Agriculture: Cole Crops Pest Management Guidelines

Lygus Bug (Western Tarnished Plant Bug)

  • Lygus hesperus
  • Description of the Pest

    Lygus bug is also known as western tarnished plant bug. Adults are true bugs about 0.25 inch long and are variably colored yellowish to green or bronze. Adults have a distinctive triangular marking on the back, and their wings consist of both membranous and hardened sections that are folded over the back. The mouthparts of these bugs are needlelike and long compared to the overall size of their bodies.

    Females lay eggs in the plant tissue, typically in the midrib areas of leaves. Nymphs are light green and are shaped similar to adults, but lack wings. First instar nymphs can be confused with aphids when casually observed, but lack cornicles and move much faster than aphids. Second and third instars have a dark spot on the abdomen, and fourth and fifth instars have four additional spots on their thoracic segments. In general, later instars can be recognized by their developing wing pads.

    Damage

    Lygus feeds by piercing plant tissues. This activity damages the plant tissue and deforms the developing leaves. Egg laying also causes lesions to develop. These injuries initially appear as holes or pits on stems and leaves and sometimes develop into lesions.

    Management

    Biological Control

    Though various natural enemies attack different life stages of the lygus bug, natural enemies are unlikely to be present in fields in sufficient numbers to control lygus bugs before they damage cole crops (which typically occurs at the young seedling or transplant stage). Natural infections with entomopathogenic fungi can sometimes kill lygus bugs, but such infections usually do not provide substantial control.

    Cultural Control

    Manage weeds around the fields to suppress lygus bug numbers. Controlling weeds along roadways, ditches, and field borders near cole crop fields to help prevent spring buildup of lygus bugs is fundamental to lygus management.

    Organically Acceptable Methods

    Use biological control, cultural controls, and organically approved insecticides to manage lygus bugs on organically certified crop.

    Monitoring and Treatment Decisions

    Lygus bug adults can move into and damage the crop at any stage of growth, but young plants are particularly susceptible to feeding injury. Thus, it is essential to scout for the movement of adult lygus bugs into the field during the early stages of crop growth.

    Lygus bugs frequently move into crop fields in spring, when weeds and native vegetation dry up. Determining the level of lygus bug infestation is difficult because the insects are cryptic (hiding), and their activity cycle during any day varies greatly. Lygus bugs become inactive and hard to find during temperature extremes and windy conditions.

    To detect lygus bugs:

    • Use sweep net sampling on the weed hosts
    • Watch for adults flying out of the crop when walking through the field.

    These are the only ways to check for the presence of lygus bug. Sticky traps are not useful for monitoring this pest.

    Confirm the presence of lygus bugs before making pesticide application decisions. No thresholds have been established.

    Common name Amount to use** 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. FLONICAMID
      (Beleaf 50 SG)
      MODE-OF-ACTION GROUP NUMBER1: 29 2.0–2.8 oz 12 0
      COMMENTS: Thorough coverage is necessary for optimal control.
     
    B. NOVALURON
      (Rimon 0.83EC) 12 fl oz 12 7
      MODE-OF-ACTION GROUP NUMBER1: 15
      COMMENTS: Registered for use in broccoli, Chinese broccoli, Brussels sprouts, broccoflower, cabbage, Chinese cabbage, cauliflower, Chinese mustard, and kohlrabi.
     
    C. FLUPYRADIFURONE
      (Sivanto 200 SL) 7–14 fl oz 12 1
      MODE-OF-ACTION GROUP NUMBER1: 4D
     
    D. FENPROPATHRIN
      (Danitol 2.4 EC) 10.66–16 fl oz 24 7
      MODE-OF-ACTION GROUP NUMBER1: 3A
      COMMENTS: Registered for use in broccoli, Chinese broccoli, Brussels sprouts, broccoflower, cabbage, Chinese cabbage, cauliflower, Chinese mustard, and kohlrabi.
     
    E. BIFENTHRIN
      (Brigade 2EC) 5.12–6.4 fl oz 12 7
      MODE-OF-ACTION GROUP NUMBER1: 3A
     
    F. ACETAMIPRID
      (Assail 70WP) See comments 12 See comments
      MODE-OF-ACTION GROUP NUMBER1: 4A
      COMMENTS: Controls nymphs better than adults. For head and stem cole crops, application rate is 0.8 to 1.7 oz and PHI is 7 days. For leafy cole crops, application rate is 0.8 to 2.3 oz and PHI is 3 days.
     
    G. THIAMETHOXAM/CHLORANTRANILIPROLE
      (Durivo) 10–13 fl oz 12 30
      MODE-OF-ACTION GROUP NUMBER1: 4A/28
      COMMENTS: Thiamethoxam and its metabolites (which include the neonicotinoid clothianidin) are highly toxic to bees; may pose a risk to pollinators in crops grown for seed. This product has potential to leach into groundwater where soils are permeable, particularly where the water table is shallow.
     
    H. THIAMETHOXAM
      (Platinum) 5–11 fl oz 12 30
      MODE-OF-ACTION GROUP NUMBER1: 4A
      COMMENTS: Controls nymphs better than adults. Not registered for use on crops grown for seed. Thiamethoxam and its metabolites (which include the neonicotinoid clothianidin) are highly toxic to bees. This product has potential to leach into groundwater where soils are permeable, particularly where the water table is shallow.
     
    I. PERMETHRIN
      (Perm-Up 25DF) Label rates 12 1
      MODE-OF-ACTION GROUP NUMBER1: 3A
      COMMENTS: Registered for use in broccoli, Brussels sprouts, cabbage, certain types of Chinese cabbage (see label) cauliflower, and collards. Do not use if leafminers are present.
     
    J. METHOMYL*
      (Lannate LV) Label rates 48 See label
      MODE-OF-ACTION GROUP NUMBER1: 1A
      COMMENTS: Not registered for use on broccoflower (cavalo), kohlrabi, mizuna, mustard spinach, or rape greens. This active ingredient is very disruptive to natural enemies. If both caterpillars and western tarnished plant bug must be controlled, it can be used; otherwise use a different insecticide. Application rates are crop-specific. Add a wetting agent to improve coverage.
     
    K. ZETA-CYPERMETHRIN
      (Mustang) 3.4–4.3 fl oz 12 1
      MODE-OF-ACTION GROUP NUMBER1: 3A
      COMMENTS: Do not use if leafminers are present. In certain cole crops exported to Canada (broccoli, Brussels sprouts, cabbage, and cauliflower), PHI of 14 days is recommended in order to meet tolerances— see FIFRA 2(ee) recommendation for more information.
     
    Organic Options (Efficacy research may be lacking on these products)
    A. BEAUVARIA BASSIANA STRAIN GHA
      (Mycotrol ESO)# 0.25–1 qt 4 0
      MODE-OF-ACTION GROUP NUMBER1: biological
      COMMENTS: Not registered for use on broccoflower, mustard spinach, and mizuna. In Canada, bees are often used to deliver the product to plants; nevertheless, it is potentially pathogenic to bees and most other insects. When applied to the soil, increases the growth and health of cabbage plants even when moisture is reduced. Check with your organic certifier to determine which B. bassiana products are organically acceptable.
      ...AND...
      AZADIRACHTIN
      (AzaGuard)# 8 fl oz 4 0
      MODE-OF-ACTION GROUP NUMBER1: un
      COMMENTS: Not registered for use on mustard spinach. Alternative to novaluron in organic cole crop production. Check with organic certifier to determine which azadirachtin products are organically acceptable.
     
    B. AZADIRACHTIN
      (AzaGuard)# 16 fl oz 4 0
      MODE-OF-ACTION GROUP NUMBER1: un
      COMMENTS: Not registered for use on mustard spinach. Alternative to novaluron in organic cole crop production. Check with organic certifier to determine which azadirachtin products are organically acceptable. High rate of azadirachtin is effective against lygus bug as a standalone application; low rate may not significantly reduce lygus bugs as a standalone application.
    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.
    1 Rotate insecticides 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; insecticides with a 1B group number should be alternated with insecticides that have a group number other than 1B. Mode-of-action group numbers are assigned by IRAC (Insecticide Resistance Action Committee).
    * Permit required from county agricultural commissioner for purchase or use.
    # Acceptable for organically grown produce.
    Text Updated: 12/20
    Treatment Table Updated: 12/20