Peach tree is likely suffering from scale

Q: Our young and once healthy peach trees have been appearing less than healthy as the summer has progressed. They are producing fruit, but I first noticed the black things on the bark that I thought were aphids. Looking online, I became aware of peach leaf curl and it appears the trees are afflicted with that. I am hopeful that you can suggest a treatment that will save these trees. This is their second summer and I would hate to lose them. — P.W., Albuquerque

Peach tree is likely suffering from scale

A: From the photos, I can see that the leaves on the peaches are a bit tattered, but it’s those “black things” that look like large drips of black coffee that have me most concerned for the health of your peach trees.

I’m fairly confident that your young peach trees are afflicted with scale. Here’s what I know and what I’ve read about these wicked critters.

First, each one of those black things that look like black coffee drips, is a house for a female scale bug. She sets up house and exudes a goop that hardens into that scale-like covering, keeping her safe from predators. The males show up as wee tiny fly-like looking insects. Variety of scale depending, the females lay a lot of eggs or give birth to several nymphs a day. Remarkable insects, these scale.

As the scale insects “poop” they secrete what’s called honeydew. This is a sweet substance favored by ants and, like aphids, ants will farm the scale to set up new sites on the trees for them to mature and create even more honeydew for the ants to harvest. So do your trees have a lot of ants traveling along the branching or trunks? If so, that’ll be another confirmation to me that these “coffee drips” are scale.

What the scale does is once it sets up house, it sucks on the host, your peach trees, and will eventually wear the tree out energy-wise, especially considering how prolific the scale can be. Not only that, the honeydew attracts another malady called sooty mold. This is a black fungus that thrives on the honeydew and again just wears out the host tree.

Ever notice, here in town, ornamental purple leaf trees that look like it’s been covered with soot? You can, if you’re looking for them, see them in varying states of decline, usually because of the sooty mold.

As soon as the temperatures have lessened to the low 80s and you’ve harvested the peaches, I’ll recommend spraying with a chemical called pyrethrin. Using it will get the nymphs and the males in the winged stage. And it should help eliminate any ants. Make sure to apply when it isn’t so wicked hot and read the product label for guidance.

Now for the females, living snugly under those scale roofs, there are a couple of things you can do. First would be to pop them off with your fingernail. Hold some sort of disposable towel and pop the scale right off. I’ve heard you can use a toothbrush too, but your true goal is to collect them as you’re popping them off. Do try sincerely to not let them fall to the ground. Dump what you collect into a coffee can one-quarter filled with soapy water to ensure the death of the collections. Gross, I know, but get to it sooner rather than later.

Then, as soon as your peaches drop their leaves this fall, spray them with dormant oil. The oil spray suffocates any of the females still living under their scale coverings. I think several sprayings would be best, perhaps monthly through the winter. Be sure to spray the trees, soaked top to bottom, the ground surrounding the trees, trunks and to the tippy-top too.

Next, I will suggest you contact the Bernalillo County Extension Service, 505-243-1386, to make sure I’m guiding you correctly. Perhaps the extension agents would be able to see peach leaf curl if that’s part of what’s bothering your peach trees and I’m not seeing it.

Happy Diggin In while you’re on your scale hunt!

Tracey Fitzgibbon is a certified nurseryman. Send garden-related questions to Digging In, Albuquerque Journal, 7777 Jefferson St. NE, Albuquerque, N.M. 87109, or to features@abqjournal.com.