April Showers and April IPM Opportunities

Image result for silver maple flowers

Photo of silver maple flowers: Carl Strang, Nature Inquiries

Unusually warm weather has hastened the flowering of many trees, shrubs and bulbs!  Although we have more seasonable daytime high’s in the forecast for the next week, night time low’s will be  above 0C in southern Ontario.  Silver maples may still be blooming north of Hwy #9 but they have finished blooming to the south. 

Where the silver maples are in full bloom, red maples and pussy willow are still in bloom, we are in the range of 1-25 GDD’s Base 10C.

Where the silver maples are finished bloom, red maples and pussy willow are in late bloom to finishing bloom;  Forsythia and Magnolia stellata are in full to late bloom, we are in the range of 25-55 GDD’s Base 10C.


Want to make this even easier?  Get your free download of BugFinder on Google Play or Apple.

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, 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 the winter weather 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.  {Note: hatching 1st instar larvae can still blow in 0.5 km from unmanaged areas nearby. }

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 from a couple years ago). Several neighbourhoods are slated for Dipel applications to manage this moth defoliator.


Overwintering eggs of Fall cankerworm (Alsophila pometaria) are nearly impossible to detect 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 late fall to trap wingless females, the males they attract and their resulting egg masses.  Dipel is registered for larvae in spring.


Forest tent caterpillar (Malacosoma disstria, above) and 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 AcerPrunus, 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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