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UC Pest Management Guidelines


Adult twospotted spider mite, Tetranychus urticae.

Apricot

Webspinning Spider Mites

Scientific Names:
Pacific spider mite: Tetranychus pacificus
Twospotted spider mite: Tetranychus urticae

(Reviewed 11/07, updated 11/07)

In this Guideline:


DESCRIPTION OF THE PESTS

These two spider mites are very similar looking as adults, have similar life histories, and are controlled in the same manner. Overwintering female mites are red or orange and are found under rough bark, in ground litter, and on winter weeds. During the season they range from yellow to green to black depending on age and host food. Both have dark spots. Adult males do not overwinter and are smaller than females. Eggs are laid on the foliage. Early in the season mites are found in the lower to central areas of the tree. The mites reproduce rapidly during warm weather between June and September. Under favorable conditions, mites develop within 7 days, with 8 to 10 generations per season.

DAMAGE

Mites are rarely a problem in apricots. In general, mite feeding causes leaf stippling and leaves can turn yellow and drop off, but apricot trees don't appear to suffer economic damage from mites.

MANAGEMENT

In many cases biological control keeps spider mites under control. (Miticides may be necessary in some orchards in summer, but only when mite populations reach damaging levels, which may occur if pesticides have been used that disrupt natural enemies.)

Biological Control
Several species play a large role in mite control, including the western predatory mite (Galendromus [=Metaseiulus] occidentalis), the sixspotted thrips, the spider mite destroyer, the brown lacewing, and the green lacewing. The western predatory mite is the most reliable mite predator. It is the same size as spider mites, but lacks spots and ranges in color from cream to amber red. This predator maintains good control unless the proportion of leaves with spider mites is higher than the proportion of leaves with predatory mites.

Cultural Control
Reduce dusty conditions in orchards by oiling or watering roadways and maintaining a groundcover. Prevent water stress, as this condition results in higher mite densities and intensified damage.

Organically Acceptable Methods
Cultural and biological control and certain oil sprays are acceptable for use on organically grown apricots.

Monitoring and Treatment Decisions
If treatment is needed early in the season and predators are present, you can use below-label rates of a miticide to reduce the pest population and help preserve predators. Treatments are not needed after the first of September, when mite populations decline naturally.

Common name Amount to Use** R.E.I.+ P.H.I.+
(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 label of product being used.
 
Caution: Never apply sulfur to apricot trees.
 
SPRING-SUMMER
A. CLOFENTEZINE
  (Apollo SC) 2–4 oz 0.5–1 oz 12 21
  MODE OF ACTION GROUP NUMBER1: 10A
  COMMENTS: This material is more effective in the early part of the year; apply after sampling indicates pest mites are increasing but before significant damage or webbing is present. Kills eggs and young larval stages. Good coverage is a must; use a minimum of 50 gal water/acre for concentrate and a maximum of 400 gal water/acre for dilute. To delay development of resistance, use only once/season.
 
B. BIFENAZATE
  (Acramite) 50 WS 0.75–2 lb 0.5 lb 12 3
  MODE OF ACTION GROUP NUMBER1: 25
  COMMENTS: Do not apply more than once per season.
 
C. NARROW RANGE OIL# 4–8 gal 1.5–2 gal 4 0
  MODE OF ACTION: Contact including smothering and barrier effects.
  COMMENTS: Be sure that trees are well watered before treating. Some of the new lower-chilling varieties, especially Poppycot, can be highly susceptible to oil damage. Use extreme care when applying oil to these varieties. Check with certifier to determine which products are organically acceptable.
 
 
**  For concentrate applications, use the amount given in 80-100 gal water/acre or lower if the label allows; for dilute application, amount is per 100 gal water to be applied in 300-400 gal water/acre, according to label.
+ 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.
# 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 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/.

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Apricot
UC ANR Publication 3433
Insects and Mites
W. W. Coates, UC Cooperative Extension, San Benito County
R. A. Van Steenwyk, Insect Biology, UC Berkeley
W. J. Bentley, UC IPM Program, Kearney Agricultural Center, Parlier
K. R. Day, UC Cooperative Extension, Tulare County
K. A. Kelley, UC Cooperative Extension, Stanislaus County
J. L. Caprile, UC Cooperative Extension, Contra Costa County
Acknowledgment for contributions to Insects and Mites:
L. C. Hendricks, UC Cooperative Extension, Merced County

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