Agriculture: Citrus Pest Management Guidelines

Twospotted Spider Mite

  • Tetranychus urticae
  • Description of the Pest

    This species has two dark spots, composed of food content, showing through the transparent body wall. The abdomen is oval and sparsely covered with spines. The adult male is smaller than the female and is characterized by its distinctly pointed abdomen. It sometimes has an orange or brown tinge and is usually more active than the female. The female is more robust than the male and is more oval in shape. Color of the female can vary; typically, it is a pale leaf-green, but it can also be tinged with yellow, brown, and sometimes orange.

    All stages of the twospotted spider mite overwinter in protected places on the tree, such as the navel of navel oranges, under the button, and where fruit touch. If the weather is mild, mites continue to feed and reproduce during winter. Activity increases in late spring and peaks in summer. Spider mites first appear on the underside of leaves and when numbers increase, they can also be found on the upper side of leaves and on fruit. They cover leaves and fruit with conspicuous webbing.

    Eggs are spherical and translucent when first laid, becoming opaque before hatching. Immature mites molt three times before becoming adults; under ideal conditions, a generation can be completed in 7 days.

    Damage

    As a result of their small size and habit of feeding on the underside of foliage, this species may go undetected until a population has caused serious damage to a tree. Light infestations result in yellow or brown spots between leaf veins. Clusters of dried, brown leaves and profuse webbing indicate a heavy infestation, which if compounded by water stress, could result in leaf and fruit drop.

    Management

    The twospotted spider mite is an occasional pest on citrus, particularly in the San Joaquin Valley. Its damage potential varies from year to year and is related to water stress and heat. Monitor for twospotted spider mite year round and spray with the most selective miticide to preserve natural enemies.

    Biological Control

    A number of predators provide substantial control of twospotted spider mites. These include the sixspotted thrips, Scolothrips sexmaculatus, the spider mite destroyer, Stethorus picipes, minute pirate bugs, Orius spp., and the beneficial mite, Euseius tularensis.

    Cultural Control

    Adequate irrigation will reduce the damage from spider mite feeding.

    Organically Acceptable Methods

    Use cultural and biological controls and certain petroleum oil sprays (such as PureSpray Green NR 440) on organically managed citrus.

    Selectivity

    Miticides available for controlling twospotted spider mite in bearing orchards include abamectin (Agri-Mek, etc.), acequinocyl (Kanemite), fenbutatin oxide (Vendex), fenpyroximate (Fujimite), hexythiazox (Onager), oil, pyridaben (Nexter), and spirodiclofen (Envidor); in nonbearing orchards, bifenazate (Acramite) can be used.

    Of these miticides, some are more selective than others. Acequinocyl, bifenazate, fenbutatin oxide, and oil cause the least harm to natural enemies, including predatory mites, but they also provide a shorter period of control of pest mites. Etoxazole, hexythiazox, pyridaben, and spirodiclofen are of intermediate selectivity because they harm both pest mites and predatory mites for up to 6 weeks but cause minimal harm to beneficial insects such as lacewings, lady beetles, and Aphytis melinus, which help control caterpillars, scale, thrips, and other pests.

    Monitoring and Treatment Decisions

    In the San Joaquin Valley, check for twospotted mites when you monitor citrus red mite in late winter and early spring. Continue monitoring twospotted mite occasionally during summer and more closely in late summer and fall. Look for yellow-brown spots on foliage, particularly in the last growth flush, indicating feeding by twospotted spider mites. High numbers of mites in summer and fall may require miticide applications, but thresholds have not been established.

    Common name Amount to use REI‡ PHI‡
    (Example trade name) (type of coverage)** (hours) (days)
    Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least harmful to natural enemies, honey bees, and the environment are at the top of the table. When choosing a pesticide, consider information relating to air and water quality, resistance management, and the pesticide's properties and application timing. Always read the label of the product being used.
    NONBEARING TREES ONLY
    A. BIFENAZATE
    (Acramite 50WS) 0.75–1 lb/acre (OC) 12 365 (1 year)
    RANGE OF ACTIVITY: Pests: narrow (mites); Natural enemies: predatory mites
    PERSISTENCE: Pests: intermediate; Natural enemies: intermediate
    MODE-OF-ACTION GROUP NUMBER1: 20D
    COMMENTS: For use in nonbearing orchards only. Do not apply more than once per year.
    BEARING TREES
    A. NARROW RANGE OIL (92% UR)
    (415, 440) 1.2–1.4% (OC) See label When dry
    . . . or . . .
    NARROW RANGE OIL (99% UR)
    (415, 435, 440, 455) 1.2–1.4% (OC) See label When dry
    RANGE OF ACTIVITY: Pests: broad (unprotected stages of insects and mites); Natural enemies: most
    PERSISTENCE: Pests: short; Natural enemies: short
    MODE OF ACTION: Contact including smothering and barrier effects.
    COMMENTS: Use highest rate for July or August applications. Narrow range 440 (or higher) spray oil is preferable in the Central Valley during warmer months because of greater persistence, but risk of phytotoxicity increases unless using products with 99% unsulfonated residues (UR). Caution: Serious hazards are associated with oil sprays to green lemons because of phytotoxicity after sweating; check label for preharvest interval.
    . . . or . . .
    NARROW RANGE OIL (92 OR 99% UR)
    (415) 6–20 gal/acre (LV) See label When dry
    RANGE OF ACTIVITY: Pests: narrow (citrus red mite) Natural enemies: predatory mites.
    PERSISTENCE: Pests: short; Natural enemies: short
    MODE OF ACTION: Contact including smothering and barrier effects.
    COMMENTS: Higher amounts of oil are for larger trees or for warmer times of the year to increase persistence. Caution: Serious hazards are associated with oil sprays to green lemons because of phytotoxicity after sweating; check label for preharvest interval.
    B. ACEQUINOCYL
    (Kanemite 15SC) 21–31 oz/acre (OC or IC) 12 7
    RANGE OF ACTIVITY: Pests: narrow (mites); Natural enemies: predatory mites
    PERSISTENCE: Pests: intermediate; Natural enemies: intermediate
    MODE-OF-ACTION GROUP NUMBER1: 20B
    COMMENTS: For use on oranges, grapefruit, and lemons only. Apply by ground using 100 to 250 gal water/acre. Do not use less than 100 gal water/acre. Allow a minimum of 21 days between applications.
    C. HEXYTHIAZOX
    (Onager) 12–24 oz/acre (OC or IC) 12 7
    RANGE OF ACTIVITY: Pests: narrow (mites); Natural enemies: predatory mites
    PERSISTENCE: Pests: intermediate; Natural enemies: short to intermediate
    MODE-OF-ACTION GROUP NUMBER1: 10A
    COMMENTS: Do not apply more than once per year. Effective against the egg stage.
    D. PYRIDABEN
    (Nexter) Label rates (OC or IC) 12 7
    RANGE OF ACTIVITY: Pests: narrow (mites); Natural enemies: predatory mites
    PERSISTENCE: Pests: intermediate; Natural enemies: intermediate
    MODE-OF-ACTION GROUP NUMBER1: 21A
    COMMENTS: When this pesticide was used during April and May in the San Joaquin Valley and thrips were abundant, there was an increase in scarring damage caused by thrips.
    E. FENPYROXIMATE
    (Fujimite SC) 4 pt (OC or IC) 12 3
    RANGE OF ACTIVITY: Pests: narrow (mites); Natural enemies: predatory mites
    PERSISTENCE: Pests: intermediate; Natural enemies: intermediate
    MODE-OF-ACTION GROUP NUMBER1: 21A
    F. SPIRODICLOFEN
    (Envidor 2SC) See comments 12 7
    RANGE OF ACTIVITY: Pests: narrow (mites); Natural enemies: predatory mites
    PERSISTENCE: Pests: intermediate; Natural enemies: intermediate
    MODE-OF-ACTION GROUP NUMBER1: 23
    COMMENTS: Application rate is 12 to 20 fl oz/acre (OC or IC) when horticultural spray oil is not used, and 18 to 20 fl oz/acre (OC or IC) when it is.
    G. ABAMECTIN
    (Agri-Mek SC) 2.25–4.25 fl oz/acre (OC or IC) 12 7
    RANGE OF ACTIVITY: Pests: intermediate (citrus thrips, mites, leafminers); Natural enemies: predatory mites and thrips
    PERSISTENCE: Pests: intermediate; Natural enemies: intermediate
    MODE-OF-ACTION GROUP NUMBER1: 6
    . . . PLUS . . .
    NARROW RANGE OIL
    (415) 0.25–1% See label when dry
    RANGE OF ACTIVITY: Pests: broad (unprotected stages of insects and mites); Natural enemies: most
    PERSISTENCE: Pests: short; Natural enemies: short
    MODE OF ACTION: Improves translaminar movement and persistence of insecticide.
    COMMENTS: For use on all varieties. Most effective in the spring when the trees are flushing. Certain formulations emit high amounts of volatile organic compounds (VOCs); use low-VOC formulations. Regulations affect use for the San Joaquin Valley from May 1 to October 31, 2020. Review the Department of Pesticide Regulation's updated fact sheet.
    H. FENBUTATIN OXIDE
    (Vendex 50WP) 0.25–0.5 lb/100 gal (OC or IC) 48 7
    . . . or . . .
    2–4 lb/acre (LV)
    RANGE OF ACTIVITY: Pests: narrow (mites); Natural enemies: predatory mites
    PERSISTENCE: Pests: short; Natural enemies: short
    MODE-OF-ACTION GROUP NUMBER1: 12B
    COMMENTS: For use on all varieties. Use higher rates during cool weather periods. Do not apply more than 1600 gal dilute spray/acre.
    ** LV - Low-volume uses 20 to 100 gal water/acre.
    OC - Outside coverage uses 100 to 250 gal water/acre.
    IC - Intermediate coverage uses 250 to 600 gal/acre.
    Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (PHI) is the number of days from treatment to harvest. In some cases the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest.
    * Permit required from county agricultural commissioner for purchase or use.
    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 (un = unknown or uncertain mode of action) are assigned by IRAC (Insecticide Resistance Action Committee).

    Important Links

    Text Updated: 02/17
    Treatment Table Updated: 02/17