Volume 38, Number 11 | May 7, 2012
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PRACTICAL PRODUCTION TIPS FOR THE PRAIRIE FARMER
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Try bait to sample wireworms Wireworms may be lurking in the ground beneath your feet. Learn how to recognize wireworm damage and use bait to get a good sample BY ANGELA LOVELL
W
ireworms are omnipresent insect pests that can attack many different crops including annual and perennial grasses, wheat, barley, corn and potatoes. They are becoming increasingly problematic, especially in areas where grassland or pasture has been broken up for cropping, due to their long life cycle and the lack of effective control methods.
WIREWORM LIFE CYCLES Perpetual populations of click beetles (the adult stage of wireworms) can be found in many undisturbed areas, such as grasslands or pasture. Click beetles emerge from the soil where they have overwintered in late April or early May, in search of new areas to colonize. Female adults prefer to lay their eggs in grasses or cereal crops, but the wireworm larvae — which hatch about three to seven weeks after the eggs are laid — will feed on other crops, including canola. Wireworm larvae generally take four to five years (yes, years!) to complete their life cycle. They spend all of this time under-
ground, so it’s often hard to detect them until there is evidence of crop damage. The larvae are hardy, and hibernate 25 centimetres or more below ground level. If they survive their first winter they can go at least two years without any food other than humus. From late May through June, the female click beetles can lay 200 to 1,400 eggs in loose or cracked soil and under lumps of soil. The young wireworms hatch in the early summer, and initially feed on the roots of germinating seeds, but cause little damage at this stage. As wireworms grow over the years, it’s common for them to feed on germinating seeds, and they may burrow into stems, causing above-ground parts of crops to turn brown, wilt and die. A large wireworm can kill two or more seedlings, and high populations can result in thin stands. These thin stands are often mistaken for poor germination, especially during dry conditions. Larval activity is governed by temperature and moisture conditions. Wireworms are most active at soil temperatures between 10 C and 20 C in the spring, at which time they move closer to the surface to find food. As temperatures increase and the
soil dries out in July and August, wireworms are forced to move deeper into the soil. Cool spring weather can restrict adult activity and lengthen the egg-laying period. Eggs are laid near the soil surface or in compact soil, and newly hatched wireworms are subject to high mortality (between 92 and 98 per cent) when moisture levels and temperature fluctuate rapidly. When fully grown, after four to five years, the larvae pupate in July and August, about five to 10 centimetres below the soil surface for about a month. At this time, the adult wireworms are formed, but they will not emerge from the ground until the following spring.
CROP DAMAGE More damage is generally seen on crops planted in silty, mediumtextured, well-drained soils and in soils that have been under previous continuous pasture for at least five years. There is usually less damage on crops grown in heavy or very light soils. Crops grown in newly broken sod can suffer great losses for one to two years, then the damage will decrease rapidly as long as there are
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PHOTOS: BOB VERNON, AAFC
A large wireworm can kill two or more seedlings, and high populations can result in thin stands. These thin stages are often mistaken for poor germination, especially during dry conditions.
In This Issue
Publications Mail Agreement Number 40069240
Wheat & Chaff ..................
2
Crop Advisor’s Casebook
5
Features ............................
6
Columns ........................... 14 Cattleman’s Corner .......... 18 FarmLife ............................ 26
Not all grasshoppers B:10.25” are pests T:10.25” LISA GUENTHER PAGE 6
UTVs hit the market
Machinery & Shop ............ 30
SCOTT GARVEY PAGE 35
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COULDA
SHOULDA
WOULDA
DID
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Always read and follow label directions. Prosaro® is a registered trademark of Bayer. Bayer CropScience is a member of CropLife Canada.
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For more information visit BayerCropScience.ca/Prosaro