Gypsy Moth & Fall Cankerworm
Posted November 7, 2017
HCA ecology staff, along with Steve Robinson, Project Manager of the City of Hamilton forestry staff hosted a Gypsy Moth & Fall Cankerworm workshop Friday, November 3. Couldn’t make it to the workshop? Here are some helpful tips to put to use on your property!
It is best to band trees after the first or second hard frost fo the season. The flightless females begin at this time to travel up tree trunks to lay their eggs. The sticky band catches them before they can do this. It helps to prevent egg laying and then defoliation in the springtime. You can remove the band in January. Cankerworms favour deciduous trees, walnut, basswood and maples are their favourite. They are a native species which outbreak 8-12 years and usually defoliate for 2-3 years in a row. The caterpillar stage lasts 3-4 weeks. Even if completely defoliated a healthy tree can push out a new set of leaves by mid-summer. The native predators and parasites reduce fall cankerworm populations over time. Healthy trees can withstand repeated defoliation over a few years provided that there are no other stressors, such as drought or other diseases affecting the tree.
Gypsy Moth banding should be done in late-April in an attempt to catch the caterpillars crawling from the ground up into the trees. Once the caterpillars are big (few inches long) they can then crawl over the band so it best to remove the band by then. Replace it with a burlap band which can be tied around the tree with a flap or an overhang. The caterpillars will hide away from the heat in the burlap. You can then squish the caterpillars every few days. For best results, leave this band on into September. Remove it in late September and dispose of the band, it should contain a number of eggs. From September to April, scrape all egg masses you can reach into a bucket of soapy water. Leave for 48 hours to kill the eggs. Each egg mass can contain up to 1000 eggs. This is the best way to remove part of the population.
Pictured to the right is an egg mass. This species is non-native and was introduced to the USA in the 1850’s in an attempt to start a silk industry. It has traveled north since then. Occurs on an 8-10 year cycle and usually lasts usually 3-4 years. It is unusual that in some areas in Hamilton we have both fall cankerworm and gypsy moth defoliating the trees, leading to further stress on the trees. Caterpillars feed for 4-6 weeks. Viruses, bacteria and our native predators can reduce numbers.
What you can do at home
- Sticky bands in November (cankerworm)
- Egg scraping September – April (gypsy moth)
- Sticky bands in April (both)
- Pheromone traps – July/August (gypsy moth)
- Burlap July – September (gypsy moth)
Homeowners can also spray BTk a biological pesticide on leaves they can reach. This is available at local hardware stores/garden centres. The cankerworms and gypsy moth will ingest it, however it washes off within a week, so reapplication is important!
Watch this short tutorial by the City of Toronto on how to create and install a sticky band trap
For more information, please contact:
Lesley McDonell, Terrestrial Ecologist at HCA
905-525-2181 ext. 231