Magnolia scale

Asked August 31, 2019, 3:00 PM EDT

I have a 5' magnolia ("sue") heavily infested with scale. I would prefer not to use chemical control. I am prepared to spray as often as necessary with horticultural oil - but what is the timing? Can I actually see the "crawlers"? Does it do any good to scrape them off (very satisfying)? There's a lot of advice on line, but I need information specific to Kalamazoo. thank you.

Kalamazoo County Michigan magnolia scale

3 Responses

Timing of horticultural oil sprays is dependent on growing degree days. The Enviro-weather website takes out the guesswork giving you emergence dates. See https://enviroweather.msu.edu/run.php?stn=kzo&mod=l_mli&da1=2&mo1=9&da2=2&mo2=9&... and scroll down to magnolia scale and you will see that the crawlers is Kalamazoo have already emerged on August 20-21. You can scrape them off; however, the female (the big bump) dies after the crawlers emerge. The crawlers are small but you should be able to see them. A 10X magnifying glass may help. Check out the following information:

I hope this is helpful,

thank you for your response. I don't see anything with a magnifying glass, but that could be a user error. Do you recommend hort oil spraying? If so, today and how often? (And in March, as indicated.) The scales are "wet" inside, if that's meaningful. What can I do for the plant itself to help it overcome this onslaught? Any ideas you have are appreciated.

If you scroll down on the first link (https://bygl.osu.edu/node/787) from the previous response you will find a picture titled "Mature Magnolia Scale Female with Crawlers 8/24/2015". This will give you a good sense of the size of the crawlers and what they look like. The hort oil (a refined petroleum product) is a contact insecticide that smothers the crawlers. Insecticidal soap (home mixtures can be harmful) can also work on the crawlers. Usually for a fall application you need to spray at least twice about a week apart once the crawlers have emerged. This should have already happened according to enviro-weather; however, this may change due to a microclimate. The spring application should happen just before bud break. Please read carefully the following link:
The best thing you can do for you Magnolia is to keep it healthy. Stressed trees invite pests.