Fallen Shoots Under Mature Spruce Trees

May-June 2006

I HAVE HAD QUITE A FEW INQUIRIES about spruce trees shedding the individual shoots of last year’s growth. Many homeowners are complaining about the sea of shoots carpeting the ground underneath large, mature specimens (e.g. Norway spruce). A couple of my colleagues have confirmed that this is typical squirrel damage. Last year’s cones can be found at the base of last year’s growth and in the process of “harvesting” the cones this winter, the squirrels have clipped off the shoot as well. They’ve been doing this for months, but we don’t really notice it until the snow melts to uncover all those fallen shoots. This type of squirrel damage has a negligible effect on tree health but will stimulate the production of adventitious buds this year, similar to pruning. It should be noted that this damage is typical of red squirrel behaviour, more so than black squirrels.

Managing Gypsy Moths
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. 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 spring 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-late May, Gypsy moth larvae tend to migrate 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 larvae begin to emerge, some control can be achieved using a Bt (Dipel, Foray) and spinosad (Success) insecticide in the first two weeks after egg hatch.

The combination of egg mass removal, low toxicity pesticide application and skirt trapping of larvae should go a long way in reducing injury level to high value landscape trees.

Emergency Use for Sudden Oak Death (SOD) Fungicides Approved
Ontario nursery growers and arborists are very concerned about protecting our ornamental and wild vegetation from Sudden Oak Death (SOD, Phytophthora ramorum). 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 decreased in 2005. Unfortuneately, this disease has been found 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, Ontario growers expressed the need for access to registered fungicides to help reduce the spread of this disease. Recently the Pest Management Regulatory Agency approved the Emergency Use Registration for Subdue MAXX and Aliette T&O in Ontario. The use pattern includes host plants in landscapes.

This regulated disease is spreading on infected 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.

A complete list of host plants can be found at: http://www.inspection.gc.ca/english/plaveg/protect/dir/sodspe.shtml. If you are bringing in high risk plants from areas infested with this disease, you might consider the use of registered fungicides. Beware that Subdue Maxx can only be used every 2-3 months (to avoid resistance). Read more about it in the article “A Strategy for using Aliette and Subdue Maxx to Prevent the Spread of Phyto-phthora ramorum” in the May of Horticulture Review.

Diseases and Insect Pests In May
Check out OMAFRA Publication 383, “Nursery & Landscape Plant Production and IPM” for more detailed monitoring tables (Chapter #3). Otherwise, view the tables on the adjacent page.

Click here to view table excerpts (pdf) from this publication.

— Jen Llewellyn, Ontario Ministry of Agriculture and Food (OMAF) Nursery Crops Specialist

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