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How to Manage Pests

UC Pest Management Guidelines


Adult winter grain mite.

Small Grains

Mites

Scientific names:
Brown wheat mite: Petrobia latens
Winter grain mite: Penthaleus major
Banks grass mite: Oligonychus pratensis

(Reviewed 2/07, updated 2/09)

In this Guideline:


DESCRIPTION OF THE PESTS

Mites are tiny arthropods that feed on the sap of host plants. Because they are so small, use a hand lens to see them. They have 8 legs (6 in the first stage). The brown wheat mite is about 0.025 inch long (0.635 mm), oval shaped and dark red or brown in color. The winter grain mite is larger, 0.04 inch long (1 mm)and dark bluish black with red-orange legs and a reddish patch on the upper side. Banks grass mite is extremely small, 0.001 inch (0.025 mm), and yellow to cream colored. It is the only prominent wheat mite that webs the leaves.

DAMAGE

Leaves injured by brown wheat mite first appear silvery and later take on a scorched appearance. Injury caused by the winter grain mite results in yellowish leaves and stunted plants. The damage caused by this mite is similar to winter-kill. Banks grass mite turns leaves silvery and the tips and margins later turn brown. Webbing is an additional sign that injury is caused by the Banks grass mite. In California, mites seldom cause sufficient damage to be of concern.

MANAGEMENT

Cultural Control
Both brown wheat mite and Banks grass mite cause the greatest injury to water-stressed grain. A timely irrigation will usually alleviate the problem. Crop rotation is detrimental to the winter grain mite.

Management Decisions
Chemical controls are not generally recommended as cultural techniques generally suffice. Application of chemicals for aphid control may lead to a build-up of mites, however, leading to the occasional need for an acaricide.

Common name Amount/Acre R.E.I.+ P.H.I.+
(trade name)   (hours) (days)

  Calculate impact of pesticide on air quality
When choosing a pesticide, consider information relating to natural enemies and honey bees as well as the environmental impact.
 
A. DIMETHOATE 4EC 0.33–0.5 pt 48 60
  MODE OF ACTION GROUP NUMBER1: 1B
  COMMENTS: For use on wheat and triticale only. Do not make more than 2 applications. Do not graze within 14 days. Highly toxic to honey bees if bees are present at treatment time or within a day after.
 
+ 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 R.E.I. exceeds the P.H.I.; the longer of these two intervals is the minimum time that must elapse before harvest may take place.
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/.

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Small Grains
UC ANR Publication 3466
Insects and Mites
C. G. Summers, Entomology, UC Davis/Kearney Agricultural Center, Parlier
L. D. Godfrey, Entomology, UC Davis
Acknowledgment for contributions to Insects and Mites:
D. Gonzalez, Entomology, UC Riverside

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