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Bug invasion has folks squirming |
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Written by Ric Swihart
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Wednesday, 17 June 2009 |
The damage, for the most part, has already been done but that doesn’t mean the “ick” factor still doesn’t apply.
The city’s urban forestry crews have been fielding many calls of late from residents concerned about the masses of forest tent caterpillars on trees in city parks and in their own yards. Unfortunately, it’s too late to deter the fuzzy critters from eating their way through the foliage.
“Now, the caterpillars are a people problem.” said John Gilbert, city urban forestry foreman.
Walking along 20 Street and 23 Avenue North Wednesday, Gilbert pointed out clumps of the caterpillars gathered for warmth against the evening and early morning chill. Green ash and poplar trees are favourite haunts.
Caterpillars were starting to wiggle and crawl over the clump — it is their season to begin searching for plants, eavestroughs, fences and any other protected area — to form a cocoon to begin the next phase of its life cycle.
Gilbert said they can move up to 100 metres from their clumps to find cocooning sites. That is where the process begins that turns the caterpillar into the creamy, tan-coloured moth that soon begins laying eggs that will begin the process in 2010 when the next crop of caterpillars will hatch.
The good news is the caterpillar population can still be controlled by residents at this point.
The best time to intervene is in the early morning or evening when they tend to clump. They can be brushed or scrapped off into a container and dumped into a bucket of soapy water to kill them. Alternatives include a solution of water and detergent, or Safer’s Insecticide Soap, which can be sprayed directly on the clump. Among the commercial control products available from garden centres is bacillius thuringiensis.
Residents can also check their yards for the telltale white cocoons, pulling them off and placing in a plastic bag for disposal. The other control time is when the egg bands are laid, usually around thin branches. Look for a narrow grey foam, insulation-type band that can contain up to 300 eggs. The band should be placed in a plastic bag and sealed.
The caterpillar is a one-generation insect each year. Populations can increase dramatically every 10 to 15 years before falling to very low numbers due to beneficial predators and parasites. Non-chemical agents are preferred to control caterpillars, as they don’t destroy those “good” bugs.
Despite appearances, Gilbert said this year hasn’t been particularly bad for forest tent caterpillars. And while Gilbert said Lethbridge has never experienced a true epidemic of tent caterpillars, they were a concern last year. Trees in Henderson Lake were severely attacked, causing defoliation.
Most trees are capable of withstanding significant defoliation and will grow more leaves as summer progresses, he said. Homeowners should keep trees healthy and well watered to minimize stress and ensure leaf development.
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Last Updated ( Monday, 10 August 2009 )
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