South Dakota Winter Wheat: Scouting for Aphid and Mite Pests

    Winter wheat has started emerging in some locations, which means that scouting efforts for aphid and mite pests need to begin. The aphids that should be scouted for include the bird cherry oat aphid, English grain aphid, greenbug, and Russian wheat aphid.

    These aphids have the capacity to reduce yield through direct feeding, and the bird cherry oat aphid, English grain aphid, and greenbug are also vectors of Barley yellow dwarf virus. In addition to aphids, the brown wheat mite and wheat curl mite are also capable of reducing yield through direct feeding. The wheat curl mite vectors Wheat streak mosaic virus, which can cause additional yield losses.

    Aphid Pests

    • Bird cherry oat aphid. This species of aphid is olive to dark green in color and can be identified by the characteristic red-orange patch that is present on the base of its abdomen near its cornicles (Figure 1A).
    • English grain aphid. This species of aphid can vary in color from light green to brown, and can be identified by its black antennae, cornicles, and leg joints (Figure 1B).
    • Greenbug. This species of aphid is light green in color, and can be identified by the dark green stripe present on its back (Figure 1C). Feeding by this aphid causes yellow discoloration and red spots on the leaves, due to a toxin present in its saliva.
    • Russian wheat aphid. This species of aphid is a dusty blue-green color and can be identified by its short antennae and greatly reduced cornicles (Figure 1D). Due to a toxin in its saliva, feeding by this aphid causes long white or yellow streaks to appear on the leaves. Plants infested by this aphid will exhibit a purple color during cold weather.

    Figure 1. (A) Bird cherry oat aphids. Photo by Adam Sisson, Iowa State University, Bugwood.org. (B) English grain aphid. Photo by Kansas Department of Agriculture Archive, Bugwood.org. (C) Greenbug. Photo by Alton N. Spark Jr., University of Georgia, Bugwood.org. (D) Russian wheat aphid. Photo by Kansas Department Agriculture Archive, Bugwood.org.

    Mite pests

    • Brown wheat mite. This species of mite is very small and is dark red-brown in color and has eight legs that are light yellow-orange (Figure 2A). The front pair of legs are nearly twice as long as the other three pairs. Identification of this pest may require a hand lens. Feeding by the brown wheat mite produces stippling, which are small white spots on the leaves. This damage may cause the leaves to turn white or brown, and is often confused with symptoms of drought.
    • Wheat curl mite. This species of mite is very small and is white in color (Figure 2B). It can be identified by its elongated body which is approximately 1/100th of an inch long. Identification of this pest may require a hand lens.

    Figure 2. (A) Brown wheat mite. Photo by Phil Sloderbeck, Kansas State University, Bugwood.org. (B) Wheat curl mite. Photo by Gary Hein, University of Nebraska-Lincoln.

     

    Figure 3. Fall infestation of bird cherry oat aphids in winter wheat. Photo by Anitha Chirumamilla.

    Scouting

    When scouting a field for aphids or mites, start at one side of the field and walk in a W or zig-zag pattern and randomly choose plants to examine. These pests are commonly found on the stems and undersides of leaves. For fall infestations, aphids tend to hide at or below ground level on wheat stems (Figure 3). Plants should be examined from several locations present on the W or zig-zag pattern.

    Table 1. Economic thresholds for aphid and mite pests of wheat.

    Pest
    Number of Pests Per Stem
    Seedling stage Boot to heading
    Bird cherry oat aphid 20 30
    Brown wheat mite 25-50 25-50
    English grain aphid 30 50
    Greenbug 5-15 25
    Russian wheat aphid 5-10 20-30

    If a pest population is above the economic threshold (Table 1), management may be necessary. Prior to insecticide application, check the weather forecast. Warm fall conditions may encourage continued pest pressure. See Table 2 for insecticides that are labeled for aphids and brown wheat mite on wheat. For the wheat curl mite, management recommendations are focused on prevention and removing alternative host plants from the field prior to planting.

    Table 2. Insecticides for aphids and brown wheat mite.1

    Insecticide Restricted
    Entry Interval
    (hours)
    Baythroid XL2
    (beta-cyfluthrin)
    12
    Besiege
    (lambda-cyhalotrhin and chlorantraniliprole)
    24
    Cobalt Advanced
    (chlorpyrifos and lambda-cyhalothrin)
    24
    Dimate 4E
    (Dimethoate)
    48
    Karate with Zeon Technology
    (lambda-cyhalothrin)
    24
    Lorsban Advanced
    (chlorpyrifos)
    24
    Mustang Maxx2
    (zeta-cypermethrin)
    12
    Nufos 4E
    (chlorpyrifos)
    24
    Proaxis
    (gamma-cyhalothrin)
    24
    Respect EC2
    (zeta-cypermethrin)
    12
    Seeker
    (sulfoxaflor and lambda-cyhalothrin)
    24
    Silencer
    (lambda-cyhalothrin)
    24
    Stallion
    (zeta-cypermethrin and chlorpyrifos)
    24
    Transform WG2
    (sulfoxaflor)
    24
    Warrior II with Zeon Technology
    (lambda-cyhalotrhin)
    24
    1 This list is not meant to be comprehensive. Always read and follow label instructions.
    2 This product is not registered for brown wheat mite.

     




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