Cool, wet conditions across the Prairies again this season may dampen yield prospects for cereal and pulse production through delayed planting and by increasing a crop’s susceptibility to wireworms. Wireworms are a growing concern for cereal and pulse growers across Canada.
Despite their increasing prevalence, farmers are sometimes unaware of wireworm infestations until large patches of seedlings are missing. Weather-induced seedling development delays can extend the period when the crop is most at risk. Here are tips for tackling wireworms on your farm this season.
SIGNS AND SYMPTOMS
Wireworms feed on germinating seeds, roots and young seedlings, killing plants directly as well as creating wounds that are ideal for disease infection. Feeding can start right at germination; seedlings may not even emerge. Telltale signs of wireworm feeding include:
Hollowed out seeds and dead seedlings;
Stems that are shredded, but not cut off (cut off stems are a sign of cutworm damage);
Plants that are wilted and yellow, but still attached to the root;
Row sections missing in otherwise healthy stands — wireworms tend to feed along crop rows; and
Thin stands, or no stand. There are approximately 30 different species of wireworm in Canada, and they differ in size and by how much damage they can have on the crop. Some species of wireworms do well under irrigation while others prefer dryland conditions. Being able to identify species is an important first step in developing long-term management strategies.
Larvae are slender, with hard, smooth jointed bodies. Young larvae are white, but change to a yellow or tan to dark-brown colour as they grow. There are three pairs of legs behind the head, and the tail segment is generally notched.
The adult stage are commonly called click beetles, and are hard-shelled, black-brown in colour and cause no crop damage at this stage in their life cycle. They make a distinctive clicking sound when they flip from their backs to their legs. Full-grown larvae range from one-half to three-quarter inches in length. Adult click beetles range from one-quarter to one-half an inch long.
Bait balls can help determine wireworm presence. There are different types of bait balls that can indicate if wireworms are present. One that proved to work well in 2010 was made out of oatmeal and honey and buried in the ground. The release of carbon dioxide attracts wireworms to the trap. To make a bait ball, mix one to one-and-one-half cups of oatmeal with two tablespoons of honey and up to a half cup of water until the mixture sticks together enough to make a ball.
Place the bait ball in a mesh bag (e. g., an onion bag) to make it easier to retrieve. Bury the bait balls in four-to six-inch deep holes and mark with flags. Place bait balls in areas of the field where you suspect wireworms are present due to a history of poor stand establishment. After 10 to 12 days, check traps to see if wireworms are present. Bait balls are not foolproof; t is still very important to monitor the crop after planting to see if typical symptoms can be seen. If they are, there is a very good chance you will find them right in the row if you dig around with a spoon or trowel.
Once in a field, wireworms cannot be completely eradicated, but you can minimize the impact on stand establishment. There are a number of cultural and chemical control options. They include:
Seedbed preparation — seed shallow and achieve good seed-to-soil contact for quick, even germination and emergence.
Seeding date, rate and depth — avoid seeding very early or very late. Strive for optimal plant populations per square foot. If you know you have a wireworm problem, consider boosting seeding rates and seed only when quick germination is guaranteed. Seed into moisture, but seeding too deep can weaken plants and leave them vulnerable.
Seed treatments — there is no post-emergent insecticide option for wireworm control, however there are seed treatments available.
TedLabunisthetechnicalLeadforSyngenta SeedCare.ThisarticlecourtesyofSyngenta Canada