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How to Manage Pests

UC Pest Management Guidelines

Darkling beetle adult.

Cole Crops

Darkling Beetles

Scientific Names: Various species in the Tenebrionid Family

(Reviewed 6/07, updated 11/08)

In this Guideline:


Darkling beetles are dull bluish black or brown beetles that chew off seedlings or feed on foliage. They can be distinguished from the predaceous ground beetles by the enlargement of the segments at the tip of the antennae. Predaceous ground beetles are usually shiny and sometimes have colorful markings unlike the dull coloration of the pest species in the darkling beetle family.


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 tend to come in from weedy areas, alfalfa, or cover crops. Feeding occurs primarily in the evening and at night.


To prevent beetle invasions from an adjacent field, fill a ditch full of water to keep them out. If treatment is needed, a bait placed around the edges of the field will usually provide adequate control.

Common name Amount/Acre R.E.I.+ P.H.I.+
(trade name)   (hours) (days)

Calculate impact of pesticide on air quality
Bee precaution pesticide ratings
When choosing a pesticide, consider information relating to natural enemies and honey bees as well as the environmental impact. Not all registered pesticides are listed. Always read label of product being used.
  (Sevin) 5% bait 20–40 lb 12 3
  COMMENTS: For broccoli, Brussels sprouts, cabbage, cauliflower.
+ Restricted entry interval (R.E.I.) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (P.H.I.) 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 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). For additional information, see their Web site at http://www.irac-online.org/.



[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Cole Crops
UC ANR Publication 3442
Insects and Mites
E. T. Natwick, UC Cooperative Extension, Imperial County
Acknowledgments for contributions to Insects and Mites:
W. J. Bentley, UC IPM Program, Kearney Agricultural Center, Parlier
W. E. Chaney, UC Cooperative Extension, Monterey County
N. C. Toscano, Entomology, UC Riverside

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