The leaf scorch is probably not caused by a disease or insect but rather a result of several dry winters, followed by hot weather and summer drought. Symptoms of drought injury on tree leaves include scorch, brown or curling at outside edges, wilting and yellowing. Leaf scorch can also be a symptom of poor plant location, compacted soil or lack of winter water. Maples are not as drought tolerant as some other deciduous trees. Drought stress may not kill the tree but can leave it susceptible to insect and disease infestations in coming years.
Periods of drought are normal for Colorado's Front Range. A regular watering program for trees should take place from April to September. During water restrictions, lawn irrigation systems will not adequately water your trees. For each inch of trunk diameter, use 10 gallons of water for each watering. Measure the tree at knee height. If you hand water using a hose at medium pressure, it will take about 5 minutes to produce 10 gallons of water. Deep root feeders and soaker hoses also provide about 2 gallons per minute. The simple formula is tree diameter x 5 minutes=Total Watering Time. Water trees three times per month in the spring and summer. The most important area to water is the distance from a point halfway between the trunk and the outer stretch of branches to about one foot beyond the "drip line" or branch extremities.
Continue watering in fall and winter during extensive dry periods, particularly October through February when there may be little snow cover. Evergreens, Norway maples, silver maples and other shallow rooted trees require supplemental watering in fall and winter. Winter watering is especially important for newly planted trees. Water when the ground is not frozen, and early in the day so water will soak in before nighttime freezing. See Fall and Winter Watering
, 7.211, or call the Cooperative Extension office in your county.