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How to Manage Pests

UC Pest Management Guidelines

| More pests | More crops | About guidelines |

Darkling beetle adult.

Cucurbits

Darkling Beetles

Scientific Names: Blapstinus spp., Caelus spp., and others

(Reviewed 11/05, updated 6/08)

In this Guideline:

DESCRIPTION OF THE PESTS

Darkling beetle adults are from 0.13 to 0.25 inch long (3 to 6 mm) and vary from black or bluish black to rusty brown. Do not confuse beetles (Tenebrionidae) with predatory ground beetles (Carabidae), which prey on various soil dwelling pests. Darkling beetles generally have clubbed antennae whereas carabids do not. Darkling beetles may be hidden by dust or a thin layer of soil. Larvae are cylindrical, wirewormlike, soil-inhabiting worms that are light yellow to dark brown and range from 0.03 to 0.33 inch (1–8 mm) in length. They are often referred to as false wireworms.

DAMAGE

Darkling beetles are generally not a problem unless large populations build up when the plants are in the seedling stage. Young plants may be girdled or cut off at or below the soil surface. After the plants reach a height of 5 to 6 inches, darkling beetles are usually not a problem. However, further feeding may occur on flower blossoms during bloom, on the undersides of leaves, and on the netting of mature melons. They can also bore into fruit where it rests on the ground.

MANAGEMENT

Keep fields and ditches free of weeds. Water barriers can aid in stopping migrating populations. Reduce organic matter in soil by fallowing. Treat whenever beetles are observed feeding on plants, flowers, or fruit. Also treat when beetles are observed moving into cucurbits or melons from fallow or alfalfa hay fields.

Common name Amount/Acre R.E.I.+ P.H.I.+
(trade name)   (hours) (days)
When choosing a pesticide, consider information relating to water quality and impact on natural enemies and honey bees.
 
A. CARBARYL
  5% bait 20 lb 12 see label
  MODE OF ACTION GROUP NUMBER1: 1A
  COMMENTS: Use suitable ground or aircraft equipment that provides good distribution. Repeat application of bait may be necessary.
 
B. PERMETHRIN*
  (Ambush 0.5% bait) 20–40 lb 12 1
  MODE OF ACTION GROUP NUMBER1: 3
  COMMENTS: Avoid applications when honeybees are actively foraging by applying in early morning or during evening hours. Do not apply more than 320 lb/acre/season.
 
C. MALATHION
  (Malathion) 8E 1.75 pt 12 Cucumber, squash: 1
  MODE OF ACTION GROUP NUMBER1: 1B
  COMMENTS: Do not apply unless plants are dry.
 
+ 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/.
* Permit required from county agricultural commissioner for purchase or use.

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Cucurbits
UC ANR Publication 3445
Insects and Mites
E. T. Natwick, UC Cooperative Extension, Imperial County
L. D. Godfrey, Entomology, UC Davis
C. G. Summers, Entomology, UC Davis/Kearney Agricultural Center, Parlier
J. J. Stapleton, UC IPM Program, Kearney Agricultultural Center, Parlier
Acknowledgment for contributions to Insects and Mites:
R. L. Coviello, UC Cooperative Extension, Fresno County
C. B. Fouche, UC Cooperative Extension, San Joaquin County
J. B. LeBoeuf, AgriData Sensing, Inc., Fresno
M. Murray, UC Cooperative Extension, Colusa/Glenn counties

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Statewide IPM Program, Agriculture and Natural Resources, University of California
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For noncommercial purposes only, any Web site may link directly to this page. FOR ALL OTHER USES or more information, read Legal Notices. Unfortunately, we cannot provide individual solutions to specific pest problems. See How to manage pests, or in the U.S., contact your local Cooperative Extension office for assistance. /PMG/r116301711.html revised: June 30, 2008. Contact webmaster.