LETHBRIDGE – Cereal leaf beetle made its move from Michigan to Ontario in 1962 and has been spreading across Canada ever since.
But it’s not alone – this pest came with a pest.
Hector Carcamo of Agriculture Canada told a provincial Agronomy Update conference in Leth-bridge Jan. 20 that researchers have identified a parasite that kills it host.
The discovery leads them to believe biological control of the beetle may be possible.
Carcamo said the wasp, known as Tetrastichulus julius, followed the cereal leaf beetle into Canada from the United States, which he said is a good thing.
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“If they arrive on their own, we don’t have to justify why we need them. And that they won’t be a risk to the environment and obtain permits from the government to bring them in.”
To avoid predation, the beetles cover themselves in their own excrement, forming a foul but protective barrier to other insects and birds.
However, Carcamo said the wasp isn’t put off by the dirty covering and will lay its eggs inside the insect.
As the larvae hatch, the outer covering will also protect them as they devour their host.
He said the cereal leaf beetle is one of the few insect pests that can be well controlled with the use of biocontrol agents such as a wasp.
Carcamo said Ontario research has found that the wasp “can provide up to 80 to 90 percent control of cereal leaf beetle.”
Research in zero till fields has also found that tillage doesn’t disturb the pupating wasp.
“This may be a success story for this pest. We need to develop this some more, but it looks very promising.”
In dry, warm summers the wasp can produce two generations in a season, providing nearly season-wide control.
Beetle damage on the Prairies was limited last year because of the cool weather, which did not favour its life cycle, but in bad years it can be such a threat to crops that it has been placed on the federally reportable pest list.
Entomologists say that under the right conditions it can do extensive damage.
“We found this insect in Lethbridge area in 2005,” Carcamo said.
“Shipments of hay from Lethbridge and Taber were restricted after that point. Since then it has spread east and was found in Saskatchewan in the summer of 2008 …. The restriction has now been lifted.”
The beetle will feed on nearly any cereal, but it thrives in winter wheat, mainly because of that crop’s early availability.
Cereal leaf beetles cut linear strips from plant leaves, perforating the leaves, while their larvae make the same marks but tend to strip only the surface of the leaf, leaving windowpane stripes.
“If the damage is very severe we see whole crops with a frosty look to them, the leaves have turned white,” Carcamo said.
“We don’t see this yet, but in Washington (state) they have them like this. It can be very bad.”
