This past summer’s efforts to slow an invasive insect infestation were successful, according to provincial officials, who hope a targeted spraying this summer will be enough to eradicate Salt Spring’s spongy moth population.
Last seen in the 1990s, the invasive moths were detected again on the island in 2021; monitoring efforts the following year revealed a growing population of the insects (from six to 14), which — while caterpillars — are voracious defoliators of several native tree and shrub species, according to the Ministry of Energy and Natural Resources.
In response, 2023 saw the implementation of a high-density trapping program, one that set out more than 700 bright green tent-shaped traps across three different zones on Salt Spring Island — near St. Mary Lake and around the Vesuvius area.
That program appears to have helped limit the growth and spread of the insects — 14 moths were detected at the end of 2023’s trapping — and one 48-hectare area is targeted for aerial spraying this spring to hopefully close the deal.
Across B.C., 13 different aerial spray events will be required by forestry officials in coming months, in several efforts to control spongy moths.
Salt Spring’s treatment area is one of the smallest, according to the ministry, partly thanks to last year’s traps keeping the population here from becoming more established.
The pheromone traps only lure male moths, although provincial research scientists estimate each unmated pair removed from the population can eliminate as many as 1,000 caterpillars the following year.
Unlike ground-based spraying, such as took place near Lee’s Hill in 2007, aerial applications are used partly because they require a lower concentration of the bacteria-based insecticide preferred by the province’s Spongy Moth Technical Advisory Committee — in this case expected to be Foray 48B, an Organic Materials Review Institute listed product certified in 2018 for use in organic production.
The spongy moth is the common name for Lymantria dispar, renamed from “gypsy moth” by the Entomological Societies of both Canada and the United States in 2022. The name references the insect’s “spongy” egg masses, often found in the branches of the same deciduous trees the hatched insects will devour — and which have been known to cause rashes when handled.
Recently, the egg masses have been found more often in human-made shelters — including under vehicle wheel wells, which has helped them spread from Ontario into B.C.
Across Canada and the U.S., particularly in the northeast, spongy moths deforest roughly one million acres of forest in an average year, according to the ministry.
Virtual open house sessions will be held in February, officials said, to provide program information and answer questions.
For more information visit www2.gov.bc.ca/gov/content/industry/forestry/managing-our-forest-resources/forest-health/invasive-forest-pests/spongy-moth.