Agriculture: Cole Crops Pest Management Guidelines

Darkling Beetles

  • Darkling beetles: Blapstinus spp., Coelus spp.
  • Description of the Pest

    Darkling beetles are dull, bluish black or brown beetles that clip off seedlings or feed on foliage. They may be distinguishable from beneficial predaceous ground beetles by the trochanters at the base of their hind legs, which can be seen by examining the undersides of adults. Predaceous ground beetles have enlarged trochanters, while the basal segment of darkling beetle legs is not enlarged. Predaceous ground beetles are usually shiny and sometimes have colorful markings, unlike the dull coloration of darkling beetles.


    Damage is similar to that caused by cutworms: seedlings are chewed off at the base and foliage may also be chewed. Damage usually begins at field edges as beetles come in from alfalfa, cover crops, or weedy areas. Feeding occurs primarily in the evening and night.


    Cultural Control

    In the low desert, use transplants instead of direct seeding to prevent most damage from darkling beetles.

    In the Central Valley, allow organic matter in the soil to completely decompose before planting cole crops to avoid attracting darkling beetles. (Note, however, that darkling beetles are not as great of a problem in cole crops in the Central Valley as they are in the low desert.)

    Monitoring and Treatment Decisions

    Before crop seedling emergence or transplanting, monitor for darkling beetles under weeds around field edges.

    If darkling beetle infestations are expected or a persistent problem in the field, place insecticide bait around field edges before planting. In the low desert, darkling beetles are controlled by insecticide applications (usually with a pyrethroid) injected into the sprinkler irrigation water either before planting or at planting. Pyrethroid applications for Bagrada bug will also control darkling beetles.

    Organically Acceptable Methods

    Use cultural control in an organically certified crop.

    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.
      (Sevin 5 bait) 40 lb 12 See comments
      COMMENTS: Not registered for use in mizuna, mustard spinach, and rape greens. For broccoli, Brussels sprouts, cabbage, cauliflower, and kohlrabi, PHI is 3 days. For Chinese cabbage, collards, kale, and mustard greens, PHI is 14 days.
      (Mustang) 3.4–4.3 fl oz 12 1
      COMMENTS: 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.
      (Asana XL) 5.8–9.6 12 See comments
      COMMENTS: Registered for use in broccoli, Chinese broccoli, cabbage, cauliflower, collards, kohlrabi, mustard greens, and tight-heading varieties of Chinese cabbage (napa cabbage). For collard greens and mustard greens, PHI is 7 days. For other registered cole crops, PHI is 3 days. Do not use if leafminers are present.
      (Perm-Up 25DF) Label rates 12 1
      COMMENTS: Do not use if leafminers are present. Registered for use in broccoli, Brussels sprouts, cabbage, certain types of Chinese cabbage (see label) cauliflower, and collards.
      (Belay) 9–12 fl oz 12 21
      COMMENTS: Use as a preplant or at-plant soil application (rate and PHI included above are 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.
      (Diazinon 50W) Label rates 96 (4 days) NA
      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