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  • Writer's pictureRoman Jefferson

Pests in the Orchard

Updated: Mar 17, 2022

I wanted to talk about two pests I’ve been seeing a lot in the orchard lately. One is called the “Flatheaded Appletree Borer” (FAB). The other is the “Peachtree Borer” (PB).

Both of these insects are wood borers. Meaning they lay their eggs on the bark, the eggs hatch into larvae, and the larvae penetrate into the tree creating galleries and generally wreaking havoc with the tree’s vascular tissue. They usually don’t kill the tree but they severely damage it, and sometimes this leads to the tree’s demise.

The FAB is a beetle with a flat head. This means when it eventually pupates and decides to exit the tree it leaves behind a D shaped exit hole. The FABs will hit a variety of hosts. In the orchard they will infest apple trees and pear trees. They usually infest young apple trees, especially if the trees are newly planted or stressed in any way. They will bore into the tree around knee height. It is hard to detect them until the damage is done.

When they exit they leave behind a pencil sized, D shaped, exit whole. The bark of the tree is usually discolored around the wound and will eventually flake off. You may also see “frass” around the flaking bark.

Peachtree borer is similar, although it is not a beetle but a clearwinged moth that resembles a wasp. PBs will attack members of the Prunus genus (peaches, plum, apricots, cherries, almonds). It too usually infests stressed or newly planted trees. They like to hit the tree at the toes though. Sometimes down at ground level or where the mulch meets the tree. In fact this is why I suggest you don’t mulch directly up to the tree. You want to leave a one inch gap between the thick layer of mulch and the tree.

PBs also do not usually kill your tree but they will severely set it back in years. You will see frass and discolored, or flaking bark. You will see a pencil sized oval whole. You will also usually see some ooze coming from the site of injury. This is cytospora canker, a fungal disease that has occuppied . Cytospora usually doesn’t kill your tree but it is generally a bad thing.

What to do to protect your trees? To begin with I would suggest planting small trees. Fruit trees are hosts to all kinds of bacterial and fungal diseases. When stressed by digging and planting them in the larger calipers they are subject to these diseases and the aforementioned pests. If you want to plant large trees you will want to protect your trees with a topical application of a pyrethroid. Permethrin is a good option due to it's long persistence on the tree in certain concentrations. This means you spray the lower portion of the tree and anything that tries to chew through the bark will ingest the insecticide and be killed. (For specifics on pyrethroids please read the label or consult a certified applicator).

You can also make sure your trees aren’t stressed. Don’t worry too much about compost, fertilizers and other soil amendments. Your tree needs soft soil to root into, good air to the roots and lots of water! So,water and mulch your trees and make sure they have a good rooting environment.

Finally, fence off your orchard so no large herbivores can get to it. Damage from deer will also set your tree back and set it on a downward “death spiral”.

For more information on Flatheaded Appletree Borer or Peachtree Borer search for CSU factsheets or contact me at

Peachtree Borer damage

Flatheaded appletree borer damage

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