Active Ingredient

Trade Names

Risk Class²

LD₅₀³

Residual⁴

acephate

Orthene

I

1.2

1 day to >3 days

aldicarb

Temik

I

0.35

>1 day to >2 days

azinphos methyl

Guthion

I

0.43

2 days to >5 days

Bacillus thuringiensis

Biobit, Cutlass, Dipel, Javelin, Thuricide

III

NA

<2 hours

carbaryl

Sevin

I

1.5 to 26.5

<2 hours to 12 days

chlorpyrifos

Dursban, Lorsban

I

0.11

5 hours to 6 days

cyhexatin

Plictran

III

NA

<2 hours

cypermethrin

Ammo, Cymbush

III

NA

<2 hours to >3 days

diazinon

Diazinon

I

0.37

<1 day to 2 days

dicofol

Kelthane

III

NA

<2 hours

dicrotophos

Bidrin

I

0.3

1 day to 1 days

diflubenzuron

Dimilin

III

NA

<2 hours to 6 hours

dimethoate

Cygon, De-fend, Rebelate

I

0.19

<2 hours to >3 days

disulfoton

Di-syston

II

6.12

<2 hours to 7 hours

endosulfan

Thiodan

II

7.8

<2 hours to 1 day

ethion

Ethion oil

III

NA

<2 hours

fluvalinate

Mavrik

III

65.8

<2 hours

fonofos

Dyfonate

II

8.68

<2 hours to 6 hours

formetanate hydrochloride

Carzol

II

9.2

<2 hours to 2 hours

lindane

Lindane

I

NA

>2 days

malathion

Cythion, Malathion

I

0.73

<2 hours to 5 days

methamidophos

Monitor

I

1.37

4 hours to 1 day

methidathion

Supracide

I

0.24

day to 3 days

methomyl

Lannate

I

1.29

<2 hours to >1 day

methoxychlor

Marlate, Methoxychlor

III

NA

<2 hours

methyl parathion

Penncap-M

I

0.11 to 0.24

<1 day to >7 days

mevinphos

Phosdrin

I

0.3

<2 hours to <5 hours

naled

Dibrom

I

0.49

2 hours to >1 day

oxamyl

Vydate

II

10.3

<2 hours to 12 hours

oxythioquniox

Morestan

III

NA

<2 hours

parathion

Parathion

I

0.18

10 hours to >1 day

permethrin

Ambush, Permethrin, Pounce

I

0.16

12 hours to >3 days

phorate

Thimet

II

10.25

<2 hours to 5 hours

phosmet

Imidan

I

1.13

8 hours to >3 days

profenofos

Curacron

II

3.46

<2 hours to 9 hours

propargite

Omite, Ornamite

III

NA

<2 hours

sulprofos

Bolstar

II

7.22

<2 hours to >1 day

thiodicarb

Larvin

II

7.08

<2 hours

trichlorfon

Dylox, Proxol

III

NA

<2 hours to 6 hours

¹Table modified from Johansen & Mayer (1990) and Delaplane (1993).
²Risk classes: I = highly toxic to honey bees, II = moderately toxic to honey bees, III = relatively nontoxic to honey bees. The risk class is closely associated with the LD₅₀.
³LD₅₀ = the Lethal Dose required to kill 50% of the test honey bees, expressed in micrograms per bee. The smaller the LD₅₀, the more toxic the product.
⁴Period of residual toxicity to honey bees after application. Evening applications of products with residuals of 8 hours or less generally cause only moderate harm to bees, even if the LD₅₀ is small. For example, mevinphos is very toxic to bees, but because it has a short residual, it is fairly safe for early evening applications.