Dealing with wireworms in your potato patch

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By Jeneen Wiche
Casey County News columnist

I have loads of potatoes this year, most of them are clean as a whistle. We get them out early so they are ready to harvest by mid to late August. This early start seems to offset any significant problem with wireworms. The tell-tale sign of wireworms: If you do have lots of tiny holes in your potatoes, you likely saw the tough little yellow or rust-colored worms when you were digging your crop. In the past few weeks as folks begin to dig their potatoes, I am hearing the inquiry, “What are the tiny holes in my potatoes, and how do I prevent them?”

The wireworm is the larval stage of the adult click beetle. Both have names that adequately describe their most pronounced feature: the click beetle makes a clicking noise when disturbed, and the wireworm is a hard-shelled slender worm that likes to eat potatoes. Well, it may not be that they are actually eating out potatoes. Scientists are not entirely sure if they are tunneling through our tubers looking for moisture or if they are looking for a little shelter.

The click beetle is benign and does no damage to crops but the wireworm is a great nemesis to root crops because of its unusually long lifecycle. An infested garden can remain so for up to 6 years because the mature hard-shelled larvae can live 2 to 6 years in this stage before it develops into a beetle. The beetle lays its eggs in pasture or sod areas, so newly dug potato patches where sod once was can be a problem; and since the wireworms can persist for many years, planting potatoes in the same plot can also be problematic.

Commercially, wireworms can be a problem because of decreased quality yields, but for the home gardener the damage is almost more cosmetic. Early tunneling in seed potatoes can result in decreased yields because of reduced plant vigor or rot; later the tunneling means that mature potatoes will have a shorter shelf life, and then you will have to do quite a bit of paring as you prepare the crop for dinner.

The best defense against wireworms is to diligently rotate your potato patch each year, avoiding a repeat planting for six years; in a perfect world, right? This is not practical for most gardeners but do try to rotate as well as you can. The wireworm is difficult to control otherwise. Chemical applications are limited and difficult because wireworms move through the soil efficiently, and soil saturation would be hard to achieve; and it would likely not persist through the growing season for continued protection for maturing tubers. Plus, who wants a chemical spill all over your potatoes?

Beyond crop rotation, there are other biological approaches to deterring wireworms. Plant out larger fields of potatoes after alfalfa (or use this as a cover crop in smaller gardens). There are some beneficial nematodes that can be applied to potato patches several months prior to planting (see www.gardensalive.com for nematodes). You can also do some seasonal cultivation of the garden, turning the soil weekly in the spring and fall to expose worms to birds, backyard chickens and other predators; and in the winter to also expose larvae to the elements.