Margaret Lauterbach

A good year is on tap for fruit, but be on the lookout for destructive pests

It’s the time of year to watch out for codling moths.
It’s the time of year to watch out for codling moths. AP file

This should be a good fruit year for the Treasure Valley, but watch out for codling moths, the parents of the “worms” in apples, pears and sometimes peaches. They’re out laying eggs, and when they hatch, the larvae burrow into the fruit the eggs are deposited on. If you’re new to this area, you should be aware that we also have cherry fruit flies whose larvae develop inside cherries. It gets tricky, trying to control these destructive insects without harming honeybees or bumblebees. Always read the label of any pesticide spray and follow their directions carefully.

A lot of fruit will spontaneously drop this month, but even so, we usually have to manually thin fruit to avoid limb breakage. I didn’t thin enough, two years running, and lost large limbs from my George IV white peach tree. Fruit that large should be at least 6 inches apart. Now, in spite of efforts to repel fruit tree borer by planting chives around the trunk, the tree is dying. Peach tree borer parents are dark, metallic, blue clear-winged moths with an orange band around the abdomen. They sort of look like wasps and they lay eggs at the base of the trunk of stone fruit trees (peach, nectarine, almond, plum and cherry). Their larvae burrow under the exterior bark where they’re shielded from pesticide sprays while they feed in sapwood for a year. If they feed all around the tree, it dies, having had its circulatory system destroyed. They have fed on the north side of my tree, and that’s the side that’s dying. This is the main reason stone fruit trees are short-lived in this area (and any area inhabited by these destructive moths). Since fruit is intended for consumption by humans, we can’t use systemic poisons.

In my garden, beans for dry use are germinating with gaps that need replanting, some failed to germinate, and other gaps are due to critters eating leaves. If plants can grow a bit, they’ll outgrow the destruction caused by earwigs and flea beetles, but if not, replanting works. Later in the season there are so many things for destructive creatures to eat, damage to any one crop is minimized.

Between our copious rains in May, I was able to thickly mulch all 40 indeterminate tomato plants with grass clippings. We don’t use herbicides on our lawn, so our own clippings are safe. I also grow a number of determinate (shorter) tomato plants on top of the raised beds, and I haven’t mulched those yet, partly because I was out of clippings. So far, though, there’s no sign of blight on any of them. Water splashing on soil can infect a plant with blight, so in more blight-prone areas, many gardeners remove low foliage to prevent blight. Compost works without reducing the plant’s fruiting.

We usually don’t have to worry about plant diseases caused by excess moisture or humidity, but this spring was extraordinarily wet. We should be on the lookout now for black spot on roses; fire blight on pears, quince, pyracantha, apples, cotoneaster and even raspberries; and peach leaf curl on peach trees. Fire blight appears as burned parts of a woody shrub or tree, and apple and pear trees are most susceptible. See for fire blight and for black spot.

Another disease attributed to moisture is powdery mildew that may infect ornamentals and plants in the vegetable garden. Good air flow around plants is one guard against this fungus, and so is sun exposure. Do not water foliage in the evening, when water will remain on the foliage during the cooler part of the day. If some powdery mildew shows on part of the plant, remove that part and put it in the trash, not the compost pile. If it’s widespread, it can be controlled with a fungicide such as Neem.

Some folks have controlled it by using hydrogen peroxide (9 parts water to one hydrogen peroxide) or skim milk (50% water to 50% skim or powdered milk). Neither of these homemade remedies is approved by officials, since pesticides must have instructions for use on their label. Some plants such as lilacs can tolerate annual attacks of powdery mildew, but others falter and fail to thrive.

Send garden questions to or Gardening, The Statesman, P.O. Box 40, Boise, ID 83707.