Woody Plant Disease Management Guide for Nurseries and Landscapes Nicole A

COOPERATIVE EXTENSION SERVICE UNIVERSITY OF KENTUCKY COLLEGE OF AGRICULTURE, FOOD AND ENVIRONMENT, LEXINGTON, KY, 40546

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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 pathogens 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 diseases 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 diseases 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 ūūAnthracnose Preventive and curative; systemic; may control other ūūPowdery mildew fungal diseases not listed ūūSome rusts ūūLate blight Bordeaux mixture Bordo-mix ūūFungal 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; effective as dormant spray Captan Captan ūūFoliar fungal Broad spectrum; preventive; not effective for water Captec pathogens molds such as Phytophthora or Pythium Orthocide Chlorothalonil Daconil ūūFungal diseases Broad spectrum Bravo ūūPowdery mildew Echo ūūNeedle diseases Manicure Copper (fixed) Copper Sulfate ūūFungal diseases General protectant fungicide and bactericide; may be Tribasic Copper ūūBacterial diseases phytotoxic to new spring growth, especially Ilex spp.; approved for organic production Copper hydroxide Kocide ūūMildews General protectant; may be phytotoxic; may discolor Champion ūūLeaf spots foliage ūūFungal diseases ūūBacterial diseases Copper sulfate + hydrated See Bordeaux mixture lime Copper sulfate Phyton 27 ūūFungal diseases Labeled for a wide variety of diseases; can be used for pentahydrate ūūBotrytis gray mold landscape, nursery, and greenhouse ornamentals; not ūūPowdery mildew phytotoxic like many other copper-based products; ūūBacterial diseases injectable for Dutch elm disease Cyazofamid Segway ūūDowny mildew Control of oomycetes (water molds) such as Pythium, ūūDamping off Phytophthora, and downy mildew pathogens ūūRoot rots ūūStem rots Etridiazole (Ethazole) Terrazole ūūDamping off Soil drench effective against oomycetes (water molds) Truban ūūRoot rots such as Pythium and Phytophthora ūūStem rots Ethazole + thiophanate Banrot ūūSoil-borne diseases Soil drench effective against fungal and oomycete methyl soil-borne diseases including Pythium, Phytophthora, Rhizoctonia, Fusarium, and Thielaviopsis

3 Table 1. Chemicals for Disease Management (continued) Target Organism(s) Common Chemical Name Trade Name(s) or Disease(s) Comments Fenahexamide Decree ūūBotrytis gray mold Gray mold control in ornamentals and fruit; powdery ūūPowdery mildew mildew control in ornamentals Fenarimol Vintage ūūPowdery mildew Locally systemic fungicide; not for use in nurseries Rubigan ūūApple scab and greenhouses; no longer available in 2013 Fludioxonil Medallion ūūFoliar diseases Foliar fungal pathogens such as Rhizoctonia, ūūBotrytis gray mold Alternaria, Septoria, Cercospora; soil-borne pathogens ūūStem and crown rots Fusarium, Rhizoctonia, Sclerotium, Thielaiopsis; not ūūRoot rots effective against oomycetes (water molds); for use on commercial ornamentals only Fosetyl-Al Aliette ūūDowny mildew Foliar and soil drench; systemic; controls Pythium, ūūRoot rots Phytophthora, and downy mildew pathogens on ornamentals, fruit, and nuts; not compatible with copper fungicides Gallex Galltrol ūūCrown gall Preventative and curative biological control Norbac-84 Iprodione Chipco ūūFungal disease Broad spectrum fungicide; nursery and greenhouse Rovral use only Mancozeb Dithane M-45 ūūFoliar diseases General protectant fungicide Mancozeb Protect T/O MBC phosphate Lignasan BLM ūūDutch elm disease Injectable systemic fungicide ElmPro Elm-Noculate Fungisol Mefenoxam Subdue ūūDowny mildew Systemic soil drench for control of oomycetes (water ūūRoot rots molds) such as Pythium and Phytophthora; treatment ūūCrown rots for foliar blights caused by oomycetes, including ūūFoliar blight Phytophthora ramorum; seed and foliar treatment for ūūSudden oak death downy mildew Myclobutanil Eagle ūūPowdery mildew Systemic protectant and curative treatment for a ūūRusts variety of fungal diseases, including Cercospora leaf ūūLeaf spots spots ūūLeaf blights Pentachloronitrobenzene Terraclor ūūRoot rots Controls root and stem rots caused by fungi such as PCNB PCNB ūūStem rots Rhizoctonia and Sclerotium spp.; not effective against Quintozene oomycetes (water molds)

Phosphorus acid Alude ūūDowny mildew Fully systemic fungicide for treatment of oomycetes Vital ūūRoot rots (water molds), such as Pythium, Phytophthora, and ūūCollar rots downy mildew ūūCrown rots ūūBacterial blight Piperalin Pipron ūūPowdery mildew For use in greenhouses for roses and other ornamentals Propamocarb Banol ūūLeaf blights For control of oomycetes (water molds) such as ūūRoot rots Pythium and Phytophthora in commercially-grown ornamentals. Not for use in landscapes.

4 Table 1. Chemicals for Disease Management (continued) Target Organism(s) Common Chemical Name Trade Name(s) or Disease(s) Comments Propiconazole Alamo ūūAnthracnose Locally systemic fungicide. Alamo is an injectable Banner ūūLeaf spots fungicide for management of Dutch elm disease and Immune ūūLeaf blights oak wilt; not for use in greenhouses ūūScab ūūPowdery mildew ūūRusts ūūDutch elm disease ūūOak wilt Pyraclostrobin + boscalid Pageant ūūFoliar diseases Broad spectrum fungicide; restricted for use in ūūSoil-borne diseases commercial landscapes, nurseries, and greenhouses Streptomycin sulphate Ag-Strep ūūBacterial diseases Effective against bacterial pathogens only; not Agrimycin effective cure for existing infections. Ineffective at low Phytomycin temperatures; may cause phytotoxicity at high rates during hot weather. Efficacy favored by slow drying Streptomycin conditions. Not labeled for urban landscapes Sulfur Sulfur dust ūūPowdery mildew Preventative treatment for fungi and some insects Thiolux ūūFungal diseases and mites. Phytotoxic on Viburnum spp. May injure Liquid lime- ūūSome insects & mites plants at temperatures above 90˚F; not compatible sulfur with oil-based pesticides; sulfur does not mix safely with many pesticide formulations; consult label Thiabendazole Arbortect ūūDutch elm disease Injectable fungicide ūūSycamore anthracnose Thiophanate-methyl AllBan ūūFoliar diseases Broad spectrum fungicide with systemic properties; Cleary’s 3336 ūūRoot rots not effective against oomycetes (water molds); foliar Topsin M spray or soil drench, usually combined with other fungicides Thiophanate-methyl + Zyban ūūFungal diseases Broad spectrum fungicide with systemic curative and mancozeb protective properties Triadimefon Bayleton ūūFlower blights Systemic fungicide for various diseases of Strike ūūLeaf blights ornamentals; not for landscape use ūūStem blights ūūPowdery mildew ūūRust Triflorine Funginex ūūRose diseases Systemic treatment for rose diseases ūūPowdery mildew Trifloxystrobin Compass ūūLeaf spots Broad spectrum fungicides for control of a wide range ūūPowdery mildew of diseases, including rots caused by Rhizoctonia; ūūBlack root rot protects against some diseases caused by oomycetes ūūStem and root rots (water molds); nursery and greenhouse use only Triflumizole Terraguard ūūFoliar diseases General protectant fungicide; not effective against ūūRoot rots soil-borne diseases caused by oomycetes (water ūūPetal blights molds); can be used as a foliar spray, soil drench, or ūūPowdery mildew soak for cuttings in greenhouses and nurseries ūūRusts Ziram Ziram ūūFungal diseases General protectant fungicide for roses and tree and vine fruit

5 Nematode Control pathogen. Retaining vigor may help Norbac 84. Destroy heavily infected Soil-borne nematodes can be prevent infection. Replace infected plants. Prune out and destroy galls controlled using nematicidal fumi- trees with resistant hosts such as: on high value landscape plants. gants like chlorinated hydrocarbon • Fagus sylvatica (beech) Disinfest tools between cuts. Ap- compounds applied before planting. • Quercus acutissima (sawtooth ply Gallex to exposed galls. Do not Follow guidelines listed previously oak) plant susceptible hosts in locations for soil fumigation. • Tilia spp. (linden) where crown gall has been a prob- Soybean cyst nematode, a quaran- • Liriodendron tulipifera (tulip lem. Euonymus alatus is resistant tine pest in many states, is common- poplar) to crown gall. ly associated with various nursery • Ulmus parvifolia (Lacebark or Genera resistant to crown gall weeds. To comply with clean stock Chinese elm) include: certification requirements, nurseries • Celtis laevigata (hackberry) • Betula (birch) shipping balled-and-burlapped plant • Carya spp. (hickory) • Berberis (barberry) material to certain states must ob- • Zelkova serrata (Japanese • Buxus (boxwood) tain a state phytosanitary certificate zelkova) • Carpinus (hornbeam) verifying that soil is free of soybean • Catalpa (catalpa) cyst nematode. See ID-110 and HO- • Cedrus (cedar) 99, and your Cooperative Extension • Cephalotaxus (plum yew) agent for more information. • Cercis (redbud) • Cryptomeria (Japanese cedar) General recommendations • Fagus (beech) for disease management • Ginkgo (ginkgo) • Gymnocladus (Kentucky Bacterial leaf spots and blights. coffeetree) Remove diseased leaves and infected • Ilex (holly) plant material. Thin plants and in- • Kalmia (mountain laurel) crease spacing to improve air circu- • Koelreuteria (golden raintree) lation. Eliminate overhead irrigation • Larix (larch) to prevent moisture accumulation • Liquidambar (sweetgum) on the foliage and splashing that • Liriodendron (tulip poplar) spreads the pathogen. Avoid han- • Magnolia (magnolia) dling wet plants to reduce spread of Bacterial leaf scorch of sweet gum (Photo by J. Hartman) • Mahonia (mahonia, grape bacterial cells. Copper-based fungi- holly) cides and bactericides limit disease • Nyssa (blackgum) spread. Streptomycin-based bacte- • Picea (spruce) ricides are labeled for commercial • Pinus (pine) use only. Fungicides are not effective • Pieris (Japanese pieris) against bacterial pathogens. • Pyracantha (pyracantha, fire- Bacterial leaf scorch. There are thorn) no effective control options. The • Pseudolarix (false larch) pathogen is transported by leaf hop- • Sambucus (elderberry) pers and spittlebugs, but vector con- • Tamarix (tamarisk) trol usually is not possible. No cure Bacterial leaf scorch of red oak • Taxodium (bald cypress) exists for bacterial leaf scorch. Both (Photo by J. Hartman) • Tilia (linden, basswood) foliar and injectable bactericides • Tsuga (hemlock) are inconsistent and are not long- Refer to PPFS-OR-W-12 for a • Zelkova (Japanese zelkova) term solutions. Destroy infected complete listing of resistant and plants when possible. In landscapes, susceptible plants. Dieback, decline, and cankers. newly symptomatic branches can be Keep trees well-watered, espe- pruned out to remove the pathogen. Crown gall. Do not take cuttings cially during periods of low rainfall. This method may prolong tree life from infected plants. Pretreat cut- Pathogens causing diseases such as but will not eradicate the disease or tings or liners with Galltrol-A or cankers and root and crown rots may

6 be secondary invaders in declining may be required for high value or in spring, spray with azoxystrobin, plants. Overwatering also may be commercial crops when conditions Bordeaux mixture, chlorothalonil, problematic. Prune out dead and favor disease. copper (fixed), fludioxonil, iprodione, dying branches. Prevent decline by mancozeb, myclobutanil, propicon- routine care and proper tree place- Fire blight. Use resistant species azole, pyraclostrobin, thiophanate- ment. Avoid salt exposure and soil or cultivars. Remove fire blight- methyl, or triadimefon. Fungicide compaction. Sever girdling roots as infected limbs and branches 12 specificity varies per pathogen. Refer needed. Control damaging insects. inches below diseased tissue. If to “Chemicals for Disease Manage- Aerate compacted soil in root zone. possible, delay pruning until winter ment” on pages 3-5, and read fun- Abiotic conditions such as environ- when the risk of spreading bacteria is gicide labels to verify that specific mental or cultural conditions may significantly reduced. Sanitize tools plants and diseases are listed. Timing cause dieback. between cuts. Prune out cankers and of applications varies by pathogen. blighted branches from November Bacterial diseases are not controlled through March, making cuts below with fungicides and therefore should the visible limits of infection; prun- be treated differently. ing from April through October has little value in fire blight control and, in fact, may spread the disease. Never prune or work in orchards or landscapes when leaves or limbs are wet. Avoid excessive fertilization. Anthrose canker on sycamore Apply copper sulfate during late dor- (Photo by J. Hartman) mancy to active cankers, twigs, and branches to help reduce overwintering populations of the bacterium. Streptomycin is not labeled for urban landscapes. Several new biological Anthracnose on sycamore leaf control agents are available, such as (Photo by C. Kaiser) Serenade® and BlightBan®. Powdery mildew. Provide growing site with good air movement and sunlight penetration by pruning and properly spacing plants. Apply azoxystrobin, fenarimol, mancozeb + thiophanate-methyl, myclobutanil, propiconazole, sulfur, thiophanate- methyl, triadimefon, trifloxystrobin, triflumizole, or ziram at regular Fireblight on Callery Pear intervals. Check fungicide labels for Chestnut blight trunk cankers (Photo by J. Hartman) specific instructions. (Photo by J. Hartman) Fungal leaf spots and leaf blights, Downy mildew. Provide growing including anthracnose. Sprays are site with good air movement and usually not needed except when aes- sunlight penetration by pruning thetics are of primary importance. and properly spacing plants. Reduce Provide a growing site with good air overhead irrigation to keep foliage movement and sunlight penetration dry. Rake and destroy fallen infected by pruning and properly spacing leaves in autumn. Apply azoxys- plants. Rake and destroy fallen in- trobin, copper, cyazofamid, fosetyl- fected leaves in autumn. If disease Powdery Mildew on dogwood AL, mancozeb, or phosphorus acid. was severe the previous year and (Photo by J. Hartman) Scheduled fungicide applications cool, wet conditions are expected

7 Root rots, cutting rots, and Plants with resistance to Verticil- trees with non-susceptible hosts list- crown rots. Provide good sanitation, lium wilt include: ed in “General Recommendations.” including clean plant materials and • Asimina triloba (papaw) Fungal cankers. Fertilize and wa- growing media. Good soil drainage • Betula spp. (birch) ter as needed to provide good grow- is essential. Remove and destroy dis- • Buxus spp. (boxwood) ing conditions for maintaining plant eased plants if possible. Avoid root • Cercidiphyllum japonicum health. Avoid injuries. Remove and and crown injury where pathogens (katsuratree) destroy cankered branches or excise can enter. Fungicide drenches may • Carpinus spp.(hornbeam) trunk cankers when bark is dry. be used if labeled for the specific • Cornus spp. (dogwood) Phyllosticta and other leaf spots. crop. Two pathogen groups are re- • Crataegus spp. (hawthorn) Chemical control is not required. sponsible for root rots. For root rots • Ginkgo biloba (ginkgo) Rake and destroy fallen leaves. If caused by water molds, use products • Fagus spp. (beech) disease is a recurring problem, use containing mefenoxam, fosetyl-Al, • Gleditsia triacanthos, inermis preventative fungicides as indicated phosphorus acid, or etridiazole. For (thornless honeylocust) under “General Recommendations.” Rhizoctonia or other fungal rots, use • Ilex spp. (holly) Taphrina leaf blister. Sprays azoxystrobin, iprodione, mancozeb, • Juglans spp. (walnut) usually are not needed. A single paraclostrobin, PCNB, thiophanate- • Liquidambar styraciflua dormant application of lime sulfur methyl, or trifloxystrobin. Crown (sweetgum) will control this disease. rots are usually not treatable; remove • Malus spp. (apple, crabapple) Tar spot. Rake and destroy fallen and destroy infected plants. • Morus spp. (mulberry) leaves. Sprays usually are not needed. Rusts. Provide a growing site with • Platanus spp. (sycamore, Verticillium wilt. See “General good air movement and sunlight planetree) Recommendations.” penetration by pruning and properly • Populus spp. (poplar) spacing plants. Remove alternative • Pyracantha spp. (pyracantha, hosts. Use resistant species or culti- firethorn) vars when possible. Fungicides may • Quercus spp. (oak) be used for preventative control • Pyrus spp. (pear) if disease was severe during the • Salix spp. (willow) previous year and wet conditions • Sorbus alnifolia (Korean are expected. Otherwise, curative mountainash) treatments should be made when • Tilia spp. (linden, basswood) Verticillium wilt with vascular streaking on symptoms first appear using a fun- • Zelkova serrata (Japanese zel- maple (Photo by J. Hartman) gicide with azoxystrobin, chlorotha- kova) lonil, myclobutanil, propiconazole, • Needled evergreens pyraclostrobin, thiophanate-methyl, triadimefon, or trifloxystrobin. Recommendations for Fungicide specificity varies with common diseases of the pathogen; refer to “Chemicals landscape plants for Disease Management” on pages 3-5 and to product labels. Timing Abelia (abelia) of applications varies by pathogen. Leaf spot. See suggestions under Verticillium wilt. Practice strict “General Recommendations.” nursery hygiene. It is difficult to Powdery mildew. See suggestions disinfest contaminated soil even under “General Recommendations.” by using soil fumigation. Rogue infected nursery plants. In the land- Acer (maple) scape, prune out infected branches Anthracnose. See suggestions or remove severely infected plants. under “General Recommendations.” Fertilize and water landscape plants Bacterial leaf scorch. No effective to reduce plant stress. Replace dis- treatment is available. Retaining vigor eased plants with resistant species. Tar spot on maple may help prevent infection. Replace (Photo by C. Kaiser)

8 Aesculus (horsechestnut, Carya (hickory) foliage is dry. Control borers, and buckeye) Fungal leaf spots. Rake and avoid other injuries. Provide water Abiotic scorch. Provide adequate destroy fallen leaves. Fungicides during dry periods. water. usually are not necessary. If disease Verticillium wilt. See suggestions Guignardia leaf blotch, leaf has been severe, sprays may be under “General Recommendations.” warranted. See suggestions under spots. Destroy fallen leaves in au- Cornus (dogwood) tumn. Spray with chlorothalonil or “General Recommendations.” Botrytis flower and leaf blight. mancozeb two to four times at 10- Castanea (chestnut) to 14-day intervals beginning when Disease is serious only in wet years. buds open. Weather conditions and Chestnut blight, Cryphonectria If wet weather occurs during bloom, severity of disease determine num- (Endothia) parasitica. There is no spray once with thiophanate- methyl ber of applications needed. Aesculus cure for this disease. American chest- or iprodione. Improve air circulation. parviflora reportedly is resistant to nut is extremely susceptible, but re- Canker and dieback. Maintain leaf blotch. sistant/tolerant hybrid cultivars have vigorous tree growth. See suggestions been developed by crossing American under “General Recommendations.” Amelanchier (serviceberry) chestnut with Asian species. Chinese Dogwood anthracnose (discula Fire blight. See “General Recom- chestnut is mostly disease-tolerant. anthracnose, lower branch die- mendations” above. Another chestnut revitalization pro- back). Prune diseased branches Powdery mildew. See suggestions gram uses a biological control meth- back to sound wood, and destroy under “General Recommendations.” od involving “hypovirulent” fungal them. Rake and destroy fallen leaves. Rust. See suggestions under strains. These weakened strains of Avoid trimmer and mower wounds “Malus.” the fungus are injected into trees as as well as other injuries. Maintain competitors against lethal strains. vigor by applying mulch; water dur- Betula (birch) ing dry periods. Do not transplant Catalpa (catalpa) Leaf spots, leaf rust. Rake and dogwood trees from the wild. See destroy fallen leaves. Fungicides are Fungal leaf spots. Rake and de- “General Recommendations.” Fun- not necessary. stroy fallen leaves. Sprays are usually gicide applications should begin at not necessary. If disease has been bud break and continue at 10- to Buxus (boxwood) severe, see suggestions under “Gen- 14-day intervals. Macrophoma and other leaf eral Recommendations.” Spray when spots. Use sanitation measures as leaves are unfolding, when leaves indicated in “General Recommen- reach full size, and two weeks later. dations.” Fertilize and protect from Verticillium wilt. See suggestions winter injury to maintain vigor. under “General Recommendations.” Sprays are not needed. Cedrus (cedar) Pseudonectria canker. Plant in well-drained soil, and protect from See “Juniper.” drying winter winds. Prune infected Celtis (hackberry) branches back to healthy wood. In Anthracnose on dogwood spring, if possible, remove and de- Witches’ broom, caused by (Photo by J. Hartman) stroy old leaves lodged in branches. Sphaerotheca phytoptophila and A strong stream of water helps. eriophyid mites. No practical con- Resistant dogwoods include: trol for affected trees is available. • Cornus kousa Chamaecyparis (false cypress, C. sinensis (Chinese hackberry) is ūūMilky Way Japanese cypress) resistant. • C. kousa x florida • C. racemosa Phytophthora root rot. Provide Cercis (redbud) good soil drainage. Drench soils with Susceptible dogwoods: Anthracnose and other leaf mefenoxam, fosetyl-Al, ethidiazole/ • C. kousa spots. See suggestions under “Gen- ethazole + thiophanate-methyl, or ūūvar. chinensis eral Recommendations.” etridiazole. See suggestions under ūūAutumn Rose Botryosphaeria canker. Prune “General Recommendations.” ūūMoonbeam and destroy affected branches when ūūWolf Eyes

9 Fungal twig blights and cankers. tion of disease-resistant cultivars is yl, or propiconazole. Begin a spray Prune diseased branches back to the most effective means of control. schedule when orange rust masses sound wood, and destroy pruned Nearly all cultivars of Cornus develop on cedars (April through branches. Maintain vigor by mulch- kousa and C. kousa x florida are May). Make three or four applica- ing. Water during dry periods. highly resistant to both powdery tions at seven- to 10-day intervals. Leaf spot anthracnose. Use re- mildew and spot anthracnose. Ex- Resistant cultivars include C. crus- sistant cultivars. See suggestions amples include: galli Cockspur and C. phaenopyrum under “General Recommendations.” • C. florida Washington. Preventative fungicides may be nec- ūūCherokee Brave essary for commercial nursery stock. • C. kousa Eleagnus (autumn olive, Begin applications at bud break and ūūMilky Way Russian olive) continue treatments until all new ūūSatomi Canker, dieback. Prune out and growth matures in late spring or ūūTemple Jewel destroy infected branches. early summer. Cultivars resistant to • C. kousa x florida spot anthracnose also are resistant ūūAurora Euonymus (euonymus) to powdery mildew. See cultivar ūūGalaxy Crown gall. Refer to “General selection under “Powdery mildew.” ūūStellar Pink Recommendations” for management Phytophthora crown canker. To recommendations and a listing of Septoria and other fungal leaf help prevent infection, avoid me- genera resistant to crown gall. spots, and spot anthracnose. chanical injuries, especially to the See suggestions Sprays usually are not necessary. Powdery mildew. lower trunk and roots, and control under “General Recommendations.” If disease was severe the previous borers. Infected nursery trees should Apply fungicide weekly beginning year and spring conditions are wet, be destroyed. For established land- when disease symptoms first appear. apply sprays at bud break and 10 and scape plantings, prune branches by 20 days later. See suggestions under removing discolored wood down Forsythia (forsythia) “General Recommendations.” to heartwood if necessary, cutting Cercospora leaf spot. See “Gen- into healthy wood approximately 1½ Cotoneaster (cotoneaster) eral Recommendations.” Fungicides usually are not necessary. inches around the edge of the can- Fire blight. See suggestions un- Prune affected ker. Trees with cankers that encircle der “General Recommendations.” Phomopsis gall. branches. more than one-half the stem should Cotoneaster apiculatus is a resistant be removed, and the area should species. Fraxinus (ash) not be replanted with dogwoods for several years. Provide good soil Crataegus (hawthorn) Anthracnose and other leaf spots. See “General Recommendations.” drainage. Mefenoxam, used as a soil Fabraea leaf spot. Destroy or No effective drench, will suppress crown canker. compost fallen leaves. Spray fungi- Bacterial leaf scorch. control is available. Retaining vigor cides when leaf buds open and repeat may help prevent infection. Replace 10 and 20 days later. Additional ap- trees with non-susceptible hosts; see plications might be necessary during “General Recommendations.” wet seasons. See suggestions under “General Recommendations.” Resistant hawthorns include Crataegus crus-galli Cockspur and C. phaenopyrum Washington. Fire blight. See suggestions under Phytophthora canker on maple “General Recommendations.” (Photo by J. Hartman) Rusts, caused by Gymnosporan- gium spp. See suggestions under Powdery mildew. See suggestions “General Recommendations.” Elimi- under “General Recommendations.” nate nearby red cedar and common Fungicides may be applied when juniper to whatever extent practical. Anthracnose leaf spot on ash (Photo by J. Hartman) fungal colonies are first visible and Spray with triadimefon, chlorothalo- re-applied at regular intervals. Selec- nil, mancozeb + thiophanate-meth-

10 Gleditsia (honeylocust) Yellows, aster yellows. Once plant juniper hosts near flowering Leaf spots. Rake and destroy plants are infected, there is no treat- crabapple, hawthorn, quince, and fallen leaves. See “General Recom- ment for yellows disease. The patho- other rosaceous plants. Manually mendations.” gen is transmitted by leafhoppers, remove galls and infected twigs in Powdery mildew. No chemical but must establish and reproduce early spring if infection is nominal. control needed. See suggestions in host plants before transmission Refer to Table 2 on page 12 for resis- under “General Recommendations.” can occur. Remove infected plants tant cultivars. Thyronectria canker. Avoid in- before replication and spread. Con- juries; alleviate stressful growing trol weeds that can serve as reservoir conditions. hosts. Manage leafhopper vectors, Tolerant cultivars are Shademas- especially in greenhouses. ter and Imperial. Ilex (holly) Hydrangea Black root rot. Practice strict Bacterial wilt. Remove diseased nursery hygiene and sanitation. Ex- leaves, if possible. Eliminate over- clude the pathogen from the nursery head irrigation. Apply a copper- by using disease-free stock plants. Cedar-hawthorne rust on hawthorne based pesticide in late spring to limit Avoid use of unsterilized agricul- (Photo by J. Hartman) disease spread. tural soils in containers, and sanitize Bud blight, gray mold, petal previously used nursery contain- Kabatina tip blight (the most blight. Practice strict nursery hy- ers. Promote good plant growth damaging tip blight in Kentucky). giene. Destroy fallen petals and and reduce stress. In the nursery Prune out infected shoots. Chemical leaves. Space plants for maximum and landscape, a soil drench using controls have not been developed. air circulation. Avoid overhead ir- etridiazole, thiophanate methyl, or Refer to Table 2 for resistant cultivars. rigation, if possible. Fungicide usu- trifloxystrobin may be applied as a Phomopsis. If possible, prune out ally is not necessary, but in severe preventative or curative if infection and destroy infected shoots. Avoid cases plants may be sprayed with is not yet severe. Destruction of in- overhead irrigation. Rogue and de- fungicides such as iprodione, man- fected plants is recommended. stroy infected plants when disease is cozeb, or thiophanate methyl. See Ilex cornuta is a resistant species. first seen in young plantings. Spray suggestions under “General Recom- Fungal leaf spots. Rake and de- with azoxystrobin, copper, manco- mendations.” stroy fallen leaves. zeb, propiconazole, or thiophanate- Cercospora and other fungal Sooty mold. Manage honeydew- methyl plus a spreader-sticker at leaf spots. See suggestions under producing insects such as aphids, two-week intervals throughout the “General Recommendations.” scales, whiteflies, and planthoppers. growing season. Refer to Table 2 for Powdery mildew. See suggestions resistant cultivars. under “General Recommendations.” Juglans (walnut, butternut) Phytophthora root rot. Provide Rust. Spray chlorothalonil, triad- Fungal leaf spots. Destroy fallen good soil drainage. Drench soils with imefon, or propiconazole just before leaves. Apply three fungicide appli- mefenoxam, fosetyl-Al, phosphorus disease is expected and again two cations as suggested under “General acid, or etridiazole. See suggestions weeks later. See suggestions under Recommendations” at two-week in- under “General Recommendations.” tervals, beginning when leaves begin “General Recommendations.” Kalmia (mountain laurel) Viral diseases. There is no cure to unfold. for viral infections in hydrangea. Thousand cankers. Remove dis- Fungal leaf spots, Phytophthora Remove infected plants, if possible. eased trees, and burn all parts. leaf spot. Hand pick infected leaves If plants cannot be removed or if Thousand cankers disease is spread and prune infected shoots; destroy symptoms are minimal, prune and by the walnut twig beetle. No cure fallen leaves. If disease has been destroy symptomatic canes. Sanitize exists for thousand cankers disease. severe in recent years, spray as sug- tools between cuts. Viruses are sys- gested under “General Recommen- Juniperus (juniper, red cedar) temic, so even symptomless canes dations” at bud break and again 10 are infected; do not propagate virus- Cedar-apple, cedar-hawthorn, and 20 days later. infected plants. and cedar-quince rusts, caused Phytophthora root rot. Provide by Gymnosporangium spp. Do not good soil drainage. Drench soils with

11 Table 2. Resistant cultivars of Juniperus Magnolia (magnolia) Resistant species/cultivars Cedar rusts Kabatina Phomopsis Leaf spots. If disease has been severe in recent years, spray as suggested J uniperus ashei X under “General Recommendations.” J. Chinensis Blue Point X — Sooty mold. Manage honeydew- Columnaris Hetzii X X producing insects such as aphids, Grey Owl X scales, whiteflies, and planthoppers. Hetzii X X Malus (apple, flowering Iowa X crabapple) Keteleeri X X X Crabapple cultivars are avail- Perfecta X X able that are resistant to multiple Pfitzeriana X X X diseases. The following flowering Pfitzeriana Glauca X crabapple cultivars are moderately to Saybrook Gold X X highly resistant to powdery mildew, Spartan X X scab, fire blight leaf spot, and rust (see also ID-68): J. conferta Blue Pacific X — • Adams J. communis—Hibernica X X X • David J. communis var depressa X • Donald Wyman J. Horizontalis—Bar Harbor X • Jewelberry Wiltonii X • Molten Lava • Profusion J. procumbans X • Red Jewel J. procumbans—Nana X • Robinson J. rigida X • Sentinel J. sabina—Broadmoor X X X • Sugar Tyme J. scopulorum—Wichita Blue X • Velvet Pillar • White Cascade • Malus sargentii Liriodendron (tulip poplar) mefenoxam, fosetyl-Al, phosphorus • M. zumi Calocarpa acid, or etridiazole. See suggestions Fungal leaf spots, Phytophthora under “General Recommendations.” leaf spot. Handpick infected leaves, and prune infected shoots. Destroy Koelreuteria (goldenrain tree) or compost fallen leaves. If disease Nectria canker. Prune back to has been severe in recent years, spray sound wood. Fertilize and water to as suggested under “General Recom- maintain vigor. mendations” at bud break and again Verticillium wilt. See suggestions 10 and 20 days later. under “General Recommendations.” Phytophthora root rot. Provide good soil drainage. Drench soils with Lagerstroemia (crape myrtle) mefenoxam, fosetyl-Al, phosphorus See sugges- Cercospora leaf spot. acid, or etridiazole. See suggestions Scab on pyracantha tions under “General Recommenda- under “General Recommendations.” (Photo by J. Hartman) tions.” Cultivars that are resistant Powdery mildew. There is no to powdery mildew usually also are need for chemicals to control this Fire blight. See “General Recom- resistant to Cercospora leaf spot. disease. Use cultural practices as mendations.” Remove non-valuable Azoxystrobin, copper, and myclobu- suggested under “General Recom- pear, apple, quince, and similar tanil may be used if disease is severe. mendations.” plants from the vicinity. Powdery mildew. See suggestions Verticillium wilt. See suggestions Timing of antibiotic applications under “General Recommendations.” under “General Recommendations.” is based on weather conditions during bloom; however favorable

12 conditions do not exist in all years Apply before rain if possible, and ex- dle pines. Space trees and prune or in all nurseries or orchards. tend the treatment schedule during branches to promote air circulation. Commercial growers may use the rainy seasons. Use disease-resistant If rainy conditions persist between MARYBLYT computer program to crabapples. mid-April and October or if trees be- help them make management deci- come infected, apply chlorothalonil, sions. MARYBLYT calculates the Picea (spruce) mancozeb, or thiophanate-methyl risk of fire-blight infections based Cytospora canker. Avoid injuries, every four weeks. Four applications on daily temperatures, rainfall, and and retain vigorous growth. Remove can be made at monthly intervals plant developmental stage. Other- and destroy all diseased branches. mid-April through June for brown wise, spray with streptomycin when Do not prune in wet weather. Dis- spot needle blight and Naemacyc- 25 percent of blossoms are open and infest tools between cuts. Chemical lus needle cast or in early July for again when 75 percent of blossoms control measures are not available. Lophodermium needle cast. are open. If temperatures are above Colorado blue spruce is most sus- 65 degrees, use fixed copper instead ceptible to this disease. of streptomycin to prevent injury. Needle blight. Sprays normally Streptomycin is not labeled for urban are not needed. This disease most landscapes. often is found on trees weakened Frogeye leaf spot and black rot by other factors. Chlorothalonil ap- canker. Leaf spot does not cause plications are effective when made severe damage, but infections can in early and late June for three con- threaten stems and branches. Elimi- secutive years. nate dead twigs and branches. Phytophthora root rot. Provide Powdery mildew. Provide a sun- good soil drainage. Drench soils with ny, well-ventilated planting site. Use mefenoxam, fosetyl-Al, phosphorus disease-resistant plants. Prune away acid, or etridiazole. See suggestions shading vegetation. For fungicide under “General Recommendations.” options, see “General Recommen- Rhizosphaera needlecast. Sprays dations.” normally are not needed. This dis- Rust caused by Gymnosporan- ease most often is found on trees gium spp. Eliminate nearby red weakened by other factors. Chloro- cedar and common juniper where thalonil applications in early and late possible, or remove and destroy cedar June may help. Colorado blue spruce Tip blight on pine rust galls and rust-infected juniper is highly susceptible, and Norway (Photo by J. Hartman) twigs. Spray with myclobutanil, spruce is resistant. propiconazole, triadimefon, or other Pieris (andromeda) Needle rust of two- and three- fungicides listed under “General needle pines (Coleosporium). Recommendations.” Make three ap- See “Rhododendron.” Goldenrod and aster plants are al- plications at 14- to 21-day intervals Pinus (pine) ternate hosts and should be removed beginning when orange rust masses before August of each year. develop on junipers (April through Gall rusts of two- and three- Pine wilt nematode. Remove and May). needle pines (Eastern gall rust, destroy affected trees. In nurseries, Scab. Rake and destroy all fallen Western gall rust). Tip blight of two- and three- cull seedlings with stem swellings. leaves and fruits in the fall. To con- needle pines. Prune and destroy trol primary infections in the spring, In landscapes, remove branch galls affected cones, twigs, and branches spray trees during pink-bud stage, and rogue heavily galled trees in during dry weather in autumn. Spray petal-fall, and at 10 and 20 days after early spring. Apply fungicides once with thiophanate-methyl at bud petal-fall. Pyraclostrobin, chloro- when yellow pustules erupt through break, again as candles are begin- thalonil, propiconazole, mancozeb, bark on galls. See “General Recom- ning to elongate, and finally when thiophanate-methyl, or mancozeb mendations.” needles are emerging from needle + thiophanate-methyl can be used. Needlecast and needle blight sheaths. Use a spreader-sticker. diseases of two- and three-nee-

13 White pine decline, a non- Populus (poplar, aspen, Pyrus (pear) infectious disease. This condition cottonwood) Fire blight. See “Malus” and is not caused by a pathogen. Provide Fungal cankers. Mulch and wa- “General Recommendations” for fire a planting site with acidic soil and ter trees as needed to reduce stress. blight control. Bradford, Aristocrat, little clay. Avoid soil compaction, Avoid wounding. Prune out and de- and other flowering pear cultivars planting too deeply, overmulching, stroy infected branches during dry are susceptible to this disease, yet drought-prone sites, and tree inju- weather. Destroy severely affected not normally heavily infected. ries. Remedial sulfur applications to trees. Lombardy poplar is extremely acidify soil may benefit trees. susceptible. White pine root decline, a fun- Leaf rust. Spray triadimefon in gal disease. Remove and destroy early summer just before disease is infected trees. Choose well-drained expected and again two weeks later. planting sites. Control wood-boring insect vectors of this disease. Prunus (cherry, flowering cherry, peach, flowering almond) Black knot. Remove and destroy knotted twigs, and excise knots on Fire blight on spurs of callery pear large limbs when trees are dormant. (Photo by J. Hartman) Spray with thiophanate-methyl when dormant and at pink-bud stage, full Quercus (oak) bloom, and three weeks later. Actinopelte leaf spot. Normally, Crown gall. See “General Recom- there is no need for fungicides. Rake mendations” for crown-gall control. and destroy fallen leaves. Propicon- For management of galls on estab- azole sprays may help. lished trees, use Gallex according to Anthracnose. See suggestions label instructions. under “General Recommendations.” Coccomyces leaf spot. Rake and Armillaria shoestring root rot. destroy fallen leaves. Spray propi- This disease most frequently affects conazole or captan at petal fall and trees weakened by other agents, such twice more at two-week intervals. as stress. There are no effective con- Spray a single application after fruit trol options. drop, if needed. Bacterial leaf scorch, Xylella. Monilinia shoot blight (brown There are no effective control op- Spores of the tip blight fungus (black rot). Remove and destroy infected tions. Refer to “General Recom- pycnidia) twigs if possible. Spray captan, chlo- mendations.” (Photo by J. Hartman) rothalonil, or propiconazole as blos- Bacterial wetwood. See recom- soms open and again 10 days later. mendations under “Ulmus.” Platanus (planetree and Pyracantha (firethorn) Dieback, decline. This condition sycamore) is not caused by a pathogen. Keep Bacterial leaf spot. Improve air trees well-watered, especially dur- Anthracnose. Anthracnose is circulation. Remove diseased leaves, ing dry periods from May through generally only an aesthetic problem. if possible. Eliminate overhead irri- When control is necessary, prune July. Control of damaging insects is gation. Use copper-based fungicides important for prevention of dieback out infected twigs and branches. in late spring to limit disease spread. Rake and destroy fallen leaves. See and decline. Alleviate soil compac- Fire blight. See “Malus” fire blight tion in the root zone. Prune out dead fungicide suggestions listed under control and “General Recommenda- “General Recommendations.” Make and dying branches to improve tree tions.” appearance. a first application before trees break Scab. Spray with pyraclostrobin, bud, a second at bud break, and a Phyllosticta leaf spot. Chemical propiconazole, chlorothalonil, thio- control is not required. Rake and third when leaves are expanding. phanate-methyl, mancozeb, or man- Trees also can be protected by thia- destroy fallen leaves. If disease is a cozeb + thiophanate-methyl at full recurring problem, use preventative bendazole injections. bloom and two and four weeks later.

14 fungicides as indicated under “Gen- as propamocarb, mefenoxam, etridi- eral Recommendations.” azole, phosphorus acid, or ethazole Powdery mildew. Usually there is + thiophanate-methyl. no need to control this disease with fungicides. See “General Recom- Rosa (rose) mendations.” Black spot. Spray chlorothalonil, Taphrina leaf blister. Spray once captan, mancozeb, propiconazole, or before bud swell with mancozeb or ziram at 7- to 14-day intervals begin- chlorothalonil. ning as leaves expand. Shorten inter- Tubakia leaf spot. Improve tree vals during wet weather. Advanced vitality, prune out dead wood, and fungicides such as trifloxystrobin prevent stress. Remove fallen leaves. can be used in rotations. Some rose Fungicides are not necessary. varieties are sensitive to chlorothalonil. Rhododendron (azalea, rhododendron) Azalea gall. Remove and destroy galls. Botryosphaeria canker and dieback. Remove and destroy infected Rose rosette virus (Photo by J. Hartman) plant parts, disinfecting tools between cuts. Avoid adverse growing Syringa (lilac) conditions, i.e. drought or freezing. Fungal leaf spots. Handpick in- Black spot on rose Bacterial blight. Prune and de- (Photo by J. Hartman) fected leaves, if possible. Spray at bud stroy dead twigs. Improve air circu- break and 10 and 20 days later with lation, and avoid overhead irrigation. thiophanate-methyl or mancozeb. Crown gall. See “General Recom- Powdery mildew. See “General Lichens. Use cultural practices mendations.” Recommendations” for powdery that promote plant vigor. Lichens Downy mildew. Avoid wetting mildew control. typically are a sign of poor plant leaves. Provide good air circula- Resistant lilacs (non-vulgaris health and plant decline. Lichens do tion. Chemical control must begin types) include Syringa patula and not damage plants. as early as possible during the dis- S. reticulata. Phytophthora shoot dieback and ease cycle. Fosetyl-Al and copper Thuja (arborvitae) foliar blight. Avoid wetting leaves. + mefenoxam should be rotated at Retain plant vigor with proper fertil- intervals indicated on labels. Tip blights. See “Juniperus” for ity, pH, and air circulation. Prune Powdery mildew. See suggestions tip blight control. and destroy infected twigs. Reduce under “General Recommendations.” Ulmus (elm) shade, if possible. As new leaves Select fungicides that also control Bacterial wetwood and slime- appear, spray mancozeb or chloro- black spot. flux. There is no cure for this dis- thalonil as preventatives, making Rose rosette. No control is avail- ease, but bacteria do not weaken two applications 10 to 14 days apart. able. The pathogen is transmitted wood or harm trees. Practice good Applications of mefenoxam, phos- by mites; miticides and removal of sanitation to prevent transmission phorus acid, or fosetyl-Al are effec- diseased plants may reduce spread. by pruning tools. tive against water mold infections. Rose rosette also is spread through Dutch elm disease. This disease is Root rot and wilt, caused by grafting stock. vectored by elm bark beetles, which Phytophthora and other fungi. Stem canker, brown canker, spend a portion of their lifecycle in Plant shrubs only in soils with graft canker. Prune and destroy dead or dying elm trees. Therefore, good drainage. Avoid overwater- infected canes. all dead or dying elm trees or un- ing. Adjust soil pH to 4.0 to 4.5 by healthy branches of elm trees should amending with acid peat or sulfur. be eliminated within 1,000 feet of Apply soil drench fungicides such the trees to be protected. Make

15 a dormant application (March or Ulmus parvifolia (Chinese elm) where Armillaria root rot has been April) of insecticide for control of also is reportedly resistant to Dutch a problem. elm bark beetles. Pruning is some- elm disease. Nectria canker. Retain plant times effective if symptoms are Yellows/phloem necrosis. Yel- vigor, and avoid plant stress. Remove detected while confined to a small lows is caused by a prokaryotic diseased plants. branch. Inject Arbotect 20-S, Lig- pathogen that is transmitted by Crown gall. See “General Recom- nasan (Correx, Elmpro), Fungisol, or leafhoppers. Like Dutch elm dis- mendations.” For galls on established Phyton 27 into the lower trunk and ease, the yellows pathogen is more trees, use Gallex according to label root flare for protection or therapy. pathogenic in North American elm directions. Do not plant trees in See publication PPFS-OR-W-02 for species. Typically, elm resistant to soil where crown gall has been a more information on Dutch elm Dutch elm disease also are resistant problem. disease. to elm yellows disease. See recom- Dutch elm disease. See sugges- In general, native elms are sus- mended cultivars in “Dutch elm tions under “Ulmus.” ceptible to Dutch elm disease and disease,” above. phloem necrosis; elms of European For More Information origin vary in susceptibility to Dutch Viburnum (viburnum) Fungicides for Management of elm disease; elms of Asiatic origin Bacterial wilt, bacterial blight. Landscape Woody Ornamentals: are resistant, though not immune. Remove diseased stems and leaves, http://www2.ca.uky.edu/agcol- if possible. Eliminate overhead ir- lege/plantpathology/ext_files/ rigation. Copper-based fungicides PPFShtml/PPFS-OR-W-14.pdf applied in late spring may limit Jones, R.K., ed. “Diseases of Woody disease spread. Ornamental Plants and Their Phytophthora foliar blight. Control in Nurseries.” North Avoid wetting leaves. Retain plant Carolina State University Coop- vigor with proper fertility, pH, and erative Extension Service. air circulation. Prune and destroy Nursery and Landscape Informa- infected twigs. Reduce shade, if pos- tion: http://www.uky.edu/hort/ sible. As new lesions appear, spray documents-list-commercial-land- mefenoxam, phosphorus acid, or scape fosetyl-Al. Pirone, P.P. “Diseases and Pests of Phytophthora root rot. Provide Ornamental Plants.” John Wiley good soil drainage. Drench soils with & Sons. mefenoxam, fosetyl-Al, phosphorus Sinclair, W.A., Lyon, H.H., and John- acid, or etridiazole. See suggestions son, W.T. “Diseases of Trees and under “General Recommendations.” Shrubs.” Cornell University Press. Powdery mildew. See “Gen- Woody Ornamental Diseases eral Recommendations.” Resistant and Disorders: http://www2. Dutch elm disease on elm cultivars include Viburnum burk- ca.uky.edu/agcollege/plant- (Photo by J. Hartman) woodii Mohawk and V. carlcephalum pathology/extension/pubs. Cayuga. html#OrnamentalWoody The following are hybrids with Woody Plant Information: http:// Asian or European parentage and Zelkova (Japanese zelkova) www.uky.edu/hort/document- thought to be resistant to Dutch Anthracnose. See “General Rec- list-home-woody-plant elm disease: ommendations.” • Dynasty Armillaria root rot. This disease This revision was adapted from • Frontier most frequently affects trees weak- Woody Plant Disease Control Guide • New Horizon ened by stress and other agents. for Kentucky by Hartman, Witt, • Pioneer No curative control options are Hershman, McNiel. • Prospector Mention or display of a trademark, proprietary product, or firm available. Do not plant trees in soil in text or figures does not constitute an endorsement and does not imply approval to the exclusion of other suitable products or firms.

Educational programs of Kentucky Cooperative Extension serve all people regardless of race, color, age, sex, religion, disability, or national origin. Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, M. Scott Smith, Director, Land Grant Programs, University of Kentucky College of Agriculture, Lexington, and Kentucky State University, Frankfort. Copyright © 2012 for materials developed by University of Kentucky Cooperative Extension. This publication may be reproduced in portions or its entirety for educational or nonprofit purposes only. Permitted users shall give credit to the author(s) and include this copyright notice. Publications are also available on the World Wide Web at www.ca.uky.edu.

Revised - 3-2012