Description of the Pest
Wireworms 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 of this insect may last several years. When fully developed, they vary in length from about 0.5 inch to 1.25 inches (12–31 mm), depending on the species. Adults of these larvae are known as click beetles. They can snap and flip their bodies into the air when turned upside down. These tan to black beetles vary from 0.25 inch (6 mm) to more than 1.0 inch (24 mm) in length, but the most common pest species are about 0.5 inch (12 mm) long.
Damage
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.
Management
Preventive treatment may be warranted for crops planted in land that was previously pasture or planted to alfalfa, vineyards and possibly grains. Otherwise, good field sanitation and measures to ensure rapid seed germination aregenerally adequate for control of this pest.
Cultural Control
Destroy plant residue from previous crops. Fallow fields for several weeks to allow organic matter to decompose. Seeds planted at depths greater than 1.5 inch (3.7 mm) 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 to use in an organically certified crop.
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 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. | ||||
| A. | IMIDACLOPRID | |||
| (Admire Pro) | 7–10.5 fl oz | 12 | 21 | |
| MODE-OF-ACTION GROUP NUMBER1: 4A | ||||
| COMMENTS: Apply at planting or transplanting and incorporate into root zone. Review and follow the California neonicotinoid regulations effective January 1, 2024. Permissible application rates may be lower and application timing may be restricted if using managed pollinators, applying more than one neonicotinoid active ingredient, or using more than one application method in the same season. |
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| B. | DIAZINON | |||
| (Diazinon 50) | 6–8 lb | 72 | 3 | |
| (Diazinon AG500) | 3–4 qt | 72 | 3 | |
| MODE-OF-ACTION GROUP NUMBER1: 1B | ||||
| COMMENTS: Labeled for use on melons and watermelons only. Broadcast just before planting and immediately work into the soil 4 to 8 inches. | ||||
| C. | METAM SODIUM* | |||
| (Vapam) | Label rates | See label | NA | |
| COMMENTS: Apply as a band treatment before planting. Fumigants such as metam sodium are a source of volatile organic compounds (VOCs) but are minimally reactive with other air contaminants that form ozone. | ||||
| ‡ | 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 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). |
| * | Permit required from county agricultural commissioner for purchase or use. |
| NA | Not applicable. |