Thanks for your question about your Princess Kay Plum tree.  You have done some personal research and are asking the right questions.  Your pictures were great.

I’m sending an article about the peach bore.  Its pupal skins are about an inch long and the ones in the pic look large, but I can’t quite tell the scale.

Most of the peach bore damage is done under the soil line.  What if you dug up a bit of the root system below the soil line and took a look there?  If we saw the gummy ooze there, it would be a good resolution for us that it was in fact the peach bore.

https://extension.colostate.edu/topic-areas/insects/peach-tree-borer-5-566/

I agree that the Princess Kay seems like a good tree for the spot you have.  It stays small, has beautiful seasonal flowers and foliage, and would look good in your spot.  

It sounds like you have researched the peach bore a lot on your own.  Usually peach tree problems are from the peach bore.  If it is in fact peach bore that infested your tree, it is probable that it could happen again.  There are treatments that can be effective, including moving mulch from touching the tree trunk, treating with insecticide on the trunk area when the insect is active (usually early July and August), fumigating with moth crystals, etc.

If you’d like more information on the specifics of treating peach bore, let me know.  

If you’d like to send another pic of what you see underground, I’m happy to assess that with you.

Gina

Weld County Master Gardener

Also, the picture with the trunk “damage” makes it look like there is a fine fabric over the trunk.  It almost looks hairy where the “rips” are.  I’m guessing it is not a fabric, but wanted to be sure.

Thanks for contacting us about your plum tree. Great diagnostic work! And thanks for the pictures. All indications are that it was peachtree borer that got your plum. See our fact sheet on these insects. Note that right now (August) the adults have emerged and are flying around the neighborhood finishing laying eggs. There are no living lifestages of the insect in the hole in the ground, nor remaining in the tree since it’s dead (dispose or burn it – great for smoking meat!). Replanting should be fine. All plums (and other stone fruits) are susceptible, so plant your favorite and just be prepared to maintain it. However, if you replant in the next month or so, a preventative trunk spray could be applied in case any adults are still around. Many insects are about 3 weeks late this year due to our cool, wet, delayed spring. You may want to use that same spray next year about the first week of July when egg laying is at its peak. Talk to a good, local nursery for spray recommendations specific for peachtree borer and that meet your organic/non-organic preferences. Follow the label. See the following for more information:

• Tree planting steps (and good diagrams) (note that we recommend keeping mulch a bit away from the trunk – it can harbor insects)
• Backyard orchard – Stone Fruits

The marks on the trunk is not part of the insect damage. This appears to be scuff marks that has rubbed off some of the young, waxy surface of the trunk. It did not penetrate the bark and cause any damage.

Karin

Thank you! Very helpful. BTW, I dug a little more into the ground at the trunk base, looking for that ooze you mentioned. Didn't see any but maybe I didn't go deep enough. I will look again when I go to pull out the dead tree. Because I love this particular tree, I will replace with the same as long as I can find it. Then -- fingers crossed it won't fall victim to the peach borer again! Thanks again for all the info.