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 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 ( 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.