Those Darling Buds of May, 2015

NorwayMapleFlowersCrop  We’ve got a warm week ahead of us and for those of us in the green industry, we  are all wishing that spring would slow down a little bit.  Buds are bursting like crazy, making bloom periods as well as the planting/harvesting season shorter.   T’is the season for little sleep, overwhelming feelings and less patience.

For Plant Phenology Indicators,  the Acer saccharum (sugar maples) (some) are blooming with leaf buds starting to open, the Acer platanoides (Norway maple) are in early-mid bloom, the Amelanchier laevis is in early bloom, the  are beginning bloom,  the Cornus mas (Cornelian cherry dogwood) is finishing bloom, the Forsythia sp. is in late bloom, the Magnolia x soulangeana (saucer magnolia) is in early bloom. This puts is at about 55-100 GDD Base 10C.  Plant phenology models for IPM can be found starting on pg. 39 of OMAFRA Guide 841, Guide to Nursery and Landscape Plant Production & IPM.   Many of these models are based on Donald Orton’s COINCIDE.


Where dogwood (Cornus spp.) has had issues with fungal leafspots (e.g. Septoria) in the past, protect emerging foliage with fungicides before precipitation or irrigation events as the Amelanchier sp. and Cercis canadensis are blooming.  Leafspots are often circular or angular with a bright purple border, making shrubs look unsightly by early summer.

<a href="/clm/species/lymantria_dispar"><em>Lymantria dispar</em></a> (Gypsy Moth) larva.

When the Cercis canadensis is starting to bloom, Gypsy moth larvae will be hatching from overwintering egg masses.  Though they can be found feeding on several species of trees, we quite often find them on beech, oak and Colorado spruce.  Where tiny black, fuzzy caterpillars can be found feeding, try an application of the biocontrol B.t. (e.g. Dipel) and the low toxicity option spinosad (Success) to manage young larvae.


Quince rust. Photo by D. Dailey O’Brien,



Where the Cercis canadensis are starting to bloom, monitor for Gymnosporangium rusts such as Cedar-apple rust (1), Cedar-Hawthorn Rust (2), Cedar-Quince rust (3) and Pear Trellis Rust (4) on Juniperus. Protect rosaceous hosts (e.g. Pyrus, Amelanchier, Malus, Crataegus) before rain or irrigation events with fungicides such as Nova, Pristine, Daconil or Dithane.

Boxwood Psyllid damage, July. (

<a href="/clm/species/cacopsylla_buxi"><em>Cacopsylla buxi</em></a> (Boxwood Pysllid) nymph on boxwood.

Monitor boxwood for bud swell and hatching of overwintering boxwood psyllid nymphs as the Cercis canadensis begins to bloom, Acer platanoides are in late bloom and Magnolia x soulangeana are dropping petals.  Eggs are very tiny, spindle-shaped and buried within the bud scales of this year’s growth with just the tip protruding out.  Boxwood psyllid eggs hatch just as buds are starting to break and expose tender new shoots. Psyllid nymphs are yellow-green and blend in very well with new growth of boxwood. Their feeding causes cupping and distortion of new growth. Spray with insecticidal soap or contact insecticides at first sign of bud break and repeat 2-3 times to suppress populations of hatching psyllids. Systemic insecticides, such as dimethoate, are registered for use in commercial nurseries.

<a href="/clm/species/pissodes_spp"><em>Pissodes sp.</em></a> (White Pine Weevil) adult.White Pine Weevil injury on Colorado spruce terminal

Look for overwintering White Pine Weevil adults in around the leaf litter below the trunks of white pine and spruce as the Forsythia blooms. They are quite active in the next couple of weeks and will be laying their eggs under the bark of the terminal shoot from last year.  Eggs will feed in the cambium and result in wilting and death of the current season’s leader in June and July.  Place freshly cut logs on the ground and check them during the day for small, mottled grey/brown/white weevils clinging to the under surface. Spray terminals with insecticides (e.g. Cygon is registered for nursery crops) as adults become active and start laying eggs on terminals.

Stem mother

Stem Mother of Balsam twig aphid on fir (Abies). She will lay her eggs on new needles as they emerge from the bud (

Monitor for STEM MOTHERS of Balsam twig aphid eggs on terminal buds on fir, white spruce, Colorado spruce and juniper, they are susceptible to dormant oil applications. These tiny, bluish grey aphid stem mothers can be found on terminal buds as they break. Apply Diazinon, Malathion and Tristar on warm days (55 to 78 GDD Base 10oC OR before bud caps loosen off) to target these stem mothers and prevent the damaging generation that follows.    This is your only opportunity to manage this pest.  Click here for  photos

It’s time for the latest edition of, WHAT’S THAT SOUND?  We’ve got two new species entering the reptile breeding season in southern Ontario.  Our first is the American Toad.  This toad call is a high, one-tone trill that you’ll hear in the background, it might remind you of an insect call.   The second is the Gray Tree Frog. This tree frog calls from up in tree canopies and resembles a friendly raccoon call.  It’s a bit early for them but I heard one calling yesterday.


I look forward to this day every year…..

Old Ben        ……May the 4th be with you

About Jen Llewellyn

OMAFRA Nursery and Landscape Specialist @onnurserycrops
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1 Response to Those Darling Buds of May, 2015

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