Shoot Boring Caterpillars

Shoot boring caterpillars were a problem this spring and again mid summer. Recently, October Glory® red maple was attacked moderately; nearby rows of Red Sunset® and 'Autumn Flame' weren't. At other nurseries fields of Red Sunset® were mildly affected. By mid August nearly all insects had pupated. Preliminary identification is a type of tortricid shoot borer, possibly Episimus tyrius. Damage to terminals is especially important.

Scout for the first sign of damage to time a spray if this shoot borer has been a problem. Keep weather and damage incidence records in order to spray just prior to infestation in future years.
Source: Dr. Frank Hale, per. comm; Mitchell, W. and P. Schultz. 1996. Identification, Seasonality, and Host Preference of Tip-Feeding Pests of Red Maples. Proc. SNA Res. Conf. 41:168-169.

Irrigation and Cold Hardiness
Remember to reduce the amount of irrigation as fall approaches. Plants require less water at this time of year and reducing irrigation can actually help the plants induce dormancy and increase cold hardiness. A water deficit severe enough to cause leaf drop can reduce cold hardiness though. Irrigate enough to avoid water stress but not so much as to induce growth. Plants should not be so water stressed that any natural rainfall stimulates growth.

Source: Effects of Cultural Practices on Cold Protection. University of Florida Fact Sheet HS-119.

Over-irrigated
This cherry has likely been overwatered. Moss on the surface of the container and on the soil at the edge of this container bay are clues. No roots were found 4-5 inches down and upon removing the plant from the pot very few white roots were found. It was growing in a heavy substrate. Overwatering during the growing season is much more injurious than overwatering during the dormant season due to the high oxygen requirement of roots during the growing season. Leaf scorch and premature defoliation are symptoms of excess water.

Source: Kozlowski, T. 1979. Tree Growth and Environmental Stress. University of Washington Press.

Moss growing on surface of substrate.

Same container, no roots 5" down or deeper.

Different pot on end of bay, receives less water, has white root mass.

Fall Irrigation Impacts Current and Next Year's Growth
Fall irrigation can impact the current year's growth of free/indeterminate and recurrently flushing trees. Free growing trees break bud in the spring and grow as long as conditions are favorable. Birches and red maples are good examples of free growing trees. Recurrently flushing trees break bud in the spring, grow, set new buds, and the cycle repeats with newly formed buds breaking and growth taking place as long as conditions are favorable. Current year's growth is increased by irrigating these trees during dry spells.

Trees with fixed/preformed growth complete most of their growth in the early part of the growing season. Irrigation in the summer and fall generally does not cause additional growth in the current year, rather it is used to develop the bud that contains the preformed growth for the following year. Adequate watering during the summer in the current year can impact the amount of growth realized the following year on fixed growth trees.

Fixed growth trees can experience an abnormal bud break late in the season. These shoots, called summer shoots, are often stimulated by late season rainfall. Oak, beech, elm and pine are known for developing summer shoots. Summer shoots are undesirable because they often lead to poor stem form and are very suceptible to cold injury since they do not have time to harden before cold temperatures.

Source: Kozlowski, T. and S. Pallardy. 1997. Physiology of Woody Plants. Academic Press and Kozlowski, T. 1979. Tree Growth and Environmental Stress. University of Washington Press.