Sugarbeets XX-4-5

Wireworms

Gary L. Hein

Wireworm larva

Wireworm damage in sugarbeet is difficult to predict because it depends on the inherent population of wireworms in the soil and on the environmental conditions that occur during sugarbeet emergence and establishment. Serious damage does not occur frequently.

Identification (and life cycle/seasonal history)

Several species of wireworms may cause damage in sugarbeet fields. Wireworms are slender, hard-bodied, yellowish larvae up to 1.5 inches long. Wireworms have extended life cycles that last two to five years depending on the species. Adult wireworms are attracted to grass hosts where they will lay their eggs; therefore, rotations that include grasses (including cereal crops) and areas with substantial grass weed pressure will increase the potential for wireworm problems.

Plant Response and Damage

Wireworms can attack germinating seed and destroy them before they are able to emerge. However, sugarbeet normally are planted while soil temperatures are too cool for optimum wireworm activity. Wireworms move up and down in the soil depending on the temperature and moisture in the soil. As the sugarbeet emerge and soil temperatures rise to 50-55^oF, wireworms move nearer the soil surface and begin feeding. At this time the wireworms will feed on the tap root and secondary roots of these small plants at a depth of only a few inches. This feeding may result in severed tap roots and cause the plant to wilt and die. Verification of the cause of this damage is important as several other pests (insects and disease) can cause this type of damage. Wireworm feeding on larger beets can result in root scarring that is of little importance. Later in the season as the soils continue to warm and the surface dries, the wireworms will move deeper in the soil and their impact on plants will be dramatically lessened. Severe wireworm damage is often spotty in the field.

Management Approaches

Wireworm damage is difficult to predict, but several factors can be used to determine the damage potential from wireworms. Field history is an important factor. Wireworms most often cause damage in fields where damage has occurred in the past. Also, fields with a history of grass (recent sod or cereal crop) or grassy weed problems are at a higher risk. Because of the multiple year life cycle of this insect, risk of damage may last for several years. One major factor in determining the risk of wireworm problems is the weather. If soil temperature and moisture conditions remain cool and wet, the risk of wireworm will increase dramatically.

      In fields with a high risk of wireworm damage, wireworms can be controlled with seed treatments or with the use of soil insecticides. In other crops, the best wireworm control results from the use of soil insecticides applied in the furrow; however, sugarbeet are very sensitive to organophosphate insecticides applied at planting. These products should not be applied in the furrow even for control of wireworms.

Product List for Wireworms:

Insecticide	Product per Acre	Preharvest Interval , remarks
Counter 15G^R, CR^R	15G: 4.0-8.0 oz/1000 row ft. CR: 3.0-6.0 oz/1000 row ft.	May be banded at planting, REI 72
Diazinon50W^R,AG500^R	50W: 6.0-8.0 lbs./A AG500: 3.0-4.0 qts./A	PHI 14 days; REI 24 hrs.
chlorpyrifos 15G (Lorsban plus generics)	6.5-9.0 oz/1000 row ft	For wireworm suppression.  T-band at planting. REI 24 hrs.
	Note: chlorpyrifos 15G is labeled for T-band application at planting, but this application can be significantly phytotoxic to beets when applied in this fashion, especially when used on lighter soils.
Mustang MAX^R Section 24c label in NE, CO, WY, MT	4.0 oz/A	Apply in-furrow or 3-4 inch T-band at planting. REI 12 hours.
Seed treatment Gaucho^R	3.0-6.3 oz/unit seed	If rates exceed 3.0 oz/unit seed must be pelleted.
^RRestricted use pesticide.
"The information herein is supplied with the understanding that no discrimination is intended and that listing of commercial products, necessary to this guide, implies no endorsement by the authors or the Extension Services of Nebraska, Colorado, Wyoming or Montana. Criticism of products or equipment not listed is neither implied nor intended. Due to constantly changing labels, laws and regulations, the Extension Services can assume no liability for the suggested use of chemicals contained herein. Pesticides must be applied legally complying with all label directions and precautions on the pesticide container and any supplemental labeling and rules of state and federal pesticide regulatory agencies.  State rules and regulations and special pesticide use allowances may vary from state to state: contact your State Department of Agriculture for the rules, regulations and allowances applicable in your state and locality."

Categories: Insects, Sugarbeets, Wireworms

Date: 04/19/2006