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How to Manage Pests

UC Pest Management Guidelines

Wireworm larvae.



Scientific names: Limonius spp. and others

(Reviewed 12/09, updated 12/09)

In this Guideline:


Wireworms are beetle larvae that are found in soil where they feed on seeds and roots. They are shiny, slender, cylindrical, hard-bodied, yellow to brown larvae that can be found at all times of the year and in almost any kind of soil. The larval (or wireworm) stage may last several years. When fully developed, wireworms vary in length from about 0.5 inch to 1.25 inches, depending on the species. Adults are known as click beetles. They can snap and flip their bodies into the air when turned upside down. The tan to black beetles vary from 0.25 inch to more than 1 inch in length, but the most common pest species are about 0.5 inch long.


Wireworm larvae injure crops by partially or completely devouring seeds in the soil, thus reducing plant stands. On plants, they can cut off small, underground stems and roots or bore into larger ones.


Cultural Control
Minimize plant residue from previous crops. Crops following pasture, alfalfa, vineyards, and grains may develop high populations of wireworms and require preventative treatment. Fallow fields for several weeks to allow organic matter to decompose. Seeds planted at depths greater than 1.5 inch take longer to germinate and are at greater risk for infestation. Do not plant into cold, moist soil.

Organically Acceptable Methods
Cultural controls are acceptable for use on organically grown produce.

Monitoring and Treatment Decisions
If wireworms have been a serious problem in the past, a preventative treatment may be necessary. Preplant or seed treatments are far superior to any postemergence practice.

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
The following materials are listed in order of usefulness in an IPM program, taking into account efficacy, information related to natural enemies and honey bees, and environmental impact. Not all registered pesticides are listed. Always read label of product being used.
  (Diazinon AG 500) 3–4 qt 24 NA
  (Diazinon AG 600WBC) 76.5–102 oz 72 NA
  COMMENTS: For wireworms broadcast insecticide just before planting and immediately incorporate into the top 4-8 inches of soil. Avoid drift and tailwater runoff into surface waters.
  (Vapam, etc.) Label rates 48 NA
  COMMENTS: Also provides control of weeds. Fumigants such as metam sodium are a source of volatile organic compounds (VOCs) but are minimally reactive with other air contaminants that form ozone. Fumigate only as a last resort when other management strategies have not been successful or are not available.
** Mix with enough water to provide complete coverage
+ 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.
* Permit required from county agricultural commissioner for purchase or use.
1 Modes of action are important in preventing the development of resistance to pesticides. 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. 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 is assigned by IRAC (Insecticide Resistance Action Committee). For additional information, see their Web site at http://www.irac-online.org/.
NA Not applicable.



[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Spinach
UC ANR Publication 3467
Insects and Mites
S. T. Koike, UC Cooperative Extension, Monterey County
M. LeStrange, UC Cooperative Extension, Tulare County
Acknowledgements for contributions to Insects and Mites:
W. E. Chaney, UC Cooperative Extension, Monterey County

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