Invasive flighted spongy moth eggs found on vessel in Detroit, first time in Great Lakes region

The Story

Eggs of an invasive moth in the flighted spongy moth complex were discovered for the first time in the Great Lakes region on a vessel inspected in the Port of Detroit, U.S. Customs and Border Protection said.

The USDA confirmed the specimens came from two distinct subspecies within the flighted spongy moth complex, which is native to Asia.

CBP said the vessel that carried the egg masses arrived in Detroit from South Korea via Hamilton, Ont.

The eggs were found during an inspection on Sept. 16.

Richard Hamelin, a University of British Columbia professor of forestry, said the discovery is concerning because spongy moth caterpillars feed on the foliage of many tree species. Hamelin also said he worked with the USDA and the Canadian Food Inspection Agency on a DNA test to differentiate the Asian and European varieties of the moth.

Hamelin said moths are attracted to ships at night because of their lights, and he suggested the finding could indicate a breakdown in inspection or an outbreak at the source.

He said the European spongy moth is already present in Ontario, including that it can kill trees such as oaks by defoliating them over more than one season, while females of the European variety do not fly.

Hamelin said the Asian variety, previously known as the Asian gypsy moth, is more concerning because it can feed on a wider range of trees, including conifers, and females can fly up to 25 kilometres.

According to Hamelin, it is not possible to know how much damage the Asian variety could cause in southwestern Ontario if it established there, because the outcome would depend on how the moth adapts to the local environment.

He said the females lay eggs on hard surfaces, making it more likely to target trees than crops such as corn, and he noted feeding experiments show flighted spongy moths feed on a broad range of trees and plants.

Hamelin said the eggs will not hatch until spring, which gives officials time to find and destroy them, and he expected stepped-up trapping and inspections on both sides of the border.

The CFIA previously carried out eradication efforts in 2022 after two flighted spongy moth complexes were detected in the township of Langley in 2021, according to information on the agency’s website.