How to Manage Pests

UC Pest Management Guidelines

Almond

San Jose Scale

Scientific name: Diaspidiotus (=Quadraspidiotus) perniciosus

(Reviewed 3/09, updated 6/09)

In this Guideline:


DESCRIPTION OF THE PEST

There is no visible egg stage with this insect; the scales emerge as mobile nymphs. Crawlers are bright yellow and tiny (about the size of the sharp end of a pin), with well developed eyes, antennae, and legs. After locating a feeding site, the crawlers settle, begin feeding, and lose their antennae, legs, and eyes, becoming immobile. They soon begin to secrete a waxy substance that covers the body. Initially the waxy covering is white (white cap), but turns darker later in the first instar (black cap). Male scales have a more elongated covering than the females; males molt four times, whereas females have a rounder cover and molt twice. The male emerges as a winged adult and the female remains wingless under the scale covering. There are three to four generations per season, taking about 7 to 8 weeks per generation.

DAMAGE

Scales suck plant juices from twigs and limbs, and inject a toxin, resulting in loss of tree vigor, growth and productivity, and death of limbs. A red halo is produced around a feeding site on 1-year-old green wood. Untreated infestations can kill fruit spurs and scaffold wood within 1 to 3 years.

MANAGEMENT

San Jose scale has many natural enemies that can frequently keep the pest under control if not disrupted by in-season applications of broad-spectrum insecticides. Many orchards that have not used broad-spectrum sprays for 2 or 3 years do not have San Jose scale problems. Low to moderate populations can be managed with oil sprays during the dormant season. The best time to spray is during the dormant season, and low-to-moderate populations can be managed with oil sprays at this time. The scale is monitored as part of the spur sample during the dormant season and with pheromone traps in the spring.

Biological Control

Natural enemies that feed on San Jose scale include two predaceous beetles: the twicestabbed lady beetle, Chilocorus orbus, and another small beetle Cybocephalus californicus. A number of small chalcid and aphelinid wasps, including Aphytis spp. and Encarsia (Prospaltella) sp., parasitize this scale. These predators and parasites are helpful in reducing scale populations, but insecticides used during the growing season for other pests disrupt this natural control, and scale populations can build as a result. Low winter mortality due to mild temperatures will also permit a buildup of scale populations.

Organically Acceptable Methods

Biological control and a properly applied oil spray during the delayed-dormant period are organically acceptable management practices for this pest.

Monitoring and Treatment Decisions

Monitor San Jose scale during the dormant season by collecting spurs and examining them for live scale as well as for tiny emergence holes, which indicate parasite activity. For details on dormant spur sampling and treatment thresholds, see the section Dormant Spur Sampling and the monitoring form (PDF).

For large-scale populations, a properly applied dormant spray with good coverage is the most effective, and will eliminate the spring flight and suppress the infestation throughout the growing season. Do not use oil sprays, however, on water-stressed trees. The following table gives a guideline for making treatment choices based on levels of infestation on dormant spur samples:

Dormant Treatment Decision Table (% Infested Spurs).
Threshold Treatment
Below 20% No Spray
20%–60% Oil at 6–8 gals/acre
Over 60% Oil with insect growth regulator

Oil alone can be effective in controlling low-to-moderate populations. If populations are high, include an insect growth regulator (pyriproxyfen-Esteem or buprofezin-Applaud) with the oil. Organophosphates are available but are associated with environmental problems and should be avoided. When the dormant organophosphate and oil spray is first omitted, San Jose scale populations tend to increase the first year, but by the second and third year parasite populations have increased to levels where they reduce San Jose scale populations and maintain them at low levels.

If dormant or delayed-dormant controls were not applied, and monitoring indicates that scale densities may require treatment, use pheromone traps to detect male emergence in spring. Place traps 6 to 7 feet high in the north or east side of trees by February 25 in southern areas and by March 15 in the north. To time treatment, accumulate degree-days using a lower threshold of 51°F and an upper threshold of 90°F. The optimum time for spring spraying with an organophosphate is 600 to 700 degree-days (DD) after the beginning of the male flight or 200 DD after crawler emergence begins. Apply pyriproxyfen (Seize) and buprofezin (Centaur) at the beginning of crawler emergence, which is 400 DD from the beginning of the male flight. Sticky tape can be used to monitor crawlers when they hatch. Late-fall or postharvest treatments are not effective.

Parasite populations can also be monitored with San Jose scale pheromone traps in spring because the parasites are attracted to the traps. To distinguish the adult male San Jose scale from the parasite Aphytis spp., look for a dark band across the back of the male San Jose scale at the base of its wings.

Common name Amount per acre** R.E.I.+ P.H.I.+
(example trade name) (conc.) (dilute)
(hours) (days)

  Calculate impact of pesticide on air quality
The following materials are listed in order of usefulness in an IPM program, taking into account efficacy and impact on natural enemies and honey bees. When choosing a pesticide, also consider information relating to environmental impact. Not all registered pesticides are listed. Always read the label of the product being used.
 
DORMANT
 
A. NARROW RANGE OIL#
  (Omni Supreme and others) 6–8 gal 1.5–2 gal 4 0
  MODE OF ACTION: Contact including smothering and barrier effects.
  COMMENTS: Cover all parts of the tree. Will control low-to-moderate infestations. See Dormant Treatment Decision Table for rate to use based on % infested spurs. Check with certifier to determine which products are organically acceptable.
 
B. NARROW RANGE OIL
  (Omni Supreme and others) 4–8 gal 1.5–2 gal 4 0
  MODE OF ACTION: Contact including smothering and barrier effects.
  COMMENTS: Cover all parts of the tree. Oil alone will control low to moderate infestations. Use with organophosphate insecticide for high infestations. Do not use oil sprays on water-stressed trees.
  . . . PLUS. . .
  PYRIPROXYFEN
  (Seize 35WP) 4–5 oz/acre 12 21
  MODE OF ACTION GROUP NUMBER1: 7C
  COMMENTS: An insect growth regulator. Do not apply more than once per growing season. Good coverage is essential for good control.
  . . . or . . .
  CARBARYL*
  (Sevin XLR PLUS) 1 qt 12 14
  MODE OF ACTION GROUP NUMBER1: 1A
  COMMENTS: If resistance to diazinon or chlorpyrifos has been a problem, carbaryl is a good alternative. Best time to apply this material is about 2–3 weeks before bloom. Because carbaryl is so toxic to honey bees, do not apply when there is any bloom in the orchard or in neighboring orchards.
 
DELAYED DORMANT
 
A. NARROW RANGE OIL#
  (Omni Supreme and others) 6–8 gal 1.5–2 gal 4 0
  MODE OF ACTION: Contact including smothering and barrier effects.
  COMMENTS: High rates of oil alone will control scales at this time. Also apply when Bt is used at bloom to control peach twig borer. Check with certifier to determine which products are organically acceptable.
 
SPRING
 
A. PYRIPROXYFEN
  (Seize 35WP) 4–5 oz/acre 12 21
  MODE OF ACTION GROUP NUMBER1: 7C
  COMMENTS: Apply at beginning of crawler emergence, which is 400 DD from the beginning of the male flight. Do not apply more than once per growing season. Good coverage is essential for good control.
 
B. BUPROFEZIN
  (Centaur WDG) 34.5–46 oz/acre 12 60
  MODE OF ACTION GROUP NUMBER1: 16
  COMMENTS: An insect growth regulator that should be applied at beginning of crawler emergence, which is 400 DD from the beginning of the male flight. Good coverage is essential for good control. Make no more than one application per season.
 
C. CHLORPYRIFOS*
  (Lorsban 4E) 2 qt 24 14
  MODE OF ACTION GROUP NUMBER1: 1B
  COMMENTS: Do not apply more than 3 foliar applications per season. Do not allow livestock to graze in treated orchards. Avoid drift and tailwater runoff into surface waters.
 
D. METHIDATHION*
  (Supracide 25W) 4 lb 1 lb 48 80
  MODE OF ACTION GROUP NUMBER1: 1B
  COMMENTS: Do not apply to foliage more than once a season. Foliar applications may be phytotoxic with some varieties. Can be disruptive to mite predators, resulting in mite outbreaks.
 
** For dilute applications, rate is per 100 gal water to be applied in 300–500 gal water/acre, depending on the label; for concentrate applications, use 80–100 gal water/acre, or lower if the label allows.
+ 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 these two intervals is the minimum time that must elapse before harvest may occur.
* Permit required from county agricultural commissioner for purchase or use.
# Acceptable for use on organically grown produce.
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). For additional information, see their Web site at http://www.irac-online.org/.
Not recommended or not on label.

IMPORTANT LINKS

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Almond
UC ANR Publication 3431

Insects and Mites

  • F. G. Zalom, Entomology, UC Davis
  • C. Pickel, UC IPM Program, UC Cooperative Extension, Sutter/Yuba counties
  • W. J. Bentley, UC IPM Program, Kearney Agricultural Center, Parlier
  • D. R. Haviland, UC IPM Program, UC Cooperative Extension, Kern County
  • R. A. Van Steenwyk, Insect Biology, UC Berkeley
Acknowledgment for contributions to Insects and Mites:
  • R. E. Rice, Kearney Agricultural Center, Parlier
  • L. C. Hendricks, UC Cooperative Extension, Merced County
  • R. L. Coviello, UC Cooperative Extension, Fresno County
  • M. W. Freeman, UC Cooperative Extension, Fresno County

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