How to Manage Pests

UC Pest Management Guidelines

Almond

Brown Mite

Scientific name: Bryobia rubrioculus

(Reviewed 3/09, updated 3/09)

In this Guideline:


DESCRIPTION OF THE PEST

The brown mite is the largest in size of all almond pest mites and emerges first in the spring. Brown mite eggs are red, without a stalk, and overwinter in masses on twigs, especially at the junction of wood growth from the two previous seasons. Eggs hatch at the same time leaf and flower buds open. Newly hatched mites are red with six legs; after the first molt they are brown with eight legs, resembling the adult. Adults are flattened with long front legs. The mites feed only during the cool parts of the day, and migrate off the leaves during midday. They are not active during hotter periods of the summer. There are 2 to 3 generations per year between February and June.

DAMAGE

Generally these mites are not considered major pests and low to moderate numbers can be beneficial in spring by providing mite predators with a food supply. Feeding by these mites can cause chlorosis, but leaves rarely drop. Infestations are generally confined to a few trees.

MANAGEMENT

Monitor for brown mite as part of the dormant spur sample and treat with dormant oil if required.

Biological Control

The western predatory mite and brown lacewing are both effective predators, but alone may not control brown mite populations. It is important to avoid using insecticides that kill these natural enemies; residues of certain pesticides, such as pyrethroids used during the dormant season, can negatively impact predator mite populations.

Organically Acceptable Methods

Biological control and certain oil sprays are acceptable for use on organically grown crops.

Monitoring and Treatment Decisions

Brown mites are best controlled by the delayed-dormant spray. Sample for these mites as part of the dormant spur sample. If more than 20% of spurs are infested, an application of oil is suggested. Occasionally there is an infestation during a cool spring when dormant treatments were inadequate—either they were applied too early in dormancy, the rate of oil used was not adequate, or it was not applied.

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.
 
DELAYED-DORMANT
A. NARROW RANGE OIL#
  (Superior, Supreme) 6–8 gal 1.5–2 gal See label 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. Do not apply oils to water-stressed trees. Check with certifier to determine which products are organically acceptable.
 
SPRING
A. NARROW RANGE OIL#
  (Omni and others) 2–4% 0.25–1% See label 0
  MODE OF ACTION: Contact including smothering and barrier effects.
  COMMENTS: Be sure that trees are well-watered to avoid phytotoxicity. Works by contact activity only, so good coverage is essential. Check with certifier to determine which products are organically acceptable.
 
** 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.
# Acceptable for use on organically grown produce.

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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