How to Manage Pests

UC Pest Management Guidelines

Citrus

Asian Citrus Psyllid

Scientific Name: Diaphorina citri

(Reviewed 9/08, updated 8/13)

In this Guideline:


Description of the Pests

The Asian citrus psyllid (ACP; Hemiptera: Psyllidae), is a tiny (0.125 inch, 3 mm in length) mottled brown insect that is about the size of an aphid.

Damage

Asian citrus psyllid attacks all varieties of citrus and very closely related ornamental plants in the family Rutaceae (mock orange, Indian curry leaf, orange jasmine and other Murraya species). This pest attacks new citrus leaf growth and, because of the salivary toxin that it injects, causes the new leaf tips to twist or burn back.

However, the more serious damage that it causes is vectoring the bacterium (Candidatus Liberibacter asiaticus) that causes Huanglongbing (HLB or citrus greening) disease. Huanglongbing causes shoots to yellow, asymmetrical leaf mottling, and abnormally shaped fruit with bitter juice. The disease can kill a citrus tree within 3 to 5 years, and there is no known cure for the disease. Asian citrus psyllid arrived in southern California from Mexico in 2008.

At this point, Huanglongbing is rapidly spreading in Mexico northward toward California. In addition, Huanglongbing may be already present in California due to previous illegal importation of infected plant material. In Florida, the psyllid and disease were rapidly spread throughout the state on nursery plants such as Murraya. It is thought that Huanglongbing was present in Florida backyard citrus trees for a number of years, and it took the arrival of Asian citrus psyllid to move the disease into commercial citrus orchards. Florida citrus growers are now treating more than eight times per year with broad-spectrum pesticides to reduce Asian citrus psyllid and slow the spread of the disease. Pesticides can reduce the number of psyllids, but an adult psyllid carries the bacteria for most of its life and can sometimes transmit the disease faster than most pesticides will kill it.

Because Asian citrus psyllid has only recently entered California, we are relying heavily on research done on this pest in Florida and Texas. Currently, treatments that are applied to California citrus orchards are designed to disinfest trees and thus minimize the risk of moving Asian citrus psyllid in bins of harvested fruit and to limit the natural spread of Asian citrus psyllid throughout California. In addition, the lower the number of Asian citrus psyllid, the less likely Huanglongbing-infected trees will be found.

Adult psyllids can be detected through visual surveys of new flush (new leaf growth) and yellow sticky cards. Immature stages (eggs and nymphs) are limited to new growth so direct visual monitoring efforts on "feather flush" is needed to detect these stages.

For more information, read UC ANR Publication 8205, Asian Citrus Psyllid, and 8218, Citrus Bacterial Canker Disease and Huanglongbing (Citrus Greening). For more information about the location of Asian citrus psyllid and Huanglongbing, and to view management strategies for various citrus growing regions, see the UC ANR Web site Asian Citrus Psyllid Distribution and Management.

If you see the Asian citrus psyllid in areas of California where it is not yet known to occur, please contact the California Department of Agriculture (CDFA) Exotic Pest Hotline at 1-800-491-1899. Personnel from CDFA will inspect plants for the presence of this psyllid and send any specimens to diagnostic laboratories for identification and determination of the presence of the Huanglongbing bacterium in psyllids and plant tissue.

Management

The following treatment guidelines have been developed for citrus growers within the quarantine zones. Apply insecticides to control Asian citrus psyllid in commercial citrus. General principles are that no one insecticide fully controls Asian citrus psyllid because all stages are difficult to contact with insecticides; the eggs and nymphs are tucked inside new foliage and adults can fly. Furthermore, some insecticides show better efficacy against one stage over another. Because systemic neonicotinoid insecticides require root activity for uptake, they are best applied during June through September.

Biological Control

Releases of the parasite wasp, Tamarixia radiata, started in 2012 in urban areas of southern California. Parasitism rates of Asian citrus psyllid nymphs can be as high as 40% once the parasite establishes. However, the parasitism rate is not high enough to lower Asian citrus psyllid numbers sufficiently to prevent disease spread. Thus, releases are focused on residential citrus where areawide pesticide applications are difficult to achieve.

Organically Acceptable Methods

Applying organic insecticides to reduce psyllid numbers and prevent the spread of the psyllid or the disease is difficult, because persistence of organic insecticides is short and they require contact with the insect body to be effective. Which organic insecticide you choose is not as important as application frequency. The persistence of organic insecticides is only hours to days (not weeks like the conventional insecticides), therefore it is necessary to apply organic insecticides frequently and ensure that coverage is thorough.

Use yellow sticky cards, conduct visual monitoring, and tap sampling (see methods below) every 2 weeks throughout the season. If psyllids are found, apply three treatments spaced 10 to 14 days apart. If psyllids are found again, resume treatments every 10 to 14 days until no psyllids are detected.

Monitoring
Yellow Sticky Cards

Yellow sticky cards are used by the California Department of Food and Agriculture to trap and detect adult psyllids at a rate of one trap per 1/4 mile (16 per square mile). Traps are more attractive when there is no young leaf flush and especially after a flush has hardened off. Psyllids are more attracted to leaf flush because there are volatile cues in addition to the color cues in leaves. This method is only effective for detecting adults.

Visual Monitoring and Tap Sampling of Leaf Flush

The best way to find psyllids is to examine tiny new leaves (feather flush) as they are developing and look for adult psyllids (adults must lay eggs in new flush), nymphs with their waxy tubules, or eggs. Small nymphs are especially hard to see; using a 10X or higher hand lens or magnified head loop is recommended. Sample 10 trees each on the north, east, south, and west borders of the orchard; borders are breaks in citrus plants, generally the size of a road. Also sample 10 trees in the orchard center for a total of 50 trees sampled per orchard (standardized sampling is necessary to compare infestations among orchards).

YOU WILL NEED:

  • A white clipboard or plastic-covered sheet of paper with a grid to help you count psyllids quickly
  • Squirt of detergent mixed with 500 ml of water
  • 1 foot section of PVC pipe or other device to beat branches
  • A 10X or higher hand lens or magnifying head loupe

INSTRUCTIONS

  1. Mist the detergent solution onto the clipboard to hold the psyllids in place
  2. Hold the clipboard 1 foot below a branch and strike the branch 3 times with the PVC pipe
  3. Count and record the number of winged psyllids (adults) collected on the clipboard
  4. Scrape the psyllids off the clipboard and reapply detergent solution if needed
  5. Examine one leaf flush per tree for all psyllid stages (egg, nymph, and adult); count and record the number of each stage (e.g., 1/0/3 denotes 1 egg, 0 nymphs, and 3 adults were found)
  6. Describe the leaf flush stage as feather flush, growing flush, or fully expanded leaves to record the suitability of the flush for nymphs

Conduct visual and tap sampling once a month, especially during periods of flush. Psyllid sampling detects new infestations and determines if pesticides are effective for both new and established populations.

Treatment Decisions for conventional orchards
New Areas of Infestation

When Asian citrus psyllid first appears in a region, numbers are low and the population can potentially be eradicated locally, if treated aggressively over a wide area. Two insecticides should be used, preferably a foliar for knockdown and a systemic for a more persistent effect.

  • The most effective foliar treatment is a pyrethroid, which is broad-spectrum and toxic to all stages it contacts.
  • The most effective systemic treatment is imidacloprid, which persists for several months (depending on tree size and irrigation system) and moves into the new leaves to kill the hard-to-reach immature stages.
    • Apply when root growth is occurring (June through September) for best root uptake.
    • Apply to soil; it remains effective for 2 to 3 months.
    • Imidacloprid requires 3 to 4 weeks for uptake into mature citrus to begin to kill pests.
    • Pre-wet soil before treatment is applied. For optimum uptake, apply to newly planted trees or trees irrigated by drip, microsprinkler, low-pressure irrigation systems. Emitters must provide even, uniform distribution of water. Lightly pre-wet soil for several hours before application to break soil surface tension. Once the irrigation system reaches operating pressure, inject the treatment into the system over a calculated time interval (generally 2 hours) to allow uniform distribution throughout the system. The use of a dye marker in the treatment solution is recommended to determine when lines are clear of the treatment. Once the solution has cleared all irrigation lines and emitters, continue irrigation to move the insecticide into the active root zone but do not overirrigate or cause runoff. Wait 24 hours before subsequent irrigations.
    • Imidacloprid is toxic to bees; do not apply during bloom because bees may be drawn to irrigation water.

If either of these insecticides cannot be used, then use any combination of two effective insecticides, but always start with a foliar broad-spectrum insecticide (pyrethroid, organophosphate, neonicotinoid, or carbamate) for good knockdown. Apply the two treatments within one psyllid generation (4 weeks) over as wide an area as possible to ensure control. The size of the area is defined by the geography and continuity of citrus trees, but at a minimum should be all orchards within 800 meters of the find site. If part of an orchard is within the 800-meter radius, the entire orchard should be treated.

Established Populations

Once Asian citrus psyllid has established, apply insecticides routinely throughout the season and also during the fall and winter months to suppress Asian citrus psyllid.

  • Fall sprays (October through December): A very important treatment period is in the late fall just before winter dormancy; psyllid numbers are dropping and populations consist primarily of adults that move less when it is cold. Apply an organophosphate, the most effective treatment in the fall, or another insecticide effective against Asian citrus psyllid.
  • Winter sprays (January through February): The second most important treatment period is early spring before feather flush forms and female psyllids begin to lay eggs. Apply a pyrethroid, the most effective treatment during the winter, because it works well in cold weather.
  • Growing season: Make applications at the beginning of new growth flushes; use any combination of broad-spectrum or selective foliar insecticides that are part of the routine management of other pests and effective against Asian citrus psyllid. In addition, during June through September, put on one application of a systemic neonicotinoid (imidacloprid or thiamethoxam) to provide extended nymphal control and to discourage psyllids from feeding.

For resistance management purposes, rotate between insecticides from different classes.

Common name Amount to use
(type of coverage)**
R.E.I.‡ P.H.I.‡
(example trade name)   (hours) (days)

  Calculate impact of pesticide on air quality
 
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. Not all registered pesticides are listed. Always read the label of the product being used.
 
BROAD-SPECTRUM FOLIAR INSECTICIDES
 
A. FENPROPATHRIN
  (Danitol 2.4 EC) 21.3 oz/100–500 gal water/acre (OC) 24 1
  RANGE OF ACTIVITY: Pests: broad (many insects and mites); Natural enemies: most
  PERSISTENCE: Pests: intermediate; Natural enemies: long
  MODE-OF-ACTION GROUP NUMBER1: 3
  COMMENTS: Use only on citrus trees 3 years or older. Do not apply in the vicinity of aquatic areas.
 
B. BETA-CYFLUTHRIN
  (Baythroid XL) 3.2–6.4 oz/100–500 gal water/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)
  MODE-OF-ACTION GROUP NUMBER1: 3A
  COMMENTS: Do not apply within 25 feet of lakes, reservoirs, rivers, permanent streams, marshes, or natural ponds, estuaries, and commercial fish farm ponds.
 
C. ZETA-CYPERMETHRIN
  (Mustang) 4.3 oz/20 (concentrated)–100 (dilute) gal water/acre (OC) 12 1
  RANGE OF ACTIVITY: Pests: broad (many insects and mites); Natural enemies: most
  PERSISTENCE: Pests: intermediate; Natural enemies: long
  MODE-OF-ACTION GROUP NUMBER1: 3
  COMMENTS: For use on all varieties.
 
D. CHLORPYRIFOS
  (Lorsban Advanced) 2–7 pt/100–500 gal water/acre (OC) 5 21
  RANGE OF ACTIVITY: Pests: broad (many insects); Natural enemies: most
  PERSISTENCE: Pests: short (low rates), intermediate (high rates); Natural enemies: short (low rates), intermediate (high rates)
  MODE-OF-ACTION GROUP NUMBER1: 1B
  COMMENTS: For use on all varieties. During the bloom period, apply from 1 hour after sunset until 2 hours before sunrise.
 
E. DIMETHOATE
  (Dimethoate 400, various) 1.5 pt/100–500 gal water/acre (OC) 14 days 15
  RANGE OF ACTIVITY: Pests: broad (many insects); Natural enemies: most
  PERSISTENCE: Pests: intermediate; Natural enemies: long
  MODE-OF-ACTION GROUP NUMBER1: 1B
  COMMENTS: For use on oranges, grapefruit, lemons, tangerines. No more than two applications on mature fruit.
 
F. CARBARYL
  (Sevin XLR Plus) 1.5–3 qts/100–500 gal water/acre (OC) 12 5
  RANGE OF ACTIVITY: Pests: broad (many insects); Natural enemies: most
  PERSISTENCE: Pests: long; Natural enemies: long
  MODE-OF-ACTION GROUP NUMBER1: 1B
  ...PLUS...
  415 NARROW RANGE OIL 0.5%    
  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: For use on all varieties. During the bloom period, apply from 1 hour after sunset until 2 hours before sunrise. May increase citrus red mite populations. Caution: Serious hazards are associated with oil treatments to green lemons because of phytotoxicity after sweating; check label for preharvest interval.
 
G. THIAMETHOXAM
  (Actara) 5.5 oz/100 gal (OC) 12 0
  RANGE OF ACTIVITY: Pests: broad (many insects); Natural enemies: most
  PERSISTENCE: Pests: long; Natural enemies: long
  MODE-OF-ACTION GROUP NUMBER1: 4A
 
H. IMIDACLOPRID + BETA-CYFLUTHRIN*
  (Leverage 360) 3.2–6.4 fl oz/100–250 gal (OC) 12 0
  RANGE OF ACTIVITY: Pests: broad (many insects and mites); Natural enemies: most
  PERSISTENCE: Pests: intermediate; Natural enemies: long
  MODE-OF-ACTION GROUP NUMBER1: 4A + 3A
  COMMENTS: Best use of this product is winter and early spring when weather is cold and multiple treatments for Asian citrus psyllid eradication efforts are not feasible.
 
I. CYFLUTHRIN*    
  (Tombstone) 3.2–6.4 fl oz/100–250 gal (OC) 12 0
  RANGE OF ACTIVITY: Pests: broad (many insects and mites); Natural enemies: most
  PERSISTENCE: Pests: intermediate; Natural enemies: long
  MODE-OF-ACTION GROUP NUMBER1: 3
 
BROAD-SPECTRUM SOIL-APPLIED INSECTICIDES
 
A. IMIDACLOPRID
  (Admire Pro) 14 fl oz/acre 12 0
  (4F Generic formulations) 16 fl oz/acre 12 0
  (2F Generic formulations) 32 fl oz/acre 12 0
  RANGE OF ACTIVITY: Pests: narrow (aphids, glassy-winged sharpshooters); Natural enemies: predatory beetles and parasites
  PERSISTENCE: Pests: long; Natural enemies: intermediate
  MODE-OF-ACTION GROUP NUMBER1: 4A
  COMMENTS: Effective against Asian citrus psyllid on young trees; based on research in Florida, levels of imidacloprid taken up by bearing trees are not sufficient to be consistently effective against Asian citrus psyllid. Very toxic to bees; do not apply during bloom because bees may be drawn to irrigation water.
 
B. THIAMETHOXAM
  (Platinum) 8–11 fl oz/acre 12 0
  RANGE OF ACTIVITY: Pests: narrow (sucking insects); Natural enemies: predatory beetles and parasitic wasps
  PERSISTENCE: Pests: long; Natural enemies: intermediate
  MODE-OF-ACTION GROUP NUMBER1: 4A
  COMMENTS: Do not apply during prebloom or during bloom when bees are actively foraging. Avoid drift to blooming crops or ground cover. Highly toxic to bees through direct exposure and by contact with residue.
 
SELECTIVE FOLIAR INSECTICIDES
 
A. CHLORANTRANILIPROLE
  (Altacor) 3–4.5 oz/100–150 gal water/acre 4 1
  RANGE OF ACTIVITY: Pests: narrow (aphids, psyllids, caterpillars); Natural enemies: parasitic wasps
  PERSISTENCE: Pests: intermediate; Natural enemies: intermediate
  MODE-OF-ACTION GROUP NUMBER1: 28
 
B. SPINETORAM
  (Delegate WG) 6 oz/100–500 gal water/acre 4 1
  RANGE OF ACTIVITY: Pests: narrow (thrips, katydids); Natural enemies: predatory thrips
  PERSISTENCE: Pests: intermediate; Natural enemies: intermediate
  MODE-OF-ACTION GROUP NUMBER1: 5
  ...PLUS...
  415 NARROW RANGE OIL 0.5%    
  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: For use on all varieties. Do not apply to citrus nurseries or to citrus in greenhouses. 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%.
 
C. SPIROTETRAMAT
  (Movento) 10 fl oz/100–500 gal water/acre 24 1
  RANGE OF ACTIVITY: Pests: broad (mites, thrips, leafminer, aphids, armored scales); Natural enemies: predatory mites
  PERSISTENCE: Pests: long; Natural enemies: short
  MODE-OF-ACTION GROUP NUMBER1: 23
  ...PLUS...
  415 NARROW RANGE OIL 0.5–1.0% 4 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; also improves translaminar movement and insecticide persistence.
  COMMENTS: Spirotetramat requires oil as an adjuvant for good uptake. The insecticide will move into new, expanding tissue with time. Insecticide takes 10 days to begin killing the pest.
 
D. DIFLUBENZURON*
  (Micromite 80 WGS) 6.25 oz/100–500 gal water/acre 12 21
  RANGE OF ACTIVITY: Pests: intermediate (katydids, peelminer, leafminer, grasshoppers); Natural enemies: predatory beetles
  PERSISTENCE: Pests: intermediate; Natural enemies: intermediate
  MODE-OF-ACTION GROUP NUMBER1: 23
  ...PLUS...
  415 NARROW RANGE OIL 0.5%    
  RANGE OF ACTIVITY: Pests: broad (unprotected stages of insects and mites); Natural enemies: most
  PERSISTENCE: Pests: short; Natural enemies: short
  MODE-OF-ACTION GROUP NUMBER1: Contact including smothering and barrier effects; also improves translaminar movement and insecticide persistence.
  COMMENTS: Apply when the adults are actively depositing eggs. This insecticide will help to prevent egg hatch. Registered for oranges, grapefruit, and tangerines with a Section 18 for lemons pending.
 
E. ABAMECTIN
  (Agri-Mek) 10 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 0.25–1.0% 4 when dry
  RANGE OF ACTIVITY: Pests: broad (unprotected stages of insects including citrus thrips, citrus leafminer, Asian citrus psyllid and mites); Natural enemies: most
  PERSISTENCE: Pests: short; Natural enemies: short
  MODE-OF-ACTION GROUP NUMBER1: Improves translaminar movement and insecticide persistence.
  COMMENTS: For use on all varieties. Apply in 50 to 250 gallons 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 90°F (for low volume applications) or 95°F (for dilute applications) or when the relative humidity has or is expected to drop below 20%.
 
F. FENPROXIMATE
  (Fujimite 5EC)) 4 pt (OC) 12 14
  RANGE OF ACTIVITY: Pests: narrow (some insects such as Asian citrus psyllid and mites); Natural enemies: predatory mites
  PERSISTENCE: Pests: intermediate; Natural enemies: intermediate
  MODE-OF-ACTION GROUP NUMBER1: 21A
  COMMENTS: Effective primarily against ACP nymphs.
 
ORGANIC INSECTICIDES
 
A. NARROW RANGE OIL (92%UR)
  (415) 0.25–0.5% (TC) 4 When dry
  . . . or . . .
  NARROW RANGE OIL (99%UR)
  (415, 435, 440, 455) 0.25–0.5% (TC) 4 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.
 
B. PYRETHRIN#
  (PyGanic EC5.0II) 18 fl oz/acre (OC) 12 0
  (PyGanic EC1.4) 64 fl oz/acre (OC) 12 0
  RANGE OF ACTIVITY: Pests: broad (insects); Natural enemies: most
  PERSISTENCE: Pests: short; Natural enemies: short
  MODE-OF-ACTION GROUP NUMBER1: 3
  COMMENTS: Short residual, requires repeated applications every 10 to 14 days. Buffering the final spay solution to a pH of 5.5-7.0 is important for efficacy. Pyrethrins degrade rapidly in sunlight.
  ...PLUS...
  415 NARROW RANGE OIL 0.5–1.0%    
  RANGE OF ACTIVITY: Pests: broad (unprotected stages of insects and mites); Natural enemies: most
  PERSISTENCE: Pests: short; Natural enemies: short
  MODE-OF-ACTION GROUP NUMBER1: Contact including smothering and barrier effects; also improves translaminar movement and insecticide persistence.
 
C. CHROMOBACTERIUM SUBTSUGAE STRAIN PRAA4-1#
  (Grandevo) 3 lb (OC) 4 0
  RANGE OF ACTIVITY: Pests: broad (soft-bodied insects); Natural enemies: few
  PERSISTENCE: Pests: short; Natural enemies: short
  MODE-OF-ACTION GROUP NUMBER1: bioinsecticide
  COMMENTS: Short residual, requires repeated applications every 10 to 14 days.
  ...PLUS...
  415 NARROW RANGE OIL 0.5–1.0% 4 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 GROUP NUMBER1: Contact including smothering and barrier effects; also improves translaminar movement and insecticide persistence.
 
D. NEEM OIL#
  (Trilogy) 1–2%/25–200 gal water/acre (OC) 4 0
  RANGE OF ACTIVITY: Pests: broad (soft-bodied insects); Natural enemies: few
  PERSISTENCE: Pests: short; Natural enemies: short
  MODE-OF-ACTION GROUP NUMBER1: Contact including smothering and barrier effects.
  COMMENTS: Short residual, requires repeated applications every 10 to 14 days.
 
E. AZADIRACHTIN#
  (Neemix 4.5) 4–7 oz/acre (OC) 4 0
  RANGE OF ACTIVITY: Pests: narrow (whiteflies, aphids, leafminers, caterpillars); Natural enemies: few
  PERSISTENCE: Pests: short; Natural enemies: short
  MODE-OF-ACTION GROUP NUMBER1: un
  COMMENTS: Short residual, requires repeated applications every 10 to 14 days.
 
** OC - Outside coverage uses 100 to 250 gal water/acre.

TC - Thorough coverage uses 750 to 2,000 gal water or more/acre, depending on tree size.
Restricted entry interval (R.E.I.) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (P.H.I.) 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.
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). For additional information, see their Web site at http://www.irac-online.org/.
* Permit required from county agricultural commissioner for purchase or use.

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Citrus
UC ANR Publication 3441

Insects, Mites, and Snails

  • E. E. Grafton-Cardwell, Entomology, UC Riverside and Kearney Agricultural Center, Parlier
  • J. G. Morse, Entomology, UC Riverside
  • N. V. O'Connell, UC Cooperative Extension, Tulare County
  • P. A. Phillips (emeritus), UC IPM Program, UC Cooperative Extension, Ventura County
  • C. E. Kallsen, UC Cooperative Extension, Kern County
  • D. R. Haviland, UC Cooperative Extension, Kern County
Acknowledgments for contributions to Insect, Mites, and Snails:
  • 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
  • T. Shea, UC Cooperative Extension, Riverside County
  • J. Stewart, Pest Management Associates, Exeter, CA
  • P. Washburn, Washburn & Sons Citrus Pest Control, Riverside, CA

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