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Last fall I decided to leave the grass clippings between the rows in my garden. My theory was that by leaving the clipping there, I only had to add more grass this spring. I didn’t till the ground, but rather just trenched in the rows. To my dismay, I found many more wireworms under the mulch than I have noticed in past years. It remains to be seen if a higher number of sightings mean more damage in the garden.

Wireworms are common throughout the world and can be damaging pests of many different crops, most frequently sod, small grains, corn and beans. They feed on seeds, preventing germination, or on the underground roots and stems of the plants, causing them to wilt or stunt their growth. I have also noticed them boring into potatoes and ripe melons.

There are many different species of wireworms; however, the one that is in most gardens is dark brown to silver with very hard bodies. In fact, one must squeeze them quite hard to kill them.

The click beetle, which is the adult stage of the wireworm, has a narrow body and is usually a brownish, grayish, or black color. In the event of getting turned upside down, they will flip the middle of their back against the ground propelling the body upward and making a clicking sound in the process. They will continue to perform this act until they have successfully turned themselves upright. The nice thing about the click beetle is they are not considered a pest, it is the larvae stage that is destructive.

The depressing part is that the majority of the lifecycle is spent underground in the worm stage, which takes two to six years to complete. As the larvae get close to maturation, they will create a cell in the ground for pupation. In a few weeks, they develop into mature adults and remain in the cell until the following spring. The adults will live 10 to 12 months, mostly around the sod surface in cracks in the soil and will die shortly after laying eggs. Eggs take anywhere from a few days to a few weeks to hatch and they are back in the garden soil for another decade.

Generally, the longer it takes for a seed to germinate and grow, the more susceptible it is to wireworm damage. Therefore, it is better to plant seeds when the soil is warm.

Commercial growers who find it necessary to plant early may need a seed treatment. However, this type of control only protects the seeds and not the seedlings. Control is primarily limited to the use of insecticides. The insecticides can be applied prior to planting or by placing it in the furrow during planting. Possible insecticides include carofuran, an organophosphate, carbonate, or a pyrethroid.

The most effective method of control for a home garden is the use of baits. Baits can be planted two to four inches deep at three to 10 feet intervals. Fill the holes with a mixture of germinating peas, beans, or corn and cover with a board or tile. In one week, uncover the bait and kill the wireworms that have been collected.

Fields that were previously fallow or were planted with sod are more often infested with wireworms. Adults are more attracted to these areas and are more likely to lay eggs in these sites. Since all generations tend to stay close to their origin, an infestation could continue for one to five years. In contrast, fields previously planted with corn or soybeans are at less of a risk of being infested.

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UPCOMING CLASSES: The next class is 'Beneficial Insects in Your Garden' presented by Bud Markhardt, Professor, University of MN, member Board of Directors for the MN Institute for Sustainable Agriculture and the Organic Advisory Task Force, MN Department of Ag. Many who heard him speak at our Gardening Bonanza in March asked us to have him back. The class will be held at the Senior Center in North Branch June 27 at 6:30 p.m.

PLANT CLINICS: Volunteer Master Gardeners will be available Mondays from 4-7 p.m. at the Extension Office in North Branch at 38780 Eight Ave. to answer your gardening questions. You can also call 651-674-4417 during these hours to speak with a Master Gardener. Samples can be dropped off during the day on Monday if you cannot stop in during clinic hours. Please note MONDAY is the only day you can drop off samples, as there is no longer staff at the North Branch Office who can answer gardening questions.

VOICE MAIL: You can leave a question for a volunteer Master Gardener at 651-674-4417. Depending on the volume of calls, they try to respond within a couple of days. During office hours ask for the Master Gardener voicemail, after hours, select ext. 18.

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