Magnolia Scale, the plague of the landscape


Magnolia Scale is just rampant this year again.  And to make matters worse, there seems to be two developmental groups of them, a smaller subset about 3 weeks behind the older ones (see photo above).  This means a second set of insecticide applications (e.g. insecticidal soap, hort oil, or traditional insecticides) if you are trying to manage this pest.  Magnolia scale females will be laying eggs soon, in the next week or so.


Pick off Magnolia scale female to uncover newly hatched crawlers hiding underneath (early August, J. Llewellyn)

Pick off scales to reveal dark grey eggs and crawlers (eggs with legs) underneath. A week or so later, you will see eggs are hatching into crawlers.  But many crawlers will hide underneath the female scales for days before they venture out, meaning they are protected from insecticide applications.

CroppedMagScaleCrawlersUnderShellComp The crawlers will gradually emerge out from under the dead female mothers. Contact insecticides (traditional insecticides, insecticidal soap, horticultural oil) can be used to manage crawlers once they emerge and start feeding on twigs (mid-late August).

If you miss the Magnolia scale crawlers, don’t worry.  They overwinter as tiny, dark grey nymphs on the undersides of twigs.  It is advisable to go in with a fall dormant oil sprays (with emphasis on contacting undersides of twigs) to significantly reduce the population in October.  Many horticulturalists say that fall dormant oil applications are the BEST way to manage this pest issue.  But your clients may have other ideas.

Plant Phenology indicators this week. 

Solidago canadensis in early bloom; Sorbus aucuparia with fruits turning orange; Hydrangea paniculata ‘Grandiflora’ and Hibiscus syriacus (full bloom). This puts us at 900-1100 GDD Base 10oC depending on location.

OMAFRA Publication 840, Crop Protection Guide for Nursery and Landscape Plants  can be found at:   It 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. 

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

  IMG_3293_01 2016 OMAF publication 840, Crop Protection Guide for Nursery and Landscape Plants, has now been posted to the website. It contains important information on managing nursery and landscape pests and weeds.  Save it on your mobile device!  Print it and have it in your vehicle!  To view the pdf, click here:


Are you seeing webbing around the ends of branches on deciduous trees such as ash, birch, walnut and cherry?  Look inside the webbing and look for yellow, fuzzy caterpillars.  These are fall webworm caterpillars and they usually start to become more noticeable on the ends of branches this time of year.  Prune out nests and destroy them to prevent future generations from infesting your trees.  Pole loppers are an awesome tool for managing fall webworm caterpillar nests!  Spot spraying with B.t. may be effective.

Have white grubs been an issue in your nursery?  Preventative applications of Acelepryn are registered to help protect nursery crops from this pest and they are effective any time the larval stage is present in the root zone. Intercept applications should be finishing up by now.  [Beneficial nematode applications for white grubs (e.g. European chafer) are not effective at this time].

Japanese beetle adults are flying and feeding on leaves of woody plants (Syringa, Tilia, Ulmus, Prunus, Rosa).  Look for metallic, coppery-green beetles with white tufts of hairs along the edge of their abdomens.  Populations aren’t that bad this year actually, but there are some hot spots so careful monitoring is required.

Japanese Beetle Mating Pair Japanese Beetle Feeding on Leaf

Adulticide insecticides for JB in the nursery include Sevin XLR and Thionex.  Pheromone traps for JB are actually too good at attracting the adults.  Always place traps far AWAY (I mean away!) from susceptible host trees and shrubs (e.g. Rosa, Prunus, Tilia, Syringa, Ulmus etc.).


 PM Syringa

We have seen tons of powdery mildew on deciduous flowering shrubs (Amelanchier, Rosa, Physocarpus) and herbaceous perennials.  Monitor for white, powdery residue on the tops and bottoms of leaves.  Protect new foliage with fungicide applications [e.g. Switch, Milstop, Regalia (biofungicide), Tivano] but where the disease pressure is moderate to high, fungicides are not going to be effective. It is getting a bit late in the season for managing this disease.  Powdery mildew ovewinters on fallen foliage, blow foliage out of gardens, collect and dispose to minimize disease next year. 

<a href="/clm/species/teranychus_urticae"><em>Teranychus urticae</em></a> (Two-spotted Spider Mite).

What a year for TSSM!  Two-spotted spider mites (TSSM) are feeding  on several types of deciduous woody (Viburnum and Spiraea and many deciduous flowering shrubs and perennials in container production). Look for chlorotic leaves with stippling, use your hand lens to see tiny, clear bodied mites with dark regions (may be faint black) on their backs. These mites are small but the damage is significant so catch them early.  Miticides registered for this mite in the greenhouse include: Sanmite, Vendex, Kanemite, Floramite, Avid.  Apollo is registered in outdoor nursery crops to knock down the egg stage and newly hatched nymphs.  In the greenhouse, biocontrol agents should be brought in to coincide with the first sign of TSSM.  Phytoseiulus persimilis is a predatory mite that feeds on TSSM when temperatures are below 26oC and it is a good choice when TSSM populations are low-moderate.  Amblyseius californicus is a predatory mite that can be brought in ahead of TSSM appearance (because it can find other sources of food).  Stethorus punctillium is a new beetle that is a good predator of TSSM.


Two-spotted spider Mite damage on Amelanchier (serviceberry).  BRUTAL

There are lots of mites feeding on deciduous trees, Ulmus, Fagus, Quercus, Malus and shrubs (Amelanchier, Rosa, Spirea etc.). Usually damage this time of year is inconsequential for tree health.


Mites on Ulmus, leaf underside



Taxus or Fletcher Scale NYMPHS have settled on needles and twigs and are feeding.   As they become older, they are more difficult to kill with insecticides.  Several contact and systemic insecticides are registered for this pest in the nursery.

black vine weevil RumexBVW1Monitor for black vine weevil ADULTS in the FIELD and LANDSCAPE for Rhododendron, Taxus, Thuja and Euonymus.  It’s too late for applications of nematodes in the field/landscape.Strawberry root weevil can also be a problem in field production of evergreens, adults have emerged.  Signs of strawberry root weevil adults include brown, flagging shoot tips (and small girdling marks at the base of the flagged shoot) on Thuja (eastern white cedar).  To scout for adult weevils, place a tarp or large piece of card board under the tree, shake branches vigorously and look for brown-black weevils “playing dead”.  Insecticides for adult weevils in the nursery include Pounce, Sevin and Thiodan.  Remember, adult weevils feed at night.  Spray insecticides in late evening to target adults and reduce UV degradation (e.g. Pounce, Scimitar).  


Cedar leaf miner (CLM) next generation larvae are starting to hatch and feed on tender new foliage.  A light sheering of tips in mid-late August should give good knockdown of this next generation of CLM larvae.  Cygon is also registered as a foliar application for CLM larvae in early August in the nursery.


Spruce Spider Mite Black KT-2 Monitor for nymphs and adults of spruce spider mite on conifers with a history of mite damage.  Spruce spider mite nymphs and adults are brown with black backs and found on new foliage this time of year.  Click HERE for a short video.  Miticides registered for SSM include Floramite and Kanemite.  Miticides may be required where pest pressure is moderate to heavy (container grown conifers with overhead irrigation).  Populations in field production and in the landscape are usually not very active until the cooler weather returns in September.


About Jen Llewellyn

OMAFRA Nursery and Landscape Specialist @onnurserycrops
This entry was posted in IPM, Weekly Nursery Landscape Report and tagged , , , , , . Bookmark the permalink.

1 Response to Magnolia Scale, the plague of the landscape

  1. Pingback: Magnola Scale Active Now - Toronto Master Gardeners

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