How to Manage Pests

UC Pest Management Guidelines


Relative Toxicities of Some of the Pesticides Used in Walnuts to Natural Enemies and Honey Bees

(Reviewed 12/07, updated 3/11)

In this Guideline:

Common name (trade name) Mode of Action1 Selectivity2
(affected groups)
Predatory Mites3 General Predators4 Parasites4 Honey Bees5 Duration of impact to natural enemies6
abamectin (Agri-Mek) 6 moderate (mites, leafminers) H L M/H II long to predatory mites and affected insects
acequinocyl (Kanemite) 20B narrow (mites) L IV
acetamiprid (Assail) 4A moderate (sucking insects, larvae) 7 III moderate
Bacillus thuringiensis ssp. kurstaki 11.B2 narrow (caterpillars) L L L IV short
bifenazate (Acramite) 25 narrow (mites) L L L IV short
bifenthrin (Brigade) 3A broad (insects, mites) H H H I–III8 long
buprofezin (Centaur) 16 narrow (sucking insects, beetles) L H9 L IV long
carbaryl (Sevin) 1A broad (insects, mites) L/H H H I long
chlorantraniliprole (Altacor) 28 narrow (primarily caterpillars) L L L/M IV short
chlorpyrifos (Lorsban) 1B broad (insects, mites) M H H I moderate
clofentezine (Apollo) 10A narrow (mites) L L L IV short
Cydia pomonella granulovirus (Cyd-X) narrow (codling moth) none none none IV none
cyfluthrin (Baythroid) 3 broad (insects, mites) H H H I moderate
dicofol (Dicofol) un narrow (pest mites and mites) H M M IV long to beneficial mites
diflubenzuron (Dimilin) 15 L H10 L IV
emamectin benzoate (Proclaim) 6 narrow (caterpillars) III
esfenvalerate (Asana) 3 broad (insects, mites) H M H I moderate
etoxazole (Zeal) 10C narrow (mites) 11 IV short
fenbutatin oxide (Vendex) 12B narrow (pest mites) L L L IV short
flubendiamide (Belt) 28 L L L/M I short
hexythiazox (Onager) 10B narrow (mites) L L L IV short to moderate
imidacloprid (Provado) 4A narrow (sucking insects) H II short to moderate
lambda cyhalothrin (Warrior) 3 broad (plant bugs, beetles, caterpillars) H H H I12 moderate
malathion 1B broad (insects, mites) H H H II moderate
methidathion (Supracide) 1B broad (insects, mites) H H H I moderate to long
methoxyfenozide (Intrepid) 18 narrow (caterpillars) L L L IV none
methyl parathion (Penncap-M) 1B M M M I
permethrin (Ambush, Pounce) 3 broad (insects, mites) L H H I long
petroleum oils broad (exposed insects, mites) L L L III short to none
phosmet (Imidan) 1B broad (insects, mites) H H H I moderate to long
propargite (Omite) 14 narrow (pest mites) M13 L L IV short
pyriproxyfen (Seize) 7C narrow (scale, beetles) L H14 L IV long
rosemary oil/peppermint oil (Ecotrol) broad (exposed insects, mites) L L L IV
spinetoram (Delegate) 5 narrow (caterpillars, aphids, scales) L/H M15 L/M III moderate16
spinosad (Entrust, Success) 5 narrow (caterpillars, aphids, scales) L/H M15 L/M III short to moderate
spinosad (GF-120) 5 narrow (husk fly)
spirodiclofen (Envidor) 23 narrow (mites) I
H = high M = moderate L = low — = no information un = unknown or uncertain mode of action
1 Rotate chemicals with a different mode-of-action Group number, and do not use products with the same mode-of-action Group number more than twice per season to help prevent the development of resistance. For example, the organophosphates have a Group number of 1B; chemicals with a 1B Group number should be alternated with chemicals that have a Group number other than 1B. Mode of action Group numbers are assigned by IRAC (Insecticide Resistance Action Committee). For additional information, see their Web site at
2 Selectivity: broad means it affects most groups of insects and mites; narrow means it affects only a few specific groups.
3 Generally, toxicities are to western predatory mite, Galendromus occidentalis. Where differences have been measured in toxicity of the pesticide-resistant strain versus the native strain, these are listed as pesticide-resistant strain/native strain.
4 Toxicities are averages of reported effects and should be used only as a general guide. Actual toxicity of a specific chemical depends on the species of predator or parasite, environmental conditions, and application rate.
5 Ratings are as follows: I–Do not apply to blooming plants; II–Apply only during late evening; III–Apply only during late evening, night, or early morning; and IV–Apply at any time with reasonable safety to bees. For more information, see How to Reduce Bee Poisoning from Pesticides (PDF), Pacific Northwest Extension publication PNW591.
6 Duration: short means hours to days; moderate means days to 2 weeks; and long means many weeks or months.
7 May cause flare-ups of spider mite populations.
8 If rate is less than 0.04 lb a.i./acre, rating is III; if 0.04 lb a.i./acre, rating is II; if 0.06 lb a.i./acre, rating is I.
9 Use lowest rates for best management of western predatory mite/spider mite ratio (propargite).
10 High toxicity to juvenile stages of predators and reduces fertility of adult green lacewings.
11 Acute toxicity low but reproductive capacity is impacted.
12 If rate is 0.02 lb a.i./acre, rating is II.
13 Use lowest rates for best management of western predatory mite/spider mite ratio (propargite).
14 Kills lady beetles.
15 Toxic against some natural enemies (predatory thrips, syrphid fly larvae) when sprayed and shortly thereafter (8-24 hours).
16 Residual is moderate if solution is between pH of 7 to 8.



[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Walnut
UC ANR Publication 3471

General Information

Acknowledgements: This table was compiled based on research data and experience of University of California scientists who work on a variety of crops and contribute to the Pest Management Guideline database, and from Flint, M. L. and S. H. Dreistadt. 1998. Natural Enemies Handbook: An Illustrated Guide to Biological Pest Control, ANR Publication 3386.

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