THE VIRGINIAN-PILOT
Copyright (c) 1994, Landmark Communications, Inc.
DATE: Sunday, December 18, 1994 TAG: 9412160103
SECTION: HOME PAGE: G4 EDITION: FINAL
SOURCE: ROBERT STIFFLER
LENGTH: Medium: 72 lines
IF THERE'S ONE problem more gardeners worry about than moles, it's boxwood. It seems that almost everyone who grows boxwood has problems with it, worries about it, writes letters about it or reads books about it.
Unfortunately, none of those solve the problem.
Virginia Tech horticulturist Diane Relf says one of the most common diseases ascribed to boxwood is decline. ``Decline'' refers to the debilitation of the plant, manifested by slower than normal growth, small leaves, loss of green color and dead twigs and branches. That may describe your boxwood.
Decline usually occurs when the root system of boxwood is impaired by parasites or unfavorable soil environment. Nutrient deficiencies can also cause decline, and sometimes it's a viral problem, said Relf from her Blacksburg office.
Decline of boxwood most often refers to a disease of English boxwood incited by root and crown fungi. Because the symptoms are similar, decline is often confused with symptoms caused by parasites or environmental factors that act directly on twigs and foliage. A single plant may have both twig blight and root rot.
The only way to learn if the roots are healthy is to wash them free of soil and inspect them for discoloration and decay. This means you've destroyed the plant, so either way you lose. An alternate plan is to send the roots with soil samples to a diagnostic lab such as the Virginia Tech lab in Blacksburg.
Decline symptoms include roots and/or plant crowns colonized by several fungi, root lesions and spiral nematodes. Often these work together to destroy the plant's health. A yellow to bronze coloration of foliage is a symptom of the decline. Death of sections of the plant is common in Hampton Roads.
Often the base area of the stem is discolored but the bark must be removed to see this symptom.
Relf says there are no fungicides or nematicides recommended for controlling boxwood diseases. To help prevent the problem, she recommends:
Provide water when necessary but avoid overwatering.
Do not overfertilize. Cottonseed or soybean meal that are slow-release are preferred by boxwood.
Thin the shrub to allow better air circulation.
With winter approaching, make sure sufficient soil moisture is available to the plant.
Use coarse organic mulch such as wood chips around the plants.
Boxwood that is declining or has blighted stems and foliage should be pruned in late February, Relf recommends. Prune dead stems back to healthy tissue. Disinfect pruning shears frequently in household bleach diluted 1:9 with water. When pruning is finished, bleach should be washed thoroughly from tools to prevent rusting.
Then have the soil tested and apply any fertilizer recommended.
Many factors can cause poor health in boxwoods, Relf says, and typically, more than one factor will be involved. Weather conditions, especially severe winters and drying winds, can cause leaves to brown and twigs to die back. Extremely cold temperatures, when there is no snow cover, can kill boxwood.
If your boxwood has died or boxwood decline disease is confirmed, do not plant English boxwood in the same site, Relf recommends. American boxwood can be planted instead, because it is resistant to decline. If Phytophthora root rot is confirmed, the site should not be used for any boxwood plantings.
If your boxwood is in decline, there's not much you can do about it, but you can prevent further decline by following the recommendations above. If your has died, yank it out now and replace with American boxwood, which looks so much like English boxwood that few people can tell them apart.
Be sure to test the soil before replanting anything, to make sure your soil is healthy. by CNB