Please give me an advice with magnolia scale treatment for a very big tree. Can I spray by myself and what product or I need to call professionals? The house is in Woodbridge.
Thank you for contacting Toronto Master Gardeners about scale on your magnolia tree. Scale has proliferated in Toronto over the past 7 years.
The Ministry of Agriculture, Food and Rural Affairs for Ontario is tracking this pest and says the following to help diagnose the problem:
“Magnolia scales are one of the largest scales in North America. Its primary hosts are Magnolia acuminata (cucumber tree), M. soulangiana (saucer), and M. stellata (star). The mature female is about 12.5 mm long, oval convex, smooth, dark brown and covered with a waxy bloom. It overwinters as a nymph on one and two-year-old shoots and the crawlers emerge in late August and September. There is only one generation per year. Honeydew and sooty mould on the branches and leaves indicate presence of magnolia scale.” http://omafra.gov.on.ca/english/crops/gardbk/gh-ch6-2ins.htm
The Toronto Master Gardeners’ website has a large amount of information on magnolia scale. Go to www.torontomastergardener.ca. At the top of the home page, you will see the heading Resources. Go there and fill in “magnolia scale” in the ‘find it here’ and the website will take you to questions and answers on scale. https://www.torontomastergardeners.ca/resources/
Late August and September is the time when scale eggs hatch and the nymphs begin crawling. At that time, you can treat the tree with dormant or horticultural oil. This is available at most nurseries. Using a sprayer and following the directions, you may be able to do this yourself (although you say that your tree is very tall). The oil smothers the nymphs, but has no effect on the adults which are covered in a waxy coating. Caution, the oil can burn the leaves.
ONNursery crops blog (from OMAFRA, the Ontario Ministry of Agriculture and Food) advises that a fall dormant oil spray (with emphasis on contacting undersides of twigs) can significantly reduce the nymph population in October. In fact, many horticulturalists say that fall dormant oil applications are the best way to manage this pest issue. https://onnurserycrops.com/2016/08/03/magnolia-scale-the-plague-of-the-landscape/
In early spring, before the leaves bud, horticultural oil can also be used effectively. By following the same directions, and being aware that the day and night temperatures must be above freezing, and no rain or high winds are in the forecast, spraying the overwintering nymphs will smother them. As there are no leaves yet, the risk of burn is minimal.
Another method which is less messy can be done now (mid summer). Use a strong blast of water from your hose to knock the magnolia scale off. At this point in their life cycle, they don’t have legs, and can’t crawl back into the tree. Take care to aim the spry to hit the bark, and avoid blowing off the leaves and flower buds. You may want to cover the area below the tree with plastic sheet to collect the scale and protect the plants below.
Another, albeit tedious, solution is to wear gloves, and perhaps a raincoat, and pick off the scale off the leaves.
Finally, if the infestation is large or the tree is big enough that you cannot do the job yourself, it may be the time to call in a professional arborist. You can find a certified arborist close to you on the Landscape Ontario site: https://landscapeontario.com/
Here is a link to our Ornamental Shrubs for Various Light Conditions: A Toronto Master Gardeners Guide, which will also be helpful: https://www.torontomastergardeners.ca/gardeningguides/ornamental-shrubs-for-sun-a-toronto-master-gardeners-guide/
Lastly, you may consider Integrated Pest Management (IPM) as an approach to gardening. This is where different methods of control are selected and used in combination, in order to treat plant problems effectively and in an environmentally responsible manner. This approach can be used in the care of ornamental shrubs. More information on this strategy can be found in this Master Gardeners Guide: https://www.torontomastergardeners.ca/gardeningguides/integrated-pest-management-a-toronto-master-gardeners-guide/
Good luck with treating the scale on your magnolia.