How to Manage Pests
UC Pest Management Guidelines
Citrus Red Mite
Scientific Name: Panonychus citri
(Reviewed 9/08, updated 9/08, corrected 6/13)
In this Guideline:
Description of the Pest
Adult female citrus red mites are oval and globular; the male is smaller and has a tapered abdomen. Each female lays 20 to 50 eggs at a rate of 2 to 3 a day, depositing them on both sides of leaves. The life cycle from egg to egg may be as short as 12 days during warm weather.
Populations increase in spring, late summer, and early fall in response to new growth; citrus red mites prefer to feed on fully expanded young leaves but will also infest fruit.
On leaves, citrus red mite feeding results in a pale stippling visible primarily on the upper surface of the leaf. In severe infestations, the stippling enlarges to dry necrotic areas (commonly called mesophyll collapse). Eventually, leaves may drop and twigs dieback. Stippling or silvering also occurs on green fruit but usually disappears when fruit change color. If large populations feed on nearly mature fruit, the silvering may persist. High populations can also cause fruit sunburn if hot weather is occurring. During fall Santa Ana winds, low levels of citrus red mite can cause a blasting or burning of foliage and leaf drop in coastal and southern California growing areas.
Citrus red mite is more of a problem when trees are water stressed and conditions are hot and dry. Research on San Joaquin Valley navels and coastal lemons showed citrus can tolerate much higher populations than previously thought and treatment is not normally required in healthy orchards under a biologically based IPM program. Populations tend to be heavier in spring and fall, especially in orchards where natural enemies are destroyed by the use of broad-spectrum insecticides such as formetanate hydrochloride (Carzol) or methidathion (Supracide). Monitor orchards and use narrow range selective miticides whenever possible.
Predaceous mites, predaceous insects, and a virus are important in regulating citrus red mite populations. The most important natural enemy is the predaceous mite (Euseius tularensis). These beneficial mites can establish their populations before citrus red mites are numerous because they have alternate food sources (pollen, citrus thrips larvae, leaf sap, nectar, and honeydew). They mainly attack immature stages of the citrus red mite. The female of both species is about the same size as the female citrus red mite but is pear-shaped, shiny, and translucent. Predator eggs are clear, oval, and about twice the size of citrus red mite eggs. Eggs hatch and develop into adults in about 8 days.
Other predators of the citrus red mite include a small black lady beetle (Stethorus picipes), a predaceous dustywing (Conwentzia barretti), and the sixspotted thrips (Scolothrips sexmaculatus). In addition, a disease caused by a virus specific to citrus red mite is widespread in citrus-growing areas. The disease becomes epidemic under warm, moderately dry conditions when mite populations are high and can rapidly reduce the mite population. Symptoms of virus-infected mites include stiff movements, legs curled under the body, and subsequent disintegration of the body. If diseased mites are mounted on a slide and examined under a polarizing microscope, internal crystals that shine in the polarized light are evident.
Besides predators and the virus, hot temperatures (above 90°F) and low humidity also reduce citrus red mite populations.
Mites increase their reproduction on water-stressed trees. Good irrigation reduces red mite outbreaks. Water roads to limit dust buildup, which also promotes mites.
Organically Acceptable Methods
Cultural and biological controls and petroleum oil sprays are acceptable on organically managed citrus.
Miticides available for controlling citrus red mite (bearing orchards only) include acequinocyl (Kanemite), dicofol (Dicofol), fenbutatin oxide (Vendex), hexythiazox (Onager), oil, propargite (Omite), pyridaben (Nexter), and spirodiclofen (Envidor). For nonbearing orchards only, bifenazate (Acramite) and etoxazole (Zeal) can be used.
Of these miticides, some are more selective than others. Acequinocyl, bifenazate, fenbutatin oxide, and oil have the least effect of all on natural enemies, including predatory mites, but they also provide a shorter period of control of pest mites. Dicofol, etoxazole, hexythiazox, propargite, pyridaben, and spirodiclofen are of intermediate selectivity because they impact both pest mites and predatory mites for up to 6 weeks but have minimal impact on beneficial insects such as lacewings, lady beetles, and Aphytis melinus, which help control caterpillars, scale, thrips, and other pests.
Monitoring and Treatment Decisions
In February in the San Joaquin Valley, survey each orchard to determine if mites are present. Scan several leaves per tree at various sites, and use a hand lens to check a few leaves for eggs and immatures. In southern California and coastal areas, depending on the local situation, consider monitoring beginning in late summer.
Monitoring in the San Joaquin Valley
In March, or as soon as mites are detectible, begin monitoring by collecting a total of 100 fully expanded leaves from throughout the orchard. Select leaves from just inside the shady region of the tree. Using this sample:
In San Joaquin Valley navel oranges, economic loss will not occur if citrus red mite densities do not exceed eight mature females per leaf by 2 to 4 weeks after petal fall. Vigorous, well-irrigated trees can tolerate more. Low-to-moderate populations are considered to be beneficial as they provide food for natural enemies. High temperatures and virus reduce mite populations in June and July and no treatment is generally required during summer.
In orchards where nonselective pesticides have destroyed natural enemies, treatments may be required in spring to prevent excessive mite populations at petal fall. Use the application times listed in the following table when applying oil sprays.
Monitoring in Southern California and Coastal Areas
Spring and summer populations of citrus red mite generally do not require regular monitoring or treatment. Fall populations can be very damaging in conjunction with the Santa Ana winds if naturally occurring control is upset by nonselective pesticides or dust. About every 2 weeks in late summer, monitor orchards as described above for the San Joaquin Valley. Consider applying a treatment before Santa Ana conditions if there are more than eight to ten citrus red mites per leaf.
In southern California and coastal areas, spring and summer populations of citrus red mite do not require treatment, but fall populations can be very damaging in conjunction with the Santa Ana winds if naturally occurring control is upset by nonselective pesticides or dust. Begin monitoring orchards in late summer, and consider applying a treatment before Santa Ana conditions if there are more than eight to ten citrus red mites per leaf.
Use of Oils
Extensive research on the use of oil sprays against various mite and scale insects has resulted in the development of recommendations that use specific rates and timing of treatments on different varieties of citrus in different regions of California in order to achieve expected pest control and limit the potential for leaf or fruit drop or fruit damage as a result of phytotoxicity. The narrow range 415, 440, and 455 oils were specifically developed for use in California to limit these concerns. Precautions for using petroleum spray oils are listed at the beginning of this guideline. Because mites are on the outside of the tree and sprayed with outside coverage, risks of phytotoxicity from oil are less than with a scale application. For additional information, see Managing Insects and Mites with Spray Oils.
UC IPM Pest Management Guidelines:
Insects, Mites, and Snails
Acknowledgments for contributions to Insect, Mites, and Snails:
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