How to Manage Pests

UC Pest Management Guidelines

Apricot

Webspinning Spider Mites

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

(Reviewed 10/14, updated 10/14)

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, and have 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. However, miticides may be necessary in some orchards in the summer, but only when mite numbers reach damaging levels. This may occur if pesticides, especially pyrethroids, 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

Use cultural and biological control and some oil sprays on organically grown apricots.

Monitoring and Treatment Decisions

If a treatment is needed early in the season and predators are present, you can use below-label rates of a miticide to reduce the pest numbers and help preserve predators. Be alert for mite damage following the use of pyrethroids to control other insect species. Pyrethroid applications can disrupt mite biological control. Treatments are not needed after the first of September, when mite numbers decline naturally.

Common name Amount to Use** REI‡ PHI‡
(Example trade name) (conc.) (dilute)
(hours) (days)

UPDATED: 10/14
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.
 
Caution: Never apply sulfur to apricot trees.
 
SPRING-SUMMER
 
A. NARROW RANGE OIL # 4–8 gal 1.5–2 gal 12 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. Addition of other pesticides is optional.
 
B. BIFENAZATE
  (Acramite 50WS) 0.75–1 lb 0.25 lb 12 3
  MODE-OF-ACTION GROUP NUMBER1: un
  COMMENTS: Do not apply more than once per season. Addition of oil is optional.
 
C. SPIRODICLOFEN
  (Envidor 2SC) 16–18 fl oz/acre   12 7
  MODE-OF-ACTION GROUP NUMBER1: 23
  COMMENTS: Do not apply more than once per season. Addition of oil is optional.
 
D. HEXYTHIAZOX
  (Onager) 12–24 oz/acre   12 7
  MODE-OF-ACTION GROUP NUMBER1: 10A
  COMMENTS: Will not control adult spider mites. Do not make more than one application per year. Addition of oil is optional.
 
E. CLOFENTEZINE
  (Apollo SC) 2–8 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 required; 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 per season. Addition of oil is optional.
 
F. ABAMECTIN*
  (Agri-Mek 0.15 EC) 10–20 fl oz 2.5–5 fl oz 12 21
  MODE-OF-ACTION GROUP NUMBER1: 6
  COMMENTS: Do not apply more than 20 fl oz/acre per application, two applications per growing season, and 40 fl oz/acre per growing season. Needs oil to work properly.
  . . . PLUS . . .
  NARROW RANGE OIL 4–6 gal 1.5–2 gal 12 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.
 
** For concentrate applications, use the amount given in 80 to 100 gal water/acre or lower if the label allows; for dilute application, amount is per 100 gal water to be applied in 300 to 400 gal water/acre, according to label.
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.
# 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 website at http://www.irac-online.org/.
* Permit required from county agricultural commissioner for purchase or use.

[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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