COOPERATIVE EXTENSION SERVICE UNIVERSITY OF KENTUCKY COLLEGE OF AGRICULTURE, FOOD AND ENVIRONMENT, LEXINGTON, KY, 40546 ID-88 Woody Plant Disease Management Guide for Nurseries and Landscapes Nicole A. Ward and Cheryl A. Kaiser, Department of Plant Pathology; Sarah J. Vanek, Winston C. Dunwell, and William M. Fountain, Department of Horticulture; Reviewed by Kenny W. Seebold and Paul A. Vincelli, Department of Plant Pathology oody plants are susceptible years. Stresses induced by adverse Cooperative Extension Service pub- to a variety of diseases, and growing conditions, maltreatment, lications, available at each county variousW cultural and environmental and lack of care are favored by vari- Extension office and on the Web stresses increase their susceptibility. ous pathogens. [www.ca.uky.edu/agcomm/pubs.asp], For example, climatic and environ- Many problems in nurseries and cover this topic. mental conditions often predispose landscape plantings may be avoided plants to disease. Levels of suscepti- by: Nursery and bility and resistance also can differ • Selecting proper plant materials Landscape Hygiene between related species or cultivars. • Creating proper planting sites Strict hygiene is necessary to During development of some culti- • Avoiding unnecessary wounding retain disease-free plants and clean vars, for instance, disease resistance • Providing routine care (includ- soil. Some pathogens overwinter on is forsaken for other traits such as ing fertilization, timely water- fallen infected leaves, while others flowering or growth habits. In many ing, and pruning) use nearby plants as overwintering cases, humans, insects, or patho- • Using preventative disease- and reservoirs. Additionally, plant patho- gens create entry wounds for other insect-control measures as genic fungi, bacteria, nematodes, pathogens. Some pathogen popula- needed and viruses are carried into the tions can be undisruptive but may Stresses often are alleviated or nursery or landscape and spread by eventually build to dangerous levels. moderated by proper plant care. footwear, tools and machines, mov- Furthermore, nursery and landscape Several University of Kentucky ing water, blowing soil, and insect plants often are susceptible to dis- eases that might not be a problem in natural habitats. Plants grown outside of their natural habitats are more likely to become stressed; these stressful conditions often are precursors to disease development. Management of woody plant dis- eases usually combines preventative and curative practices, including a focus on plant health, sanitation, cultivar selection, and pesticides. Cultural Practices Proper care of trees and shrubs often prevents many nursery and landscape problems. Susceptibility to disease is influenced not only by current conditions, but also by conditions and care during previous Cedar-apple rust (left) and cedar-quince rust (right) on juniper (Photo by University of Gerogia CES) Agriculture and Natural Resources • Family and Consumer Sciences • 4-H Youth Development • Community and Economic Development EXTENSION vectors. Nurseries especially are • Wash boots and hand tools as it is essential to first consider the vulnerable to outbreaks of conta- well as mechanical equipment. growing conditions. Diseases often gious diseases, so extra precautions • Divert surface water into are best controlled when fungicides are necessary. ditches or culverts to prevent and bactericides are applied before • Purchase clean nursery stock. its movement from one nurs- or soon after infection begins. Do not order or accept plants ery block to another. Systemic pesticides can eradicate that are likely to be infected • Remember that irrigation wa- new infections, but damaged leaves with nematodes, crown gall ter can carry pests and patho- often retain discoloration or visual bacteria, highly destructive gens. Select a clean source, damage. soil-borne fungi, viruses, or and keep it from becoming Coverage rates vary with pesticide phytoplasmas. Certified clean contaminated. See your county formulations. When using broad nursery stock sometimes is Extension agent for advice on spectrum, protectant fungicides, warranted. recycling irrigation water. it is essential to cover every leaf, • Prune or remove infected • Restrict traffic from outdoor twig, and branch that may become plants to eliminate sources of areas to indoor propagation infected by the pathogen. Systemic inoculum (spores or bacterial areas. Clean footwear with a fungicides, on the other hand, are cells that serve as the patho- germicidal agent such as LF-10 transported throughout the plant, so genic material that initiates or Amphyl at entrances. complete coverage is less important. disease). When collecting cut- Familiarity with pesticide labels tings in the field, inspect stock Using Pesticides improves an applicator’s ability to plants carefully and avoid any Most of the diseases listed in this make decisions regarding pesticide plants that show disease symp- publication do not require regular formulations. toms or abnormalities. chemical treatments for control. Use Some spray mixtures require wet- • Rogue (destroy) diseased routine chemical application for dis- ting, spreading, or sticking agents plants or prune diseased parts ease control only when the plant is of (surfactants). These surfactants are from plants as soon as disease high value and a particular disease is particularly necessary when pesti- is observed. Burn or bury the a known threat (has occurred in pre- cides are applied to waxy leafed or discards. Never leave diseased vious seasons, is present in nearby hard-to-wet broadleaf evergreens cuttings in nurseries or land- landscapes, is expected in an opera- or conifers. Follow directions on scapes. Do not compost dis- tion, or is especially devastating). labels, which include restrictions eased plants or cuttings. Foliar sprays. Small trees and regarding the selection of compat- • Disinfest tools regularly when shrubs may be sprayed with hand- ible surfactants. pruning or when collecting pumped, bucket, hose-end, back- Injections and implants. Control cuttings. An easy, effective pack, or small power sprayers. Large of diseases of certain trees is most way to do so is to swab or dip trees often must be sprayed with effective by injecting fungicides into cutting blades with rubbing large spray machines for proper the sapstream at the trunk’s base or alcohol, a 1:5 solution of Lysol™ coverage. on the flare roots. Injections are use- concentrated disinfectant, or a Timing of pesticide applications ful when sprays are not practical or 1:5 solution of bleach (undilut- varies by pathogen. Most patho- effective, such as when the plant is ed bleach is corrosive to metal gens favor wet or humid conditions too large or the pathogen is confined tools). Commercial sanitizers (rain, irrigation, fog), therefore some to vessel tissue. Annual injections also are available. persistent diseases may require are not recommended, as the injury • Equipment moving between protectant sprays before conducive caused by injection is probably more nursery blocks should pass conditions occur. Additional sprays damaging than the problem being through a central area where it might be needed during long periods addressed. Implants are less effective can be washed to remove soil. of such conditions. than injections and rarely are used. For example, equipment may Pathogens often have optimal Soil drench. Soilborne pathogens be parked on a bed of coarse conditions for infection and coloni- often require treatment of soils. rock or a steel grating set over zation. While some prefer cool, wet However, some systemic pesticides a pit, so that contaminated spring and fall weather, others prefer applied to the foliage translocate soil does not wash through the warm summer weather. If preventa- to plant roots where they protect nursery. tive pesticide applications are used, roots and crowns. Pesticides can be 2 applied in bands directly to soil, in medium-sized growers; only large should be followed precisely. Some trenches before planting, or through commercial operations are prepared fungicides are labeled for commer- drip irrigation. Pesticide labels indi- to manage this costly option. cial production and cannot be ap- cate which application methods are plied in landscape situations, while most effective. Chemicals for Disease other pesticides are not labeled for Soil fumigation. General-pur- Management greenhouses or closed environ- pose soil fumigants are designed to Fungicides are listed alphabeti- ments. Therefore, it is essential that eradicate soil-inhabiting organisms cally in Table 1 by common chemi- applicators follow label instructions including fungi, bacteria, nema- cal name, followed by trade name, and contact an Extension agent or todes, insects, plants, and seeds. usage information, and remarks. state specialist if more information Highly restricted materials usu- Pesticide recommendations change is needed. ally are not available to small and periodically, so label instructions Table 1. Chemicals for Disease Management Target Organism(s) Common Chemical Name Trade Name(s) or Disease(s) Comments Azoxystrobin Heritage ū Anthracnose Preventive and curative; systemic; may control other ū Powdery mildew fungal diseases not listed ū Some rusts ū Late blight Bordeaux mixture Bordo-mix ū Fungal and bacterial Broad spectrum; organic; may be phytotoxic to some Copper sulfate + hydrated pathogens Ilex spp. or young foliage of other plants, especially lime during hot weather;