Gypsy moth rebound a Dundas Valley concern

Community Apr 20, 2017 by Richard Leitner Dundas Star News

Trees in two areas of the Dundas Valley are expected to experience “noticeable defoliation” this summer from rebounding populations of invasive gypsy moths.

Lesley McDonell, terrestrial ecologist for the Hamilton Conservation Authority, said surveys earlier this year found egg mass counts far below those during the last major infestation in 2008 but still high enough to be a concern in some locations.

These include an area east of the Hermitage parking lot in Ancaster and in a stand of walnut trees south of Little John Road by University Plaza in Dundas, she said in a presentation to the authority’s conservation advisory board.

McDonell said staff isn’t recommending an aerial spraying of the biological insecticide Btk, as occurred in 2008 in the west end of the valley and south of Little John, because it kills more than just gypsy moths.

“Gypsy moths develop in the same way a lot of our moths and butterfly species do, (with) the same sets of stages at the same time, so Btk kills every moth and butterfly at the same stage of development as the gypsy moths,” she said.

McDonell said gypsy moth populations are cyclical and can be kept in check by a fungus and virus that require a wet spring or a week of minus 40C weather.

She said possible human interventions this year include scraping egg masses in the coming month and placing sticky bands around the trunks of heavily infested trees in the summer to catch and kill the moths in their caterpillar stage.

Pheromone moth traps may also be used in some areas.

This year’s surveys found egg masses ranging from 275 to 4,580 per hectare by the Hermitage — enough for heavy defoliation at the upper end — but still below the 2,600 to 10,000 in 2008.

The walnut stand south of Little John Road had 7,150 egg masses per hectare, the level for severe defoliation. Counts in 2008 were 26,000 to 40,000 per hectare.

The latest counts were light in the west end of the valley and just 10 per hectare in Iroquoia Heights Conservation Area.

McDonell said authority staff is concerned about the health of the valley’s trees because of a fall cankerworm infestation last spring and the summer drought that followed.

“The trees are stressed, so we will be watching some of these severe areas closely to see how they react and then to see how the gypsy moth population levels change over time,” she said.

Gypsy moth rebound a Dundas Valley concern

'Noticeable defoliation' expected in two areas, conservation authority says

Community Apr 20, 2017 by Richard Leitner Dundas Star News

Trees in two areas of the Dundas Valley are expected to experience “noticeable defoliation” this summer from rebounding populations of invasive gypsy moths.

Lesley McDonell, terrestrial ecologist for the Hamilton Conservation Authority, said surveys earlier this year found egg mass counts far below those during the last major infestation in 2008 but still high enough to be a concern in some locations.

These include an area east of the Hermitage parking lot in Ancaster and in a stand of walnut trees south of Little John Road by University Plaza in Dundas, she said in a presentation to the authority’s conservation advisory board.

McDonell said staff isn’t recommending an aerial spraying of the biological insecticide Btk, as occurred in 2008 in the west end of the valley and south of Little John, because it kills more than just gypsy moths.

“The trees are stressed, so we will be watching some of these severe areas closely to see how they react."

“Gypsy moths develop in the same way a lot of our moths and butterfly species do, (with) the same sets of stages at the same time, so Btk kills every moth and butterfly at the same stage of development as the gypsy moths,” she said.

McDonell said gypsy moth populations are cyclical and can be kept in check by a fungus and virus that require a wet spring or a week of minus 40C weather.

She said possible human interventions this year include scraping egg masses in the coming month and placing sticky bands around the trunks of heavily infested trees in the summer to catch and kill the moths in their caterpillar stage.

Pheromone moth traps may also be used in some areas.

This year’s surveys found egg masses ranging from 275 to 4,580 per hectare by the Hermitage — enough for heavy defoliation at the upper end — but still below the 2,600 to 10,000 in 2008.

The walnut stand south of Little John Road had 7,150 egg masses per hectare, the level for severe defoliation. Counts in 2008 were 26,000 to 40,000 per hectare.

The latest counts were light in the west end of the valley and just 10 per hectare in Iroquoia Heights Conservation Area.

McDonell said authority staff is concerned about the health of the valley’s trees because of a fall cankerworm infestation last spring and the summer drought that followed.

“The trees are stressed, so we will be watching some of these severe areas closely to see how they react and then to see how the gypsy moth population levels change over time,” she said.

Gypsy moth rebound a Dundas Valley concern

'Noticeable defoliation' expected in two areas, conservation authority says

Community Apr 20, 2017 by Richard Leitner Dundas Star News

Trees in two areas of the Dundas Valley are expected to experience “noticeable defoliation” this summer from rebounding populations of invasive gypsy moths.

Lesley McDonell, terrestrial ecologist for the Hamilton Conservation Authority, said surveys earlier this year found egg mass counts far below those during the last major infestation in 2008 but still high enough to be a concern in some locations.

These include an area east of the Hermitage parking lot in Ancaster and in a stand of walnut trees south of Little John Road by University Plaza in Dundas, she said in a presentation to the authority’s conservation advisory board.

McDonell said staff isn’t recommending an aerial spraying of the biological insecticide Btk, as occurred in 2008 in the west end of the valley and south of Little John, because it kills more than just gypsy moths.

“The trees are stressed, so we will be watching some of these severe areas closely to see how they react."

“Gypsy moths develop in the same way a lot of our moths and butterfly species do, (with) the same sets of stages at the same time, so Btk kills every moth and butterfly at the same stage of development as the gypsy moths,” she said.

McDonell said gypsy moth populations are cyclical and can be kept in check by a fungus and virus that require a wet spring or a week of minus 40C weather.

She said possible human interventions this year include scraping egg masses in the coming month and placing sticky bands around the trunks of heavily infested trees in the summer to catch and kill the moths in their caterpillar stage.

Pheromone moth traps may also be used in some areas.

This year’s surveys found egg masses ranging from 275 to 4,580 per hectare by the Hermitage — enough for heavy defoliation at the upper end — but still below the 2,600 to 10,000 in 2008.

The walnut stand south of Little John Road had 7,150 egg masses per hectare, the level for severe defoliation. Counts in 2008 were 26,000 to 40,000 per hectare.

The latest counts were light in the west end of the valley and just 10 per hectare in Iroquoia Heights Conservation Area.

McDonell said authority staff is concerned about the health of the valley’s trees because of a fall cankerworm infestation last spring and the summer drought that followed.

“The trees are stressed, so we will be watching some of these severe areas closely to see how they react and then to see how the gypsy moth population levels change over time,” she said.