Purple Robe Locust Tree Problem - Ask Extension
Sawbust appearing between tree limbs, on trunk and on ground at the base of my 4-year old purple robe locust. Although I have never before seen any si...
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Purple Robe Locust Tree Problem #403412
Asked May 30, 2017, 3:42 PM EDT
Sawbust appearing between tree limbs, on trunk and on ground at the base of my 4-year old purple robe locust. Although I have never before seen any signs or pests on the tree, I am assuming it has a locust borer problem. Would you recommend the best treatment and course of action - many thanks!
George
George
Larimer County Colorado
Expert Response
Hi George,
Yes, you are correct. Unfortunately Purple Robe black locust is a magnet for locust borers, which are a type of longhorn beetle. And it can kill small trees. Depending on the health of your current tree, it's difficult to determine if it will survive. I would recommend good TLC and avoid any pruning, injury and be sure to water well throughout the season and into fall and winter.
Insecticides at this point are only preventative and not curative. In addition, insecticides are not very effective on this insect.
Yes, you are correct. Unfortunately Purple Robe black locust is a magnet for locust borers, which are a type of longhorn beetle. And it can kill small trees. Depending on the health of your current tree, it's difficult to determine if it will survive. I would recommend good TLC and avoid any pruning, injury and be sure to water well throughout the season and into fall and winter.
Insecticides at this point are only preventative and not curative. In addition, insecticides are not very effective on this insect.
Many thanks for this helpful information Allison. Is there an insecticide I should obtain to best treat at some point after the current cycle to help prevent the locust borer from returning, and a place in the Fort Collins area to get it?
Thank you again!
George
Thank you again!
George
Hi George,
Here's the thing...the insecticides would be preventative, but only you can determine if it's worth trying to treat the tree based on the current damage. This insect tends to attack stressed or weakened trees up front. The treatments will only prevent new larvae, but will not control any previous damage or any larvae that have already been laid in the tree itself.
As I mentioned, trying to keep the tree as healthy as possible is a really good control plan...water regularly, avoid additional stress and monitor the tree's health. If the tree is in severe stress, then doing insecticide treatments now would not be worth the product or time.
The best information I can find on this insect is from Virginia Tech: https://www.pubs.ext.vt.edu/content/dam/pubs_ext_vt_edu/ENTO/ENTO-141/ENTO-141-pdf.pdf
Here's the thing...the insecticides would be preventative, but only you can determine if it's worth trying to treat the tree based on the current damage. This insect tends to attack stressed or weakened trees up front. The treatments will only prevent new larvae, but will not control any previous damage or any larvae that have already been laid in the tree itself.
As I mentioned, trying to keep the tree as healthy as possible is a really good control plan...water regularly, avoid additional stress and monitor the tree's health. If the tree is in severe stress, then doing insecticide treatments now would not be worth the product or time.
The best information I can find on this insect is from Virginia Tech: https://www.pubs.ext.vt.edu/content/dam/pubs_ext_vt_edu/ENTO/ENTO-141/ENTO-141-pdf.pdf
