Those Darling Buds of May 2 4

Painted Turtle sunning itself at Tortuguero National Park.:

Oh yes Oh yes the long weekend is finally here!

And so is the heat!  (Photo: One more shot Rog on Flickr)

Climatologists are expecting daily high’s of 20C and above for the next several days.  Night time low’s are also going to increase so we should start and see plant and pest development really take off after this weekend.

Plant Phenology indicators this week, Hamilton/Niagara/GTA/London

  1. Acer platanoides (Norway maple, late bloom, leafing out);
  2. Amelanchier laevis (serviceberry, full bloom)
  3. Cercis canadensis (redbud, full bloom)
  4. Prunus x cistena (purple leaf sandcherry, full bloom)
  5. Syringa vulgaris (common lilac, early bloom).
  6. Aesculus hippocastanum (horse chestnut, early bloom)
  7. Spirea x vanhouttei (bridal wreath spirea, full bloom)

If you are referring to the Phenology and Monitoring tables in OMAFRA publication 841, Guide to Nursery and Landscape Plant Production & IPM, look at the Tables starting with 2-3 on pg. 39.  This puts us at about 30-55 GDD Base 10C in areas south of Hwy 9.  Areas in the southwest corner of the province will be more advanced.

PLEASE NOTE: The Following Pesticide Recommendations are meant for Exception Uses (e.g. agriculture-nursery production or trees in the landscape) under the Cosmetic Pesticide Ban unless the active ingredient is listed under Class 11 pesticides in Ontario Regulation 63/09, effective April 22, 2009.

The Crop Protection Guide for Nursery and Landscape Plants (OMAFRA publication 840) contains the crop pest recommendations for nursery and landscape.  The new 2016 version of Publication 840 will be available online in the next few weeks.  The pest recommendations can also be found on our online, searchable database:  Check out NurseryTracker on your phone or tablet!!!

Nursery-Landscape Insect Pest ID: Dave Cheung’s Common Pests of Nursery-Landscape database to help ID your problem pests.



Fletcher scale nymph on Taxus, early May (J. Llewellyn)


Slightly more mature Fletcher scale nymph on Taxus, early May (J. Llewellyn)

Continue to monitor for yellow-brown overwintering nymphs of Fletcher scale (Lecanium fletcheri).  These scale nymphs may still be susceptible to registered contact and systemic pesticides.  Where heavy populations are detected, spraying asap may help reduce damage and honeydew.  These scale insects produce a lot of honeydew in June.  Monitor Taxus (yew) and Thuja (eastern white cedar)

<a href="/clm/species/otiorhynchus_sulcatus"><em>Otiorhynchus sulcatus</em></a> (Black Vine Weevil) larva. In production nurseries where black vine weevil larvae are a problem in container crops (e.g. perennials, evergreens), monitor containers for larvae and pupae. Once soils reach at least a consistent 10-12oC and treat with Heterohabditis bacteriophora (H.b.) or Met52.  This should result in a significant reduction in populations in under two weeks.  Order your nematodes in advance.  Since Heterohabditis nematodes require moist, warm soil, we find that they work best in container production.  Met52 can also be applied preventatively at potting.

<a href="/clm/species/plagiodera_versicolora"><em>Plagiodera versicolora</em></a> (Imported Willow Leaf Beetle) adult on willow.<a href="/clm/species/plagiodera_versicolora"><em>Plagiodera versicolora</em></a> (Imported Willow Leaf Beetle) eggs on willow.<a href="/clm/species/plagiodera_versicolora"><em>Plagiodera versicolora</em></a> (Imported Willow Leaf Beetle) larvae.

Imported Willow leaf beetle (Plagiodera versicolora) is pretty common on Salix in containers and in the field. Adults overwinter inside cracks within the bark of the host tree. Adults emerge in spring to feed and lay eggs on the underside of leaves. The yellow eggs are laid in an irregular pattern and hatch within a few days. The larvae feed on the undersides of leaves for about 3-4 weeks before pupating on the underside of leaves. The pupae are yellowish brown with black markings. There are multiple generations a year.

Leaf spot on Cornus (T. Lohrer)

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.

PseudomonasSyringaBloomerang In container nurseries, where Pseudomonas blight on lilac (and other deciduous shrubs) was a problem last season, you may want to consider an application of  copper as they bud out.  Research also indicates that the copper becomes more effective if combined with Dithane.  The bacteria overwinter next to the buds and can infect leaf tissue once bud caps split open.  Again, infection and spread of this bacterial disease can be reduced where temperatures and humidity levels are moderated (i.e. ventilation under poly) and new foliage is more gradually hardened off to outdoor conditions.

If you are bringing in SOD (Sudden Oak Death, Phytophthora ramorum) host nursery stock from high risk areas, you will want to monitor for SOD symptoms. Camellia, Rhododendron, Viburnum, Pieris, Kalmia and Syringa are considered to be high risk host genera, as they are most common genera found positive for SOD in retail and wholesale nurseries. Fungicides registered for SOD in nurseries include: Acrobat 50 WP, Chipco Aliette WG and Subdue Maxx.  For a complete list of SOD regulated hosts, check out:


<a href="/clm/species/thrips_calcaratus"><em>Thrips calcaraus</em></a> (Introduced Basswood Thrips) adult.<a href="/clm/species/thrips_calcaratus"><em>Thrips calcaraus</em></a> (Introduced Basswood Thrips) damage.

Introduced Basswood thrips (Thrips calcaratus) has been found inside buds and among emerging leaves on Tilia americana. Introduced Basswood thrips can cause severe damage that often leads to some defoliation.  We have seen it in some other nurseries (field production) this spring.  Introduced basswood thrips is most damaging on Tilia Americana. It overwinters in the soil, adults emerge as basswood buds are breaking.  Adults feed on buds, sometimes killing them and causing them to drop.  Females lay eggs along leaf midrib on leaf underside.  Larvae appear in early June.  Feeding of larvae and adults can cause damage and premature leaf drop.  Researchers believe there is only one generation per year. If damage starts to become evident on Tilia, treat with Success (spinosad) a naturalyte insecticide that is very effective against western flower thrips (and several other Lep and sawfly, beetle pests). Another biological option is Beauvaria bassiana (Botaniguard, Bio Ceres) and it is often used in rotation with Success due to resistance to spinosad of Western Flower Thrips in gh crops.

Once ash trees have leafed out, injectable insecticides may be used to protect the trees from new infestations of Emerald Ash Borer (Agrilus planipennis). Trees must be actively transpiring in order to maximize insecticide uptake into the cambium. Registered injectable insecticide products include: AceCap 97, Confidor 200 SL, IMA-jet and Tree-Azin.  The regulated areas for EAB outlines restrictions on the movement of all ash species (Fraxinus sp.) materials and all species of firewood from these regulated areas of Ontario and Quebec.

The Asian Long Horned Beetle was detected in the vicinity of Pearson International Airport in Toronto/Mississauga and efforts are continuing to eradicate this beetle from the area. The Asian Long-horned Beetle Infested Place Order is being enforced in the area encompassing: all parts of the City of Toronto and City of Mississauga, in the Province of Ontario, located within the area commencing at the point of intersection between Dixie Road (formerly Hwy. 4) and Derry Road (formerly Hwy. 5) and proceeding northeastward along the south side of  Derry Road to Bramalea Road. This means that tree materials, including nursery stock, trees, logs, lumber, wood, and wood and bark chips from tree species that are susceptible to the Asian Long-horned Beetle, may not move out of, or through, this area.

EuropeanChaferLarvaSoilECLarvaPinus          Take a look at the roots of poor looking evergreens (Thuja, Picea, Pinus) and field grown ornamentals and look for populations of European chafer, May/June Beetle larvae and other white grub species in the soil. Sandy soils are especially hospitable to white grub species.  Preventative applications of Intercept (imidacloprid) are registered for white grubs (nursery production) and the application period is in June and July (during the adult flight period). Beneficial nematode applications are not recommended this time of year and are much more effective when applied to early instar larvae, mid-August.


Boxwoods in the landscape not looking so good coming out of the winter?  Are you seeing a lot of yellow leaves? Can you see any yellow-green spots?


Boxwood leafminer larva inside leaf (J. Llewellyn)

Carefully break open the leaf with your knife or finger nail, look for tiny yellow pupae inside.  These are boxwood leafminer ADULTS SHOULD BE EMERGING SOON.   The tiny orange midge adults will be emerging out of these leaves when the new growth emerges.  Adult midges will be laying their eggs on newly emerged leaves and those eggs will hatch into the next generation of leaf miners.  Treating new foliage with insecticides just prior to or at the beginning of leaf emergence can help reduce successful egg hatch and leafminer establishment.  You can also prune out new foliage in August and the clippings will desiccate, making it impossible for the leafminer to complete its lifecycle.

<a href="/clm/species/dasyneura_gleditschiae"><em>Dasyneura gleditschiae</em></a> (Honey Locust Pod Gall Midge) galls.<a href="/clm/species/dasyneura_gleditschiae"><em>Dasyneura gleditschiae</em></a> (Honey Locust Pod Gall Midge) adult.

Where honeylocust podgall midge was a problem in the past, monitor trees for overwintered adult midges soon. These adults will be emerging as the buds start to swell. Adults will be laying eggs on buds in early spring (reddish eggs on buds and new leaves). Research in Oregon suggests that delayed dormant oil applications targeting the first couple of egg clutches can help reduce the incidence of pod gall midge. This involves applications of product early in the season, starting before foliar emergence.

<a href="/clm/species/diaphnocoris_clorionis"><em>Diaphnocoris clorionis</em></a> (Honey Locust Plant Bug) nymph.

Honeylocust Plant bug NYMPHS (D. Cheung)


Where foliage is starting to emerge on honeylocust, monitor for newly hatched nymphs of the honeylocust plant bug.  You can find them by shaking branches over a light coloured surface and examining it for fallen nymphs.  By controlling the first generation of nymphs, you can really reduce the damage from this pest.

<em><a href="/clm/species/malacosoma_americanum">Malacosoma americanum</em></a> (Eastern Tent Caterpillar) web nest.

Eastern tent caterpillars have hatched and these tiny, black fuzzy larvae are feeding and making webby tents in branch crotches. The larvae can cause severe defoliation in May, where populations are high. Young larvae hide in webby tents during the day, remove and destroy tents during daylight hours in the first week or two after their appearance. Where larvae start to feed, try an application of the biological insecticide B.t (Dipel, Foray) on the foliage during the evening hours. Larvae will turn black and die approximately 3-5 days after eating the B.t. residue on the foliage.

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

Gypsy moth larvae have hatched (when trilliums are in bloom), they spin threads in order to blow and disperse to other hosts.  So you’ll find them just about everywhere this time of year.   Some control can be achieved using Bacillus thuringienesis (Dipel, Foray) and spinosad (Success) insecticide once they settle in their new feeding site.

<a href="/clm/species/pyrrhalta_viburnicola"><em>Pyrrhalta viburnicola</em></a> (Viburnum Leaf Beetle) damage on viburnum.

Viburnum leaf beetle egg masses can still be pruned out and destroyed at this time (where leaves haven’t begun to emerge yet), to avoid destructive populations this spring. Look for raised bumps on the undersides of 1 and 2-year-old twigs. The bumpy caps can be picked off to reveal the yellow eggs underneath. Monitor these eggs as they will hatching into larvae as foliage emerges. The larvae are vulnerable to chemical control only during the first 7-10 days after hatch. Larvae feed on the interveinal tissue from the undersides of the leaves, keep that in mind if you are doing insecticidal applications (Success, Actara, horticultural oil).


Fireblight of Malus

Apple scab on Malus leaves

Now is the time that Fireblight (apple, pear, see above) and Apple Scab (apple) diseases are spreading to new, emerging growth in the nursery.  Foliar (floral) applications of products for Fireblight (such as copper, Kasumin, streptomycin) should continue to reduce numbers of fireblight bacteria on floral structures (stigmas) throughout the bloom period.  The floral stigmas are the main entry point for fireblight into the tree.

Fireblight is a big concern right now because the crop is in full bloom, we’ve had warm temperatures and rain and there is so much disease inoculum from last year.  The Ontario Fireblight Prediction Models can be found below:

IronWoodAnthracnoseWhere Ironwood trees (Ostrya virginiana) were infested with anthracnose spots last year, you may consider an application of broad spectrum fungicide (e.g. copper) as buds start to swell. The usual symptoms caused by this fungus, Apiosporopsis carpinea, are irregular necrotic spots ranging in size from pinpoints to 5-6 mm in diameter. They will increase in number and coalesce during the season and will cause marginal and apical browning, curling and leaf cast.

Black knot is easy to see on Prunus sp. at this time. Monitor gardens and adjacent wild areas for Prunus shrubs and trees for large black growths on previous years twigs. If you have the time to prune, prune the cankers out, back quite close to the main stem BEFORE LEAVES EMERGE. Destroy all pruned twigs. Pruning too shallow retains the undetectable, developing canker on the tree and does nothing to limit the disease. Fungicides may give some suppressions when sprayed at green tip, pre-bloom and blossom time. Fungicides include Daconil and Maestro. Fungicides need to be applied ahead of precipitation events during bloom and shoot emergence In the nursery/orchard, Daconil has been shown to be the most effective fungicide. (Fruit-bearing mature Prunus: Daconil cannot be applied after shuck split or fruit will be injured). For more information:



Monitor for Balsam twig aphid stem mothers near buds on fir, white spruce, Colorado spruce and juniper.  The tiny, bluish grey aphid stem mothers can be found on terminal buds as they break.


Tap branches over a dark surface to see tiny whitish Balsam twig aphid stem mothers (use a hand lens to confirm id).  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.

BTA Photos:

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

Overwintering white pine weevil adults are active and are mating on last year’s leader of pine and spruce, when the Forsythia starts to bloom. Monitor for small black/brown snout beetles around the foliage and in the duff layer below the canopy. Its getting late but an application of insecticide on last year’s leader may help reduce successful egg-laying and damage to this year’s leader.

<a href="/clm/species/oligonychus_ununguis"><em>Oligonychus ununguis</em></a> (Spruce Spider Mite) adults on cedar.

Monitor for newly hatched nymphs of spruce spider mite on conifers with a history of mite damage (Abies, Picea, Thuja). Spruce spider mite eggs appear as very tiny, round, reddish-brown spheres that adhere to the UNDERSIDES of twigs and foliage this time of year. YOU WILL REQUIRE A HAND LANDS TO SEE THEM CLEARLY. Monitor lower branches, on the North and Easter side of the tree, this is where most of the feeding damage is done. These eggs are susceptible to dormant hort oil applications in the next few weeks, where temperatures permit and plant species are not sensitive.  Miticides will be effective once eggs hatch to nymphs, usually around bud break and early foliar emergence.

Pine shoot beetle adults have emerged. The tiny beetles take flight after 2-3 days where temperatures reach 10-12oC. Adults lay eggs underneath the bark of stressed or dead pine trees and stumps. Those larvae will develop later in April and May. Remove brood material (i.e. trap (sentinel) logs, snags, dead/dying trees) before new progeny adults emerge (210 GDD, Base 10C) to comply with the CFIA. All brood material must be burned, chipped (less than 2cm diameter) or buried (30 cm deep) to comply with CFIA standards.

JuniperTipBlightClose Brown shoots on juniper may be a symptom of juniper tip blight (Kabatina blight). A small grey band or pinched grey canker can be found at the base of the infected shoot, this is where the spores come from. Where plants are still dormant, PRUNE OUT DEAD SHOOTS during DRY conditions (and remove shoots) to reduce disease spread. Disinfect pruning shears between each cut (e.g. rubbing alcohol, other sterilants) to reduce disease spread. Pruning is not suggested once new growth appears, as it will help spread this disease. Where cankers are found, copper and Dithane are registered to protect emerging new growth this spring and again in late summer.  [Juniper tip blight caused by Phomopsis sporulates in early spring whereas that cause by Kabatina sporulates in late summer. ]

Dothistroma needle blight (

Dothistroma needle blight is a fungal disease affecting pines (Austrian, mugo).  The fungus overwinters on infected needles and will sporulate during wet weather.  Persistant cool, wet weather favours disease development.  Where infestations are affecting plant health, protect emerging needles with fungicides (copper, daconil) until they are fully grown.





About Jen Llewellyn

OMAFRA Nursery and Landscape Specialist @onnurserycrops
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