Direct examination can verify a disease. Carefully excavate roots by removing a small patch of the bark. The most effective way to reduce the possibility of root injury and disease is to keep the tree healthy and vigorous. A healthy root environment consists of adequate growing space for the root system, well-conditioned soil 16 inches to 24 inches deep, and sufficient water and oxygen. To check the water and soil condition of the root environment, dig a hole outside the drip line of the tree and determine if the soil is dry, wet or compacted.
Soil moisture is adequate if the soil can be made into a ball with little pressure.
Long, deep watering over the entire root system with time for the soil to dry between watering is better for trees than frequent light watering. Watering once a month during a long, dry winter also is helpful. Avoid any practice that injures the roots. However, if these practices cannot be avoided, try to minimize damage. To minimize soil compaction, remove compacted soil and replace it with noncompacted soil.