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.

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The Thursday Report – July 21

Environment Canada is calling for very hot and humid weather to continue into this weekend and early next week.  There is a 40-50% chance of precipitation in southern Ontario for tomorrow, with a greater chance of showers on Monday.  The UV index is very high so please take care out there and wear sunscreen, a hat and drink lots of hydrating fluids.

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Research Shows: Some Norway Maple Cultivars Are Not Invasive

Acer platanoides ‘Crimson King’ (

When you consider all of the trees that are grown for street plantings in the urban landscape, you will quickly come to realize that the number of possibilities can be quite small because of poor soil conditions and exposure.  Our streets used to be lined with gorgeous, vase-shaped elms…until Dutch elm disease came along.  The ash tree was a popular and drought resistant species…until emerald ash borer came along. Of course it was a mistake to plant so many of one species (or one cultivar).  We weren’t thinking about how easy we were making it for pests to spread and infest trees along these long, continuous rows.   Continue reading

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July 6 – IPM in the Nursery and Landscape

Soaker hose installation around newly transplanted caliper tree (

Hot, dry conditions continue for much of southern Ontario.  Environment Canada says we’ve had one of the driest Junes on record, since 1991.  This has put a lot of stress on plants and water resources.  Newly planted nursery stock and landscape plants should be watered.  A long, slow, gentle irrigation will help penetrate into the root zone will help reduce transplant stress.  Aim for 25mm of irrigation per week directed to the root zone.  

Irrigating container grown crops to combat high evapotranspiration rates?  Check EC and nutrient analysis of container leachate to see if you’ve got enough nutrients left in your controlled release fertilizer.  Formulations of CRF aren’t lasting as long because of higher release rates and irrigation practices due to hot, dry conditions.  Supplemental fertilizer may be required to prevent nutrient deficiencies on actively growing crops.

Plant Phenology indicators this week: 525-600 GDD Base 10oC) : Catalpa speciosa (late bloom), Syringa reticulata (finishing bloom), Sambucus canadensis (mid bloom), Hydrangea arborescens ‘Grandiflora’ (early bloom), Daucus carota (very Continue reading

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Make Hay While The Sun Shines

MakeHayWhileTheSunShines                                      Great weather for making hay but soil moisture levels in some fields and landscapes are getting low.  The popular trend towards installing drip irrigation in field production nurseries and well maintained landscapes is sure paying off in 2016.    Continue reading

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Japanese Beetle Adults Starting to Emerge

<a href="/clm/species/popillia_japonica"><em>Popillia japonica</em></a> (Japanese Beetle) adult on cedar.                 Japanese Beetle (Popillia japonica) adults are starting to take flight in southern Ontario! Continue reading

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Scale Crawlers are OUT!

One of the most filthiest scale insect pests known to horticulturalists, the Euonymus scale (Unaspis euonymi) is a tiny little armored scale that covets evergreen Euonymus fortunei in the garden or landscape.  Adult females have a dark cover that is wider at the posterior end, sea-shell in appearance with white margins. The smaller males have a white, narrow cover and they resemble white flecks with the naked eye.


The good news is, the crawlers have hatched Continue reading

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