Since winter damage and boxwood blight cause leaf browning and defoliation, there is some potential for confusion. The boxwood blight fungus has a short life cycle and infections can spread quickly between plants, especially under humid, warm and wet conditions that favor disease development. Other stressing factors can be compounded, resulting in plant death. Older, mature boxwood plants may attempt to re-leaf after the defoliation. Young plants with boxwood blight are typically more severely impacted and can be killed. Infected leaves become tan and readily drop from the plant, leaving bare stems. Symptoms of boxwood blight include circular, tan leaf spots with a dark purple or brown border and black stem lesions or blackening of the stems. Boxwood blight has been confirmed in several states, but as of May 2015 it has not been confirmed in Michigan. Boxwood blight is a devastating fungal disease of boxwoods that can rapidly spread through a landscape or nursery. Winter damage to boxwoods should not be confused with boxwood blight. Fortunately, winter damage on evergreens often appears worse than it actually is and frequently plants can recover after some careful pruning to remove affected shoots. Because they are broadleaved evergreens, boxwoods are subject to damage from winter desiccation as well as cold damage, both of which can lead to extensive browning. We have seen widespread damage on boxwoods in particular. Many researchers are working on finding a cure or a control for Boxwood Blight.As noted in earlier Michigan State University Extension articles, such as “ Assessing cold injury in conifers,” the past two winters have been hard on many landscape plants, especially evergreens. If you are replanting an area where boxwood grew, consider another species outside the Buxus (boxwood) family. There are several treatable diseases that share symptoms with the new boxwood blight. If you think you have an infected plant, remove it, bag it in plastic and place it away from any other boxwood. Clean your tools and replace your gloves before going from one plant to the next. Don’t prune, examine or otherwise work with wet boxwood. Water your boxwood via drip irrigation, never with overhead sprinklers. Once the plant is home, isolate it for a month or longer. If you do buy boxwood, buy only from reputable nurseries. H ow do I protect my boxwood? Think carefully before buying any new boxwood until research finds a cure. If the boxwood puts out new leaves, those, too, will die. When you think of how closely spaced boxwood leaves are, you realize that this is probably not a practical method for the homeowner.Īttacked by blight, boxwoods lose their leaves. Fungicides intended to prevent the spread of the disease must be applied to both sides of every leaf and all of the stems. Only high humidity or water on the leaves, not a wound on the plant, is required for the fungus to infect the plant. Warm and humid conditions create an environment where the fungus spreads quickly. The carriers may be asymptomatic because they were treated with fungicides that have masked, but not killed the disease. Disease spore on infected leaves that have fallen to the ground can survive five years.īut researchers believe that currently the most common method of transmission is when supposedly ‘clean’ plants are brought into an area of established boxwood. Because they are sticky, they are probably also spread by animals including birds and contaminated clothing and tools. How does it spread? The fungal spores are spread by both wind and water (rain or sprinklers). Blight-affected boxwood leaves rapidly turn brown and then fall off
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