Jumping for Joy in the Foliage (June 8)


What a spring for cankerworms!  A few species of cankerworms (Geometrids) can be found feeding on trees and shrubs in the landscape and nursery.  The greater Hamilton area is seeing significant populations of Fall Cankerworm, pale-green larvae that move like inchworms.  All of these larvae are susceptible to insecticides.  Those products that contain the biological Bacillus thuringiensis (B.t.) will take a good 3 days before larvae stop to feed and die. (Above Photo: Lauren Stitt, Landscape Ontario Nursery Scout).  Lower photo: fall cankerworm (D. Cheung)

<a href="/clm/species/alsophila_pometaria"><em>Alsophila pometaria</em></a> (Fall Cankerworm) larva.

Plant Phenology indicators this week, Hamilton/Niagara/GTA/London (275-350) GDD Base 10C)

  1. Catalpa speciosa (northern catalpa, early bloom)
  2. Cornus alternifolia (pagoda dogwood, late bloom)
  3. Kolkwitzia amabalis (beautybush, full bloom)
  4. Robinia pseudoacacia (black locust, full to late bloom)
  5. Sorbus aucuparia (early to mid bloom)
  6. Spirea nipponica (snowmound spirea, late bloom)
  7. Syringa reticulata (Japanese tree lilac, early bloom)
  8. Viburnum opulus, Viburnum trilobum (snowball vibunum, highbush cranberry viburnum, full to late 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 Table 2-3 on pg. 39.

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:  www.nurserytracker.com.  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.



Where dogwood (Cornus spp.) has had issues with leafspots (e.g. Septoria) in the past, protect emerging foliage with fungicides before precipitation or irrigation events.  Leafspots are often circular or angular with a bright purple border, making shrubs look unsightly by early summer.  In some cases, bacteria may also be associated with the lesions.  We are conducting a survey on Cornus leaf spots this year to help identify the various causal agents.  Susceptible species include Cornus alternifolia, C. stolonifera, C. alba.  [This disease is more of an issue in container production.]   


The recent hot, dry weather has been perfect for powdery mildew development and we are starting to see the beginning of it in some deciduous flowering shrubs and trees (Rosa, Amelanchier, Quercus robur, and Hydrangea).


If you look with your hand lens you will be able to see the powdery looking strands of the fungal mycelium.  This is a sure sign of powdery mildew.  Where powdery mildew has been a problem in the past, protect healthy foliage with fungicides such as Compass, Milstop, Nova, Palladium, Rhapsody (biological) and Switch.  Ensure that foliage is dry going into the evening hours as overnight leaf wetness periods lead to heavy spore production for powdery mildew.


Gymnosporangium rusts are starting to show up on Rosaceous hosts (Malus, Pyrus, Crataegus, Amelanchier) in the southwestern end of the province.  Gymnosporangium rusts are responsible for cedar-apple, cedar-hawthorn, quince and pear trellis rust.  The fungus overwinter in galls of the alternate hosts, Juniperus.  Like 2015, we had such a dry May this year that they didn’t start sporulating until just over a week ago.  Protect Rosaceous hosts with fungicides (Banner, Nova) before the next rain/irrigation and about 7-9 days after that to help reduce lesions on rosaceous plants.


Bacterial leaf spot diseases can be a real issue on ornamentals after periods of high temperatures couple with high humidity.  Last week’s weather were the PERFECT CONDITIONS that support bacterial leaf spots!  Bacterial leaf spots often are very vein-limited.  Leaf veins will outline the margin of the spots, making them appear the way farm fields do from a low altitude airplane.  Protect emerging growth with bactericidal sprays, such as Copper, Kasumin and suppression using the biologicals Serenade/Rhapsody and Regalia Maxx.  There are several susceptible crops but we often see bacterial leaf spot on Acer, Hydrangea, Viburnum etc.


Left: Healthy; Middle: Rhizosphaera Right: Stigmina (K. Thurston, OMAFRA)

Where new foliage has not hardened off yet, monitor for needlecast and blight diseases on conifers in the area.  Diplodia tip blight on 2 and 3 needled pines and Rhizosphaera needlecast and Stigmina on blue Colorado spruce are our most common needlecast diseases in Ontario.  Diplodia tip blight appears as brown, stunted needles at the tips of branches.  Rhizosphaera appears as brown-purplish needles from the previous year’s growth, symptomatic needles begin to drop in late spring.  Stigmina appears on green and chlorotic needles, but doesn’t always lead to needle drop.  To confirm it is Rhizosphaera, look at the undersides of the needles.  Those little white dots (stomata) will turn black and the black spots will protrude during sporulation.  New, soft growth is especially susceptible to foliar diseases, but infection may also take place later in the season (we don’t know).  Where there is a history of damage, treat with registered fungicides (copper oxychloride, Banner Maxx, Daconil) as buds start to open and protect new foliage.  Apply fungicides prior to precipitation events (spore dispersal).  Unfortunately, most of these blights and needlecasts can be found sporulating for much of the year..



Are you seeing stunted, distorted leaves on Malus?  It could be thrips.  Uncoil foliage and examine closely with hand lens or dissecting microscope for thrips.  I think thrips are causing some damage on deciduous trees in nursery production that is doing undiagnosed because they feed only on newly emerging buds.


Thrips are tiny, cylindrical insects with narrow ends (this is a magnified photo under the dissecting microscope).  They can bend their body in right angles as they turn quickly on foliage trying to get away from the sunlight.  This species could be Pear thrips.  Insecticides for thrips include Success or Beleaf, Deltaguard, Pyrate, Kontos where thrips are still present.

<a href="/clm/species/synanthedon_exitiosa"><em>Synanthedon exitiosa</em></a> (Peachtree Borer) adult male.

Several species of Prunus (e.g. Prunus x cistena, P. serotina) are susceptible to the Greater Peachtree Borer (Synanthedon exitosa).  Continue to place out peachtree borer pheromone-baited sticky wing traps out in the nursery for the next few weeks.  Hang traps on NON-PRUNUS crops and hedgerows to attract Male Peachtree borer moths away from susceptible Prunus (cherry) crops.  Scrape off moths each week, count and reapply tanglefoot.  The males will get stuck in the sticky trap and will be unable to fulfill their *destiny*.  Meaning less PTB borers next year.   Pheromones and sticky wing traps are available from several suppliers, including Natural Insect Control.


The black locust are blooming and that means Emerald ash borer adults have emerged. 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, 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.

Potato leafhopper NYMPHS and ADULTS are feeding on woody nursery stock in the NURSERY.   Monitor for potato leafhopper on nursery crops such as Acer (platanoides, saccharum), Quercus and Ostrya.  Adults will fly away quickly but nymphs are about 2 mm long and scuttle SIDEWAYS, rather quickly, across the leaf and to the other side (they don’t have wings). Susceptible crops are those that are flushing new leaves (leafhopper’s favourite food source).  Older, hardened off foliage is not usually as susceptible.  Leafhoppers (and aphids) suck plant sap from soft, expanding foliage and cause foliage and stems/petioles to wilt, turn brown/black (‘Hopper Burn”) and become stunted and malformed.


Older, hardened off foliage will become flecked from potato leafhopper feeding but younger foliage is more severely damaged.  Monitor populations and treat where new foliage is emerging. Leafhoppers are also attracted to yellow sticky cards, for monitoring.  Registered insecticides include Tristar and Sevin XLR.

whiteGrubClose                                     Have white grubs (e.g. European chafer, June beetle) or Japanese Beetle phytosanitary restrictions been an issue at your nursery?  Preventative applications of Intercept (imidacloprid) and Acelepryn (chlorantraniliprole) are registered for white grubs in nursery production and the application period will begin soon.  Japanese beetle adults usually start to show up mid – late June in southern Ontario.  Apply preventative soil drench applications for JB at the beginning of the adult flight period, usually when the Tilia cordata start to bloom you can monitor for them.

<a href="/clm/species/otiorhynchus_sulcatus"><em>Otiorhynchus sulcatus</em></a> (Black Vine Weevil) adult.               In production nurseries where black vine weevil are a problem in container crops (e.g. perennials, evergreens), monitor crops for adults.  Adults will chew semi-circle notches out of leaf margins.  Adults hide in dark, damp places during the day (e.g. under pots, under pot rims, other crevices). Some smart growers place out wet boards for weevils to hide under or bang pots to free weevils hiding under container lip…..so adults can be harvested and destroyed.  Adulticides for black vine weevil include: Actara, Scimitar, Sevin.  In August/early September, treat container media of targeted crops with Heterohabditis bacteriophora (H.b.) or Met52.   Met52 can also be applied preventatively at potting.

Strawberry root weevil adults have emerged and are feeding on various evergreen and deciduous hosts in field and container grown ornamentals.  Adulticides for black vine weevil include: Actara, Scimitar, Sevin.

SRW’s will chew notches in small twigs, girdling them and causing the shoots to turn brown.  Look for Strawberry root weevil adults in spruce, eastern white cedar and sometimes in juniper. Feeding from the larval stage is much more damaging but by reducing populations of adults, you can help reduce future populations of larvae.


Fletcher Scaleimage0004

Fletcher scale (Lecanium fletcheri) are developing rapidly this week on Taxus and Thuja.  These scale nymphs are no longer susceptible to insecticides.  These scale insects are starting to produce a lot of honeydew as they are in their heaviest feeding period.  Some are just starting to lay eggs (container production).  Monitor Taxus (yew) and Thuja (eastern white cedar) for crawlers in late June in container production and early July in field/landscape.

Monitor for  nymphs of spruce spider mite on conifers with a history of mite damage (Abies, Picea, Thuja).Spruce spider mites appear as very tiny, brown mites with black backs.  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. Miticides are effective against nymphs and adults.




About Jen Llewellyn

OMAFRA Nursery and Landscape Specialist @onnurserycrops
This entry was posted in Christmas Trees, Insects, IPM, Nursery Production and tagged , . Bookmark the permalink.

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