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Nursery & Forest
Volume 63 Number 2 Date 05/10/2018 VOLUTELLA BLIGHT - This destructive disease of pachysandra was found on the cultivar 'Green Carpet' in a Racine County greenhouse. Symptoms include stem cankers and circular necrotic leaf spots that gradually increase in size until the entire leaf turns brown or black and dies. An opportunistic pathogen, Volutella blight infects plants weakened by abiotic or biotic factors, such as moisture stress or scale insects. Management includes sanitary, cultural, and chemical measures like removal of debris and diseased plants, growth and vigor maintenance of plants, and/or possibly the application of approved fungicides. PLANT VIRUSES - Nursery inspectors again observed a variety of greenhouse plants infected with viruses in the past week. The Astilbe varieties 'Ellie,' 'Look At Me,' and 'Younique Salmon' tested positive for tobacco rattle virus, as did Epimedium 'Rose Queen.' Iris 'Chasing Rainbows,' 'Edith Wolford,' 'Immortality,' 'Lenora Pearl,' 'Maid of Orange,' 'Sangria,' and 'Stellar Lights' were infected with potyvirus. Virus symptoms were also observed on fig, horseradish, hosta 'Spartacus', and sedum 'Mr. Goodbud.' Viruses are highly transmissible through routine greenhouse operations and have become increasingly prevalent in the nursery trade. There are currently no controls for plants infected with viruses. Once plants are diagnosed with any virus, they must be removed promptly from the growing area and destroyed. -- Shanon Hankin and Marcia Wensing, DATCP Nursery Inspectors WHITE PINE WEEVIL - The vibrant yellow blooms of the forsythia shrub are a phenological indicator of white pine weevil emergence and can be used to time scouting and control measures. Soon after the distinctive yellow flowers appear in spring, the adult white pine weevil resumes feeding and laying eggs on the terminal shoots of pines and spruce. The presence of weevils and oviposition holes suggests egg hatch is imminent and treatments should be initiated promptly. Since insecticides are most effective prior to egg hatch (before larvae tunnel into the shoots), growers are urged to closely inspect their trees in the next two weeks for signs of activity. In areas where the treatment interval has passed, removal of wilted leaders should be planned for June or July. Adult white pine weevils are one of the earliest pests to resume activity each spring, requiring just 7-58 degree days (base 50°F) before emerging from overwintering sites. WINTER INURY - After a long, cold winter season, many conifers and broad-leaved evergreens throughout the state are showing reddening of needles caused by winter burn, winter desiccation, or both. Symptoms of the former appear in response to rapid temperature fluctuations in late winter and early spring, while the latter develops when moisture lost through transpiration cannot be replaced due to frozen soil, resulting in dehydration. Foliar discoloration is typically more severe on southern and western exposures which receive more direct sunlight. Damage is usually restricted to the needles and not the buds and often resolves by early summer. Pruning out affected branches should be postponed until new growth emerges later this month or in June. Irrigation is also recommended for trees affected by winter desiccation. -- Konnie Jerabek, DATCP Nursery Inspector 
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