Home & Garden: Dealing with fruit pests | PostIndependent.com

Home & Garden: Dealing with fruit pests

Curt Swift
Free Press Gardening Columnist
This photo shows evidence of peach tree borer.
Curt Swift |

A pest common to all area peach orchards is also a major problem for anyone with peach, apricot, plums, and cherries growing around their homes and in their gardens. The pest is the peach tree borer, also known as the peach crown borer. The adult is a clear wing moth, a moth that lacks the scales common to the wings of most other moths and butterflies. This moth looks more like a hornet than a moth, but like any moth has feather-like antennae. Wasps have thread-like antennae with a ball on the tip.

The larvae are what cause the problem, eating the roots off any and all Prunus species. This includes the Cistena plum, a common shrub found in home landscapes throughout the valley. This shrub is sold by some dealers as purple leaf sand cherry or bush cherry. Its upright oval growth habit makes it difficult to check to determine if the peach tree borer has invaded its roots. Peach tree borer damage is much easier to determine when you examine peach trees and other stone fruit trees. The black, Vaseline-like gum around the base of the tree is a sure sign your tree is infested by this borer. When the larvae bore through the bark and wood the tree produces a gum that mixes with the feeding excrement produced by the feeding larvae. This blackened gum is characteristic of the peach tree borer, but it is not always evident. I find probing with a finger around the base of stone fruit trees is a quick diagnostic tool. If my finger comes out of the ground coated with a gummy substance I know I’ve found an infestation of this damaging insect.

If you don’t catch the problem soon enough the amount of damage these borers cause can result in the decline and death of the plant. Peaches on a severely damaged tree dry out and hang like mummies on the branches.

Checking the stone fruits in your backyard orchard and landscape is critical to the survival of these plants. If you notice the black, Vaseline-like ooze around your trees and shrubs, treating with moth crystals consisting of Paradichlorobenzene is recommended. Place a layer of these crystals an inch or two out from the trunk and cover with a layer of soil. The crystals should not touch the bark. The fumes produced will fumigate the soil and gum, killing the larvae feeding on the roots. Applying a liquid insecticide at this time is not effective as it cannot penetrate the gum to reach the grub-like inch long larvae.

Another treatment needs to be made in early July and again in early August. Mark your calendar for a treatment on July 1 and Aug. 1 so you don’t forget. A drench of an insecticide such as P-38 or another Permethrin product will help prevent hatching larvae from entering and feeding on the roots. This treatment can be applied with a hand or backpack sprayer or with a bucket or sprinkling can. Be sure to soak the trunk at least eight inches up from the ground and soak the soil.

Organic orchardists often use parasitic nematodes to treat their stone fruit trees. You can buy them on line. Just do a search using Heterorhabditis. Don’t apply nematodes if you are using PDB or an insecticide.

Free Press columnist Dr. Curtis E. Swift is a retired horticulture agent with the Colorado State University Extension. Reach him at Curtis.Swift@alumni.colostate.edu, 970-778-7866 or check out his blog at http://SwiftsGardeningBlog.blogspot.com. He owns Swift Horticultural Consulting and High Altitude Lavender.

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