How to Manage Pests
UC Pest Management Guidelines
Brown Soft Scale
Scientific Name: Coccus hesperidum
(Reviewed 2/17, updated 2/17, corrected 1/19)
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. Brown soft scale numbers 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.
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 ofpests.
Management of brown soft scale focuses on preserving its natural enemies and controlling ants. Avoid the repeated use of broad-spectrum insecticides for other pests that disrupt the biological control of soft scales. 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 numbers to increase to higher levels.
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
Use biological control and organically approved oils, such PureSpray Green (NR 440), on an organically certified crop.
Monitoring and Treatment Decisions
Monitor brown soft scale from June through October when biological control may be disrupted 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.
UC IPM Pest Management Guidelines:
Insects, Mites, and Snails
E. E. Grafton-Cardwell, Entomology, UC Riverside and Kearney Agricultural Center, Parlier
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