The cereal leaf beetle made its North American debut in southwest Michigan in 1962. Fifty years later, it’s concerning Alberta farmers. This four-to-six millimetre bluish-black and red adult beetle was first discovered in Alberta in 2005.
One larva per flag leaf can cause a five to six bushel loss of grain, per acre. The larvae can consume up to 10 times their body weight in plant biomass, leaving translucent strips at the site and golden/brown lower leaves. Camouflaged in their own fecal matter, they continue to grow and molt until mid- to late-July, when they drop to the ground to pupate. Three weeks later, the adult beetle will emerge, feed briefly and prepare to overwinter in haystacks within fields.
Both the larvae and the adults feed on the leaves of the plant. The larvae do not penetrate the leaf entirely, resulting in damage resembling a windowpane—but an adult beetle can cut right through the leaf, producing hollow linear holes in the foliage.
Field studies reveal that populations of a parasitic wasp (Tetrastichus julis) specific to this beetle have also been found in fields. The parasitic wasp is both a beneficial and an effective natural enemy that can keep up with the pest populations.
- Scout fields in late-May to early-June, to spot emerged larvae
- Do not spray insecticides—it tends to do more damage than good, as it will kill the parasitic wasp as well as the beetle
- Practice conservation tillage or no tillage to encourage the parasitic wasps, which overwinter a few centimetres below the soil surface
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