![]() Initial symptoms are generally first observed in late spring or early summer when close examination of boxwood leaves may reveal round, dark or light brown leaf spots with darker borders and potentially a yellow halo. ![]() Generally, part of the plant will become chlorotic or brown, and leaves will rapidly fall to the ground, leaving bare branches behind. In boxwood, often the first symptom noticed is a large amount of rapid defoliation (leaf drop), which is indicative of a severe infection. Boxwood blight ( Calonectria pseudonaviculata) is a fungal pathogen of species in the plant family Buxaceae, which includes the popular boxwood, sweetbox and Pachysandra spp. It is a legitimate concern because the disease has been found in Michigan and 27 other states. For fungicides that provide preventative management or are labeled for your state, contact your local arborist.Since boxwood blight has been found in Michigan for the first time in summer of 2018, growers, landscapers and consumers alike are concerned that their boxwoods could have boxwood blight. Treatment may be necessary for the next 3 to 5 years. Removing soil to a depth of 8” to 12” may help eliminate disease inoculumįungicides should be applied every 7 to 14 days through the growing season to protect susceptible boxwoods.Remove fallen leaves as the pathogen can survive in plant debris for up to 5 years.Once the pathogen is detected, immediately remove the entire plant.Sterilize pruning and shearing equipment before moving to a new area.Do not shear boxwoods when they are wet.Monitor boxwoods during growing seasons for symptoms.Hold new boxwoods for three weeks before planting and look for symptoms.Purchase boxwoods from a reputable nursery. ![]() Here are some tips for prevention and cultural practices that may help manage the disease: Prevention: Recommendations may change as more is known about disease management. There are currently no curative products available. ![]() There are some cultural controls and products that can help prevent disease spread. Prevention is key to managing this disease. The pathogen can be spread by contaminated tools, clothing, equipment, and infected plants. The fungus overwinters in the soil with the leaf litter. Rain splash and irrigation water transmit the pathogen. White spore masses form on the leaves and stems. Warm, humid conditions will facilitate the spread of the fungus. Repeated infection can result in a weakened plant, which can lead to plant death. The fungus forms black, diamond-shaped lesions on the stem tissue. Infected plant leaves turn brown or yellow and quickly drop from the plant. Initial symptoms include light or dark brown leaf spots often with dark borders. Boxwood Blight Symptoms:Īll above-ground parts of the plant can become infected. Other susceptible hosts include Japanese and Allegheny spurge (Pachysandra sp.) and sweetbox (Sarcococca sp.). Hosts:īoxwood blight infects all boxwood species the most susceptible hosts are English, American and Korean boxwood. It has been reported in more than 20 states along the east coast and in Canada. The disease is widespread in Europe and was identified in the United States in 2011. Boxwood blight is a serious disease caused by a fungal pathogen, Calonectria pseudonaviculata previously named Cylindrocladium buxicola. ![]()
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