Sycamore Trees -- Big and Problems

Subject: Control of Anthracnose on Sycamore Trees

Advice for the Home Gardener from the Help Desk of the
UC Master Gardener Program of Contra Costa County

MGCC Help Desk Response to Sprays for Control of  Anthracnose on Sycamores:  Thank you for contacting the UC Master Gardener Program Help Desk with your question about treating anthracnose on Sycamore trees.  You have done a lot of research on this problem, so I am not sure we can tell you anything you do not already know. Sycamore, full-grown in suburbia is a large tree, and were a common tree planted usually several decades ago, but smaller lots and today's suburbia limit their planting these days. While they are often prized for their majesty (and heigh 60-100') they can e a problem from dropping branches, debris from leaves and branches, and anthracnose, especially if planted to close to a house and other trees. 

As you know, anthracnose is a fungal disease which can cause unsightly changes to Sycamore trees.  The effects on the tree can be brown spots on infected leaves to distortion of branches, cankers and dieback.  Unless signs consistently occur every year, trees are usually not seriously harmed; they just may not be aesthetically pleasing.  The fungi survive over winter on infected leaves and twigs or dead leaf litter under the trees.  Rain in the spring splashes the fungus onto new growth and starts the infection cycle again.  Infections are worse in years with heavy spring rain than those with dry springs.  The best management mechanism is to remove infected twigs, branches, nd leafs during the fall or winter to decrease the re-infection of the trees in the spring.  If there is a wet spring, spraying new growth with fungicides can be protective: however, University of California does not recommend fungicide applications for trees other than ash.  I believe you have already reviewed this document but the UC web link to the Integrative Pest Management (IPM) on anthracnose is below.

I reviewed the pesticide labels of the two products we discussed - Agri-Fos and Reliant.  If there is a difference in the products, it was not apparent to me.  It does appear that Agri-Fos is not labeled for use on sycamores for anthracnose and Reliant is allowed to be used as a foliar spray and as an injection into the tree trunk in sycamores for anthracnose.  Why these products, with the same active ingredient in the same concentration, are labeled differently is not apparent to me.  So, we forwarded this part of your question onto our local Urban IPM advisor to see if he can provide clarification on this…. And we heard back from our Urban IPM Coordinator. Here is his response:

 “Product registrants can seek wide or narrow spectrum labels, depending on targeted markets, costs, and efficacy information. In this case, the manufacturers of Reliant have included sycamore anthracnose while the manufacturers of Agri-Fos have not. It seems that Reliant is an older product that is registered for use against a very wide range of agricultural pathogens, so maybe it was cost-effective to include anthracnose. It's also likely that the inert ingredients of these two products are different. Agri-Fos, for instance, is usually injected or otherwise introduced internally, while Reliant is sprayed.

The more important consideration here is that phosphonates (active ingredients in both these products) are not considered effective sprays as per the UC IPM 'Anthracnose' 
Pest Note

I think the last paragraph is the most important for this discussion, that phosphonates are not considered effective sprays against anthracnose."

Finally, as we discussed on the phone, you may try consulting another certified arborist to see what their recommendations for management would be.  We cannot recommend a specific company, but would recommend you find a certified arborist through the following website. 

Best of luck and we will let you know if we find out more Please do not hesitate to contact the Help Desk again if you have more questions. 

Help Desk of the UC Master Gardener Program of Contra Costa County (SEH/SES)

Notes: Contra Costa MG's Help Desk is available almost year-round to answer your gardening questions. Except for a few holidays (e.g., last 2 weeks December), we're open every week, Monday through Thursday for walk-ins from 9:00 am to Noon at 2380 Bisso Lane, Concord, CA 94520. We can also be reached via telephone:  (925) 608-6683, email:, or on the web at MGCC Blogs can be found at You can also subscribe to the Blog.