It may be time to get out the mothballs.
If you’ve been suddenly seeing a lot of moths in the Lower Mainland, it’s because there’s an outbreak originating on the North Shore.
The District of North Vancouver had issued a public notice on August 18 that North Vancouver is experiencing an outbreak of western hemlock looper moths.
Lambdina fiscellaria lugubrosa is native defoliator of the coastal forest ecosystem, especially in the Fromme and Lynn Valley area. However, these moths feed on Western Hemlock trees, causing damage to forested areas.
According to the District of North Vancouver, these outbreaks can last three to four years, and the current one is in its second year. The moth populations build every 11 to 15 years on the coast. (In the B.C. Interior, outbreaks occur every 20-plus years.)
The B.C. Forestry Ministry website says the moths feed voraciously from July to October.
The district states that there is evidence of tree mortality taking place in hardest hit areas. Other than letting the outbreak run its natural course, there aren’t any effective measures that can be taken to stop the moths.
“The killing or removal of these susceptible trees is an important component of ecosystem dynamics and essential in recharging ecosystems by allowing younger trees to emerge, while supporting the recycling of nutrients,” the district explains. “This is a natural and important process.”
Meanwhile, a geotechnical engineer will assess any risks due to significant tree loss on slopes with stability or erosion issues.
The B.C. government states that the Southern B.C. Interior manages damage by monitoring populations in susceptible stands and if significant damage occurs, aerial spraying of the biological insecticide Bacillus thruringiensis var. kurstaki (Btk) may be used.