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Garden Help Desk: Greater peachtree borers are the pits

By Usu Extension - | Apr 11, 2021
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Feeding by the Greater peachtree borer can cause severe damage to the trunks of stone fruit trees, especially peaches and apricots. If the damage is extensive, the tree can be girdled and killed. Stone fruit trees may need protective trunk sprays every year to prevent borer damage.

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Even when it doesn't seem extensive, damage by the Greater peachtree borer will affect the health, vigor and productivity of your stone fruit trees. Annual protective sprays will help to prevent damage.

Question: I have young peach trees with borers. I understand there isn’t a good way to get rid of them except to dig them out from under the bark, but that seems pretty damaging. All the systemics I’ve seen say they can’t be used on fruiting plants, but could I use a systemic then just remove all fruit for that year? Any other options?

There are a couple of reasons why you don’t want to apply a systemic soil drench to your trees.

First, you can’t legally apply the systemic products you’ve been looking at to your fruit trees if the labels on the products tell you not to do it. The label is the law when it comes to pesticides.

More importantly, the systemic insecticides you’re looking at won’t be effective for the Greater peachtree borer, which is a clearwing moth. There are a few products that can be used after bloom, but they aren’t effective for this pest. You’d be putting a pesticide out into the environment, but not getting the results you hoped for.

Are you sure the problem is the Greater peachtree borer? The moths lay their eggs near the base of stone fruit trunks or on nearby soil, and the larvae tunnel through the bark and feed on the cambium. If you’re seeing oozing or gumming on the trunk more than 12 inches or so above the soil line, the Greater Peachtree borer isn’t the problem.

Once peach tree borer eggs hatch the larvae tunnel through the bark to feed on the cambium layer beneath the bark. They’ll pupate the following spring and emerge as adult moths in mid-summer.

Greater peachtree borers are hard to deal with reliably once the larvae are in the tree. You can try to dig it out, but that can damage a young tree. You could also try pushing a wire into a borer hole to see if you can kill the larva. If you remove a few inches of soil around the base of the tree you might expose larvae just below the soil line and remove them.

The most important thing you can do is prevent larvae from getting into your trees to begin with. To do that, you’ll need to apply protective sprays on the lower trunk and soil every year. Begin about the third week of June and reapply the spray as often as needed to keep the trunk protected through September. There are effective conventional and organic products available.

Keep vegetation like lawn, ornamental ground covers, bedding plants, etc. away from the trunk of the tree. The Greater peachtree borer prefers a dark, moist environment for egg-laying and keeping the area around the trunk clear will make your trees less attractive to the moths.

While planting garlic around the tree is a popular recommendation on the internet, research has not shown this to be a reliable control for these borers. Sprinkling moth balls or moth crystals around the tree is another common piece of advice, but the practice isn’t safe and has limited benefit.

Question: Why is my lawn so bumpy? It gets a little worse every year. How can I get rid of night crawlers in my yard? They are huge and they leave mounds that make my grass uneven.

Earthworm activity is just one reason lawns can get bumpy. Age, increasing shade or insect damage can cause lawns to thin out and feel lumpy. Repeated freezing and thawing during the winter can cause soil heaving and unevenness in lawns.

Nightcrawlers (earthworms) are generally beneficial and it’s best to tolerate their activity if you can. They aerate the soil, recycle nutrients as they feed on thatch and other plant materials and fertilize the soil with their castings. When earthworm populations are high, though, their castings can cause bumpiness in the lawn, but there are some things you can do to improve the problem.

Water more deeply but less often. Frequent watering is a very common cause of earthworm problems in lawns. Earthworms will stay closer to the surface of the soil for air if the soil is too moist. Spending more time near the soil surface means more castings to cause lumpiness in the lawn.

Provide adequate, but not excessive, fertilizer for your lawn, and mow at about 3 inches tall to improve the density of your lawn. A nice, thick lawn will cushion the bumps that earthworms are leaving.

Reduce thatch by aerating your lawn. This will reduce the earthworm population. Lightly rolling your lawn may improve things a little, but don’t use a heavy roller, as that can cause soil compaction and other problems.

There aren’t any chemicals registered for earthworm control and since earthworms provide so many beneficial environmental services for our lawns it’s best to manage them with good lawn care.


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