid effects on bee population)Banned in France since 1999	highly toxic
dicofol		Acaricide			Relatively non-toxic
petroleum oils					Relatively non-toxic
2,4-D	http://extoxnet.orst.edu/pips/24-D.htm ingredient in over 1,500 products	Synthetic auxinherbicide			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)

Highly toxic and banned in the US

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