How to Manage Pests

UC Pest Management Guidelines

Within each of the major groups of pests in citrus, there are selective and broad-spectrum pesticides that can be used to control them. For instance, citrus thrips can be controlled with the broad-spectrum organophosphate dimethoate and the carbamate insecticide formetanate hydrochloride (Carzol) or with selective insecticides such as sabadilla (Veratran), abamectin (Agri-Mek), or spinosad (Success). Lepidopterous pests, such as fruittree leafroller and citrus cutworm, can be controlled with broad-spectrum organophosphate and carbamate insecticides (chlorpyrifos–Lorsban and methomyl–Lannate) or with selective Bacillus thuringiensis microbial insecticides (Javelin, Dipel, MVPII, Cutlass) or the stomach poison cryolite (Prokil Cryolite and Kryocide). Finally, armored scale can be controlled with broad-spectrum organophosphate and carbamate insecticides (chlorpyrifos–Lorsban, methidathion–Supracide, and carbaryl–Sevin), by selective narrow range oil treatments, or by releases of Aphytis parasites. Botanical, microbial, and oil insecticides are not disruptive to most natural enemies. In addition, some broad-spectrum pesticides can be relatively selective when used infrequently and at very low rates: for example, 0.5 pint per acre of chlorpyrifos (Lorsban) for katydids, compared to high rates (6 to 12 pints per acre) used for California red scale.

Some insecticides are selective or safe for one group of natural enemies but not another. For example, lacewings are naturally tolerant of pyrethroids, but parasitic wasps and predatory mites and beetles are very susceptible to this group of pesticides. Insect growth regulators such as pyriproxyfen (Esteem) and bupofezin (Applaud) are safe for parasitic wasps but are very toxic to vedalia beetle needed for cottony cushion scale control. The miticide dicofol (Kelthane) is safe for predatory and parasitic insects but is quite toxic to predatory mites.

Once a broad-spectrum pesticide has been applied, residues on the plant may be harmful to natural enemies for weeks or months. For example, if adult Aphytis wasps are placed in a jar with leaves that were sprayed in the field with the dilute rate needed to control California red scale, chlorpyrifos (Lorsban) residues are toxic to adult Aphytis for 3 to 6 weeks, methidathion (Supracide) affects adults for 9 weeks, and carbaryl (Sevin) affects adults for 5 months after the treatment. In the case of the predatory mite Euseius tularensis, some San Joaquin Valley populations have developed resistance to chlorpyrifos (Lorsban) and their populations are unaffected by this pesticide, but they are easily killed for several months by the carbamate formetanate hydrochloride (Carzol). Occasional, single treatments of broad-spectrum pesticides are much less harmful to natural enemies than multiple broad-spectrum treatments.

It is important to carefully consider the selectivity of a pesticide when making a treatment decision. This includes the effect the pesticide has on nontarget species, its persistence in the environment, and whether or not resistance to the pesticide has developed. These factors are listed in Table 2 and under each recommendation in the guideline. Range of Activity is listed first and denotes the degree of selectivity each pesticide recommendation has, along with the group of organisms primarily affected by the treatment. For example, the range of activity for dimethoate is listed as "Broad (insects and beneficial mites)." This means dimethoate affects most groups of insects and beneficial mites. On the other hand, Bacillus thuringiensis is listed as "Narrow (caterpillars)" because it only affects caterpillars. Persistence, or the length of time a pesticide remains effective, is listed next and is categorized as short (days), intermediate (a few weeks), or long (many weeks or months). And finally, in instances where resistance has been observed in either the pest or natural enemy, this information is included.

PUBLICATION

UC IPM Pest Management Guidelines: Citrus
UC ANR Publication 3441
General Pesticide Information
E. E. Grafton-Cardwell, Kearney Agricultural Center, Parlier
J. G. Morse, Entomology, UC Riverside
N. V. O’Connell, UC Cooperative Extension, Tulare Co.
P. A. Phillips, UC IPM Program, UC Cooperative Extension, Ventura Co.
C. E. Kallsen, UC Cooperative Extension, Kern Co.
D. R. Haviland, UC Cooperative Extension, Kern Co.
Acknowledgments for contributions to the insect, mite, and snail section:
J. Barcinas, E. S. I., Corona, CA
R. Dunn, Badger Farming Co., Exeter, CA
J. Gorden, Pest Management Associates, Exeter, CA
H. Griffiths, E. S. I., Corona, CA
D. Machlitt, Consulting Entomology Services, Moorpark, CA
C. Musgrove, retired entomologist, Riverside, CA
K. Olsen, S & J Ranch, Pinedale, CA
T. Roberts, E. S. I., Corona, CA
J. Stewart, Pest Management Associates, Exeter, CA
P. Washburn, Washburn & Sons Citrus Pest Control, Riverside, CA

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