Family Plot

Scale

Scales are one of the most destructive insects on plants. TSU Extension Specialist Amy Dismukes talks about hard and soft scale and how to treat infestations on your plants.

Hard scale feeds on the very outside of the phloem layer of the plant so it is difficult to control with a systemic insecticide. They need to be controlled in the juvenile stage with horticultural oils or insect growth regulators like Talus. There are multiple generations of hard scale each year, but the best time to control them is in early spring when the crawlers are active. If you have a limited infestation, you can prune out and dispose of the problem branches.

Soft scales feed deeper in the phloem layer and suck more sap that they can use. Because they have more sap passing through them, they can be effectively controlled by systemic insecticides like Imidacloprid or Dinotefuran. They also only have one generation per year. Soft scale produce honeydew which provides a surface for fungus to grow. This fungus is called sooty mold and creates a black layer on leaves, patios, sidewalks, and cars that are under plants infested with sap-sucking insects like scale.

Related Videos:
What do I do about the scales on my euonymus
Treating Crape Myrtle Bark Scale

Related Resources:
Armored (Hard) Scale - Trees and Shrubs
Soft Scales

October 17, 2020

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Viewer Questions

What kind of tree is this? Most limbs are dying or dead. What can
we do?

This is either a blue spruce or Colorado spruce. Certified Arborist Wes Hopper says spruce trees commonly get rhizosphaera needle cast or cytospora canker which are both fungal infections. The problems appear when the trees get stressed. The fungus can be treated with a fungicide. Also, Wes recommends keeping the tree watered and fertilized with a low nitrogen fertilizer. This is a northern tree and growing outside its natural habitat will be a cause of stress. >>Watch

This unusual leaf is on a very large Magnolia. What is it?

This is something that is very rare. Certified Arborist Wes Hopper had to dig to find some answers. This is either auxiliary or median prolification. This is the same thing that happens in bell peppers when a small pepper grows inside another pepper. >>Watch

This summer I've noticed wood dust on our hickory tree. What could be causing this?

This tree is probably infested with ambrosia borers. Certified Arborist Wes Hopper says this type of ambrosia borer only attacks trees that are diseased, dying or severely stressed. The borers are boring through the vascular tissue of the tree which is cutting off nutrients. They are also creating a fungal garden with ambrosia fungus inside the tree. His advice is to hire a certified arborist to spray the tree with a permethrin insecticide. >>Watch

My sumac trees are too tall. When should I cut back my sumac trees?

Once the tree has gone dormant for the winter you can cut them. Certified Arborist Wes Hopper says the nutrients will have been stored in the roots for the winter and the trees will come back from the ground in spring. He also recommends pruning them after they bloom to keep them a manageable size. >>Watch

I planted a sweet cherry fruit tree and the leaves are curling. What is going on?

This is probably cherry leaf scorch. Certified Arborist Wes Hopper says you should fertilize the tree in late fall. UT Extension Agent Chris Cooper says you should rake up and dispose of the leaves in the fall to reduce disease pressure next year. >>Watch