Managing Gypsy Moth Again

May-June 2007

Diseases and Insect Pests in May (pdf) ...

THIS SPRING, MANY HOMEOWNERS and professional arborists are looking for low toxic solutions that might combat the pending hatch of millions of gypsy moth larvae. When larvae begin to emerge, some control can be achieved using Bt (Dipel, Foray) and spinosad (Success) insecticides in the first few weeks after egg hatch.

Homeowners can actually do quite a bit to protect their trees, but they need to commit some time to the cause. Egg mass removal has been a major service for tree care companies this past couple of years but cultural control doesn’t stop there. Some keen homeowners can install a burlap “skirt” at the base of the tree to create a shady, protected area for larvae to hide during the day. During mid-to-late May, gypsy moth larvae will actually crawl down from the canopy to shady places in the bark crevices in order to hide during the heat of the day. This daily migration down the tree usually peaks in late May, so make sure you get your skirts installed as soon as possible. Homeowners will need to inspect burlap skirts and underlying bark crevices daily (1-3 pm is best) and remove/destroy larvae.

When the adults begin to emerge in late June and July, install sticky bands around trunks to help prevent females from walking up tree trunks to lay their eggs. Adult females are unable to fly and a sticky band will force them to lay their eggs on the band (where we can easily access them for removal). Also, the natural pheromones of the trapped females will attract males to the sticky surface where they too will become trapped and unable to complete their life cycle. The combination of egg mass removal, low toxicity insecticide application, skirt trapping of larvae and installation of sticky bands should go a long way in reducing injury level to high value landscape trees.

CFIA Combating ALHB in Toronto
Additional discoveries of Asian long-horned beetle (ALHB) were detected in the Toronto-Vaughan quarantine zone this past winter in the area of Finch Avenue and Weston Road. By the third week of April, the Canadian Food Inspection Agency (CFIA) had removed approximately 2,400 trees (they had originally planned on removing 800) in an ongoing effort to eradicate ALHB. Compensation for replacement costs of trees is available. For more information, contact CFIA at 1-800-442-2342 or check out their ALHB page.

Emergency Use for SOD Fungicides Available Again for 2007
Ontario nursery growers and arborists are very concerned about protecting our ornamental and wild vegetation from Sudden Oak Death (SOD, Phytophthora ramorum). This pathogen has been associated with the dieback and mortality of hundreds of thousands of trees in the wild and in the coastal counties of California and Oregon. Fortunately, this pathogen has not been found in Ontario to date. It has been found on ornamental hosts in British Columbia, but the number of facilities testing positive for SOD is quite low. This disease has been discovered on nursery stock at many facilities in the United States, especially in California, Oregon and Washington

Since one of the major pathways of SOD movement is through infested nursery stock, British Columbia and Ontario growers expressed the need for access to registered fungicides as a key part of their best management practices to help reduce the spread of this disease. Recently the Pest Management Regulatory Agency approved an Emergency Use Registration for Subdue MAXX and Aliette T&O in Ontario. Beware that Subdue Maxx can only be used every 2-3 months (to avoid resistance). This registration includes host plants in landscapes.

This regulated disease is spreading on infected, high risk ornamental host plants such as Camellia, Rhododendron, Viburnum, Pieris, Kalmia and Syringa. These six genera are considered “high risk” hosts because they are the most common genera of nursery stock found positive for SOD and because the pathogen sporulates heavily on them. There are 69 host genera that are regulated for SOD in Canada, a complete list be found at list be found at:

If you are bringing in high risk plants from areas infested with this disease, you might want to evaluate your risk of introducing SOD into Ontario. There is a risk management tool on the Landscape Ontario website (SOD, Is Your Nursery At Risk?) that you might find useful, even if you aren’t a nursery grower: go to You should also be aware of the most common symptoms of SOD, especially on high risk host plants. For pictures of symptoms, check out For more information, visit the Canadian Food Inspection Agency SOD information page at:

Contact Information

This column is written by Jen Llewellyn, Ontario Ministry of Agriculture and Food and Rural Affairs (OMAFRA) Nursery Crops Specialist

Email any questions you have directly to Jen and we'll publish her response.

P: 519-824-4120 ext. 52671 • F: 519-767-0755

OMAF website:

Nursery Landscape Agriphone: 1-888-290-4441

Our mission is to enhance and promote the care and benefit of trees for present and future generations in Ontario through education, research and awareness.