Cold winter weather has delayed spring plans to spray an area of Saanich around Elk Lake against the gypsy moth.
Tim Ebata, forest health officer with the Ministry of Forests, Lands and Natural Resource Operations, said models used to time the spraying have shown that gypsy moth caterpillars will not be hatching until about mid-May.
“The developmental rate [of the caterpillars] is driven by degree-days, the numbers of days that exceed a specific temperature threshold, and because of our cold winter and now spring, things have been delayed although we’ve had past programs that have started this late,” he said.
The earliest spraying date could have been April 15, as per the spraying permit that runs until June 30.
“If we get a sudden warm period, it may move up the date a bit,” said Ebata. “We do the…projections every week so we will be fine tuning the date and will be notifying the public through [a news release] when it will start at least a week ahead of time.” The public can also receive real-time updates through a website (www.gov.bc.ca/gypsymoth), a 24-hour-information line (1-866-917-5999), a listser message and social media.
Once spraying gets underway, the province will use a twin-engine plane to deliver three treatments using a pattern that resembles a car race-track.
“It is the fastest, quietest and most efficient means of treating the area [because it minimizes the numbers of required turns] and we expect each treatment to be completed in one morning,” said Ebata.
A fourth treatment may be necessary if an unexpected weather event, usually a surprise rain, washes off the pesticide, he said.
The pesticide in question — Foray 48B —contains Bacillus thuringiensis varkurstaki (Btk), a natural substance present in urban, forest and agricultural soil that does not harm humans, mammals, birds, fish, plants, reptiles, amphibians, bees or other insects.
It only affects gypsy moth caterpillars after they have ingested it. Ottawa has continuously approved the substance since 1961 and the Organic Materials Review Institute has recently approved it for organic farms.
While Health Canada’s Pest Management Regulatory Agency has determined that exposure to Foray 48B poses no significant health threat, those who may be concerned with exposure can simply stay indoors for up to an hour after the application to ensure all air borne droplets have reached the ground, said Ebata.
“Residents may want to move or cover items they don’t want spray deposits but if they do get covered, the spray will naturally erode with normal weathering in about seven days or they can be washed off with water and a bit of scrubbing,” he said.
Ebata also addressed recent public concerns about the effects of Btk on monarch butterflies. “Monarch butterflies are rare and occasional visitors to the Lower Mainland and B.C.’s eastern interior and even rarer still on Vancouver Island,” he said. “There have been no records of Monarchs being found in the spray area nor is the host, milkweed, a native plant on the coast.”
Ebata said that young monarch larvae would likely succumb to Btk, if hypothetically young monarch larvae would be feeding at the time of application.
“But the insect is not known to be found in the area,” he said. “If anyone has planted milkweed in the hopes of attracting monarchs and they live in the spray block, I would advise them to cover the milkweed just prior to the treatments.”
If left untreated, gypsy moths could spread to new areas of the province via vehicles, containers, rail and the Swartz Bay ferry terminal, a development with potentially devastating consequences for the provincial forest industry, provincial officials have previously said.
