A question came in this week about scale:
“I have two large tree mallows (grown as shrubs) with a very heavy scale
infestation. A local nursery recommends using a petroleum oil spray. Is
there another effective, greener solution?”
Yes, I can definitely suggest an alternative to petroleum sprays, but first – a little understanding about what scale is:
Scale is an insect, but it looks and behaves more like a mollusk. There are soft bodied and hard bodies scales, which have a shell that travels with it. These insects will almost literally suck the life out of your plants. They can be difficult to get rid of once they appear in large numbers, but there are controls.
Neem Oil – neem is a tree that originates in India. The fruit and seeds are used to extract the oil, which is a wonderful protection against garden pests like scale. It basically coats the leaves and stems of the affected plant and suffocates the insects. You will find products with neem that range in low to high concentrations. The closer you can get to straight neem, the better. Here are a couple of options:
Organic Neem Oil – from Planet Natural – has 70% neem
Concern Garden Defense – has only .9% neem, but is usually in a base of canola oil.
You’ll find other horticultural oils that are food-based instead of petroleum-based products. Garden’s Alive has one as well that I have used on my lemon trees with scale:
Oil Away Insecticidal Spray – uses cotton seed oil as a base.
Here is a really great website that shows you all the different kinds of scale:
and a photo of scale’s natural enemy:
I hope this helps. Thanks for writing in!