How to Manage Pests

UC Pest Management Guidelines

Citrus

Brown Soft Scale

Scientific Name: Coccus hesperidum

(Reviewed 9/08, updated 6/13)

In this Guideline:


Description of the Pest

Female brown soft scales lay a few eggs at a time during summer. Eggs hatch almost immediately and crawlers start to feed. Young scales move around until they are about half grown. They have mottled, yellowish, rounded shells. The young molt twice and reach maturity on leaves or twigs; they rarely move onto fruit. There are three to five overlapping generations a year. Populations are usually highest from mid-summer to early fall.

Citricola scale, another soft scale that is similar to brown soft scale, may be found infesting the same trees, but because brown soft scales have multiple overlapping generations, colonies of this pest contain multiple life stages.

Damage

Heavy feeding by the soft brown scale reduces tree vigor, kills twigs, and reduces yields. Sooty mold grows on excreted honeydew and may affect fruit grade. The honeydew also attracts ants, which interfere with the biological control of a number of pests.

Management

Management of brown soft scale focuses on preserving its natural enemies and controlling ants. Avoid the repeated use of organophosphates and carbamates, especially formetanate hydrochloride (Carzol), for the control of other pests; instead use sabadilla (Veratran), abamectin, or spinetoram (Delegate) to control citrus thrips and Bacillus thuringiensis or cryolite for orangeworms in spring. Individual treatment of this scale is rarely necessary. If natural enemies do not control the scales, a spot treatment with an oil spray is usually sufficient. In areas with citricola scale or black scale, populations of brown soft scale may be beneficial if they are not too large because their generations overlap and provide parasites with susceptible life stages to attack throughout the year, thus allowing parasite populations to build to larger levels.

Biological Control

A complex of Metaphycus spp. parasites attack brown soft scale. The most common of these is M. angustifrons in southern California. In addition, the lady beetles Rhyzobius (Lindorus) lophanthae, Chilocorus orbus, and C. cacti prey on brown soft scales. Ants will protect brown soft scale from parasitism and predation because they feed on the honeydew that soft scales produce. Maximizing parasitism by controlling and reducing ants is critical for brown soft scale control because pesticides are not very effective against this scale species.

Organically Acceptable Methods

Biological control and organically approved oils, such PureSpray Green (NR 440), are acceptable for use on an organically certified crop.

Monitoring and Treatment Decisions

Monitor brown soft scale from June through October when disruption of biological control may be a problem. Check the level of parasitism by looking for parasite exit holes and for developing parasites within the scale body. Organophosphate and carbamate insecticides are not very effective in controlling this pest. Usually, reduction of these insecticides in combinations with ant control will resolve the brown soft scale problem.

Common name Amount to use R.E.I.‡ P.H.I.‡
(example trade name) (type of coverage)** (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.
 
A. NARROW RANGE OIL (UR92%)
  (415, 440) 1.2–1.4% (TC) 4 When dry
  . . . or . . .
  NARROW RANGE OIL (UR99%)
  (415, 435, 440, 455) 1.2–1.4% (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.
  COMMENTS: To avoid phytotoxicity problems, see timings for California red scale. Apply higher rate of narrow range oil in July or August only. Narrow range 440 spray oil (or higher) 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 treatments to green lemons because of phytotoxicity after sweating; check label for preharvest interval.
 
B. CHLORPYRIFOS*
  (Lorsban Advanced) 0.5–0.75 pt/100 gal (TC) 5 days See comments
  . . . or . . .  
  2–7 pt/acre (LV)  
  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; however it may cause ridging on lemons. Apply thorough coverage spray in 1,200–1,600 gal/acre; do not apply during daylight hours of bloom period. Preharvest interval is 21 days for up to 7 pt/acre and 35 days above 7 pt/acre. Do not apply during Dec., Jan., or Feb. See label for additional restrictions. Rates greater than 8 pt/acre are allowed only in Fresno, Tulare, Kern, Kings, Stanislaus, and Madera counties.
 
C. CARBARYL*
  (Sevin XLR Plus) 2 qt/acre (TC) 12 5
  RANGE OF ACTIVITY: Pests: broad (many insects); Natural enemies: most
  PERSISTENCE: Pests: long; Natural enemies: long
  MODE OF ACTION GROUP NUMBER1: 1A
  COMMENTS: For use on all varieties. May cause outbreaks of citrus red mite and citrus thrips.
 
D. CARBARYL*
  (Sevin XLR Plus) 2 qt/acre (TC) 12 5
  RANGE OF ACTIVITY: Pests: broad (many insects); Natural enemies: most
  PERSISTENCE: Pests: long; Natural enemies: long
  MODE OF ACTION GROUP NUMBER1: 1A
  COMMENTS: For use on all varieties. May cause outbreaks of citrus red mite and citrus thrips.
  . . . PLUS . . .
  NARROW RANGE OIL
  (415) 0.5–1.4% 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.
  COMMENTS: For use on all varieties. Reducing the rate of carbaryl increases survival of natural enemies. Reducing the rate of the oil reduces the risk of phytotoxicity, especially in warmer growing areas of the state. Do not apply during bloom. 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. For tank mixes, observe all directions for use on all labels, and employ the most restrictive limits and precautions. Never exceed the maximum a.i. on any label when tank mixing products that contain the same a.i.
 
E. METHIDATHION*
  (Supracide 25W) 0.5–1 lb/100 gal (TC) 30 days 14
  RANGE OF ACTIVITY: Pests: broad (many insects); Natural enemies: most
  PERSISTENCE: Pests: long; Natural enemies: long
  MODE OF ACTION GROUP NUMBER1: 1B
  COMMENTS: For use on all varieties. Do not apply during bloom. Preferred timing is immediately postbloom before fruit becomes infested. May increase citrus red mite populations.
 
F. METHIDATHION*
  (Supracide 25W) 0.5 lb/100 gal (TC) 30 days 14
  RANGE OF ACTIVITY: Pests: broad (many insects); Natural enemies: most
  PERSISTENCE: Pests: long; Natural enemies: long
  MODE OF ACTION GROUP NUMBER1: 1B
  . . . PLUS . . .
  NARROW RANGE OIL
  (415) 0.5–1.4% 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.
  COMMENTS: For use on all varieties. Reducing the rate of methidathion increases survival of natural enemies. Reducing the rate of the oil reduces the risk of phytotoxicity, especially in warmer growing areas of the state. Do not apply during bloom. May increase citrus red mites. Caution: Serious hazards are associated with oil treatments to green lemons because of phytotoxicity after sweating; check label for preharvest interval. For lemons, do not exceed 10 lb/acre or apply more than once per season when tank mixed with oil.
 
G. MALATHION
  (Malathion 8 Flowable) 7.5 pt/acre (TC) 72 7
  RANGE OF ACTIVITY: Pests: broad (many insects); Natural enemies: most
  PERSISTENCE: Pests: intermediate; Natural enemies: intermediate
  MODE OF ACTION GROUPNUMBER1: 1B
  COMMENTS: For use on all varieties.
 
** LV - Low-volume uses 20–100 gal water/acre.
  TC - Thorough coverage uses 750–2,000 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.
* 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). For additional information, see their Web site at http://www.irac-online.org/.

IMPORTANT LINKS

[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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