how to confirm two lined Chestnut borer

[Joster19]

hello all, I have been told by my herbicide vendor that if you see tip die back in oaks, it's pretty much a guarantee the tree has two-lined Chestnut borer. given that all the dieback is way up In the canopy, how do you confirm this is the case?

I have a client who has lost several oak trees to Bur oak blight, I am seeing a couple more trees with tip die back, we are considering the potential to treat at least one of the tougher looking ones for borers and I told them the tree might also have BOB. these with tip die back aren't the most valuable trees on the property, set back in the woods,, but they would hate to lose more.
there is a chance one of the more valuable trees has BOB, but won't know until later summer. I'm concerned if we treat one of the less valuable trees for borers now but then find two or three of the trees of BOB, they will be regretting having spent money on borers now- would appreciate any counsel on this circumstance as well!

thanks

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[Brando CalPankian]

hello all, I have been told by my herbicide vendor that if you see tip die back in oaks, it's pretty much a guarantee the tree has two-lined Chestnut borer. given that all the dieback is way up In the canopy, how do you confirm this is the case?

I have a client who has lost several oak trees to Bur oak blight, I am seeing a couple more trees with tip die back, we are considering the potential to treat at least one of the tougher looking ones for borers and I told them the tree might also have BOB. these with tip die back aren't the most valuable trees on the property, set back in the woods,, but they would hate to lose more.
there is a chance one of the more valuable trees has BOB, but won't know until later summer. I'm concerned if we treat one of the less valuable trees for borers now but then find two or three of the trees of BOB, they will be regretting having spent money on borers now- would appreciate any counsel on this circumstance as well!

thanks

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A canopy inspection is the best way to check. They're flat headed borers like EAB, so they'll have D shaped holes. Trace the dieback back until you can find larvae, if feasible.

That said, 2LCB is not a primary vector for decline in most cases. They attack drought stressed and culturally compromised trees. Improving culture is the long term method for keeping them away, I e vert mulch, beneficial fungi, watering, Cambistat, etc.

You could try a soil drench instead of injections as a lower cost method to stamp out the infestation if that's what's going on. Then money could be used for deep Root fert and the like to improve tree health and keep them away.

Where are you located?

 

[FJR]

Also keep in mind the symptoms of decline in the upper canopy correlate with other oak related issues, more on the abiotic side. Also keep in mind most oak related stress is a combination of more than one issue.

 

[evo]

Look for a beetle with 6 lines?
Sorry couldn’t help myself

 

[Joster19]

dumb question but when you say canopy inspection, you're talking about climbing up into the tree? I'm in central Iowa

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[ATH]

If you are finding a lot of D-shaped holes on the trunk, that's indicative of a pretty high infestation. So, yeah, probably either climb or bucket access to look for those holes higher up.

Can you reach any declining branches with a pole saw?

Do NOT cut anything out of oak now...wait until a hard frost in October or later due to oak wilt.

Here is a factsheet about two-lined chestnut borer:

Twolined-Chestnut-Borer-Fact-Sheet.pdf

widnr.widen.net

 

[ATH]

Also keep in mind the symptoms of decline in the upper canopy correlate with other oak related issues, more on the abiotic side. Also keep in mind most oak related stress is a combination of more than one issue.

Yep...two-lined chestnut borer is most often part of a bigger disease complex. "Oak decline" (or any decline for that matter, but Oak decline has probably been studied more than most in the hardwood regions) has 3 components:

*Predisposing factor (growing on a poor site, over-crowding, planted too deep, etc...
*Inciting factor - something that stressed the tree significantly in a short time period. Drought, for example. Or: adding soil over the roots of an existing tree, lightning strike, flood that saturated the soil for a week, etc..
*Contributing factors - two-lined chestnut borer, Armillaria, scale, etc... These may be what an autopsy report says killed the tree...but they are generally not killers of healthy trees - they move in on stressed trees. So when addressing these, you need to ask "what caused the stress that allowed this to thrive?" and then see about addressing that.

 

[Joster19]

thank you for all your thoughts, it seems to me recommending treatment of tlcb alone is not a very good investment, Rather to encourage them to treat for treat vigor. If they were to say boost vigor of a construction impacted tree with paclo or, another circumstance, if they were to treat for bur oak blight, then would you recommend treating for borers as well? or wait to see if the other treatments improve the trees first?

I like helping people who want to invest in their trees, but want to be able to help them think through how much they really want to invest in any given tree

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[ATH]

Yes, if the tree is in declined from those other things, it's not improbable that two-lined chestnut bores are involved as well so I would treat for them. I think you're on the right path though, it doesn't make sense to treat just for them without addressing underlying issues.