Agriculture: Citrus Pest Management Guidelines

Citrus Thrips

  • Scirtothrips citri
  • Description of the Pest

    Adult citrus thrips are small, orange-yellow insects with fringed wings. During spring and summer, females lay about 25 eggs in new leaf tissue, young fruit, or green twigs; in fall, overwintering eggs are laid mostly in the last growth flush of the season. Overwintered eggs hatch in March about the time of the new spring growth. First-instar larvae are very small, whereas second-instar larvae are about the size of adults, spindle-shaped, and wingless. They feed actively on tender leaves and fruit, especially under the sepals of young fruit. Third- and fourth-instar (propupa and pupa) thrips do not feed and complete development on the ground or in the crevices of trees. When adults emerge, they move actively around the tree foliage.

    Citrus thrips do not develop below 58°F (14°C). They can produce 8 to 12 generations during the year if the weather is favorable.

    When monitoring citrus thrips, you must be able to distinguish them from flower thrips, which feed on flower parts but do not damage citrus. Shortly after petal fall, immature flower thrips can be seen moving around young fruit, but they soon pupate and adults disperse to other plants, consequently they are only concentrated in citrus orchards for a short period in spring. For more information on distinguishing citrus thrips from other thrips, including all stages of citrus thrips and flower thrips, see UC ANR Publication 3303, Integrated Pest Management for Citrus, 3rd edition.

    Damage

    All varieties of citrus can be affected, however, citrus thrips is of greatest economic importance to San Joaquin navel oranges, satsuma mandarins, and all types of desert citrus. On fruit, the citrus thrips punctures epidermal cells, leaving scabby, grayish or silvery scars on the rind. Second-instar larvae do the most damage. They feed mainly at the calyx end under the sepals of young fruit and are larger than first instars. As the fruit grows, damaged rind tissue moves outward from beneath the sepals and presents as a conspicuous ring of scarred tissue, commonly called a ‘ring scar.'. A second type of scarring can occur around the stylar (bottom) end of the fruit. This scarring may be smoother than calyx-end scarring. Stylar-end scarring almost always occurs with calyx-end scarring and is a more common damage for mandarin varieties (true mandarins and their hybrids, satsumas, and clementines) than for sweet oranges. Thrips scarring may be severe enough to asymmetrically restrict fruit growth, causing a deformity in fruit shape. Fruit are most susceptible to scarring from petal fall until they are about 1.5 inch (3.7 cm) in diameter. Thrips damage is higher on fruit located on the outside canopy where fruit is also susceptible to wind damage and sunburn.

    Management

    Citrus thrips numbers can vary greatly from year to year. Monitor to determine if a pesticide application is needed in a particular year. Navel oranges are more susceptible to damage than are Valencia oranges, which often do not require a pesticide application. Citrus thrips densities tend to be lower, and thrips scarring found much less frequently on the C. reticulata 'true' mandarins and their hybrids (Tango, W. Murcott Afourer and relatives) compared to oranges, clementines, and satsumas. Therefore, citrus thrips treatments for ‘true mandarins' and their hybrids are generally needed less often than oranges, clementines, and satsumas.

    Treatment of young, nonbearing trees to protect foliage is not recommended except in severe cases. Although the citrus foliage is often heavily damaged by citrus thrips, healthy trees can withstand the damage and frequent pesticide applications can lead to insecticide resistance, making control of thrips on fruit more difficult in later years.

    Citrus thrips is less of a problem in orchards that receive minimal broad-spectrum pesticide applications than in orchards that are treated with broad spectrum insecticides. Because of pesticide-induced hormoligosis (i.e. stimulation of thrips reproduction) and reduction of natural enemies, thrips numbers tend to increase after sprays with organophosphates, carbamates, pyrethroids, foliar neonicotinoids, and the miticide pyridaben (Nexter).

    There are 7 to 8 generations of thrips per year and it is the 2nd and 3rd generation that attack the young fruit soon after petal fall.  Citrus thrips is less of a problem in cold, wet years because the cold delays thrips development and the wetness increases pupal mortality. In this situation, the 2nd and 3rd generations appear after the fruit has reached 1.5 cm in diameter and is less susceptible to damage.

    Biological Control

    A number of natural enemies attack citrus thrips, including the predaceous mite Euseius tularensis, spiders, lacewings, dustywings, and minute pirate bugs. Densities of greater than 0.5 predatory mites (E. tularensis, E. hibisci, E. stipulatus) per leaf assist with control of citrus thrips. They are also a very good "indicator" species, giving an indication of the level of general natural enemies present in an orchard.

    In some years, when citrus thrips densities are excessively high, no amount of E. tularensis or other natural enemies in combination with selective pesticides can keep citrus thrips below an economic threshold.

    Organically Acceptable Methods

    Use biological control, sprays of the Entrust formulation of spinosad with an organically approved oil, or Veratran D applied with molasses or sugar bait in organically managed orchards.

    Resistance

    Citrus thrips has a history of rapidly developing resistance to chemicals that are used repeatedly and frequently for its control. For example, resistance to dimethoate and formetanate hydrochloride (Carzol) developed in a number of citrus thrips populations in the San Joaquin and Coachella valleys in the 1980s; beta-cyfluthrin (Baythroid) resistance was documented in the 1990s, and spinetoram (Delegate) resistance appeared in the 2010s in San Joaquin Valley orchards. Although citrus thrips disperse considerably, citrus thrips resistance problems are generally localized. Thus, resistance problems are most likely to occur in groves where insecticides with the same mode of action are repeatedly applied to control citrus thrips.

    With the limited number of pesticides available for control of citrus thrips now and in the foreseeable future, it is wise to monitor citrus thrips levels carefully and limit pesticide applications only to populations that are expected to cause significant levels of fruit scarring. It is also important to time and apply pesticides optimally so that reapplications are not required. Do not apply pesticides just to prevent foliar damage. Instead, focus on protecting young fruit.

    Selectivity

    The selective botanical insecticides sabadilla (Veratran D), spinosad (Success or Entrust), abamectin (Agri-Mek, etc.), spinetoram (Delegate), cyantraniliprole (Exirel) and the combination abamectin plus cyantraniliprole (Minecto Pro) are relatively nontoxic to beneficial insects and mites.  

    The broad-spectrum organophosphate (dimethoate), carbamate (formetanate hydrochloride&–Carzol), and pyrethroids (beta-cyfluthrin&–Baythroid, fenpropathrin&–Danitol) insecticides are toxic and fairly persistent (greater than 5 weeks) against both beneficial mites and beneficial insects so they disrupt biological control.

    Citrus thrips treatments are applied as outside coverage to the trees and this helps to allow natural enemies to survive in the interior and return to the outside of the tree as residues decline. Multiple applications of either selective- or broad-spectrum insecticides will significantly reduce populations of predatory mites. 

    Monitoring

    Check young fruit for immature thrips and monitor the undersurface of inside foliage (they avoid light) for predaceous mites. Monitor from petal fall until fruit is greater than 1.5 inches in diameter. For oranges, the monitoring time is about 6 to 8 weeks in spring. For lemons, monitor June through October.

    Monitoring Fruit for Citrus Thrips

    Select trees that are three to four rows in from the outside edge of the block. Sample 25 young fruit from each corner of the block for a total of 100 fruit. Take only one to two healthy, dark green fruit from outside, sunny branches of each tree. Look for thrips on the stem end of the fruit under the calyx. Count fruit as infested only if it has one or more wingless first-or second-instar nymphs (ignore pupae and adults). Record the total fruit infested with immature citrus thrips and calculate the percentage of infested fruit (example form). On very susceptible varieties, such as San Joaquin Valley navels, monitor fruit at least twice a week after petal fall, and continue monitoring as long as susceptible fruit is on the tree.

    Monitoring Predatory Mites

    Examine the underside of twenty 5-leaf terminals with fully expanded leaves from shady areas of the canopy (a total of 100 leaves) and count the number of adult predatory mites. Calculate and record the average number of predatory mites per leaf (example form). A minimum of 0.5 predatory mites per leaf is needed to assist with biological control of citrus thrips.

    Treatment Decisions

    Treatment thresholds vary by growing region, cultivar, beneficial mite numbers, and the type of insecticide that will be applied. A significant factor affecting threshold levels is whether the orchard is sheltered from wind damage (lower threshold) or has a history of outside fruit scarring from seasonal winds (higher threshold). As fruit get larger, treatment thresholds go up. Less susceptible varieties such as Valencia oranges and Tango mandarins may not require monitoring or pesticide applications. For coastal lemons, orchards that have a history of outside fruit scarring from seasonal winds have a higher threshold for tolerance of thrips.

    Sabadilla (Veratran D), spinetoram (Delegate), spinosad (Entrust, Success), abamectin (Agri-Mek), cyantraniliprole (Exirel), or premixes (Minecto Pro) are recommended to avoid severe mortality of natural enemies. When an application of sabadilla, spinetoram, spinosad, abamectin, or cyantraniliprole is planned, beneficial mite numbers are considered significant if you have at least 0.5 predators per leaf. Insecticides should be applied only when immature thrips are found on fruit, rather than on a calendar basis. In some years, cold weather slows thrips development and they are not present on the young fruit.

    When monitoring indicates a pesticide application may be needed, it is essential to properly time and apply the pesticide in order to reduce the need for a second application, and thus reduce the long-term development of resistance. Apply the pesticide using outside coverage (OC) by reducing spray blower wind velocity. Ground application is more effective than air application. However, because of their smaller size, coastal lemon trees receive adequate control with an aerial application. 200 gallons per acre is more effective than lower or higher gallonage, except with the sugar or molasses bait treatments using sabadilla. Firm data on optimal gallonage with sugar baits are not available, but some growers believe that lower gallonage is more effective because the bait concentration is increased. Do not apply sabadilla and sugar bait just before or during periods of heavy dew, fog, or drizzle. Such weather conditions cause the sugar bait to separate from the toxin, rendering the treatment ineffective.

    For more information on monitoring and management of citrus thrips see UC Ag Experts Talk: Citrus Thrips.

    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.
     
    SELECTIVE
    A. SABADILLA
      (Veratran D)# 10–15 lb/acre PLUS up to 12 0
        1–2 gallons molasses or 5–10 lb sugar in 50–200 gal (OC)    
      RANGE OF ACTIVITY: Pests: narrow (citrus thrips); Natural enemies: predatory thrips
      PERSISTENCE: Pests: short; Natural enemies: short
      COMMENTS: For use on all varieties. Wait for spray to dry to harvest. Acidify water in the spray tank to a pH of 4.5 before adding sabadilla; use citric acid or other approved acidifying agents. Sabadilla is a stomach poison that contains sugar as a bait and must be consumed by the thrips in order to be effective. Add an additional 1 to 2 gallons/acre of molasses or 5 to 10 lbs/acre of sugar for best results. Time application of this insecticide to coincide with mid-hatch. Applications are most effective during warm weather; in cool weather thrips don't feed well on bait and it degrades with time. Use higher rates with more dilute applications. Do not combine with fertilizers because this reduces feeding by the thrips on the bait. This insecticide is most effective if substantial numbers of predators such as the predaceous mite Euseius tularensis are present. Apply by ground at 3 mph with reduced wind velocity to achieve outside coverage. Don't apply during periods of heavy dew, fog, or drizzle.
     
    B. SPINETORAM
      (Delegate WG) 4–6 oz/acre (OC) 4 1
      RANGE OF ACTIVITY: Pests: narrow (thrips, orangeworms, katydids); Natural enemies: predatory thrips
      PERSISTENCE: Pests: intermediate; Natural enemies: intermediate
      RESISTANCE: Some citrus thrips populations in Kern County.
      MODE-OF-ACTION GROUP NUMBER1: 5
      . . . PLUS . . .
      415 NARROW RANGE OIL
      (various products) 0.25–1% See label See label
      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 insecticide persistence.
      COMMENTS: For use on all varieties. Do not apply to citrus nurseries or to citrus in greenhouses. Most effective if substantial numbers of predators such as the predaceous mite Euseius tularensis are present. Time application to coincide with early to mid-hatch (see the thresholds listed above). To avoid potential phytotoxicity of oil to the fruit, do not apply 30 days before or after a sulfur application, and do not apply to small fruit (less than 1 inch in diameter) on a day when the ambient temperature has or is expected to exceed 95°F or when the relative humidity has or is expected to drop below 20%. Use ground application at 3 mph with reduced wind velocity so as to achieve outside coverage. Repeated applications will result in citrus thrips resistance. For resistance management purposes, do not apply mode-of-action group 5 insecticides (spinetoram and spinosad) more than twice a year. Do not apply more than a total of 12 oz/acre per crop.
     
    C. ABAMECTIN
      (Agri-Mek SC) 2.25–4.25 fl oz/acre (OC) 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 . . .
      415 NARROW RANGE OIL
      (various products) 0.25–1% See label See label
      MODE OF ACTION: Improves translaminar movement and insecticide persistence.
      RANGE OF ACTIVITY: Pests: broad (unprotected stages of insects and mites); Natural enemies: most
      PERSISTENCE: Pests: short; Natural enemies: short
      COMMENTS: For use on all varieties. Apply in 100–250 gal water/acre. Do not apply in citrus nurseries. To avoid potential phytotoxicity of oil to the fruit, do not apply 30 days before or after a sulfur application and do not apply to small fruit (less than 1 inch in diameter) on a day when the ambient temperature has or is expected to exceed 95°F or when the relative humidity has or is expected to drop below 20%. Most effective if substantial numbers of predators such as the predaceous mite, Euseius tularensis, are present. Time application to coincide with early to mid-hatch (see the thresholds listed above). Use ground application at 3 mph with reduced wind velocity so as to achieve outside coverage. Repeated applications will result in citrus thrips resistance. 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.
     
    D. CYANTRANILIPROLE
      (Exirel) 20.5 fl oz/acre (OC) 12 1
      RANGE OF ACTIVITY: Pests: aphids, leafminer, psyllids, sharpshooters, thrips; Natural enemies: none
      PERSISTENCE: Pests: intermediate; Natural enemies: none
      MODE-OF-ACTION GROUP NUMBER1: 28
      . . . PLUS . . .
      415 NARROW RANGE OIL
      (various products) 0.25–1% See label See label
      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 insecticide persistence.
      COMMENTS: Do not make ground applications within 25 feet or air applications within 50 feet of water bodies. Do not exceed 61 oz of Exirel or 0.4 lb a.i./acre of cyantraniliprole-containing products/acre per year. Apply by air in a minimum of 10 gallons/acre.
     
    E. CYANTRANILIPROLE/ABAMECTIN
      (Minecto Pro) 10-12 fl oz/acre 12 7
      RANGE OF ACTIVITY: Pests: broad (many insects); Natural enemies: predatory mites
      PERSISTENCE: Pests: intermediate; Natural enemies: intermediate
      MODE-OF-ACTION GROUP NUMBER1: 28/6
      ...PLUS...
      415 NARROW RANGE OIL
      (various products) 0.25–1% See label See label
      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; also improves translaminar movement and insecticide persistence.
      COMMENTS: Do not exceed a total of 24 fl oz of Minecto Pro or 0.40 lbs a.i. of cyantraniliprole-containing products or 0.047 lbs a.i. of abamectin-containing products/acre per calendar year. Do not apply to nurseries. Aerial application is allowed only for citrus leafminer or Asian citrus psyllid.
     
    F. SPIROTETRAMAT
      (Movento) 8–10 fl oz/acre (OC) 24 1
      RANGE OF ACTIVITY: Pests: broad (mites, thrips, leafminers, aphids, armored scales); Natural enemies: predatory mites
      PERSISTENCE: Pests: long; Natural enemies: short (except via leaf or host feeding)
      MODE-OF-ACTION GROUP NUMBER1: 23
      . . . PLUS . . .
      415 NARROW RANGE OIL
      (various products) 0.5–1% See label See label
      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; also improves insecticide uptake.
      COMMENTS: For use on all varieties. Most effective if substantial numbers of predators such as the predaceous mite Euseius tularensis are present. Time application to coincide with early to mid-hatch (see the thresholds listed above). To avoid potential phytotoxicity of oil to fruit, do not apply 30 days before or after a sulfur application, and do not apply to small fruit (less than 1 inch in diameter) on a day when the ambient temperature has or is expected to exceed 95°F, or when the relative humidity has or is expected to drop below 20%. Use ground application at 3 mph with reduced wind velocity so as to achieve outside coverage unless the pesticide application is also intended for red scale control, in which case intermediate coverage and 500 or so gpa might be best. Must be applied with oil or an adjuvant to improve penetration. Do not apply before bloom, during bloom, or 10 days after petal fall. Repeated applications will result in citrus thrips resistance. For resistance management purposes, do not apply more than once a year (i.e., do not apply in spring for citrus thrips management and in summer for red scale).
     
    G. SPINOSAD
      (Entrust SC)# 4–10 fl oz/acre (OC) 4 1
      (Success) 4–10 fl oz/acre (OC) 4 1
      RANGE OF ACTIVITY: Pests: narrow (thrips, orangeworms, katydids); Natural enemies: predatory thrips
      PERSISTENCE: Pests: intermediate; Natural enemies: intermediate
      RESISTANCE: Some citrus thrips populations in Kern County.
      MODE-OF-ACTION GROUP NUMBER1: 5
      . . . PLUS . . .
      415 NARROW RANGE OIL
      (various products) 0.25-1% See label See label
      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 insecticide persistence.
      COMMENTS: For use on all varieties. Most effective if substantial numbers of predators such as the predaceous mite Euseius tularensis are present. Time application to coincide with early to mid-hatch (see the thresholds listed above). To avoid potential phytotoxicity of oil to the fruit, do not apply 30 days before or after a sulfur application, and do not apply to small fruit (less than 1 inch in diameter) on a day when the ambient temperature has or is expected to exceed 95°F or when the relative humidity has or is expected to drop below 20%. Use a ground application at 3 mph with reduced wind velocity to achieve outside coverage. Repeated applications will result in citrus thrips resistance. For resistance management purposes, do not apply mode-of-action group 5 insecticides (spinetoram and spinosad) more than twice a year. Do not apply to citrus nurseries or to citrus in greenhouses.
     
    BROAD-SPECTRUM
    A. BETA-CYFLUTHRIN
      (Baythroid XL) 6.4 fl oz/acre (OC) 12 0
      RANGE OF ACTIVITY: Pests: broad (many insects); Natural enemies: most
      PERSISTENCE: Pests: intermediate; Natural enemies: intermediate (low rates), long (high rates)
      RESISTANCE: Some citrus thrips populations in the San Joaquin Valley
      MODE-OF-ACTION GROUP NUMBER1: 3A
      COMMENTS: Only a single application may be made per crop season. To reduce the potential for resistance, make a total of only one pyrethroid application (for all pest species) per year or, if feasible, only one application every 2 to 3 years. Do not apply in the vicinity of aquatic areas.
     
    B. FENPROPATHRIN
      (Danitol 2.4EC) 21.33 fl oz/acre (OC) 24 1
      RANGE OF ACTIVITY: Pests: broad (many insects and mites); Natural enemies: most
      PERSISTENCE: Pests: intermediate; Natural enemies: long
      RESISTANCE: Some citrus thrips populations in the San Joaquin Valley
      MODE-OF-ACTION GROUP NUMBER1: 3A
      COMMENTS: Apply in 50 to 200 gal water/acre. Use only on citrus trees 3 years or older. To reduce the potential for resistance, make a total of only one pyrethroid application (for all pest species) per year or, if feasible, only one application every 2 to 3 years. Do not apply in the vicinity of aquatic areas.
     
    C. FORMETANATE
      (Carzol SP) 1–1.25 lb/acre (OC) 216 (9 days) See comments
      RANGE OF ACTIVITY: Pests: broad (many insects); Natural enemies: most
      PERSISTENCE: Pests: intermediate; Natural enemies: long, unless washed off
      RESISTANCE: Some citrus thrips populations
      MODE-OF-ACTION GROUP NUMBER1: 1A
      COMMENTS: For use on oranges, lemons, limes, tangerines, tangelos, and grapefruit. Apply at the beginning of hatch; less effective if resistance has developed. Do not apply after fruit reach a diameter of one inch. If unharvested grapefruit and Valencia oranges are present from the previous crop, an application may be made to the new crop. However, a preharvest interval of 30 days must be observed for the unharvested crop. Use a ground application at 3 mph with reduced wind velocity to achieve outside coverage.
     
    D. DIMETHOATE
      (Dimethoate 400) 0.5–1.0 pt/acre in 100 gal; 2 pt/acre maximum(OC) See comments 15
      RANGE OF ACTIVITY: Pests: broad (many insects); Natural enemies: most
      PERSISTENCE: Pests: intermediate; Natural enemies: intermediate
      RESISTANCE: Some citrus thrips populations
      MODE-OF-ACTION GROUP NUMBER1: 1B
      COMMENTS: For use on oranges, grapefruit, lemons, tangerines. Reentry interval is 14 days in areas that receive less than 25 inches of annual rainfall and 10 days otherwise. No more than two applications on mature fruit. Apply at the beginning of hatch. Less effective if resistance has developed. Use a ground application at 3 mph with reduced wind velocity to achieve outside coverage.
      . . . or . . .
      (Dimethoate 2.67) 0.75–1.5 pt in 100 gal; 3 pt/acre maximum (OC) See comments 15
        . . . or . . .    
        in 5–10 gal (A)    
      COMMENTS: For use on oranges, grapefruit, lemons, tangerines. Reentry interval is 14 days in areas that receive less than 25 inches of annual rainfall and 10 days otherwise. No more than two applications on mature fruit. Apply at the beginning of hatch. Less effective if resistance has developed. Use a ground application at 3 mph with reduced wind velocity to achieve outside coverage.
    ** A - Aircraft applications 5 to 20 gal/acre
      OC - Outside coverage uses 100 to 250 gal water/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.
    # Acceptable for use on organically grown produce.
    * 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 are assigned by IRAC (Insecticide Resistance Action Committee).

    Important Links

    Text Updated: 07/20
    Treatment Table Updated: 07/20