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Nursery & Forest
Volume 56 Number 6 Date 05/26/2011 TOBACCO RATTLE VIRUS - Nursery inspectors continue to submit ornamentals from all areas of the state with symptoms of this virus. Of the 10 perennials processed by the Plant Industry Lab on May 20, seven samples --including barrenwort, bleeding heart and peony-- tested positive. The symptoms were obvious on some plants and subtle on others. Tobacco rattle virus has a wide host range and is spread during propagation of infected plant parts. Prevention is the only way to keep this virus and others out of production areas and home gardens. NORTHERN ROOT-KNOT NEMATODE - An anemone sample submitted to the DATCP Plant Pathologist was diagnosed with both tobacco rattle virus and northern root-knot nematode. Nematode symptoms can manifest as stunting, yellowing and wilting, but all are inconclusive until the roots are examined for knots and the nematode (Meloidogyne hapla) is identified. Other disorders diagnosed in the past two weeks were rose mosaic virus complex and hosta virus X. --Anette Phibbs, DATCP Plant Industry Laboratory PLANT HARDINESS RATING - Standard inspections of nursery retailers often reveal improperly labeled stock suited for warmer hardiness zones. For example, the flowering dogwood cultivars 'Galzam' and 'Galani', as well as viburnum 'Judii' and 'Tomentosa' were being offered for sale at a Polk County nursery. These plants are hardy in zones 5-8, but are not adapted to Zone 3 conditions in the far northern areas of the state. It is illegal to sell or distribute plants that are insufficiently hardy and will not survive or grow in Wisconsin. Retailers are required to provide signs or labels for woody landscape plants indicating the hardiness rating. Customers should not presume all trees and shrubs offered for sale by local retailers are adequately cold hardy for their area. BLACK SPOT ON ROSE - This common fungal disease was noted on roses in Dane, Jefferson and Washington counties. The initial symptoms appear as small, round black spots on the foliage, which later enlarge and cause leaves to turn yellow and drop prematurely. Humid, wet conditions favor spread of black rot, so increasing air circulation to keep leaf surfaces dry and removing infected leaves is recommended. DAYLILY RUST - The daylily variety 'Prairie Blue Eyes' was infected with this rust disease in a Washington County nursery. The most recognizable symptom is long, brownish-yellow streaks that develop on the leaves. As the disease progresses, small, raised yellow-orange pustules appear on the leaf undersides. These pustules eventually release orange spores that are wind-dispersed to other daylilies. The disease cycle involves a secondary host, Patrina spp. Daylily rust is not known to overwinter in Wisconsin; the spores arrive on infected daylilies from out of state or on southerly winds. --Liz Meils, DATCP Nursery Inspector GYPSY MOTH - Btk treatments were conducted in Grant, Iowa and Lafayette counties on May 23 and in Dane, Green, Iowa, Richland, Rock and Vernon counties on May 24. Treatments for May 26-27, and possibly through the Memorial Day weekend, are planned for the following counties: Clark, Eau Claire, Grant, Iowa, Jackson, Lafayette, La Crosse, Sauk, Trempealeau, Richland and Vernon. Some sites will be receiving a second application of Btk for late hatching gypsy moth egg masses. --Nkauj Vang, DATCP Gypsy Moth Program 
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