Avoid excessive root pruning when planting. Spread fertilizer evenly. Piles of fertilizer on the ground will damage roots growing directly underneath. Limit use of Simazine. High rates of Simazine will damage roots.
Allow ground covers to grow between trees to keep the soil cool.
Fraser fir roots will grow closer to the surface of the soil where there is more oxygen and less water. Contact your county Extension agent to learn more about ground cover management through the use of suppressive rates of post-emergent herbicides. Quarantine areas of the field where trees are dying with Phytophthora. Soil from these infested areas can carry the fungal spores. Don't carry mud on boots or equipment to areas of the field where trees are not dying.