University of Kentucky College of Agriculture Plant Pathology Extension
PPFS-OR-W-18 Plant Pathology Fact Sheet Verticillium Wilt of Woody Plants Nicole A. Ward, Extension Plant Pathologist Cheryl A. Kaiser, Extension Associate
Introduction Verticillium wilt also Verticillium wilt can affect a results in discoloration wide range of ornamental of water-conducting trees and shrubs, as well as tissues in roots, trunk, a number of tree fruits and and major limbs.
woody small fruits (Table 1). Olive-green, brown, Over 400 herbaceous and or black streaking woody plant species have may be observed in been reported as hosts for affected branches this disease. by peeling away the bark and cutting into the sapwood Symptoms (Figure 3). Often, Verticillium wilt symptoms however, discoloration may occur on branches occurs in limbs some scattered over the entire tree distance back from or they may be confined to one those branches that side (Figure 1). In Kentucky, actually show wilting evidence of this disease is symptoms. usually first observed during periods of drought stress Figure 1, Verticillium wilt of catalpa. Notice that Several other diseases most symptoms have developed on the right side. during summer. and environmental stresses can cause Typical symptoms include: similar symptoms, so visual appearance • Sudden wilting and yellowing of leaves alone is insufficient to conclusively diagnose • Leaf scorch, browning (Figure 2), and Verticillium wilt. Positive diagnosis requires dying of leaves isolating the fungus from discolored sapwood. • Failure of branches to leaf out in spring Contact your county Extension office for • Sparse and/or undersized leaves information on submitting samples for • Death of part or all of a tree verification of this disease.
Agriculture & Natural Resources • Family & Consumer Sciences • 4-H/Youth Development • Community & Economic Development Figure 2 Figure 3
Figure 2. Early symptoms of Verticillium wilt include browning of foliage, particularly between veins and at leaf margins. Wilt symptoms are the result of restricted movement of water and nutrients to leaves and branch tips. Figure 3. Vascular streaking beneath the bark of a maple branch infected with Verticillium wilt.
Cause and Spread Disease Management Verticillium wilt is caused by the soil-borne Verticillium wilt disease cannot be cured, but fungus, Verticillium dahliae. Infection typically the life of trees showing mild symptoms can occurs through roots; however, windblown possibly be prolonged with proper tree care: spores may also enter through wounded tissue • Prune and destroy symptomatic twigs aboveground. and branches. Sanitize pruners between cuts with a commercial sanitizer, 10% After entering host tissue, the pathogen invades Lysol disinfectant, 10% bleach, or rubbing water-conducting tissues and is transported alcohol. throughout the tree via the sap stream. As the • When disease is detected, apply a fungus moves systemically through the plant, fertilizer high in nitrogen to promote tree infected water conducting tissues die. Water vigor. stress and nutrient shortage result, ultimately • Water trees liberally as needed during causing the symptoms described above. summer, especially the first few years after planting. Research indicates that The Verticillium fungus can survive in the trees that are watered generously are soil for many years as microsclerotia. These infected less frequently than those under tiny durable resting structures are spread water stress. Do not overwater. whenever infested soil particles are moved via foot traffic, tools, wind, or water. Germinating Trees with severe symptoms cannot be saved. microsclerotia are capable of infecting roots of • Remove and destroy entire affected tree susceptible plants (Table 1). Microsclerotia do or shrub. not survive as well in wet conditions. • Replant with resistant plant species (Table 2) or cultivars.
Additional Resource Woody Plant Disease Management Guide for Nurseries and Landscapes, ID-88 http://www.ca.uky.edu/agc/pubs/id/id88/id88.pdf Table 1. Partial listing of woody hosts Table 2. Partial listing of woody plants susceptible to Verticillium wilt. considered resistant to Verticillium wilt. Common name Genus Common name Genus Ash Fraxinus Apple Malus Azalea Rhododendron Beech Fagus Barberry Berberis Birch Betula Black Locust Robinia Crabapple Malus Brambles (e.g. blackberry) Rubus Chestnut Castanea Buckeye Aesculus Dogwood Cornus Catalpa Catalpa Firethorn Pyracantha Currant, Gooseberry Ribes Gingko Gingko Elm Ulmus Hawthorn Crataegus Golden Raintree Koelreuteria Hickory, Pecan Carya Honeysuckle Lonicera Holly Ilex Horse Chestnut Aesculus Honey Locust Gleditsia Kentucky Coffee Tree Gymnocladus Hornbeam Carpinus Lilac Syringa Juniper Juniperus Magnolia Magnolia Katusuratree Cercidiphyllum Maple Acer Linden Tilia Osage Orange Maclura Mountain Ash Sorbus Persimmon Diospyros Mulberry Morus Privet Ligustrum Oak Quercus Redbud Cercis Pawpaw Asimina Rose Rosa Pear Pyrus Russian Olive Elaegnus Poplar Populus Sassafras Sassafras Rhododendron Rhododendron Smoke Tree Cotinus Sweetgum Liquidamber Stone fruits (e.g. cherry, peach) Prunus Sycamore Platanus Tree-of-Heaven Ailanthus Walnut Juglans Tuliptree (tulip poplar) Liriodendron Willow Salix Tupelo Nyssa Zelkova Zelcova Viburnum Viburnum Needled evergreens Picea, Pinus, Taxus, etc. Weigela Weigela Yellowwood Cladrastis
March 2013
Photos by John R. Hartman, University of Kentucky
Revised from “Verticillium Wilt of Woody Ornamentals” (PPA-18) by John Hartman, 1996
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