Homegrown, Honeycrisp apple trees

I wanted to know if honeycrisp apple trees grow in your locale, or is it too warm? I saw they need 800 chilling hours.

— Bev

Honeycrisp apples will grow in this area. If fact, they’re grown commercially in western Colorado.

One thing about this variety is that it ripens best in cooler areas.

I don’t know how many are being grown in the Grand Valley. I do know that it’s grown at higher elevations around Cedaredge and the North Fork Valley.

This doesn’t mean it won’t grow down here; it’s just that the apple’s flavor is developed best when it’s cooler.

I have four Carpathian walnut trees that have started to bear. Last year, I had a problem with the walnut husk fly. While the nuts were edible, they do not come out of the husk like they are supposed to. It seems that the fly emerged in late July or early August. Can you tell me when to spray and how often? Will the yellow sticky traps I use for the cherry trees work for the walnut husk fly?

— John

Walnut husk fly is a fairly common problem here in western Colorado. This insect is closely related to the western cherry fruit fly that has become widespread in the area.

Its life cycles are a bit different because of the different ripening seasons of its target fruit.

The female walnut husk fly deposits eggs below the surface of the husk of the developing fruit in early summer. These eggs hatch into small white maggots, feeding inside the husk. The skin of the husk usually remains intact, but the fleshy interior begins to decay.

Most backyard gardeners don’t do anything to control this pest because it rarely affects the meat inside of the nut. The damage is usually limited to staining of the shell and, as you mentioned, the husk is difficult to remove.

You can get around this by putting the damaged nuts into a damp burlap bag for a few days to soften the husks, making them easier to remove.

As the maggots mature in mid- to late summer, they drop to the ground to pupate in the soil where they’ll spend the winter to emerge as adult flies next year. There is only one generation per year.

If you want to try to control them, the strategy is to spray in the summer to control the adult flies before the female has a chance to lay eggs.

A number of insecticides will give good control, but I’d recommend Malathion, Spinosad or Permethrin.

You’ll want to spray multiple times during the summer. Plan on spraying every seven to 10 days starting the first of July and going through August.

If you elect to spray, you’ll have to mix the insecticide with an attractant bait. This will help the insecticide last longer and will greatly enhance your control efforts.

There are baits available, but they’re usually only available in large quantities for the commercial grower. Your best bet is to mix 4–6 tablespoons of molasses per gallon of spray.

In addition to spraying, there are a couple of cultural practices that will help reduce their numbers. It won’t eliminate the problem, but it should help.

First, place infested husks into a tightly sealed plastic bag for disposal so the maggots don’t have a chance to pupate.

The second thing is to spread a tarp under the tree from the first of July to the first of September to prevent the maggots from entering the soil to pupate.

Dennis Hill is the nursery manager at Bookcliff Gardens, online at www. bookcliffgardens.com. Send questions to Bookcliff Gardens, 755 26 Road, Grand Junction 81506; or e-mail info@bookcliff gardens.com.


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