By Sherri Roberts, PAg, Crops Extension Specialist, Weyburn
The majority of the province has received more than adequate moisture to get this season’s crop off to a good start. If you are seeing poor emergence and you know your seeds germination rate was high, wireworms may be the culprit causing you spotty and patchy emergence.
Wireworm are attracted to the carbon dioxide that is given off by a germinating seed. Several generations, larval instars, as well as several different species of wireworm can be present in a field.
The insect’s larval stage causes crop damage, not the adult click beetle. There are 11 native species of wireworm that have been identified as prairie pests. Of these, six are important pests, and two are widespread: the prairies grain wireworm, Selatosomus aeripennis destructor, and Hypnoidus bicolor (there is no common name). Adult click beetles will overwinter in the soil, emerge for several weeks in the spring to lay their eggs and then die. Larvae, depending on the species, will then spend anywhere from three-11 years in the soil. Several generations as well as several different species of wireworm can be present in a field.
If you suspect wireworm damage, you can place baits in those areas of the field where emergence has been poor. Start by placing a peeled potato on a stake. Dig down about four-six inches in an area where the emergence has been poor. Cover the potato up with your stake being the marker where the potato is placed. Come back in about seven-10 days. Gently dig the potato back up. Examine the potato for wireworms. Baits made of oatmeal or a thick mix of flour, water, and honey at depths of 4-6 inches can also work. Check after two weeks. Place baits where or when decaying organic matter, respiring plant roots, or germinating seeds are not present. These act as sources of carbon dioxide and will attract larvae too. They can tunnel baits, so look inside too. Use at least 20 bait traps per 10–25 acres.
If damage has been so severe as to require replanting, there are seed treatments available to deal with wireworms. Consult the Saskatchewan Guide to Crop Protection or contact the Agriculture Knowledge Centre.