How to Manage Pests

UC Pest Management Guidelines


Relative Toxicities of Pesticides Used in Rice to Natural Enemies and Honey Bees

(Reviewed 4/04, updated 2/09, pesticides updated 10/15, corrected 10/16)

In this Guideline:

Common name (Example trade name) Mode of action1 Selectivity2 (affected groups) General predators3 Parasites3 Honey bees4 Mosquito fish (Gambusia sp.) Duration of impact to natural enemies5
carbaryl (Sevin 4F) 1A broad (insects, other invertebrates) H H I H long
carbaryl (Sevin XLR Plus) 1A broad (insects, other invertebrates) H L I H long
clothianidin (Belay) 4A lygus, aphids M/L M/L I long
copper sulfate pentahydrate narrow (insects, other invertebrates) M L M moderate
diflubenzuron (Dimilin) 15 narrow (insects, other invertebrates) M L II L moderate
lambda-cyhalothrin (Warrior) 3A broad (insects, other invertebrates) H H I H long
malathion 1B broad (insects) H H I L/M moderate
zeta-cypermethrin (Mustang) 3A broad (insects, other invertebrates) M M I H long
H = high    M = moderate     L = low     — = no information
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 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.
4 Ratings are as follows: I—Do not apply or allow to drift to plants that are flowering; II—Do not apply or allow to drift to plants that are flowering, except when the application is made between sunset and midnight if allowed by the pesticide label and regulations; III—No bee precaution, except when required by the pesticide label or regulations. For more information about pesticide synergistic effects, see Bee Precaution Pesticide Ratings.
5 Duration: short means hours to days; moderate means days to 2 weeks; and long means many weeks or months.



[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Rice
UC ANR Publication 3465

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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