Agriculture: Small Grains Pest Management Guidelines

Mites

  • Banks grass mite: Oligonychus pratensis
  • Brown wheat mite: Petrobia latens
  • Winter grain mite: Penthaleus major
  • Description of the Pest

    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 per acre REI‡ PHI‡
    (Example trade name) (hours) (days)
    Not all registered pesticides are listed. 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. Always read the label of the product being used.
     
    A. DIMETHOATE
      (Dimethoate 4EC) 0.33–0.5 pt 48 35
      MODE-OF-ACTION GROUP NUMBER1: 1B
      COMMENTS: For use on wheat and triticale only. Do not make more than two applications per year. Do not graze within 14 days. Highly toxic to bees; do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging.
    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 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).
    Text Updated: 02/09
    Treatment Table Updated: 07/16