Homegrown: Pinyon pine, aspen tree saplings

Our pinyon pine has a black pine needle scale for which I spray acephate annually. It was free of the pest all year until now.

My question is: What should I do now? Is the scale still active on the warmer days?

— Paul

Pine needle scale has become a common problem the past several years in the area.

This insect is a problem on Austrian, ponderosa, scotch and mugo pines.

The adult scale is a small black (there’s a species of white needle scale as well) speck on the needle. They form a hard waxy coating that makes them somewhat difficult to control with systemic insecticides.

They suck the sap from the tree, weakening it and causing the needles to brown and fall off.

Left untreated, it will result in a very thin, sad looking tree. Eventually, the scale will kill the tree.

The scale you see are pretty much all adult females and most of them are dead this time of year, but they’ve left a clutch of dozens of eggs that will hatch next spring.

The young scale that hatch out are called crawlers and they lack the hard waxy shell of the adult. Consequently, they’re very susceptible to insecticide sprays and easy to kill at that point.

The trick is timing. The crawlers are active for two or three weeks before they settle down and form that protective shell.

Depending on the weather, crawlers will hatch anywhere from late April to late May.

You can check for the presence of the crawlers by tapping a branch over a sheet of white paper. The tiny crawlers will be a rosy purplish pink color.

Once you see evidence of them, apply several insecticide sprays over the three weeks following emergence. The acephate you have should work well, but so will permethrin, cyfluthrin, All Season Spray Oil, and insecticidal soaps.

An alternative way to control them that doesn’t depend on such careful timing is to apply a dormant oil (similar, but different to the All Season Spray Oil) spray in early March. Be sure to completely and thoroughly cover all the needles of the tree.

In addition, I’d probably plan on applying a couple applications of All Season Spray Oil about the first of May and again about May 20.

To heighten the effectiveness of the All Season Spray Oil, mix some of your acephate with it according to label directions.

Pine needle scale can sometimes produce two generations a year, the second one emerging in mid- to late summer.

Treatment at that time is important in knocking down and keeping down the populations of this little monster. Apply a couple applications of the mixture of All Season Spray Oil and acephate.

I have aspen trees in my lawn, and this year they sprouted perhaps 100 saplings. I also find roses and cottonwoods performing the same magic.

Can these shoots be sprayed with herbicide without damaging the parent plant? What can be done to limit this propagation in the future?

— Doug

Unfortunately, spraying something on the suckers also would hurt the mother tree.

It’s the nature of aspen trees to sucker. Suckering is less common in cottonwoods and roses, but certainly not unheard of.

I usually just cut the suckers off with a shovel, jabbing it into the ground at the base of the sucker and trying to sever the root that the sucker is coming from. It’s a bit of work, but if you keep after it two or three times a year, you’ll keep them down.

Another possibility is to use a product that’s called Sucker Stopper.

It’s a hormone that prevents suckering in many trees.

It’s recommend that you cut off the sucker and spray the cut end. You can do this either in the spring or mid-summer.

It prevents regrowth of the suckers in that area for one season. Unfortunately, you’ll have to do this every year.

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Dennis Hill is the nursery manager at Bookcliff Gardens, http://www.bookcliff gardens.com. Send questions to Bookcliff Gardens, 755 26 Road, Grand Junction 81506; or e-mail .(JavaScript must be enabled to view this email address).


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