April Snowstorms Bring May Flowers

Image result for silver maple flowersThere may still be snow in the bush but at long last, its been warm enough to support bloom on several early flowering plants.  It looks like the warming trend will continue, according to the 7 day weather forecasts.  After this weekend, night time low’s will be mainly above 0C.  Which means we will be accumulating some much needed heat units (Growing Degree Days) in the next week. (Photo of silver maple flowers: Carl Strang, Nature Inquiries).

Where the Silver maples are in full bloom, red maples and pussy willow are just beginning to bloom, we are between 1-25 GDD’s Base 10C.





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DCEastSprGallOWFem       Cooley spruce gall and Eastern spruce gall adelgid overwintering females can be found on the undersides of last year’s twigs, next to the base of the needles.  Take a look at these tiny females with your hand lens.  If they are still blue-purple, that means they haven’t laid their eggs yet.  If you can’t see the blue-purple and they are covered in thick, white woolly wax that means egg-laying has started and pesticides will not be as effective.  Insecticides include Tristar, Sevin, Malathion and horticultural oil.  Be mindful that horticultural oil may remove the glaucus needle sheen on some conifers.

Manual IPM:


Gypsy moth (Lymantria dispar) egg masses are grey from overwintering but they can be detected on tree trunks, branches (e.g. Acer, Picea pungens, Quercus, Tilia etc.) as well as other wooden objects.  Scrape off egg masses, collect and destroy to prevent hatching of hundreds of caterpillars.

vacuum3 City of Toronto forestry staff have been busy manually removing (yes, that’s a vacuum) Gypsy moth eggs masses from several key oak  (Photo: Tina Orchard, City of Toronto). Toronto surveyed close to 3000 trees all across the city this winter with focus on oak dense communities.  Egg mass removal was carried out on approximately 600 trees of various species. They have noted another 275 infested city trees where manual removal wasn’t possible and the trees will require treatment this spring.  Where significant egg masses could be seen on neighbouring private trees, Toronto forestry staff took the extra time to alert residents.


Overwintering eggs of Fall cankerworm (Alsophila pometaria) are near impossible to find and don’t make very good candidates for manual removal this time of year. (Left image:  http://www.dcnr.state.pa.us, Right image: rutgers.edu). Some horticulturalists report that the egg masses can be smothered with dormant horticultural oil, but the coverage has to be 100%. This is why most horticulturalists use tree bands in the fall to trap wingless females, the males they attract and their resulting egg masses.

Joel Harrison-Off, Toronto’s Forest Health Care Inspector reported that approximately 700 sticky band traps were set up in select areas across Toronto in late October, by city staff and volunteer groups.  The focus was on protecting dense, mature oak areas. Traps were removed by mid-December and virtually all of them came heavily loaded with both female and male moths.  Toronto’s observations indicate that fall cankerworm populations will be relatively high again this spring, especially around areas in close proximity to naturalized woodlots and ravines.


Eastern tent caterpillar (Malacosoma americanum) eggs masses are grey and encircle twigs of last year’s growth.  They actually glisten in the sun so monitor for these on sunny days before leaf emergence.  Larvae will be hatching soon.  Prune out, collect and destroy eggs masses to prevent hundreds of caterpillars hatching and feeding on Prunus, Malus, Crataegus.


Look for cone-like structures hanging from the ends of branches at this time as signs of Bagworm (Thyridopteryx ephemeraeformis). This pest has been found in the Windsor and Coburg areas.  These “cones” are really overwintering structure that house the female and her hundreds of eggs.  Remove, collect and destroy cones to prevent significant defoliation on host plants (Gleditsia, Thuja, Picea).

VLB Egg mass

Viburnum leaf beetle (Pyrrhalta viburni) egg masses can be found as raised grey-brown bumps, in rows along the UNDERSIDES of last years twigs.  Pick off the raised bumpy cap to see lots of yellow eggs underneath.  Prune out, collect and destroy egg masses to prevent widespread defoliation of our lovely flowering viburnums this spring.



About Jen Llewellyn

OMAFRA Nursery and Landscape Specialist @onnurserycrops
This entry was posted in Arboriculture, IPM, landscape and tagged , , , , , , . Bookmark the permalink.

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