Crabapple issue? w/pics ( kinda )

[Blakesmaster]

Had an Ho ask me about this tree. As you can see it's quite large for a crabapple and I'd hate to injure it in anyway. The leaves have been getting some dark spots on them, turning yellow and falling off. Seemed fairly common to me ( I always assumed it was the heat this time of year that caused it but I'm no expert when it comes to this stuff ) but the HO said it never happened before. A few smaller branches looked like they had lost all their leaves which did give me some cause for concern. Perhaps it's some sort of fungus? I thought maybe a rigorous pruning and some mulch would be a good idea. Perhaps just tell the HO to water it more this time of year? I'd just hate to start injecting anything into this tree just to make a buck if it doesn't really need it. Anyway, here's a few pics.

 

[Blakesmaster]

A few more, sorry about the poor quality. Any help is appreciated.

 

[Blakesmaster]

Any help guys?

 

[S Mc]

I would strongly recommend against a rigorous pruning...this tree doesn't have much left to work with.

The picture with your leaf samples do look like an assortment of fungal pathogens at work. But I would not be surprised at that. Not only are Malus sp host to numerous pathogens but, and correct me here if I am wrong, you have had a wet, warm spring. Ideal for those pathogens to become active.

I would take the fact that the homeowner says this has never happened before with a grain of salt. It is probably more noticeable this year. What you need is weather conditions that are no longer suitable for the pathogen to progress.

The other thing to consider is you are seeing the damage of the fungal pathogen progress now...not necessarily that the pathogen is still active, only the ramifications of it.

If you do not want to take leaf samples to your local extension office for specific diagnosis, then you could at least give them a call to see what is most active in your area. This would assure you on whether the pathogen at work is indeed temporary of not much concern or one that may truly warrant treatment.

Most fungal pathogens on leaves are not considered a problem. With that said, this tree doesn't have many to work with. However, leaves are the most readily "replaceable organ" on a tree. So unless there is a particular virulent pathogen at work (and I don't suspect that), I would be highly reticent to wound the tree further, either by injections or pruning, in treatment.

As always improving the tree's cultural situation may be the best long term help. I am constantly having to remind myself that your Eastern trees are structurally much different than our western trees. But this crabapple is very sparse, which leads me to think it is struggling with competition for light and nutrients. Is there anyway you can mitigate that? You don't show the base of the tree, is it healthy? What is the watering schedule? Go through a checklist with your client to see how this tree is cared for and see if you can suggest improvements for its long term care.


Sylvia

 

[Blakesmaster]

Thanks, Sylvia. This is not an uncommon thing to find in local crabapples, I had just pruned one earlier that day that had a good amount of yellowing leaves with similar spots so I wasn't overly concerned about this one. If I can remember correctly this tree looked fairly healthy at the base, no excessive rot or fungus present but it was lacking a mulch ring and competing for nutrients with the lawn. And you are correct that it's fighting for light from the monster silver maple seen just behind it. It did have a large amount of dead wood in the tree so I may advise the HO to have me prune that out, maybe a mild tip reduction and addition of a mulch ring and see how it progresses. Very rarely do I see one this old and large so perhaps it's just become a bit more susceptible to the pathogens you described?

 

[Blakesmaster]

I just did some more research online and it appears it might be apple scab. Generally associated with very wet regions, which mine usually is in the spring, and high humidity, which we currently are experiencing. Apparently harsh pruning is definitely not the answer as it will spur fresh growth which is extremely susceptible to apple scab ( assuming that's what we're dealing with ). If I was to use a fungicide I've missed the opportunity as you stated and my research turned up, it's best done in the spring just after the leaves form. I'll probably forego the reduction and just remove the dead wood and mulch at this time.

 

[treeseer]

if any ends are thick or heavy I wouldn't hesitate to pole prune them back a bit. nmow's a very good time to take maybe 10%--think dose--and more in winter. winter also good time for growth regulator which i believe tested well against scab and has a much wider window for app.

 

[Urban Forester]

That is Apple Scab and that crabapple is an Hopa and has NO resistance to scab. Treatment (2011) will keep more leaves on the tree, but because of its non-existant resistance lesions will still form in years where weather conditions are right.