Q - Why are my maple trees dropping their leaves so early?

A - (from the Maine Forest Service)

Several maple foliage diseases have been prevalent and causing some concern throughout central and southern Maine. Tar leaf spot seems to be an annual problem now on Norway maples. Leaves of red, silver, and sugar maples have also been damaged to varying degrees by anthracnose fungi and, to a lesser extent, tar leaf spot. Wet weather conditions during May were highly conducive to leaf infection by these pathogens in many regions of the state. Noticeable leaf curling and leaf drop have been reported on ornamental maples in Kittery, Portland, Lewiston, Auburn, Rockland, Lincoln, and Millinocket during late July and August.   Leaf spot and anthracnose diseases rarely cause significant long-term damage. Nearly all trees inspected have shown good bud development and are expected to leaf out normally next spring. Sanitation practices such as thorough raking and composting or removal of the shed leaves are prudent. Disease intensity next spring will depend largely on weather conditions which favor infection, more so than on inoculum level.   It is unrealistic to expect a complete absence of these diseases, even when sanitation practices and fungicide applications are used.

Grass clippings and trees injured by Imprelis should not be used for composting or mulching

Imprelis, an herbicide sold by DuPont to licensed lawn care professionals, is used on residential, industrial and institutional lawns and on golf courses. Imprelis may cause injury to certain species of trees, specifically the Norway Spruce and white pine. Grass clippings that have been treated with Imprelis may be a significant cause of injury to these evergreens and other plants. Grass clippings that have been treated withImprelis should not be used for composting, and trees that may have been injured from Imprelis should not be used for compost or mulch. 

The active ingredient in Imprelis is aminocyclopyrachlor.  This active ingredient is related to other herbicides, including clopyralid and aminopyralid, which have caused plant damage when present in compost or manure as a result of their use on turf and/or pasture grasses. Aminocyclopyrachlor shares certain characteristics with these herbicides (persistence in soil and plant material, systemic nature in plants, and high seedling emergence toxicity), which are thought to have contributed to carryover in compost/manure and subsequent plant damage.

Aware of the potential for aminocyclopyrachlor to cause similar problems, the agency [EPA] required labeling restrictions to mitigate the risk of plant damage from aminocyclopyrachlor-contaminated compost. These restrictions prohibit the use of grass clippings from treated areas in compost or mulch and require commercial applicators, such as lawn care company personnel, to notify homeowners not to use treated grass clippings in mulch or compost.

If you have immediate questions, or concerns, contact DuPont's customer service center at (800) 342-5247 (prompt 99).

Featured Bulletins: 

Best Ways to Wash Fruits & Vegetables at Home 

Edited by:

Theresa Tilton, Administrative Assistant 

Contact Info
Donna R. Coffin, Extension Educator

SURFACE MAIL RECIPIENTS CAN CONTACT THEIR COUNTY EXTENSION OFFICE FOR FURTHER INFORMATION WHEN WEB LINKS ARE INCLUDED IN AN ARTICLE.

Piscataquis County Office 207-564-3301 or 800-287-1491

165 East Main Street Dover-Foxcroft, ME 04426

Penobscot County Office 207-942-7396 or 800-287-1485

307 Maine Avenue Bangor, ME 04401