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The spray program just makes things worse. Moth damage was less
historically in areas that were not sprayed.
Monday, July 27, 1998 The Halifax Herald Limited
Virus should kill dreaded moth, scientist says
By ANDREW THOMPSON
Truro - There are signs Mother Nature is starting to take up the fight
against the destructive tussock moth.
Tom Smith, a forest entomologist at the Nova Scotia Agricultural
College, said the insects - now in the caterpillar stage - are showing
signs of overpopulation stress and starting to contract a naturally
occurring virus.
He said he's seeing indications the virus is infecting caterpillars in
his own backyard in Central Onslow, Colchester County.
"I did notice some of the sick larvae that are hanging onto the
foliage," he said at an open house Saturday at NSAC. "I noticed one
sick one hanging onto my compost bin, so they are starting to die from
the virus."
He said a caterpillar with the virus will get bloated and ooze orange
fluid. The fluid carries the virus that gets picked up by the wind and
will infect other tussock moth populations.
The insects are starting to form cocoons as part of their transition
into moths, which will lay their eggs in September. Evidence the virus
is kicking in means most of the larvae will die naturally next year,
he said.
"If the larvae do hatch, there is going to be enough virus around that
it should collapse the population," he said.
The last local infestation of the tussock moth occurred in the
mid-1970s in southern New Brunswick and northern Nova Scotia. The
cycle usually only lasts three years but this is the fifth year of the
cycle. The hot dry summer of 1997 meant the virus wasn't able to
spread through the insect population.
"Last year's hot dry weather was ideal for the insects and bad for the
virus," Mr. Smith said.
But he said the insect's numbers have grown so much they are under
stress because there isn't enough food to support the population.
This news comes as a relief to woodlot owners, farmers and home
gardeners because the insect has had a devastating effect on forests
and agricultural crops over the past two years.
The provincial government completed a $6-million spray program of
selected woodlots in the province. The program covered fewer than half
the 640 small woodlot owners who applied to have the biological
pesticide Btk sprayed on their woodlands. About 100 people
participated in the spray program, including department staff and
private-sector workers, and 57,000 hectares owned by the Crown and
large companies was sprayed.
Many homeowners in central and northern Nova Scotia have purchased a
variety of pesticides, including Btk, to protect their home gardens
and plants from the moth. Mr. Smith said the moth population is mature
and the eating patterns have slowed down. This means it isn't
necessary to spray for the moth anymore."
He said only if the larvae is about one to 1.5 centimetres in length
does anybody have to worry it will damage a plant. The insects can be
found on the underside of leaves.
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