Q: I heard about an invasive species called Lymantria dispar dispar moth in our area. What kind of damage does it do, and how can I help to control it in my neighbourhood?
A: The LDD moth (Lymantria dispar dispar – formerly commonly known as the ‘gypsy moth’ – wording has been updated to avoid the use of an ethnic slur), has been declared an invasive species by the government of Canada, and is widespread throughout the eastern portion of our country. They are one of the primary defoliating pests, and have over 500 potential host plants. This can make LDD moth epidemics very difficult to predict and control.
What makes the LDD moth so devastating is that they have multiple larval stages (called instars), all of which can do damage to host plants. When the eggs hatch in May, residents of affected areas will quickly notice masses of small black/brown fuzzy caterpillars all over building roofs and decks. As the caterpillars develop through their instars, they become larger as they continue to feed, with the final stage showing characteristic red and blue dots on their spines. The caterpillars then pupate into adult moths – immobile white females, and brown males which are very active at ground level during daytime hours (typically July-August). The females lay egg masses on tree trunks, lawn equipment and motor vehicles. These egg masses are very recognizable due to their orange/tan colour, erratic shape, and highly textured appearance.
Although the LDD moth has many hosts, their favourites are oak trees (Quercus spp.). If you have oak trees in your neighbourhood, it’s a safe bet that the LDD moth will be around. They are also known to feed on some maples, birch, crabapple, poplar and willow, to name a few. With that many food sources, it’s almost impossible to know if and/or when the LDD moth will come to your area.
The easiest way to start controlling the LDD moth in your area is to look for egg masses. You can do this two times a year: when they are freshly laid in July/August, or in the spring after they have overwintered. Check tree trunks, lawn tractors, ATVs and garden shed walls. If you find an egg mass, scrape it cleanly off and deposit it in a bucket of hot water and bleach. Ensure that you clean any scraping tools with the same solution between scrapes!
If you have a known tree in your yard that is plagued with LDD every year, you can wrap the base of the trunk with a sticky trap just after caterpillars start to appear. Caterpillars walk up and down the tree trunks every day to feed, and these traps are a great way to catch and dispose of them.
If you are considering planting a new tree, it may be a good idea to stay away from oaks for the near future. Do some research on LDD resistant varieties and choose from one of those instead.
Lastly, get your neighbours involved! The more people that are aware and actively working to reduce LDD moth populations, the better overall control we will have over this invasive pest. Spread the word!