British Columbia: Arbutus care

Hi everyone, (first post here) and thanks in advance if any of you can offer some help... noticing that many of you have had the same issues I am having with brown spots and "dying" limbs of Arbutus trees. I have about 8 on my property that are affected ranging from only a few brown spots on the leaves to about half the tree appearing as though it was doused in gasoline and burned. From what I've read so far this can be from any number of different fungi, so I'll spare you with asking for an online/blind diagnosis... but I'd like to ask if there is ANYTHING I can do to help them.. ie: is there any particular fertilizer that arbutus seem to like and thrive in?
Also, someone once told me to "cut off" the affected limbs ((so the tree doesn't waste energy trying to grow into them)) but he wasn't an expert so I'd like to check with the pros on that one first... to cut or not to cut? fertilizer? anything else I can do to help them? Thanks again.
Paul.

 

Fertilizers might not be a good approach. A layer of mulch and making sure that the trees are getting enough sunlight would be more beneficial in the long term health of the trees. There has been a lot of discussion and good advice at this site, check this...http://www.botanicalgarden.ubc.ca/forums/showthread.php?t=36560&highlight=ar

 

I had the same problem last year and was advised to increase the water. Well, I watered HEAVILY and the tree dramatically improved.

 

The situation is a combination of pressures -- Arbutus is fairly weak in resistance to disease. Arbutus Canker would be the likely cause of the dieback of entire limbs on your trees, and is a very common primary pressure leading to mortality of Arbutus on the south Island. I've had the misfortune of removing several in the past season that succumbed to poor conditions for the tree's vigor to compete with the advance of fungal attacks.

The best thing you can do for your trees - Remove dead and dying tissue. Proper pruning practices are essential here. Monitor soil conditions for moisture. Provide adequate moisture, as in water deep and infrequently to maintain soil moisture but NOT saturation. A layer of mixed mulch 5-10cms deep on top of the root plate serves a multitude of functions that benefit the tree almost immediately. The larger diameter you are willing to commit, the better.

Monitoring. Monitoring is the key heading forward - A relationship with a certified arborist who is familiar with the local factor particularly with Arbutus in your case, is your best possible resource. Fertilizer and heavy over watering is only the answer for more rapidly mobilizing the fungi. A proper site analysis/sample is key before considering fertilizer.

 

While spontaneous seedlings popping up in watered flower beds do often appear to enjoy the conditions there, existing, long-established native specimens should not need any irrigation or fertilization - and could be adversely impacted by either. In nature species is an indicator of dry sites in climates with dry summers. It also does not like shade, removal of competing trees around it may assist a crowded specimen.

 

Removal of a competing tree to give an arbutus better access to light may also eliminate a longer lived tree to buy a pioneer species 5 more years of existence.

 

I would not bother with this if an arbutus looked like it was too far gone. Otherwise, in my experience arbutus in situations where human activity has affected the stand composition are liable to have been overwhelmed by red alder, bigleaf maple, young Douglas-firs and other quick-growing species that will not yet have produced specimens as old and ornamental as the arbutus on that site may be.

Although the longevity of madrone is not known, the species has been referred to as "giving evidence of being long lived" (27). Trees 200 to 250 years old have been recorded and large specimens are estimated to be 400 to 500 years old.

http://www.discoverlife.org/mp/20o?...silvics_manual/volume_2/arbutus/menziesii.htm

 

Re: Arbutus leaves dying

We have about a 25 ft Arbutus tree.. we are seaside in Tsawwassen. The tree has been incredibly healthy until this spring. The tree is seeding, and the leaves are turning light brown from the edges. There is some evidence of worm like holes or worm / grub like tracks on a number of the leaves but not all. About 75 % of the leaves appear partially dead. Anyone seen this or have any idea how to treat it ?

 

Excessive watering of an arbutus with canker, branch dieback and leaf blight could serve to make conditions more favourable for these problems. I have found young, dense stands of arbutus suffering from canker and leaf blight respond well to VERY careful thinning (removal of weaker trees) and careful pruning of affected limbs and removal of individual blackened leaves on remaining trees. Here it is important to remove all debris you prune (including individual blackened leaves you remove) to reduce the inocula in the area.

Rather than putting the material in your yard waste bin, where it will be composted, if you have the option to burn it, do so. You may save trees in other areas from the same fate.

Besides directly removing the density of spores, the pruning should serve to increase airflow through the tree/stand. Also, be sure to clear any brush/mulch etc from the area directly adjacent to the base of the tree. You don't want damp, stagnant air here.... a canker in this area has high potential to kill the whole tree....

 

thx for your reply...

I have heard and read about leaf blight.... but I was leaning towards thinking this might be something else. Everyone speaks of the leafs or branches going black... and evidence of black spots or spores, ours doesnt have any of that. Literally the perimeter of alot of the leaves have gone a crispy brown... and quite a few of them appear to have some evidence of a grub or worm trail in the layers of the leaves...

 

Sounds like two separate things. The leaf margins going crispy brown sounds right for fungal disease... the tracks sound like a leaf miner. For starters, see what you can do to manually remove as many affected leaves as possible, and take them as far away from the tree as possible....

 

Oh... ok... I had never read that the fungus creates the brown perimeter dying of the leaves.

What is a typical leaf miner M/O ? There appear to be "entry" holes near the base of the leaf... and in some occasions an extensive trail of movement....

Unfortunately, about 75% of the leaves of the tree are affected.. so removal might be catastrophic ?

What about watering / fertilizing ? I have typically watered and applied LIME this time of year.. which I havent done yet. The tree has been incredibly healthy

 

Have there been any changes to the rooting area in the last 2 years (changes to grade, soil cover, possible leaching of salt or chemicals, etc..) anywhere near or upslope of the tree?

 

No changes to the rooting area. However, it is immediately seaside... and we have had some larger than normal storms lately and it may have had some extra exposure to salt water. We have seen that once before.. and we heavilly watered and it recovered... but I have never seen the leaf miners... May just be a salt issue with some coincidental leaf miner infection ? Sounds like I should do the heavy water program to see if I can reduce salinity.

 

If you do, make sure it is a slow, deep watering. Make absolutely sure the stem and leaves do not get watered...a drip hose several feet away and more from the root collar is good. Only water once a week max. Arbutus are very well adapted to living near salt water... I was thinking more of looking for human-caused changes to the landscape.... but I suppose it is possible that some of the very intense recent winds could have sprayed quite a bit salt water directly on the leaves, causing scorch. In this case, maybe leave it to the rains to rinse them off.

Sun scald can also look like this... has there been any changes to the sun exposure of the tree (large tree/building removed nearby etc...)?

 

thx for your thoughtful answers... I think you are right. It has definitely been sprayed heavilly with Salt water in the last month with the unusually big wind storms we have had. It is literally right beside our seawall... so there was likely salt water directly into the rootwell too.

I will give that a try. Would you recommend a lime application at the same time ?