Oak trees on the property...some healthy...some not-so-much

[Keneastman]

Thank you for any help you might be able to provide. We live on a ranch just south of Hemet, California. While Socal has been experiencing a drought in the past 10+ years, our 300' well has been providing the property with plenty of water. We have about 40 oak trees (most of them very large) on the property and some look quite healthy. There are probably about 10 that don't look so good. We've lost another half dozen for some reason or another (disease??). We've noticed dark "splotches" on the unhealthy trees (pictures "Unhealthy Oak 1d.jpg", 1e, and 1f). You'll see in one of the pictures ("Unhealthy Oak 1d.jpg") that we cut off a branch that was 14" in diameter. We cut it off because we didn't want it to fall on an outbuilding that was under it. You can see that it was rotting from the inside. A few years ago, we cut a bunch of lower branches off a similarly unhealthy oak tree and it turned out that the part of the tree that was left took a major turn for the positive. It is now (apparently) very healthy and green. Could this be a water issue? A disease issue that we can combat? Would whittling off significant branches spur the remainder of the tree to heal? Any thoughts are welcome.

 

[buzz sawyer]

What is the story on the ground beneath and around the trees? Looks pretty bare?

 

[Keneastman]

Hi Buzz. The primary tree that I too k pics of is completely bare under the canopy and for 30 yards in all directions. The tree is in front of a barn and we've kept the area clear so we can get equipment in and out without issue. Virtually all of the other oaks have oak-material under them...fallen leaves and small branches. Some of the trees have a foot of that kind of material under them. The field ares around the trees are mowed 2-3 times per year to reduce fire danger.

 

[buzz sawyer]

I was concerned about heavy equipment / traffic that may damage the roots. Hopefully someone more knowledgeable than I will chime in.

 

[ATH]

I agree @buzz sawyer - the declining trees look like there has been a lot of soil compaction under them. The healthy trees look to be more out in the open. There is usually a correlation between soil compaction and declining tree health.

 

[Keneastman]

Try zooming in on pictures "Unhealthy Oak 1d.jpg", 1e, and 1f. You'll see dark splotches. Do you think that might be a specific (and hopefully dependable) disease? The tree I sent the most pics of is, in fact, probably in the most compressed soil of all the unhealthy trees. Several of the others are in soil similar to the healthy trees. Here's another I took pics of that's unhealthy. You can also zoom and see a clear pic of the splotches (2c). Note that there's no excessive soil compaction.

Thank to you both!!! I'm hoping to save these beautiful oak trees.

Ken

 

[ATH]

Do you have sudden oak death in your area? We don't here, so I'm not terribly familiar with it, but it can cause bleeding cankers like other Phytophthora...

 

[Raintree]

Sometimes the simplest answer makes the most sense. Trees declining do to long term drought stress.

 

[Keneastman]

Do you have sudden oak death in your area? We don't here, so I'm not terribly familiar with it, but it can cause bleeding cankers like other Phytophthora...

I'm not sure. How sudden is "sudden"? These are unhealthy for years and then their decline become more rapid and they're essentially dead in maybe 2 or 3 years.

 

[ATH]

Read all about it:
https://www.aphis.usda.gov/aphis/ou...s/pests-and-diseases/phytophthora-ramorum/sod

 

[Keneastman]

In case it helps...I'm posting another few pics. We took down another dying oak this weekend and the first 3 pics are of the tree. Unhealthy at the top but you can see that, at the base, the wood looks reasonably healthy. The last pic is of one that's not doing well, right between 2 others that are healthy. Any other thoughts on this? Truly thankfor for your help.

 

[Keneastman]

Read all about it:
https://www.aphis.usda.gov/aphis/ou...s/pests-and-diseases/phytophthora-ramorum/sod

That's awesome. I spent an hour going through it and a couple of other web-articles to find treatments...to no avail for saving existing trees. There were articles about the affects of treatment in Petri dishes, but not on existing trees. Do you know if treatments for existing trees is available?

 

[ATH]

Not for that disease. Maybe try Reliant bark sprays? But I haven't dealt with it because we don't have it here. I'd have a lab confirm if you expect that is what you have.

RAL can rest for residual DNA so you could cut out one of those black spots and they'll tell you if it is Phytophthora ramorum
https://www.vetdna.com › ho...PDF
Horticulture - Submittal Form [PDF]

I'm not saying that it is...I was just floating the possibility. Soil compaction and moisture stress are most certainly viable culprits.

 

[Keneastman]

Not for that disease. Maybe try Reliant bark sprays? But I haven't dealt with it because we don't have it here. I'd have a lab confirm if you expect that is what you have.

RAL can rest for residual DNA so you could cut out one of those black spots and they'll tell you if it is Phytophthora ramorum
https://www.vetdna.com › ho...PDF
Horticulture - Submittal Form [PDF]

I'm not saying that it is...I was just floating the possibility. Soil compaction and moisture stress are most certainly viable culprits.

Great info. Really appreciate your help. I plan to do exactly what you recommended. Have a great week.

Ken