CropTalk
Volume 21 | Issue 1
What’s new with Bayer CropScience products
They’re back… Over the past half dozen years, wireworm populations appear to be growing – and causing problems – for Western Canadian growers
D
eep in the soil, wireworms are poised to wreak havoc in your cereal crop. Wireworms are the larvae of adult click beetles and since 2004 their numbers have been increasing, as has the yield damage they cause as they’ve been spreading across Western Canadian cereal crops. Each spring, female click beetles emerge from the soil, laying anywhere from 200-400 eggs. Three weeks later the eggs hatch into hungry wireworm larvae, that survive underground by feeding on the plant roots and germinating seeds of cereals and grasses. Newly hatched wireworms have to feed – or they die. Once the larvae is established – it can withstand long periods without food. Over-wintering wireworms are responsible for feeding as well – not just newly hatched larvae.
So how do they cause so much crop injury? Wireworms hollow out seeds before germination and feed at the base of seedlings. The damaged seed results in patchy crop establishment, poor germination and ultimately, a substantially decreased yield. Often, plants wilt and die creating thin plant stands. Wireworms have a long and complex lifecycle. Even if there are no seeds present when they hatch, the wireworms will burrow up to a metre into the soil where they can feed off the soil for three-five years. With very little food, they are able to lay dormant in the soil, sleeping through hot, dry summers and cold winters until the soil temperature is more to their liking – between 10-22C. The best way for growers to fight wireworm damage is with an effective cereal seed treatment. Raxil® WW combines the insecticide Stress ShieldTM with Raxil MD to protect seed from wireworm damage and seedling diseases. Known for its ease of application and its long-lasting coverage, Raxil WW can be used with conventional seed-treating equipment. When wireworms feed on plants treated with Raxil WW, they stop eating and enter a coma-like state, allowing the crop to continue growing unhampered by these pests.
24 | Farm Forum | Winter 2012
Recipe for a Bait Ball Bait balls are used to check for wireworms in the soil, by drawing the wireworms to a carbon dioxide source. Bait balls are made by mixing a cup of wheat flour or oatmeal with a half-cup of water until the mixture can be formed into a ball. The ball can be buried directly in the ground, or tied in a nylon stocking, cheesecloth or another porous material. Bait balls should then be buried in 4-6 inch deep holes in fields where wireworm presence is suspected. Twenty bait balls in a one-acre area will indicate the presence of wireworms, however it will not tell population levels. Bait balls should be checked at seven to 10 days. Bait ball surveys conducted by Agriculture and Agri-Food Canada in 2010 showed that of the 30 species of wireworm that inhabit Western Canada, a small species of wireworm made up 70% of the population, while a large wireworm species accounted for 13% of the wireworms caught. While the large species eat more, the small ones generally have much higher populations and cause more damage.
The best way for growers to fight wireworm damage is with an effective cereal seed treatment. Raxil WW combines the insecticide Stress Shield with Raxil MD to protect seed from wireworm damage and seedling diseases. Wireworms are difficult to deal with because of their long life span, and because they spend so much of their time deep underground. Right now researchers have yet to find a way to permanently eliminate them from the soil. But products such as Raxil WW will protect your crop at the critical emergence point in time, minimizing damage to cereal crops. CT