A Few Pests Out There

The rain has stopped for now, but a chance of showers are still in the forecast for much of southern Ontario.  Even if its not raining, a few minutes of working outside and it will feel like it is :0

Annuals love this weather and they are going to just EXPLODE in growth this week!

But so are the WEEDS.  And some diseases and insects.  Ugh.


Arboriculture and Landscape Professionals:  ISA Workshop: “IPM in the Woody Landscape”.  Thursday, July 2 at the University of Guelph Arboretum Centre.  Come spend the day learning about current pests and physiological problems on trees and shrubs.  There is a special session on soils, tailored especially for arborists.  This workshop will be delivered through lecture and field tours of the University of Guelph Arboretum. IPM in the Woody Landscape will be led by OMAFRA’s Jen Llewellyn and Christoph Kessel. CEU’s are available!  To register, contact Kathleen at ISA Ontario at 1-888-463-2316 orinfo@isaontario.com

For Plant Phenology Indicators this week,  the Syringa reticulata (Japanese tree lilac) are in mid bloom, Catalpa speciosa (northern Catalpa) in early bloom, the Viburnum dentatum are in late bloom, the and the Weigela florida are in  late bloom. This puts us at about 350-450 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.

PLEASE NOTE: The Following Pesticide Recommendations are meant for Exception Uses (e.g. agriculture) 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 plants that was previously found in publication 383. Publication 840 is a .pdf file, accessible online and on cd.

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.

Picture7compWhere a second flush of new growth is emerging on nursery container grown Euonymus fortunei, now is the time to protect that new growth against Euonymus anthracnose with fungicides.  Euonymus anthracnose (Colletotrichum gloeosporioides) appears as a leaf spot and a grey, velvety stem canker that causes twig dieback (see photos above).   Infection and spread can be very successful during warm, humid conditions.  Where there is a history of disease in the crop, protect new growth with Daconil, rotating with a combo of Dithane and Copper.  The risk of disease is especially high during rainy weather or where crops are irrigated overhead in the late afternoon or night time hours (long leaf wetness periods).  Growers who have been able to limit overhead irrigation to post-sunrise morning have noticed a significant decrease in this disease.


Careful not to confuse Low Temperature Injury (above) with Euonymus anthracnose leaf spot and stem canker.  If you were to examine the stem below the brown foliage, you would see absolutely no sign of stem canker here.


Powdery mildews are starting to show up on deciduous flowering shrubs (Amelanchier, Rosa), perennials and trees (Quercus, Acer, Platanus). Monitor for white, powdery residue on the tops (and bottoms) of leaves.  Protect healthy foliage with fungicide applications (e.g. Switch, Milstop, Regalia (biological) and Tivano) where the history of disease pressure is moderate to high.  Other traditional fungicides include Banner, Copper, Nova and sulphur.  In its early stages, powdery mildew can be confused with hard water spots and pesticide residues on foliage. If you are still unsure, get out your hand lens and look for powdery, wooly, raised fungal growth for powdery mildew. Dried residue from hard water looks like tiny, white crystals on the surface.

Japanese Beetle Feeding on Leaf Have white grubs been an issue in your nursery?  Preventative applications of Intercept (imidacloprid) and Acelepryn (chlorantraniliprole) are registered for white grubs (nursery production) and the best time to apply control products is during the adult flight period (which should be starting in the next week or so).  Adult Japanese Beetles will be flying soon.  To help qualify for the Japanese beetle certification program, an application of insecticide on nursery stock can be made.  Beneficial nematode applications for white grubs (e.g. European chafer) are not effective at this time.

<a href="/clm/species/empoasca_fabae"><em>Empoasca fabae</em></a> (Potato Leafhopper) nymph.

Potato leafhopper nymphs can be found feeding on juvenile nursery stock in production nurseries.  Leafhopper nymphs are very tiny, green and hide on leaf undersides next to veins.  You’ll need a hand lens to see them.  The do not fly and are susceptible to insecticides (Sevin XLR, Pounce, Intercept) at this time. Leaf injury looks like brown-black necrosis with leaf distortion and stunting.  Injury often resembles disease or low temperature injury.

EAB adults casting shadows on leaves (Markham)

Injectable insecticides may be used to protect ash 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 , Imi-jet and Tree-Azin.  Check out the Management Strategy for Emerald Ash Borer and Bronze Birch Borer.   Emerald ash borer adults start to emerge when the black locust (Robinia pseudoacacia) are blooming.

WhPineWeevilCrossSectLarvaeDiebackTerminalColSpruce                     Look for crooked, wilting and browning terminal shoots on pine and spruce, it could be boring larvae from white pine weevil.  Where 2015 terminals are wilting, slice into bark of 2014 terminals and look for tiny, fat, white, legless grubs feeding under the bark.  Insecticide control is too late at this point, prune out and destroy all symptomatic terminals and train a new leader.  DO NOT LEAVE CLIPPINGS ON THE GROUND.


Look for 2015 needles turning straw-brown as a sign of early instar sawfly feeding damage.  Look for tiny larvae of  Yellow-headed spruce sawfly feeding on tender new needles of spruce (e.g. Colorado spruce).  Larvae are green with lighter longitudinal stripes, yellow-brown heads.  As larvae get bigger, they consume entire needles and can cause significant defoliation.  2014 sawfly damage will be quite obvious where populations were significant last year.  There are several insecticides registered including Dragnet, Dylox, Pounce and Success to target young larvae.  This is a damaging pest of spruce in the GTA and has caused significant damage to spruce trees.

<a href="/clm/species/synanthedon_exitiosa"><em>Synanthedon exitiosa</em></a> (Peachtree Borer) adult male.   <a href="/clm/species/synanthedon_exitiosa"><em>Synanthedon exitiosa</em></a> (Peachtree Borer) larva.       Peach tree borer (Synanthedon exitosa) adults are flying for the next few weeks. Look for cankered regions and chewed bark/wood in the lower stems of Prunus (Prunus x cistena) as a sign of larval damage.  The clearwing moths that emerge resemble wasps.  Adults are very much attracted to sticky wing traps that are baited with peach tree borer pheromones. Place pheromone traps out in early-mid June (‘Red Prince’ Weigela in full bloom) and monitor for peak flight of adults.  You can expect peak egg hatch around 10-14 days later, if you are thinking of treating newly-hatched larvae (stem treatment Thionex).  The same ‘clearwing moth’ pheromones and traps can be used to monitor for Viburnum borer.  Viburnum borer chews the stem (at and below the soil line) and causes significant injury to container grown Viburnum.  Viburnum borer will be starting to emerge in container production at this time.  To purchase traps, try ordering from IPM suppliers such as www.greatlakesipm.com andwww.naturalinsectcontrol.com.   Some growers are trying soil drench applications of beneficial nematodes (Steinernema carpocapsae) after peak adult flight, as a biological way to suppress hatching larvae.

image0009image0010    The first generation of Euonymus scale crawlers have hatched in container production and will be in the field and landscape very soon.  Euonymus scale look like tiny white flecks (males) and tiny brown sea shells (females) along twigs and the undersides of leaves.  Look for bright, orange crawlers around populations of adults and on the undersides of leaves and twigs. Where insecticide applications are warranted, multiple applications may be required to get good knockdown since crawler emergence is staggered over a few weeks.  Try insecticidal soap and the summer rate of horticultural oil.

About Jen Llewellyn

OMAFRA Nursery and Landscape Specialist @onnurserycrops
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