Agriculture: Cole Crops Pest Management Guidelines

Wireworms

  • Limonius spp.
  • Description of the Pest

    Wireworms are slender, cylindrical, brown-to-yellow larvae that grow to 0.5 to 1.25 inch long depending on the species. They are the soil-dwelling larvae of click beetles. Adult beetles are hard-bodied, black to tan, and about 0.25 to 1 inch long. When adults are upside down, they can flip their body into the air, making a pop or snap sound.

    Damage

    Wireworms devour seeds, clip off seedlings and small roots, and bore into roots and underground stems. Damage is more common in spring-planted crops where the soil is high in organic matter, such as fields that have recently been in or adjacent to alfalfa, pasture, or uncontrolled weeds. Wireworms do not significantly damage older plants.

    Management

    After seedling emergence or right after transplanting, check the crop for wireworms, especially in spring-planted crops and where soil or that of the border areas is high in organic matter. Soil fumigation and some pesticides applied to control other pests will also kill wireworms, but pesticide application specifically for wireworms is seldom necessary. Preplant pesticide application or seed treatments in fields with a history of wireworm damage provide superior control compared to any postemergence practice.

    Cultural Control

    Destroy plant residue from previous crops and weeds around field borders. Fallow fields for several weeks before planting cole crops to allow organic matter to decompose.

    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.
     
    Seed Treatment
    A. CLOTHIANIDIN
      (NipsIt Vegtables) Label rates 12 NA
      MODE-OF-ACTION GROUP NUMBER1: 4A
      COMMENTS: Registered for use on only broccoli seeds in California, but seed treated in and obtained from another state can be legally used in California even if the chemical is not registered on the crop in California. Contact your retail seed dealer for information and availability. Application rate per seed depends on the amount of seed planted per acre.
     
    Preplant
    A. CLOTHIANIDIN
      (Belay) 9–12 fl oz 12 21
      MODE-OF-ACTION GROUP NUMBER1: 4A
      COMMENTS: Use as a preplant or at-plant soil application (rate included above is for soil application only). Highly toxic to bees for more than 5 days after an application. This product has potential to leach into groundwater where soils are permeable, particularly where the water table is shallow.
     
    B. DIAZINON
      (Diazinon 50W) 6–8 lb 96 (4 days) NA
      MODE-OF-ACTION GROUP NUMBER1: 1B
      COMMENTS: Preplant or transplant water application only (see label for more information). Not registered for use on kohlrabi, mizuna, mustard spinach, and rape greens. Avoid drift and tailwater runoff into surface waters.
    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 the 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).
    Text Updated: 12/20
    Treatment Table Updated: 12/20