Cercis (redbud) | |
| Canker caused by Botryosphaeria spp. (Plate 81, 59-62) | Prune and destroy affected branches during dry weather. Avoid injuries by humans and insects. |
Chaenomeles (quince) | |
| Fire blight caused by Erwinia amylovora | Destroy nearby neglected pear, apple, and quince. Prune out infected parts when plants are dry, making each cut several inches below areas of visible discoloration. Disinfect pruning tools between each cut. |
| Leaf spot caused by Entomosporium sp. (Plate 38) (Fabraea leaf spot) | Rake and destroy fallen leaves. Apply thiophanate-methyl, Camelot O‡, chlorothalonil, *Spectro 90 WDG‡, myclobutanil, or mancozeb per label directions. |
Chamaecyparis (white cedars) | |
| Blight caused by Phomopsis juniperovora | See Juniperus. The following cultivars, all of C. pisifera, are reported to be resistant: 'Filifera,' 'Aureovariegata,' 'Plumosa Aurea,' 'Plumosa Argentea,' 'Plumosa Lutescens,' and 'Squarrosa Sulfurea.' |
Cornus (dogwood) | |
For additional information on disease resistant dogwoods, see https://hdl.handle.net/1813/56367.2. |
| Crown canker caused by Phytophthora cactorum (Plate 176) | Avoid mechanical injuries, especially to the lower trunk and roots. Control borers as needed. Trees with cankers encircling more than half of the stem should be removed and the area should not be replanted with dogwood. For trees with smaller cankers, apply fluoxastrobin, *Pageant Intrinsic‡, Banol Fungicide or metalaxyl-m (mefenoxam) per label directions or use an appropriate formulation of one of the mono-and di-potassium salts of phosphorus acid for the site. |
| Flower and leaf blight caused by Botrytis cinerea (Plate 25, 35) | Disease is serious only in wet years. If wet weather occurs during bloom and the tree has a history of disease, spray once with chlorothalonil, thiophanate-methyl, *Spectro 90 WDG‡, *Junction‡, iprodione, thiophanate-methyl + iprodione, copper sulfate pentahydrate, potassium bicarbonate, *Pageant Intrinsic‡, *Mural‡, or mancozeb per label directions. |
| Anthracnose caused by Discula destructiva (Plate 52) | Rake and destroy fallen leaves and prune diseased twigs to whatever extent possible. Keep trees well watered. Spray with chlorothalonil, potassium bicarbonate, copper sulfate pentahydrate, copper hydroxide, *Junction‡, propiconazole, myclobutanil, or mancozeb (*Mancozeb DG‡, *Dithane 75DF) or tryfloxystrobin per label directions. Plant flowering dogwoods on open, airy sites to avoid anthracnose or minimize its impact. Most species and hybrids of Cornus - except C. florida and C. kousa 'Autumn Rose,' 'Moonbeam,' and 'Wolf Eyes' - are resistant to this disease. 'Spring Grove' and 'Sunset' cultivars of C. florida and several C. florida X C. kousa hybrids are also resistant. |
| Powdery mildew caused by Microsphaera sp. or Phyllactinia sp. (Plate 3, 3-6) | Powdery mildew on dogwood has become increasingly severe in recent years. Mildew infections may be most prominent during the latter half of the growing season. Apply copper sulfate pentahydrate, myclobutanil, triadimefon, potassium bicarbonate, neem oil, or *Spectro 90 WDG‡ when mildew becomes evident and make additional applications per label directions. |
| Spot anthracnose caused by Elsinoe corni (Plate 29, 8) | If disease was severe the previous year, spray with mancozeb, *Junction‡, myclobutanil, fluoxastrobin, *Mural‡, or azoxystrobin at monthly intervals, beginning when flower buds have opened to the cup stage and continuing until new flower buds have formed, or apply potassium bicarbonate per label directions. |
| Twig blights and cankers caused by Myxosporium everhartii and other fungi | Prune diseased branches back to sound wood and destroy them. Water during dry periods. |
Corylus (filbert, hazelnut) | |
| Eastern filbert blight caused by Anisogramma anomala (Plate 78) | Prune infected branches as they appear and burn or bury them. Remove heavily infected plants. Do not plant Corylus spp. in sites with a history of the disease. Chemical control may not be practical in all landscape situations. Where needed, apply copper hydroxide per label directions. |
Cotoneaster (cotoneaster) | |
For additional information on disease resistant cotoneaster, see https://hdl.handle.net/1813/56368.2. |
| Fire blight caused by Erwinia amylovora (Plates 76, 77, 187) | Destroy nearby neglected pear, apple, and quince. Prune out infected parts when plants are dry, making each cut several inches below areas of visible discoloration. Disinfect pruning tools between each cut. Where necessary, apply copper sulfate |
| Fire blight caused by Erwinia amylovora (Plates 76, 77, 187) (continued) | pentahydrate according to label directions. The following are said to be resistant to fire blight: C. adpressa var. praecox, C. apiculatus, C. bacilliarus, C. deilsiana var. elegans, C. distichus, C. francheti, C. harrovianus, C. microphylla, C. newryensis, C. nitens, C. salicifolius var. repandens, C. simonsii. |
Crataegus (hawthorn) | |
For additional information on disease resistant hawthorn, see https://hdl.handle.net/1813/66887. |
| Fire blight caused by Erwinia amylovora (Plates 76, 77, 187) | Use sanitation as for fire blight on cotoneaster. Avoid heavy fertilization. Apply fosetyl-Al (for suppression), or copper hydroxide at 7- to 10-day intervals beginning when flower buds swell and continuing until bloom period ends OR use an appropriate formulation of one of the mono-and di-potassium salts of phosphorus acid for the site OR inject Tree Tech OTC‡ per label directions. |
| Leaf spot caused by Entomosporium sp. (Plate 27, 38) (Fabraea leaf spot) | Destroy or compost fallen leaves. Spray with mancozeb, myclobutanil, chlorothalonil, *Mural‡, or *Spectro 90 WDG‡ as leaf buds open and twice thereafter at 10- to 14-day intervals. May need additional applications in rainy years. Do not plant highly susceptible English hawthorns. C. crus-galli is resistant. |
| Rusts caused by Gymnosporangium spp. (Plates 118, 119, 129-133) | Eliminate nearby red cedar and common juniper where possible. Spray with chlorothalonil, *Spectro 90 WDG‡, *Pageant Intrinsic‡, mancozeb, triadimefon, thiophanate-methyl, propiconazole, *Mural‡, or myclobutanil when orange rust masses appear on juniper (around mid-May) and three times thereafter at 7- to 14-day intervals or per label directions. C. crus-galli, C. intricata, C. laevigata 'Autumn Glory,' C. phaenopyrum, C. pruinosa, and C. viridis 'Winter King' are said to be resistant to G. globosum. |
| Scab caused by Venturia inaequalis (Plate 43) | Destroy or compost fallen leaves. Spray with mancozeb, potassium bicarbonate, neem oil, myclobutanil, thiophanate-methyl, trifloxystrobin, or *Spectro 90 WDG‡ at pink bud and at petal fall, plus two more applications at 7- to 14-day intervals or per label directions. Extend the schedule during rainy years. |
Fagus (beech) | |
| Bark disease caused by Nectria spp. and associated scale insects (Plates 214, 215, 91) | Disease control depends on control of the beech scale. Malathion will kill crawlers when they are active in late summer. Horticultural oil will kill adults but may be phytotoxic. Spray only infested parts of the tree in cool weather. |
| Bleeding canker caused by
Phytophthora sp. (Plates 176-178) | Raise host vigor by improving root health via timely irrigation, aeration, addition of leaf mulch (4-inch-deep maximum) to root zone delimited by the dripline, and redirection of foot traffic to minimize compaction. Several products containing the active ingredient mono- and di- potassium salts of phosphorous acid are registered in NYS for treating Phytophthora infections on stems of beech trees. Individual products may be labeled for either injection or direct application to the bark (as a spray), but little efficacy data is available at this time regarding these methods. Thus far, research conducted within our department has only focused on application as a directed bark spray, and this method has shown some promise. If the injection method is to be used, we do recommend that it be performed by a trained applicator. It is important to note that all trees may not respond equally well to these treatments. Note: Recommended applications to the trunk/bark are at high concentrations. To protect other plants around the base of the tree(s) from a possible phytotoxic reaction, cover them with a tarp before making the application. |
| Canker caused by Endothia gyrosa (Plate 91, 81) | Fertilize and water trees and aerate soil to keep tree vigor high. Prune diseased branches back to the next-largest branch. Disinfect saw blades between cuts. |
Fraxinus (ash) | |
| Anthracnose caused by Discula sp. (Plate 48, 48) | Destroy or compost fallen leaves. If disease was severe the previous year and spring conditions are wet, spray with mancozeb, *Junction‡, or *Spectro 90 WDG‡ at budbreak and twice thereafter at 10- to 14-day intervals. |
| Yellows caused by a phytoplasma (Plate 198) (formerly mycoplasma-like organisms) | Symptoms-including foliage discoloration, growth reduction, and crown death-are more severe on water-stressed trees. Improve root zone health via irrigation when drought threatens. Tree Tech OTC‡ is labeled for use as an injection to suppress this disease. |
Hedera (English ivy) | |
| Leafspot caused by Xanthomonas hortorum pv. hederae (syn. X. campestris pv. hederae) (Plate 74, 185) | Remove and destroy affected leaves in autumn. Apply fosetyl-Al (for suppression), copper hydroxide, *Agri- Fos, or Camelot O‡ as symptoms appear during the growing season or use an appropriate formulation of one of the mono-and di-potassium salts of phosphorus acid for the site. 'Gold Dust' is resistant. 'Brokamp' and 'Hahn Variegated' are highly susceptible. |
Juglans (walnut, butternut) | |
| Bacterial blight caused by Xanthomonas arboricola pv. juglandis (syn.=X. campestris pv. juglandis (Plate 75, 186) | Prune and destroy infected shoots if possible, disinfecting tools between cuts. Apply *Junction‡ at prebloom, bloom, and early nutlet stages. |
| Anthracnose caused by Gnomonia leptostyla (conidial state =Marssoniella; syn.=Marssonina) (Plate 54, 51) | Destroy or compost fallen leaves. Spray with mancozeb, *Junction‡, propiconazole, thiophanate-methyl, chlorothalonil, or *Spectro 90 WDG‡ three times at two-week intervals beginning at budbreak. |
Juniperus (juniper, red cedar) | |
| Rust caused by Gymnosporangium sp. (Plate 115, 129-133) | Do not plant near hawthorn, flowering crab, quince, or similar plants. Remove galls from plants in spring where practical. Spray severely affected plants with triadimefon, *Pageant Intrinsic‡, *Mural‡, azoxystrobin, myclobutanil, mancozeb, or *Junction‡ two times at three-week intervals beginning in early August or follow label directions. Use disease-resistant selections for new plantings. |
| Blight caused by Phomopsis juniperovora (Plate 64, 72) | Prune and destroy infected shoots where practical. Avoid overhead irrigation. Rogue and destroy infected plants in young plantings. Spray with mancozeb, propiconazole, copper sulfate pentahydrate, copper hydroxide, *Mural‡, azoxystrobin, *Fungisol w/debacarb‡, thiophanate-methyl (3336F or 3336 EG), or *Junction‡ at two-week intervals throughout the growing season or per label directions. |
| Blight caused by Kabatina juniperi (Plate 64, 72) | Use thiophanate-methyl (3336F or 3336 EG), *Protect DF‡, or *Fungisol w/debacarb‡, to treat according to label directions. In sites with a history of this disease, plant resistant selections. |
| Disease-Resistant Junipers. Many species of Juniperus have been reported to be resistant to at least one of the common diseases. However, because all three are ubiquitous, resistance to at least two of the three is advisable. Listed below are taxa with such resistance. For additional information on disease resistant junipers, see https://hdl.handle.net/1813/ 56372.2. |
| Species | Resistant to: | |
| Variety | Phomopsis | Kabatina | Rusts | |
| J. chinensis | | | | |
| Femina | X | | X | |
| Hetzii | | X | X | |
| Iowa | X | | | |
| Keteleeri | X | X | X | |
| Pfitzeriana | X | X | X | |
| Sargentii | X | X | X | |
| sarg.-glauca | X | X | | |
| J. communis | | | | |
| Depressa | X | | X | |
| Hibernica | | X | X | |
| Saxatalis | X | | X | |
| J. Sabina | | | | |
| | Broadmoor | X | | X | |
| Knap Hill | X | | X | |
| Skandia | X | | X | |
| J. virginianae | | | | |
| Tripartita | X | | X | |
Kalmia (laurel) | |
| Leaf spots caused by Pseudocercospora kalmiae (syn.=Cercospora sp.) (Plate 16) | Handpick infected leaves and prune infected shoots if practical; destroy or compost fallen leaves. If disease has been severe, spray with mancozeb, triadimefon, *Pageant Intrinsic‡, or thiophanate-methyl, myclobutanil, or chlorothalonil at budbreak and again 10 and 20 days later. |
Koelreuteria (goldenrain tree) | |
| Coral spot canker caused by Nectria cinnabarina (Plates 99, 100, 87, 88) | Prune back to sound wood and cover pruning wound with a dressing. Fertilize and water to maintain vigor. |
Ligustrum (privet) | |
| Anthracnose caused by Glomerella cingulata (syn. = Colletotrichum gloeosporioides) (Plate 56) | Prune and destroy infected branches during dry weather. Spray with chlorothalonil, mancozeb, thiophanate-methyl, *Pageant Intrinsic‡, or *Spectro 90 WDG‡, potassium bicarbonate, or *Junction‡ weekly as long as disease is active, or per label directions. Amur privet (Ligustrum amurense), Ibota privet (L. ibota), Regal privet (L. obtusifolium var. regalianum), and California privet (L. ovalifolium) are reported to be resistant. |
| Alternaria leaf spot caused by Alternaria alternata | Alternaria leaf spot was found to be prevalent on California Privet in Long Island during the 2009 and 2010 growing seasons, and appears to be causing leaf spot, yellowing and leaf drop. Do not confuse this with Anthracnose (see above). Although it is not yet known if other factors are contributing to this problem, several fungicides are registered for leaf spot diseases on privet and may be useful in managing the disease where it has become severe and include: potassium bicarbonate, thiophanate-methyl + iprodione, trifloxystrobin, Daconil Weather Stik, *Pageant Intrinsic‡, *Junction‡, and *Protect DF. Make applications at 7-28 day intervals during the first half of the growing season as directed on product labels. |
Lonicera (honeysuckle) | |
| Leaf blight caused by Insolibasidium deformans (syn.=Herpobasidium sp.) (Plate 42, 126) | Remove and destroy fallen leaves. Spray with mancozeb, or *Junction‡ at 10-day intervals beginning in late May and continuing until late June. |
Malus (apples, flowering crab) | |
For home orchard guidelines, see other publications. The following crabapples have been evaluated through a program of yearly assessment for disease incidence at sites throughout the eastern half of the United States: 'Adams', 'Jackii', 'Baskatong', 'Centurion', 'Dolgo', 'Donald Wyman', 'Harvest Gold', 'Henry Kohankie', 'Indian Summer', 'Liset', 'Ormiston Roy', 'Prof Springer', 'Red Jewel', 'Robinson', 'Sentinel', and 'Sugar Tyme'. For additional information on disease resistant crab apples, see https://hdl.handle.net/1813/56373.2. |
| Powdery mildew caused by Podosphaera leucotricha (Plate 4, 5) | Apply propiconazole, triadimefon, copper sulfate pentahydrate, myclobutanil, thiophanate-methyl, *Pageant Intrinsic‡, *Spectro 90 WDG‡, trifloxystrobin, neem oil, or potassium bicarbonate at two-week intervals when mildew first appears on twigs or foliage. |
| Fire blight caused by Erwinia amylovora (Plates 76, 77, 187) | Avoid overfertilization, especially heavy spring applications of nitrogen. Cut out cankers and blighted branches in mid-January when tree is dry, making cuts at least 1 ft. below the visible limits of infection. Cover wounds with shellac or other wound dressing. Disinfect tools between cuts. Remove worthless pear, apple, quince, and similar plants from the vicinity. Where disease has just begun to appear, apply copper sulfate pentahydrate, copper hydroxide or use an appropriate formulation of one of the mono-and di-potassium salts of phosphorus acid for the site, or inject Tree Tech OTC‡ per label directions. |
| Rust caused by Gymnosporangium spp. (Plates 118, 119, 129-133) | Eliminate nearby red cedar and common juniper to whatever extent practical. Spray with myclobutanil, triadimefon, thiophanate-methyl, chlorothalonil, trifloxystrobin, propiconazole, (or inject *Shepherd Fungicide‡), *Spectro 90 WDG‡, *Pageant Intrinsic‡, or mancozeb. Make three applications at 7- to 14-day intervals or per label directions beginning when orange rust masses develop on junipers (around mid-May). |
| Scab caused by Venturia inaequalis (Plate 95, 42) | Spray propiconazole (or inject *Alamo‡, or *Shepherd Fungicide), myclobutanil, copper sulfate pentahydrate, mancozeb, trifloxystrobin, thiophanate-methyl, chlorothalonil, potassium bicarbonate, neem oil, *Pageant Intrinsic‡, or *Spectro 90 WDG‡ per label directions or use an appropriate formulation of one of the mono-and di-potassium salts of phosphorus acid for the site. |
Pachysandra (pachysandra, spurge) |
| Blight caused by Volutella pachysandricola | Plants grown in full sun are most likely to become diseased. Those in full shade usually remain healthy. Where plants are already established and disease has become intolerable, rogue and destroy diseased plants. Spray copper sulfate pentahydrate, copper hydroxide, elemental copper (with lime), mancozeb, chlorothalonil, or *Spectro 90 WDG‡ two or three times at 10-day intervals beginning when new growth starts. |
Parthenocissus (Boston ivy, Virginia creeper, woodbine) |
| Leaf spot caused by Guignardia bidwellii (Plate 35) | Handpick and destroy infected leaves where possible. Sprays are seldom necessary. |
Picea (spruce) | |
| Canker caused by Leucostoma kunzei (Plate 93, 83) | Keep trees lightly fertilized and watered and avoid all wounds. Remove and destroy all diseased parts, disinfecting tools between cuts. Do not prune in wet weather. *Fungisol w/debacarb‡, micro-injections may be used in landscape situations. |
| Needlecast caused by Rhizosphaera kalkhoffii (Plate 16, 27) | This disease is rarely severe enough to warrant control measures. In Christmas tree plantations where damage has become intolerable, use *Protect DF‡, or chlorothalonil, *Spectro 90 WDG‡, or copper hydroxide per label directions. |
| Twig blight caused by Sirococcus sp. (Plate 2, 58) | Rogue and destroy heavily infected trees. Spray chlorothalonil, *Spectro 90 WDG‡, *Mural‡, or azoxystrobin before new shoot growth is ½ inch long and spray twice thereafter at three- to four-week intervals. |
| Weir's cushion rust (Chrysomyxa weirii) (Plate 128, 143) | Fungus causes bright orange blisters on one-year-old needles in the spring and premature shedding of those needles. Apply neem oil or chlorothalonil when budbreak is 10 percent complete and make two more applications at 7- to 10-day intervals. |
Pinus (pine) | |
| Blister rust of eastern white pine caused by Cronartium ribicola (Plate 131, 146) | No control measures are necessary on Erie and Ontario Lake plains, in lower Hudson Valley, or on Long Island. Elsewhere, to whatever extent possible, eradicate wild currants and gooseberries within 500 ft. and maintain 200 ft. separation between white pines and cultivated red currants. To eliminate cankers on pine, prune off cankered lateral branches or excise stem cankers by removing bark at least 4 inches above and below and 2 inches on either side of discolored bark. |
| Gall rust of 2- and 3-needled pines caused by Peridermium harknessii (syn.=Endocronartium harknessii (Plate 136, 151) | In nurseries, cull seedlings with stem swellings. In plantations, cut off branch galls and rogue heavily galled trees before May 1. Apply mancozeb three times at two-week intervals when yellow pustules begin to erupt through bark on galls or apply triadimefon when needles emerge from fascicles and re-apply every 14- to 21-days during spore production. |
| Needlecast of 2- and 3-needled pines caused by Lophodermium spp. (Plate 11, 22) | Spray heavily infected trees with mancozeb, *Junction‡, chlorothalonil, or *Spectro 90 WDG‡ monthly from July 1 to October 1, or apply copper hydroxide, or triadimefon per label directions. Do not plant highly susceptible strains of Scots pine such as short-needled varieties 'Spanish' and 'French Green.' |
| Needlecast of 2- and 3-needled pines caused by Cyclaneusma minus (Plate 14, 26) | This common disease causes two- and three-year-old needles to turn yellow to light brown in late summer and fall. It rarely if ever threatens tree health and usually doesn't warrant efforts at control. Where symptoms have become intolerable, spray trees with mancozeb, *Junction‡, chlorothalonil, or *Spectro 90 WDG‡ once at budbreak and thereafter at six- to eight-week intervals until spore dispersal ceases in late fall OR apply copper hydroxide per label directions. |
| Needlecast of 2- and 3-needled pines caused by Ploioderma lethale (Plate 12, 23) | Prune out heavily infected (lower) branches to lessen inoculum levels and control weeds to increase air circulation around trees. In silviculture nurseries and Christmas tree plantations, apply copper hydroxide per label directions. |
| Needle blight of 2- and 3-needled pines caused by Mycosphaerella pini (= Dothistroma septospora) (Plate 19, 13) | Spray with *Protect DF‡, *Pageant Intrinsic‡, or *Junction‡ once at budbreak and twice again at 10- to 14-day intervals. |
| Needle rust of 2- and 3-needled pines caused by Coleosporium asterum (Plate 129, 144) | Goldenrod and aster plants are alternate hosts for the rust. In plantations, mow or otherwise control these weeds annually before August. Where disease is severe, treat with *Pageant Intrinsic‡, triadimefon or neem oil. |
| Sweetfern rust of 2- and 3-needled pines caused by Cronartium comptoniae (Plate 133, 148) | Sweet fern and sweet gale are alternate hosts for the rust. These plants should be controlled before August in plantations and eradicated in the immediate vicinity of nurseries. In nurseries, cull seedlings with stem swellings or showing rust pustules. Where disease is severe, treat with triadimefon. |
| Twig blight of 2- and 3-needled pines caused by Diplodia pinea (syn.=Sphaeropsis sapinea) (Plate 63, 64) | Prune and destroy affected cones, twigs, and branches during dry weather in autumn. Spray with thiophanate-methyl plus a spreader-sticker, or apply *Spectro 90 WDG‡, *Protect DF‡, *Junction‡, or propiconazole just before budbreak and make two more applications at 10-day intervals. See Cornell Tree Pest Leaflet A-7, Diplodia Tip Blight of Pines. |
| | |
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Platanus (plane and sycamore) |
| Anthracnose caused by Apiognomonia veneta (conidial state =Discula platani) (Plate 51, 50) | This disease rarely threatens the life of its host. For aesthetic reasons only, apply *Junction‡, chlorothalonil, *Spectro 90 WDG‡, copper sulfate pentahydrate, Twosome‡, Camelot O‡ (sycamore only on label), copper hydroxide or elemental copper about two weeks before budbreak, at budbreak, and when leaves are fully expanded, or inject with thiabendazole hypophosphite, propiconazole (*Alamo‡, *Shepherd Fungicide) or *Fungisol w/debacarb‡, per label directions or use an appropriate formulation of one of the mono-and di-potassium salts of phosphorus acid for the site. For new plantings, choose anthracnose-resistant London plane (P.X. acerifolia). |
| Canker stain caused by Ceratocystis fimbriata (Plate 174, 116) | Remove diseased trees. Avoid wounding healthy trees. If necessary to prune healthy trees, disinfect tools between trees. |
Populus (poplar, aspen, cottonwood) |
| Leafspot caused by Marssonina spp. (55, 40) | Rake and destroy infected leaves in the fall. Where disease is a persistent nuisance, make three applications of chlorothalonil, mancozeb, *Spectro 90 WDG‡, thiophanate-methyl, *Mural‡, or *Junction‡ at 10- to 14-day intervals beginning at budbreak. |
| Shoot blight/stem canker caused by Mycosphaerella spp. (syn. = Septoria) (Plate 32, 11) | Rogue and destroy severely diseased trees. Prune cankered branches, disinfecting tools between cuts. Spray salvageable trees with chlorothalonil, mancozeb, *Spectro 90 WDG‡, *Pageant Intrinsic‡, or thiophanate-methyl, three times at 10- to 14-day intervals beginning at budbreak or per label directions. Cv 'Assiniboine' is resistant. |
Prunus (cherry, flowering cherry, peach, plum) |
For home orchard guidelines, consult Cooperative Extension educators. For additional information on disease resistant Prunus, see https://hdl.handle.net/1813/56374.2. |
| Black knot caused by Dibotryon morbosum (Plate 71, 75) | Prune knotted twigs to whatever extent practical, and excise knots on large limbs before April 1. Destroy pruned material. |
| Leaf curl caused by Taphrina deformans (Plate 6, 1) | Apply *Spectro 90 WDG‡ in the spring before budbreak. |
| Crown gall caused by Agrobacterium tumefaciens (Plate 73, 190) | See "Crown Gall" under "Diseases of General Importance or Occurrence." |
| Leaf spot caused by Blumeriella jaapii (Plate 28, 39) (formerly known as Coccomyces sp.) | Spray with propiconazole, *Protect DF‡, myclobutanil, *Spectro 90 WDG‡, *Pageant Intrinsic‡ or thiophanate-methyl at petal fall plus two more applications at two-week intervals. |
| Shoot blight/Brown rot caused by Monilinia spp. (Plate 58, 37) | Prune and destroy infected twigs if practical. Spray with (on labeled species or varieties), propiconazole, mancozeb, chlorothalonil, *Spectro 90 WDG‡, or thiophanate-methyl, as blossoms open and again 10 days later or per label directions. |
Pseudotsuga (Douglas-fir) | |
| Needlecast caused by Rhabdocline spp. (Plate 15, 28) | Plant on slopes and control weeds to promote air drainage and dry conditions among lower branches. If disease develops, rogue severely infected trees plus any stems not destined for market and prune lower branches from the remainder. Pruning and roguing should be done before May 1 but cut branches and trees can be left on the ground. Apply copper hydroxide, chlorothalonil, or *Spectro 90 WDG‡ before new growth is ½ inch long and make additional applications at three- to four-week intervals until July 1. |
| Swiss needlecast caused by Phaeocryptopus gaumannii (Plate 15, 28) | Time treatments as for Rhabdocline. Use mancozeb, chlorothalonil, *Mural‡, or *Spectro 90 WDG‡. |
Pyracantha (firethorn) | |
For additional information on disease resistant firethorn, see https://hdl.handle.net/1813/56375.2. |
| Fire blight caused by Erwinia amylovora (Plates 76, 77, 187) | Prune out diseased parts when plants are dry, disinfecting tools between cuts. Make cuts several inches below visible limits of infection. Remove worthless pear, apple, and quince from the vicinity. Spray with fosetyl-Al (for suppression), *Junction‡, copper hydroxide or copper sulfate pentahydrate three times at 10- to 14- day intervals beginning when plants flower, or inject Tree Tech OTC‡ per label directions, or use an appropriate formulation of one of the mono-and di-potassium salts of phosphorus acid for the site. Hybrids reported to be resistant include 'Apache', 'Navaho', 'Pueblo', 'Rutgers', 'Shawnee', and 'Teton'. |
| Scab caused by Venturia pyracanthae (Plate 44, 43) | Spray with *Protect DF‡, thiophanate-methyl, potassium bicarbonate, neem oil, *Junction‡, copper hydroxide, *Pageant Intrinsic‡, or *Spectro 90 WDG‡ at full bloom and two and four weeks later. Yunan firethorn (P. crenato-sessata) is reported to be resistant. |
Pyrus (pear) | |
For home orchard guidelines, consult Cooperative Extension educators. For additional information on disease resistant pear, see https://hdl.handle.net/1813/66890. |
| Fire blight caused by Erwinia amylovora (Plates 76, 77, 187) | Prune out diseased parts when plants are dry, disinfecting tools between cuts. Make cuts several inches below visible limits of infection. Remove worthless pear, apple, and quince from the vicinity. The Bradford pear (Pyrus calleryana cv. 'Bradford') is reported to be tolerant. P. beautifolia 'Dancer' is resistant. Where severe treat with fosetyl-Al (for suppression), *Junction‡, copper hydroxide, or copper sulfate pentahydrate per label directions, or use an appropriate formulation of one of the mono-and di-potassium salts of phosphorus acid for the site. Tree Tech OTC‡ is labeled for use as an injection to suppress this disease. |
| Scab caused by Venturia pyrina (= Fusicladium sp.) (Plate 44, 43) | Spray with *Pageant Intrinsic‡, thiophanate-methyl, myclobutanil or mancozeb per label directions. |
| Pear trellis rust caused by Gymnosporangium sabinae | Spray with mancozeb, myclobutanil, *Pageant Intrinsic‡, *Mural‡, or thiophanate-methyl on a 7-21 day interval or as per label directions. |
| Other rust caused by Gymnosporangium spp. (Plates 117-120, 129-133) | Eliminate nearby red cedar and Juniperus chinensis to whatever extent practical. Spray with myclobutanil or thiophanate-methyl when orange rust masses appear on juniper and thereafter at 7- to 14-day intervals or per label directions. |
Quercus (oak) | |
For information on disease resistant oaks, see https://hdl.handle.net/1813/56376.2. |
| Anthracnose of white oak caused by Apiognomonia sp. (Plate 50, 49) (conidial state = Discula sp.) | Destroy fallen leaves in autumn. Spray with *Protect DF‡, elemental copper (with lime), *Junction‡, or *Spectro 90 WDG‡ once before budbreak, once at budbreak, and once when leaves are half of full size, or use *Fungisol w/debacarb‡ for injection in the spring. |
| Leaf spot caused by Tubakia dryina (Plate 21) | This disease develops late in the growing season and rarely threatens tree health. Where management must be undertaken, use *Junction‡ or copper hydroxide or spray with propiconazole once at budbreak and twice thereafter at 10- to 14-day intervals. |
| Leaf blister caused by Taphrina caerulescens (Plate 6, 2) | This disease rarely is severe enough to affect host health or appearance. Where it has become so, spray once in spring before bud swell with mancozeb, *Junction‡, or *Spectro 90 WDG‡. |
| Oak Wilt caused by Ceratocytis fagacearum (Plate 118) | Although white oak and bur oak are considered to be somewhat resistant, this disease can infect all oak species common in NYS and may kill trees in the red oak group within weeks or months of infection. If Oak Wilt is confirmed, take the following steps to minimize the spread of the fungus. |
| | - Examine oaks on your property regularly, paying special attention to red oaks with rapidly wilting leaves in June or July.
- Remove diseased trees immediately and take steps to ensure that the wood dries quickly enough to minimize formation of sporulating mycelial mats.
- Use a backhoe, trencher, or vibratory plow to disrupt root grafts between diseased and healthy trees.
- Do not prune oaks in the spring (April 15-July 15 in NY State) unless they pose an imminent danger to life or property!
- In sites with a history of oak wilt, cover all new wounds - including pruning wounds, lawnmower dings, weed whacker abrasions and any other injury that exposes fresh wood - with paint.
- Inject currently healthy red oaks in the vicinity of diseased trees with propiconazole (*Alamo) per label instructions. This product is registered in New York State for control of several tree diseases, including oak wilt, but it must be applied by a professional arborist. Follow label directions.
- Dispose of diseased trees by chipping small branches and burying or burning larger debris. Logs split for firewood should be completely sealed with vinyl tarp for 12 months.
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| Shoestring root rot caused by Armillaria sp. (Plate 148, 162-164) | This disease most frequently affects trees weakened by defoliation or other factors. Restore tree vigor via watering and fertilization and control of defoliators. |
Rhododendron (azalea, rhododendron) |
For additional information on disease resistant Rhodendron, see https://hdl.handle.net/1813/66892. |
| Azalea gall caused by Exobasidium vaccinii (Plate 8, 124) | Pick and destroy galls. Spray with triadimefon, *Junction‡, or *Spectro 90 WDG‡ three times at 10- to 14-day intervals beginning at budbreak. |
| Canker and dieback caused by Botryosphaeria spp. (Plate 82, 59-63) | Prune and destroy infected parts, disinfecting tools carefully between cuts. Cultivars reported to be resistant include 'Boursalt', 'Chionoides White', 'Cunningham's White', 'English Roseum', 'LeBar's Red', 'Roseum 2', 'Sweet simplicity', and 'Wissahickon'. Where needed, treat with *Protect DF‡. |
| Shoot blight caused by Phytophthora sp. (Plate 178) | For existing plantings, prune and destroy infected twigs. As new leaves appear, spray with mancozeb, chlorothalonil, copper hydroxide (azalea only), fosetyl-Al, *Pageant Intrinsic‡, *Mural‡, or azoxystrobin, making three applications 7- to 10-days apart, or use an appropriate formulation of one of the mono-and di-potassium salts of phosphorus acid for the site. |
| Flower blight caused by Ovulinia azaleae (Plate 24, 34) | If disease was severe the previous year, spray twice with triadimefon, chlorothalonil, thiophanate-methyl, mancozeb, myclobutanil, propiconazole, potassium bicarbonate, *Junction‡, or *Spectro 90 WDG‡, per label directions. |
| Root rot and wilt caused by Phytophthora cinnamomi (Plate 140, 181) | Several other rhododendron problems have symptoms similar to those caused by Phytophthora. Be sure of correct diagnosis. Avoid planting in heavy or frequently saturated soils. Rogue and destroy infected plants, including roots, when symptoms appear. Drench soil with *Pageant Intrinsic‡, metalaxyl-m (mefenoxam), etridiazole, propamocarb hydrochloride, or fosetyl-Al according to label instructions, or use an appropriate formulation of one of the mono-and di-potassium salts of phosphorus acid for the site before replacing with new plants in a site with a history of disease. Choose resistant species/cultivars such as 'Caroline', 'Martha Isaacson', 'Pink Trumpet', 'Prof. Hugo deVries', or 'Red Head'. |
| Powdery mildews caused by Erysiphe spp. (syn.=Microsphaera sp.) (Plate 3, 4) | Spray with triadimefon, thiophanate-methyl, Ultrafine oil‡, *Spectro 90 WDG‡, *Pageant Intrinsic‡, *Mural‡, azoxystrobin, trifloxystrobin, neem oil, myclobutanil, or potassium bicarbonate when disease incidence becomes intolerable. |
Rosa (rose) | |
For information on disease resistant roses, see https://hdl.handle.net/1813/66893. |
| Flower blight caused by Botrytis sp. (Plate 25, 35) | Disease is most severe in years with unusually high rainfall or in sites where overhead irrigation is excessive. Remove and destroy blighted flowers and spray with mancozeb, thiophanate-methyl, thiophanate-methyl + iprodione, chlorothalonil, iprodione, copper sulfate pentahydrate, trifloxystrobin, fluoxastrobin, *Pageant Intrinsic‡, *Mural‡, *Junction‡, or *Spectro 90 WDG‡, or apply potassium bicarbonate per label directions. |
| Blackspot caused by Diplocarpon rosae (Plate 28, 39) | Remove and destroy cankered canes. Spray at 7- to 14-day intervals with propiconazole, myclobutanil, copper sulfate pentahydrate, copper hydroxide, chlorothalonil, lime sulfur, mancozeb, thiophanate-methyl, fluoxastrobin, neem oil, horticultural oil, potassium bicarbonate, *Mural‡, *Junction‡, or *Spectro 90 WDG‡ beginning as leaves expand. Or apply Camelot O‡ for suppression. Many species and cultivars are reported to be resistant to blackspot. |
| Crown gall caused by Agrobacterium tumefaciens (Plate 73, 190) | See "Crown Gall" and "Diseases of General Importance or Occurrence" or see Cornell Tree Pest Leaflet A-5, Crown Gall. |
| Downy Mildew caused by Peronospora sparsa | Use good sanitation practices, and treat with fosetyl-Al, potassium bicarbonate, *Agri-Fos, *Pageant Intrinsic‡, *Mural‡, azoxystrobin, neem oil, or copper sulfate pentahydrate, fluoxastrobin, or trifloxystrobin as a protective spray per label directions, or use Camelot O‡ for suppression. |
| Powdery mildew caused by Podosphaera pannosa (syn.=Sphaerotheca pannosa) (Plate 3, 4, 5) | Spray lime-sulfur, triadimefon, myclobutanil, propiconazole, thiophanate-methyl, *Junction‡, *Spectro 90 WDG‡, copper hydroxide, fluoxastrobin, trifloxystrobin, *Pageant Intrinsic‡, *Mural‡, azoxystrobin, copper sulfate pentahydrate, neem oil, horticultural oil, or potassium bicarbonate when mildew appears on leaf surface, and repeat applications at 10- to 14-day intervals as needed or use Camelot O‡ for suppression. |
| Rust caused by Phragmidium sp. (Plate 114, 128) | Spray with *Protect DF‡, *Junction‡, myclobutanil, lime sulfur, propiconazole, *Mural‡, azoxystrobin, fluoxastrobin, trifloxystrobin, or neem oil when orange rust pustules are first seen on undersides of leaves. Repeat as needed. |
Salix (willow) | |
| Leaf rust caused by Melampsora spp. (Plate 123, 142) | Spray foliage with triadimefon, neem oil, Camelot O‡, or mancozeb once at budbreak and twice thereafter at two-week intervals or per label directions. plantclinic.cornell. edu/factsheets/willowleafrust.pdf. |
| Blight, black canker caused by Venturia saliciperda and Glomerella miyabeana (Plate 46, 45) | Prune heavily to remove diseased parts or spray with *Pageant Intrinsic‡ for Venturia, or *Junction‡ at 7- to 10-day intervals when disease first appears. Salix babylonica (weeping willow) and S. pentandra (laurel willow) are somewhat resistant. |
| Canker caused by Cytospora spp. (syns.=Valsa spp. & Leucostoma niveum) (Plate 95, 85) | Keep trees well watered. Avoid wounding. Prune out and destroy infected branches during dry weather. plantclinic.cornell.edu/factsheets/cankerdiseasespoplar.pdf. |
Sorbus (mountain ash) | |
| Fire blight caused by Erwinia amylovora (Plates 76, 77, 187) | Prune out diseased parts when plants are dry, disinfecting tools between cuts. Make cuts several inches below visible limits of infection. Remove worthless pear, apple, and quince from the vicinity. Where disease has just begun to appear, apply *Junction‡, copper hydroxide, or copper sulfate pentahydrate, or inject Tree Tech OTC‡ per label directions. |
| Cankers caused by Cytospora sp. And Fusicoccum sp. | Keep trees well watered. Avoid wounding. Prune out and destroy infected branches during dry weather. |
| Rusts caused by Gymnosporangium spp. (Plates 117-120, 129-133) | Eliminate nearby red cedar and common juniper to whatever extent practical. Spray with thiophanate-methyl, *Pageant Intrinsic‡, *Mural‡, or *Junction‡ when orange rust masses appear on juniper and thereafter at 7- to 14-day intervals or per label directions. |
| Scab caused by Venturia inaequalis (Plate 43, 42) | Apply *Protect DF‡, *Junction‡, copper sulfate pentahydrate, thiophanate-methyl, *Pageant Intrinsic‡, or neem oil at budbreak and repeat at 7- to 21-day intervals during leaf expansion while conditions for disease development exist. |
Syringa (lilac) | |
For information on disease resistant lilacs, see https://hdl.handle.net/1813/56377.2. |
| Bacterial blight caused by Pseudomonas syringae (Plate 75, 183, 184) | Prune to prevent dense growth. Cut out and destroy infected shoots as soon as symptoms appear, disinfecting tools between cuts. When disease incidence has become intolerable, apply copper hydroxide, copper sulfate pentahydrate or *Junction‡ per label directions. |
| Powdery mildews caused by Erysiphe syringae (syn.=Microsphaera sp.) (Plate 3-5) | Spray thiophanate-methyl, *Spectro 90 WDG‡, triadimefon, copper sulfate pentahydrate, myclobutanil, neem oil, *Pageant Intrinsic‡, *Mural‡, or Ultrafine oil‡ when mildew appears on leaf surface and repeat applications at 10- to 14-day intervals as needed. |
Thuja (arborvitae) | |
For information on disease resistant Arborvitae, see https://hdl.handle.net/1813/56378.2. |
| Leaf blight caused by Cercospora sp. | Destroy heavily infected plants. Spray salvageable specimens with mancozeb, copper hydroxide, *Pageant Intrinsic‡, or *Junction‡ three times at two-week intervals beginning at bud-break or per label directions. |
Tsuga (hemlock) | |
| Canker caused by Leucostoma, Cytospora, and Valsa spp. (Plate 92, 83). Also dieback and decline. | Do not plant hemlock on neutral or alkaline sites or where plants will be subject to water stress or salt exposure. Water established plants during dry periods and keep them lightly fertilized. Prune out dead and dying branches. |
| Rust caused by Melampsora spp. (Plate 124, 142) | Apply triadimefon or neem oil once when buds break and twice thereafter at 7- to 14-day intervals. Where disease has been severe, do not plant hemlock. |
Ulmus (elm) | |
For more information on these diseases, see Cornell Tree Pest Leaflet A-9, Dutch Elm Disease and Elm Yellows. For additional information on disease resistant elms, see https://hdl.handle.net/1813/66896. |
| Black leaf spot caused by Stegophora ulmea (Plate 49, 47) | Premature defoliation by this disease does not threaten tree health. Apply mancozeb or *Junction‡ three times at two-week intervals beginning at budbreak if the effect of the disease on a particular tree has become intolerable. |
| Dutch elm (DED) caused by Ophiostoma novo-ulmi or O. ulmi (Plate 177, 119) and elm yellows (EY) caused by a phytoplasma (formerly mycoplasma-like organisms) (Plate 188, 197) | Where both diseases occur, chances of preserving a susceptible elm are poor. Tree Tech OTC‡ is labeled for use as an injection to suppress EY but will not cure infected trees. For DED: - Eliminate all potential beetle-breeding elm material within 700 feet of trees to be protected. Sanitation is useful even where zones extending several hundred feet from valuable elms cannot be established.
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| - Trunks can be injected with thiabendazole hypophosphite, *Alamo‡, *Fungisol w/debacarb‡, *Shepherd Fungicide, or copper sulfate pentahydrate for protection or therapy. Good success has been obtained with both macro- and micro-injection equipment. Follow manufacturer instructions for application. Combine eradicative pruning (step 4) with therapeutic treatments as soon as symptoms are seen.
- Prune out DED-infected branches, making sure the pruning cut shows no evidence of vascular discoloration. Pruning alone is effective in a minority of cases if symptoms are detected while confined to a small branch and a large branch bearing the small one is immediately removed. Chances for recovery are much better if fungicide injection is also used.
- Disease-resistant elms. In general, native elms are susceptible to both diseases. Elms of European origin vary in susceptibility to DED, and elms of Asiatic origin are resistant. EY can cause witches'-brooms, yellowing, and decline in European and Asiatic elms, but natural infections in North America are rare. The following can be grown in New York State: Siberian elm (U. pumila), Chinese elm (U. parvifolia), Scots elm (U. glabra), U. davidiana, U. japonica, U. laciniata, U. minor, U. laevis, and U. wilsoniana.
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| | Cultivars with resistance to DED from Asiatic and European species include 'Accolade', 'Allee', 'Athena', 'Autumn Gold', 'Central Park Splendor', 'Christine Buisman', 'Commendation', 'Danada Charm', 'Discovery', 'Dynasty,' 'Frontier', 'Groeneveld', 'Homestead', 'Jacan', 'Pathfinder', Patriot', 'Pioneer', Prospector', 'Regal', 'Sapporo Autumn Gold', 'Thompson', 'Triumph', 'Urban', and 'Vanguard. |
| | Clonal cultivars have also been developed from Ulmus americana and include 'Independence', 'Jefferson', 'New Harmony', 'Princeton', and 'Valley Forge'. 'American Liberty Elm' is a name given to a group of DED-resistant American elms rather than a single selection, and that cohort also has some DED resistance. |
| | DED-resistant elms were tested at Cornell for resistance to a North American strain of EY. The Eurasian hybrid 'Homestead' was apparently highly resistant, and most plants of U. wilsoniana cv. 'Prospector' did not react to inoculation. The Eurasian hybrids 'Frontier' and 'Patriot' seemed to tolerate infection well enough for us to recommend them as possible choices in areas where both DED and EY occur. All of the DED-resistant American elms tested ('Independence,' 'New Harmony,' 'Valley Forge,' and 'Jefferson') were highly susceptible to EY and should not be planted in sites where the disease already occurs in native elm populations. 'American Liberty Elm' is also susceptible to EY and should not be planted where yellows is a known threat. |
Viburnum (viburnum) |
For information on disease resistant viburnum, see https://hdl.handle.net/1813/56379.2. |
| Downy mildew caused by Plasmopara viburni (Plate 175) | Spray with mancozeb, neem oil, potassium bicarbonate, *Pageant Intrinsic‡, *Mural‡, or *Junction‡ at two-week intervals between April 1 and June 15. |
Vinca (periwinkle) | |
| Stem canker, leaf spot, and Botrytis blight caused by Botrytis cinerea | Rogue and destroy affected stems. Thin stand to promote better air circulation. Then, if disease has been severe, treat plants with a soaking spray of *Pageant Intrinsic‡, mancozeb, thiophanate-methyl, thiophanate-methyl + iprodione, or iprodione, or apply potassium bicarbonate per label directions. |
| Stem blight caused by Phomopsis sp. | Prune and destroy affected shoots. Spray with mancozeb per label directions as symptoms become apparent. |
1Plate numbers refer to numbers in the first edition of Diseases of Trees and Shrubs by W. A. Sinclair, H. H. Lyon, and W. T. Johnson, Cornell University Press. Numbers in bold-italic type are references for the 2nd edition published in 2005. Available from Cornell Press at: www.cornellpress.cornell.edu. |