Dr. Lorraine Maclauchlan gives Osoyoos resident and BC Grapegrowers Association president Manfred Freese a close-up look at the eggs of the destructive Douglas-fir tussock moth that are ready to hatch. She explained that these specimens picked near Osoyoos can literally drip from the trees as they hatch and greatly damage the fir and pine areas in the Okanagan Valley. Photos by Diane Zorn – Special to the Osoyoos Times
OSOYOOS TIMES-May, 27,2009
By Diane Zorn
Special to the Osoyoos Times
Dr. Lorraine Maclauchlan, a forest entomologist, was at the Osoyoos Best Western Sunrise Inn on May 21 to share information with the public on the likely infestation of Douglas-fir tussock moth caterpillars in the local area.
According to the provincial Forests and Range Ministry, an outbreak of the moths is happening along the Hwy. 3 corridor between Hedley and Osoyoos and is expected to spread into other parts of the Okanagan Valley.
However, the public failed to show up to the information meeting.
Only one person and the media attended the slide show and were shown a display of freshly picked cocoons from Douglas fir trees near Osoyoos.
“People are not aware of it yet, but when the caterpillars start dropping from the trees, and people notice the trees dying, they may start to get excited,” Maclauchlan said, indicating a plastic dish containing moth larvae.
Each short branch contained numerous moth egg masses that had been picked that day just outside of Osoyoos.
The moth outbreak is already evident near Spotted Lake.
Maclauchlan said that this may be the second year of a cycle that will see a severe outbreak.
The moth can strip a mature Douglas-fir tree bare in one year, leaving it dead.
These insects seem to appear about every 15 years in great enough numbers to decimate large stands of forest.
Since they tend to forage at lower elevations, the moths largely affect communities and recreation land.
“That’s where people build their homes, go camping, hike and bike,” Maclauchlan said. She has already seen dead trees in the Kamloops area where the infestation is into its third year.
The natural cycle seems to last three to four years before the moth’s numbers decline and the insects disappear again.
The last infestation in the Okanagan Valley was in the early 1990s.
The flightless female moth will lay her eggs in August.
Then, in late May or early June, hundreds of tiny caterpillars emerge attached to silk threads that float on the wind to other trees where the larvae begin to feed, turning the tree needles brown.
Damage begins at the crown of the tree and becomes more pronounced by July as the caterpillars feed.
This particular caterpillar has distinctive tufts of black spines that protect the larva from predators and also tend to cause allergic reactions in about 20 per cent of people.
Fortunately, this is a moth that the Forest and Range Ministry can help eradicate.
A group of U.S. and Canadian scientists working co-operatively in Hedley were successful in finding a naturally occurring virus that will kill the caterpillars.
Maclauchlan said the process of cultivating and sustaining a live virus for more than 15 years until an outbreak happens is an expensive program that only the government can afford to manage, so this is one situation where private property owners can look to the ministry for help.
The ministry monitors this species of moth by trapping and will notify landowners for permission to spray when they detect a large outbreak.
If people notice Douglas-fir or ponderosa pine trees turning brown and observe voracious caterpillars with a pattern of four white tussocks and long fine hairs along its back, they should contact the ministry.
Information is available online at http://www.for.gov.bc.ca/rsi/ForestHealth/Tussock_Moth.htm.
People are warned to avoid physical contact with the creature to avoid any possible allergic reaction.
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