How to Manage Pests

UC Pest Management Guidelines

Citrus

Whiteflies

Scientific Names:
Woolly whitefly: Aleurothrixus floccosus
Citrus whitefly: Dialeurodes citri
Bayberry whitefly: Parabemisia myricae
Ash whitefly: Siphoninus phillyreae

(Reviewed 2/17, updated 2/17, corrected 1/19)

In this Guideline:


Description of the Pests

Whiteflies are tiny, flying insects that derive their name from the mealy white wax covering their wings and body. While adult whiteflies are similar in appearance, the immature stages are more distinctive. The pupa and other immature stages of the woolly whitefly are covered with curly, waxy filaments and are exclusively found on the undersides of leaves; pupae of the bayberry whitefly have a clear wax fringe around the body margin; pupae of the citrus whitefly have a distinctive Y-shape on their backs; and pupae of the ash whitefly have a thick band of wax down the back and a fringe of tiny tubes, each with a liquid droplet at the end.

Damage

Whiteflies suck phloem sap, which in some cases can cause leaves to wilt and drop when there are high numbers of whiteflies. However, the primary concern with whiteflies is the honeydew they produce. Honeydew excreted by nymphs and adults collects dust and supports the growth of sooty mold; large infestations blacken entire trees, including fruit, as well as attract ants, which interfere with the biological control of whiteflies and other pests. The sooty mold can also affect tree yields by reducing photosynthesis and requiring extra handling time for cleaning.

Management

Applying insecticides for whiteflies is generally not necessary; exceptions are usually limited to where biological control has been severely disrupted. Enhance biological control by avoiding nonselective insecticides for other pests and by controlling sugar-feeding ants.

Biological Control

Several natural enemies attack the immature stages of whiteflies and provide partial to complete biological control when undisturbed by ants, dust, or an insecticide application. Conserve natural enemies by controlling other pests with the least disruptive pesticides available and by controlling sugar-feeding ants.

Cultural Control

Alternate row pruning to provide refuge for parasites may provide some benefits.

Monitoring and Treatment Decisions

Inspect for whitefly throughout summer by looking for immature stages on the undersides of leaves directly above areas with honeydew, sooty mold, or both. Consider applying an insecticide if honeydew and sooty mold contamination of fruit reaches levels that are not tolerable. Applications specifically targeting whitefly are usually not needed because usually at least one neonicotinoid (e.g., Assail, Admire, Nuprid, Provado) or insect growth regulator (e.g., Esteem, Centaur) that will suppress whiteflies has already been used one or more times on most citrus orchards to control scale and sharpshooter pests. No official treatment thresholds for whitefly exist.

Common name Amount to use REI‡ PHI‡
(Example trade name) (type of coverage)** (hours) (days)
Calculate impact of pesticide on air quality
Bee precaution pesticide ratings
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.
 
A. ACETAMIPRID
  (Assail 70WP) 3.4–5.7 oz/acre (TC) 12 7
  RANGE OF ACTIVITY: Pests: broad (many insects); Natural enemies: most
  PERSISTENCE: Pests: intermediate; Natural enemies: intermediate
  RESISTANCE: None
  MODE-OF-ACTION GROUP NUMBER1: 4A
  COMMENTS: Residues last for 4 to 6 weeks. Apply in 300 to 1000 gal water/acre; use higher volume if insects are inside the canopy on the wood. Toxic to vedalia beetle and should not be used in cottony cushion scale-infested orchards.
 
B. BUPROFEZIN
  (Centaur WDG) 34.5–46 oz/acre (TC) 12 3
  RANGE OF ACTIVITY: Pests: narrow (scales, whiteflies); Natural enemies: predatory beetles
  PERSISTENCE: Pests: intermediate; Natural enemies: intermediate
  MODE-OF-ACTION GROUP NUMBER1: 16
  COMMENTS: For use on all varieties. Toxic to vedalia beetles. Most effective if applied after peak emergence of the first generation of crawlers. Apply after the crawlers have settled down and formed white caps. Slow-acting; This product does not kill the scale until they molt, so a decrease in whitefly numbers is usually not observed until the next generation.
  . . . PLUS . .
  NARROW RANGE OIL
  (415) 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 and barrier effects; also improves insecticide spread and persistence.
 
C. IMIDACLOPRID
  (Admire Pro, soil applcaition) 7–14 fl oz/acre 12 0
  (Admire Pro, foliar applcaition) 3.5–7 fl oz/acre 12 0
  RANGE OF ACTIVITY: Pests: narrow (aphids, glassy-winged sharpshooters, Asian citrus psyllid, citrus leafminer, weevils, whiteflies); Natural enemies: predatory beetles and parasites
  PERSISTENCE: Pests: long; Natural enemies: intermediate
  RESISTANCE: Some glassy-winged sharpshooter populations
  MODE-OF-ACTION GROUP NUMBER1: 4A
  COMMENTS: Apply to soil; remains effective 4 to 5 months. Moderately effective against nymphs and adults. Pre-wet soil before imidacloprid is applied. For optimum uptake, apply to newly planted trees or trees irrigated by drip, microsprinkler, or 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 insecticide 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 insecticide. 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. Apply in citrus orchards May to July. Toxic to vedalia beetle and should not be used in cottony cushion scale-infested orchards.
 
D. PYRIPROXYFEN
  (Esteem 0.86 EC) 10 oz/acre (TC or LV) 12 1
  RANGE OF ACTIVITY: Pests: narrow (armored scale insects); Natural enemies: predatory beetles
  PERSISTENCE: Pests: long; Natural enemies: long
  MODE-OF-ACTION GROUP NUMBER1: 7C
  COMMENTS: For use on all varieties. Toxic to vedalia beetles. Do not apply until the second generation of scale crawler activity (1800 DD after the biofix of first male flight). This is to allow the vedalia beetle time between March through June to eliminate cottony cushion scale populations. This application timing may not prevent scale from infesting fruit. Apply after the crawlers have settled down and formed whitecaps. This product does not kill the scale until they molt, so a decrease in whitefly numbers is usually not observed until the next generation.
  . . . PLUS . . .
  NARROW RANGE OIL
  (415) 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 insecticide spread and persistence.
 
** LV - Low-volume uses 20 to 100 gal water/acre.
  TC - Thorough coverage uses 750 to 2,000 gal water or more/acre, depending on tree size.
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.
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).

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Citrus
UC ANR Publication 3441

Insects, Mites, and Snails

E. E. Grafton-Cardwell, Lindcove Research and Extension Center, Exeter and Entomology, UC Riverside
J. G. Morse, Entomology, UC Riverside
D. R. Haviland, UC Cooperative Extension, Kern County and UC IPM Program
B. A. Faber, UC Cooperative Extension, Santa Barbara and Ventura counties

Acknowledgments for contributions to Insect, Mite, and Snails:
J. Barcinas, E.S.I., Corona, CA
R. Dunn, Badger Farming Co., Exeter, CA
J. Gorden, Pest Management Associates, Exeter, CA
C. E. Kallsen, UC Cooperative Extension, Kern County
D. Machlitt, Consulting Entomology Services, Moorpark, CA
C. Musgrove, retired entomologist, Riverside, CA
K. Olsen, S & J Ranch, Pinedale, CA
N. V. O'Connell, UC Cooperative Extension, Tulare County
P. A. Phillips, UC IPM Program, UC Cooperative Extension, Ventura County
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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