One such rare and fatal plant disease is boxwood blight. Roots rot if soil is kept too wet. American boxwood (Buxus sempervirens) and littleleaf boxwood (B. microphylla) can be used as a replacement as they are resistant to decline. Table 1. Further Reading: Photographic Guide of Boxwood Pests & Diseases on Long Island, by Margery Daughtrey, Senior Extension Associate, Cornell University Before new growth appears in the spring, leaves on the tips of infected branches lose their green color and then fade to a light straw color. Send photos of suspicious boxwood symptoms to the Home & Garden Information Center’s. Death of the entire plant is characteristic of this disease. japonica ‘Green Beauty’. Soil treatments with dinotefuran or imidacloprid will control leafminers, but may take two weeks or more to begin providing season long control. Box tree moth larva. Disinfect pruning shears frequently in household bleach diluted 1:9 with water or rubbing (isopropyl) alcohol for 10 seconds. For information on species, varieties and culture, see HGIC 1061 Boxwood. As the disease spreads within a boxwood shrub, additional leaf spots form and coalesce until entire leaf surfaces are infected, and these blighted leaves then drop from the plant. This fungal infection springs to life and spreads quickly during prolonged periods of the day and night temperatures between 60-70 degrees combined with abundant rainfall and high humidity. Adults may be controlled by a registered residual insecticide in late May into June. Join our mailing list to receive the latest updates from HGIC. are found throughout Maryland. Boxwood Diseases Boxwood Blight (Calonectria pseudonaviculata, syn. Distorted, splotchy leaves afflicted with boxwood leaf miners. There are no known resistant boxwoods, but a few have been tested and found to be more tolerant, such as B. sinica var. Yellowing of older inner foliage or premature leaf drop may indicate a lack of nitrogen. I have two boxwoods on the northeast side of my house that are well established an several years old I would assume (moved in 1.5 years ago.) Adults also feed on boxwood, but are less damaging than the nymphs. The first application should be made after the dead leaves and dying branches have been removed and before growth starts in the spring. Volutella buxi may cause a dieback or stem blight on English and American boxwoods,and often follows winter injury (see the Canker section below). Prevention & Treatment: A thorough diagnosis of the associated factors is important before corrective action is taken. The most obvious symptoms are the many tiny black raised fruiting bodies found on dying or dead straw-colored leaves. Leafminers are very common boxwood pests and one of the most problematic, especially for B. harlandii, B. microphylla and some B. sempervirens cultivars. Boxwood Troubles . . Boxwood mites are yellowish-green or reddish and are 0.5mm long. Pests include leafminers, psyllids, and boxwood mites. This small mosquito-like insect completes its life cycle once per year, emerging in the early spring to mate and lay eggs. Inspect plants for winter damage in the spring and prune out affected areas. A heavy infestation can cause serious loss of leaves and result in death of the boxwood. The bark rots and peels at the crown. The fungus can remain alive in fallen leaves which can then serve as the source of infection for subsequent years. Webbing and frass (excrement) also are present around infested plants. japonica) are also susceptible. Plant root rot-susceptible plants in well-drained areas or in raised beds. Though not currently present in Maryland (as of March 2020), box tree moth (Cydalima perspectalis) is a potential new threat to boxwoods in the United States. Prevention & Treatment: Root rot is favored by high soil moisture and warm soil temperatures. 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