Maple Anthracnose

The early spring is when initial infections by several foliage and needle diseases occur. The common anthracnose diseases of hardwoods, including maple anthracnose and ash anthracnose, sometimes cause leaf browning by mid-summer, and premature leaf fall in autumn. Spring seasons with unusually long or frequent wet periods can initiate a high level of needle disease such as spruce needlecast of white and Colorado blue spruce, and tip blight of pines. Both of these needle diseases have been quite severe in recent past years.

Applications of fungicide are usually not necessary in most years; normal spring weather, with good drying days between rain showers is most often the rule. However, if trees were severely infected last spring, and forecast conditions indicate an especially wet season in your area, fungicide applications may be prudent. Fungicides that control these diseases are protectants, and must be applied before leaf or needle infection takes place. This requires applications of the fungicide at the time of budbreak (usually about the first week in May for hardwoods, and two or three weeks later for pines and spruces). As leaf and needle tissue continues to grow and expand, an additional one or two applications of fungicide is required to cover the new tissues. Management programs should remain flexible; if extended periods of wet weather persist, the number of applications can be increased, or timing between applications can be shortened. If early spring conditions are dry, reduce the number of recommended applications or lengthen the time interval between recommended applications. Always refer to the product label, and never apply more frequently or in higher doses than stated on the label.