REGINA – Nature’s grim reapers are finally stalking the Bertha armyworm, but producers should not assume that the pest’s cyclical outbreak is over.
Many producers in Manitoba and Saskatchewan are noticing dead Berthas in their fields, which Manitoba entomologist Lynn Manaigre said are victims of natural fungi and viruses.
The appearance of the natural controls “is good news in that they’re hard at work doing what we hope they are doing, but it doesn’t mean we will not have an outbreak here next year,” she said. Bertha armyworm outbreaks usually last about three years, say pest specialists.
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Both the fungus and the virus ravaging the scattered Bertha populations are highly dependent on humidity, said Manaigre. Recent heavy rains and warm weather have created the necessary condition.
But the fungus and virus might not reappear as strongly next year if conditions are drier, said Manaigre. The only way to get a true picture of how large the Bertha outbreak will be in 1996 is to wait for the spring results of moth traps, she said.
Saskatoon agrologist Larry Gramiak said he is hearing scattered reports of Berthas being killed by their natural predators, but “at this moment I’m still talking to people who are getting out spraying.”
And he said if the Bertha armyworm usually has a three-year outbreak, producers there should expect at least one more year of problems.
“In west-central Saskatchewan this is really our first year. Next year I expect the problem will be more severe than this year,” said Gramiak.
Berthas infected by the fungus turn a lighter color, sicken and die with their back legs still attached to the host plant’s leaves. Those stricken by the virus will appear to be crystallized and stuck onto plant leaves, Manaigre said.
