The Asian spongy moth problem

The Asian spongy moth attacks many hardwood or deciduous trees as well as several conifers, including Douglas fir, hemlock, larch, pine, and spruce. Since the female Asian spongy moths can fly – unlike the European spongy moth already widespread in the Northeast USA– it spreads more rapidly.

Asian spongy moths are found in the Russian Far East, China, Korea, and Japan. Like all moths, they are attracted to lights – including lights at ports where ships are loaded. The females then lay their eggs on the ships.

To protect our forests, U.S. and Canadian customs agencies inspect ships coming from northern Asia; ships found with moth eggs attached to the ship or its cargo must return to the open sea and clean off the eggs. Inspecting the ships is difficult, time-consuming, dangerous – and not always a perfect process – which leaves our forests vulnerable.

The U.S., Canada, and Mexico have adopted a regional standard that makes China, Korea, and Japan responsible for ensuring that the ships travelling to North America are not carrying spongy moth eggs. They must inspect the ships, monitor moth populations in ports and nearby forests, and take other actions to reduce the likelihood of moths laying eggs on the ships. For example, moths are not attracted to lights of a certain wavelength, so using those specific types of lighting reduces the risk while allowing port operations to continue.

This program was applied to Russia in the mid-1990s. It has worked: few ships from Russia now carry spongy moth eggs.

China, Korea, and Japan are now gearing up their programs – but improvement is needed. In 2012, 31 ships with egg masses were detected by U.S. Customs and Border Protection and required to leave port until they could pass inspection.

Given how difficult it is to inspect ships, it would be easy for some egg masses to escape detection and hatch – starting another outbreak in North America. If it gets established, the Asian spongy moth could easily be transported on firewood, just like the European spongy moth. Remember – even if a pest outbreak has not been officially detected, the risk is still present.