Agricultural Research Service • U.S. Department of Agriculture

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Agricultural Research Service • U.S. Department of Agriculture Contents Paee Leaf and flower diseases and control methods - 1 Fungus and bacterial diseases — -- 1 Anthracnose - — 1 Phyllostieta spot — 2 Tar spots - 2 Bacterial spot -— - - 4 Leaf blister - -- - 4 Shoot droop_ - - - - 4 Bulls-eye spot - - - — 5 Gray mold spot - 5 Leaf scab 6 Bigleaf brown spot- — 6 Septoria spot - — "? Powdery mildews - - '' Flower blight - ' Noninfectious disorders _ — '' Leaf scorch "^ Leaf distortion and dwarfing ^ Premature reddening or yellowing _ 8 Gas poisoning 8 Abnormalities of unknown cause - 9 Spray materials and schedules - — 9 Cankers and other damage to woody parts - 10 Eutypella trunk canker ..„ - 10 Nectria canker 10 Bleeding canker_ 11 Basal canker „ - IS Schizoxylon canker 14 Other cankers - — - 14 Trunk splitting, frost beaks, and bark freezing 14 Sapsucker damage 15 Root diseases— — - — 16 Root-knot nematode 16 Root rots____ _ 16 Root damage from adverse soil conditions 16 General infections _ .— 17 Slime flux and wetwood 17 Verticillium wilt 18 Red stain of boxelder 19 Sap streak_ __ 19 Silver leaf- — _ _ 19 Wood decay ___ _. 19 Common and scientific names of maples _ _. __ 22

Washington, D.C. Issued December 1961 For sale by the Superintendent of Documents. U.S. Government Printing Office Washington 25. D.C. - Price 1.5 cents By CURTIS MAY, plant pathologist. Crops Research Division, Agricultural Research Scrvicf Diseases F^ ^ of Shade and Ornamental Maples

Pathogenic organisms attack foliage of sugar, Norway, and shade and ornamental maples and sometimes other species of maple. cause diseases of the leaf and Air pollutants may adversely af- flower, woody parts, and root. fect maple and limit its usefulness Leaf scorch, a noninfectious dis- in some localities. order, often seriously damages

LEAF AND FLOWER DISEASES AND CONTROL METHODS Leaf blights and spots of maple spots are numerous, they may sometimes damage large trees and merge until the whole leaf is af- frequentljr are serious on small or fected. Usually they appear from recently transplanted trees or late May until August. Affected trees growing under adverse con- leaves of Norway maple have ditions. Leaf diseases mar their purple to brown diseased tissue appearance and detract from their along the veins (fig. 1, A). On landscape value. sugar maple large green- or red- brown anthracnose lesions occur FUNGUS AND BACTERIAL along or between the veins, and DISEASES often they extend to the leaf margin (fig. 1, B). On Japanese maple Anthracnose the disease may aff'ect the entire Anthracnose is caused by Gloeo- young leaf, which often becomes sporiuvi apocryptum Ell. & Ev. blackened and shriveled. Trees This fungus invades and kills the are not always seriously damaged leaf tissue, producing small to by anthracnose. large circular to irregular spots Spores of the anthracnose fun- or necrotic areas, which turn light gus are produced in acervuli on brown, purplish, or black. If the the diseased leaves and are spread AGR. HANDBOOK 211, U.S. DEPT. OF AGRICULTURE

FIGURE 1.- -Leaves affected by anthracnose: A, Nonvay maple (/TíÍ); B, sugar maple ( X % ). by spattering rain and wind. tral part of the spot may be some- These spores are 5 to 12 by 21/2 what transparent. Usually the to 5 microns and are oblong to spots are small, irregularly circu- narrowly elliptic. lar, and reddish brown with nar- Anthracnose can be controlled row to broad purplish borders by spraying with a fungicide (see (fig. 2, A). p. 9). This measure will help The spots have minute black prevent disfiguration and loss of fruiting bodies, or pycnidia, of the leaves. It will benefit weak and causal fungus. Not all the spots recently transplanted trees and produce the fruiting bodies. trees that are diseased year after Spores are .5 to 6 by 8 to 9 microns. year. An application of fertilizer A closely related fungus, Plujl- will usually improve the vigor of losticta negundinis Sacc. & Speg., trees that are weakened by re- causes a similar leaf spot on box- peated severe attacks of an- elder. The fungus Septoria aceris thracnose. (Lib.) Berk. & Br. attacks leaves Phyllosticta Spot of the bigleaf maple and also causes leaf spot (fig. 2, B). Small Phyllosticta spot is caused by reddish-tan to brown spots de- the fungus Phyllosticta minima velop with a narrow yellow (Berk. & Curt.) Ell. & Ev. This border. On other maple species disease is widespread and some- the margin is usually irregular times serious. On difl:erent maple species the spots vary consider- and indefinite. ably. On sugar and Rocky Moun- Spraying with a fungicide tain maples the spots commonly should reduce damage from phyl- have a narrow purplish border. losticta spot (see p. 9). The diseased tissue often falls Tar Spots out, and holes are left in the leaf. Black spots on the leaves are On Japanese maple, which may be the conspicuous symptom of tar severely damaged by the disease, spots. The fungi Rhytisma aceri- the spots are straw to tan colored nmn (Pers.) ex Fr. and R. punc- with a definite margin. The cen- tatum (Pers.) ex Fr. cause the DISEASES OF SHADE AND ORNAMENTAL MAPLES

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FIGURE 2.~A, Maple leaf affected by phyllosticta spot (X li;) ; B, bigleaf maple leaf attacked by the fungus Septoyia aceris i^-, Vz).

disease. When first invaded the do not coalesce. R. acerinum, the leaves develop minute water- cause of common tar spot, attacks soaked spots. Soon small dark many species of maple, but seldom dots appear on the upper leaf the Norway and sycamore maples. surface between the veins. The dots enlarge and soon coalesce, It is rare on the Pacific coast. R. and the entire spot becomes black pu.nctatum, the cause of black- and thickened. speckled tar spot, has been re- R. acerinum (fig. 3, A) is likely ported on many species, especially to produce one or more relatively silver, mountain, and striped large black spots, whereas R. maples. It is abundant on bigleaf imnctatum (fig. 3, B) produces maple on the Pacific coast. It is numerous small ones that often not so frequently encountered in

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FIGURES.—Maple leaves with tar spots caused by the fungi (A) Rhytisma acerinun and (B) R. punctatum. (X Vz-) AGR. HANDBOOK 211, U.S. DEPT. OF AGRICULTURE the Eastern United States as R. acerin^tm. First infections of tar spots in the spring are from ascospores, which are produced in the blackened areas on fallen overwintered leaves. Rod-shaped conidia are produced in the spots on leaves on the tree. They are spread by wind and rain in the summer. For information on control measures for tar spots, see page 9. Bacterial Spot Bacterial spot is caused by Pseudomonas aceris (Ark) Starr & Burkh. This bacterial disease afï'ects bigleaf maple in Califor- FIGURE 4.—Maple leaves affected by leaf nia. It was found on nursery seed- blister. ( ■ Vi.) lings and on wild tree leaves hanging close above water. The Domed blisters—convex as seen disease seems to be relatively un- from the upper leaf surface—and important economically. curling, twisting, and dying of the Japanese and vine maples and leaf are characteristic symptoms boxelder are reported to be sus- of leaf blister (fig. 4). This is ceptible to bacterial spot. Affected not a common disease. leaves develop pinpoint to one- Leaf blister can probably be quarter inch water-soaked spots controlled by applying a fungicide with yellowish margins. Later while the trees are dormant. The the spots become brown. Lesions spray must be used before the develop on the petioles. bud scales separate and the buds One outbreak of the disease on open. seedlings growing under humid Shoot Droop conditions was controlled by aeration. Shoot droop, a disease of the leaf and shoot of trident maple in Leaf Blister Japan, is reported to be caused by Several species of fungi of the the bacterium Pseudomonas acer- genus Tapkrina cause leaf blister. nect Ogawa. Irregular spots ap- These fungi are closely related to pear along the midrib. They en- those causing peach leaf curl and large and become gray or black. leaf blister of oak. Affected leaves wither, turn black, The following species have been and finally dry. The following reported on maple: maples are said to be susceptible

Taphrina species Maple bartholomaei Mi-^ (synonym: aceris (Dearn. & Barth.) Mix) biertooth carveyi Jenkins -. ____ silver darkeri Mix -- _____ vine deai-nessii Jenkins red letífera (Pk.) Sacc _ red and mountain sacchan Jenkms sugar and black DISEASES OF SHADE AND ORNAMENTAL MAPLES

midal conidiophores, which are repeatedly trichotomously or di- chotomously branched. The spores are hyaline, globose, 2 to 4 microns in diameter, and easily de- tached from the conidiophore. The fungus produces sclerotia sparingly in culture on Leonian's medium and also forms eight- sided crystals, as described by Bowen ^ for the closely related C. depraedans (Cke.) Hoehn. Sclero- tia have not been found in nature. Gray IMold Spot Cristulariella depraedans (Cke.) Hoehn. causes gray mold spot. The spots are separate or conflu- ent, irregular, and grayish without a definite margin or concen- FIGURE 5.—Norway maple leaf affected tric circles (fig. 6). This fungus by bulls-eye spot. (X 1-) to shoot droop: Acer shirasaioa- nu)n Koidz., amur, devil, hawthorn, Japanese, redvein, siebold, silver, and boxelder. Bulls-Eye Spot Bulls-eye spot is caused by the fungus Cristulariella pyramidalis Waterman & Marshall. The disease is characterized by the development of numerous targetlike spots on the foliage of boxelder and silver, sugar, Norway, and sycamore maples (fig. 5). The spots are yellowish gray with light-brown concentric rings on the upper surface of the leaf. Spots vary in size and may coalesce. On the lower surface of the leaf the spots are brown and without the concentric rings. The spots commonly are larger on leaves of the sugar maple than on those of other species. The dis- FlGURE 6.—Gi-ay mold spot on sugar ease has not been adequately stud- maple leaf. (X 1.) ied to determine its damage po- tential. It occurs sporadically and " BOWEN, P. R. A MAPLE LEAF DISEASE CAUSED BY CRISTULARIELLA DEPRAEDANS. may appear in midsummer. Conn. Agr. Expt. Sta. Bui. 316: 625- Spores are produced on pyra- 647, illus. 1930. AGR. HANDBOOK 211, U.S. DEPT. OF AGRICULTURE produces sclerotia in culture, but they have not been found in nature. Very little is known about this disease. It appears late in the summer and apparently is not serious, but it can cause some de- foliation. Leaf Scab The fungus Cercospora negundinis Ell. & Ev. causes leaf scab. Small brownish-red spots with indefinite margins appear on leaves of boxelder (flg. 7). Under a hand lens the spots appear scabby or cracked. They have numerous whitish areas with minute black fruiting bodies on the older parts. Spores of the fungus have

FIGURE 8.—Bigleaf maple leaf affected by bigleaf brown spot. (X V¿-)

indistinct septa, are long and narrow, and vary from 5 to 6 by 50 to 110 microns. The disease has been reported from Nebraska and Wisconsin. It has not caused serious damage. Bigleaf Brown Spot On bigleaf maple the fungus lUosporium mactdicola Sacc. causes bigleaf brown spot (fig. 8). A large brown spot up to 3 inches in diameter develops. It usually is rather concentrically zoned and has an indefinite margin. The diseased area frequently spans main veins. Older parts of the spot FIGURE 7.- -Boxelder leaflet with leaf break out and leave ragged holes. scab. (X 1.) The spots are dark on the upper DISEASES OF SHADE AND ORNAMENTAL MAPLES leaf surface and lighter on the fungicide after they develop on underside. The fungus Cercospor- the leaves, but no research has ella aceris Dearn. & Barth, causes been reported on their control on a similar spot on bigleaf maple. maple. Further study may prove that the two fungi are identical. No study Flower Blight has been made of control meas- The fungus Ciboria acerina ures for bigleaf brown spot. Whet. & Buchew. causes flower blight, a disease of the inflores- Septoria Spot cences of red and silver maples. The fungus Septoria aceris It has been reported from New (Lib.) Berk. & Br. causes sep- York. The flowers are killed and toria spot on leaves of several seed formation is prevented, but maple species. The spots are com- the disease is of minor economic monly small and reddish tan to importance. brown. On bigleaf maple the spots have a narrow yellow mar- NONINFECTIOUS DISORDERS gin, but on other species the bor- Leaf Scorch der is usually indefinite and ir- Leaf scorch is a physiological regular. The fungus also at- disease affecting particularly su- tacks immature fruits and causes gar and Norway maples. Margins browning. The extent of damage of the leaves or the tissues be- caused by this fungus cannot be tween the veins of affected trees estimated. turn brown in the summer, par- Powdery Mildews ticularly during or after hot, dry The mildews commonly found periods. Maples in poor condition on maple are Uncinida circinata are predisposed to develop this Cke. & Pk., Microsphaera alni DC. disease. Maintenance of vigor by ex Wint., and Phyllactinia corylea controlling pests, applying fer- Pers. ex Karst. These fungi tilizers including minor elements have distinguishing characteris- when needed, and watering dur- tics, which enable a specialist to ing hot, dry weather will prevent identify them. or alleviate leaf scorch on many Powdery mildews often produce trees. a whitish superficial growth on Leaf Distortion and Dwarfing maple leaves, particularly near Maples are sensitive to many the end of the growing season. herbicides. 2,4-D and 2,4,5-T The mycelia of the fungi cover the cause twisting, curling, cupping, leaf, but they feed on the interior browning of margins, and dwarf- through absorbing hyphae, which ing of developing leaves (fig. 9). penetrate the leaf cells. Black Abnormally narrow lobes are roughly spherical fruiting bodies common and give a shoestring ef- of the mildews commonly are fect. Phenyl urea herbicides abundant on the surface of in- cause somewhat similar symp- fected leaves in the autumn. The toms. Leaves affected by sodium powdery mildews overwinter as arsenite usually turn black and ascospores in the black fruiting fall. Since the fallen leaves con- bodies on fallen leaves. They tain arsenic, they should be gath- usually do not seriously damage ered and destroyed. maple. In soils that drain quickly, Powdery mildews generally may flooding may help to reduce dam- be controlled by spraying with a age from 2,4-D and 2,4,5-T. Un- AGR. HANDBOOK 211, U.S. DEPT. OF AGRICULTURE Premature Reddening or Yellowing Young, recently transplanted trees that fail to grow and have small leaves that turn red or yellow prematurely may have defective root sy.stems. Poor internal soil drainage can cause oxygen deficiency. Low oxygen in the soil prevents normal root development (see p. 16). Gas Poisoning If leaves die suddenly, one should consider the possibility of gas leaking into the soil from underground pipes. Leaves may wilt and turn brown suddenly or affected trees may decline slowly with top dieback as the most prominent symptom. The bark sometimes cracks. Roots may become bluish black. Some types of gas contain toxic chemicals and others can kill or injure trees by displacing oxygen from the soil in which the roots FIGURE y.—Effect of 2,4-D on red maple leaves. ( / V2.) are growing. Usually oxygen-deficient soil has a sour, disagreeable odor. fortunately the danger from herb- Dig a hole a foot or more deep, icides generally is not recognized remove some soil, and smell it, or until after damage appears. Trees smell the air in the hole after a that receive weak dosages may few minutes. The sour, foul odor eventually recover from the ef- is readily detectable if oxygen de- fects of 2,4-D or 2,4,5-T, but ficiency is serious. damage may persist for 2 years. Gas also may contain sub- Incorporation of activated char- stances that have a characteristic coal, sludge, or other organic ma- odor, which can be detected by terials into soil on which the smelling soil removed from the phenyl urea herbicides have been hole. Gas companies usually will used may reduce their damage to test for leaks if notified that one trees. However, research is needed is suspected. before such treatments can be To treat trees affected by gas recommended. poisoning, first stop the leaks. Poisons may be absorbed through the roots, leaves, or Sometimes aerating the soil will buds. Toxic vapors are formed save trees that would die if not by some herbicides. The vapors treated. Thorough aeration may can damage trees at considerable be accomplished by injecting distances from where the herbi- compressed air or by flooding in cides are applied. soils that drain quickly. Some- DISEASES OF SHADE AND ORNAMENTAL MAPLES times replacement of soil may be the northern Sierras, the drain- practical. ages of the Sacramento and Kla- math Rivers, and throughout the ABNORMALITIES OF coastal mountains of northern UNKNOWN CAUSE California. Tatter-leaf, an irregular, shot- The cause of puckering of some hole condition of maple leaves Norway maple leaves (fig. 10, B) (fig. 10, A), has been observed in has not been determined. This Logan, Utah, Orange, N.J., New condition may be due to a genetic Britain, Conn., and Wisconsin. factor or possibly a virus. The cause has not been determined. However, frost damage to SPRAY MATERIALS AND the leaf before it unfolds from the SCHEDULES bud is suspected. Bordeaux mixture, dichlone, A silvery scablike condition Puratized Agricultural Spray has been observed on leaves of (phenyl mercuri triethanol am- the Crimson King variety of Nor- monium lactate), and zineb have

FIGURE 10.- -A, Tatter-leaf of maple (X Vz) ; B, puckering of Norway maple leaf (X %). way maple. Neither the cause nor eff'ectively controlled anthracnose, the significance of the abnormal- phyllosticta spot, and tar spots.- ity is known. Two or three applications with a The causes of dieback of maple 2- to 3-week interval between in Wisconsin and of a recently them often give satisfactory re- sults. The first application for reported dying of sugar maple in anthracnose should be made when New York are not known. the new leaves are about half de- Also, the cause of a viruslike disease of bigleaf maple in the - Mention of a trade product does not imply its endorsement by the U.S. De- West has not been determined. partment of Agriculture over similar This disease has been found in products not named. 10 AGR. HANDBOOK 211, U.S. DEPT. OF AGRICULTURE veloped and the second about 2 Bordeaux mixture sometimes week.s later. If rains are frequent causes a marginal drying of leaves or violent during the early part of sugar and Norway maples. of the growing season, a third Black flecking of leaves of Nor- application may be needed and way maple after spraying with the interval between applications Bordeaux mixture has been re- shortened. In wet seasons an extra ported, but extensive damage to application may be needed in mid- maple from this spray has not summer to control anthracnose been common. Puratized Agricul- and phyllosticta spot. tural Spray sometimes causes a Spraying maples with an or- yellow spotting of leaves of Nor- ganic mercury or copper fungicide way and silver maples and russet- is recommended to prevent tar ing of sugar maple. spots. The first spray should be No research information is applied when the leaf buds are available on the effectiveness of opening. In wet seasons one spraying to control leaf diseases to four additional applications other than anthracnose, phyllos- should be made at 10- to 21-day ticta spot, and tar spots. Research intervals, depending on the fre- is needed to determine which quency and amount of rain and spi'ay materials and schedules how much of the fungicide is will control most effectively the washed from the leaves. maple leaf diseases. CANKERS AND OTHER DAMAGE TO WOODY PARTS EUTYPELLA TRUNK to 6 weeks on white mycelium. In CANKER old cultures mycelium may de- The fungus Eutijpella parasí- velop light-bufl: to cream-colored tica Davidson & Lorenz causes patches. The long, slender, curved eutypella trunk cankers of sugar conidia are pointed at the ends and red maples and boxelder. and 26 to .34 microns by 1 micron. Trunks of young trees may break Ascospores are slightly curved, at the canker. On older trees de- irregularly two or more seriate, cay may start at the cankers and dark brown, slightly attenuated gradually weaken the trunk. at the end, and 8 to 11 by 2 to Characteristics of the canker 2.3 microns. are swelling and distortion of the No control measures are known trunk, firmly attached bark, heavy for eutypella trunk canker on white to buif mycelial fans under shade trees. the bark at the margin of the NECTRIA CANKER canker, slightly raised concentric Nectria cankers develop on rings or ridges of callous tissue, trunks and other woody parts at and long-necked, black beaks of the top of both young and old the fungus fruiting bodies in trees. They have been reported older parts of the canker (fig. 11). on mountain, red, silver, sugar, The fungus penetrates the sap- Norway, sycamore, bigleaf, Japa- wood, which becomes brown and nese, and striped maples and on brittle. Cankers usually are 2 to boxelder. The cankers resemble 8 feet aboveground, but they may superficially those caused by Eu- occur at 30 feet. typella. However, the bark falls In culture on malt agar the from older parts of nectria cank- fungus may produce spores in 4 ers and dry wood is exposed, DISEASES OP SHADE AND ORNAMENTAL MAPLES 11 The alternate killing and formation of callus account for the so- called target or catface configura- tion of the canker. Infection by Nectria often takes place through injuries in tender bark of twigs. During the growing season the fungus may invade cambium and wood through injuries in the bark. Wood invaded by Nectria is streaked with oliva- ceous green, but the fungus does not penetrate deeply (fig. 12, B). The cankers are entrance points for wood-decaying fungi. The cankers are commonly caused by the fungus Nectria galligena Bres., but other closely related species of Nectria may also be involved. N. galligena produces two-celled elliptic ascospores. They range from 12 to 20 by 4 to 6 microns. The microconidia are formed in the summer and early autumn in cream-colored pustules of recently killed or dying bark. Later bright- to dark-red globose perethecia may form in these pustules (fig. 12, C). Ascospores may be for- FIGURE 11.—Maple disfigured by euty- cibly expelled from the perethecia. pella trunk canker. (X Ys.) Affected smaller woody parts may be pruned, but usually trunk whereas the bark usually clings cankers are incurable. Trees in to the central part of eutypella low vigor often bear numerous cankers. nectria cankers, but the relation- On larger woody parts nectria ship between the vigor of maples cankers are characterized by and the damage by nectria cank- roughly concentric ridges of cal- ers has not been adequately lous tissue (fig. 12, A). Rough studied. excrescences or overgrowths commonly form on affected limbs and BLEEDING CANKER branches. The fungus invades The fungus Phytophthora cac- the bark through injuries. Dead toriim (Leb. & Cohn) Schroet. branch stubs also afford a point causes bleeding canker of maple. of entry for the Nectria. The Circular to elongated cankers are fungus grows in the bark and kills found in the trunk or branches of it while the tree is dormant. When infected trees. On young smooth- the tree resumes active growth, a barked trees the cankers cause ridge of callus forms, which is sunken or depressed areas in the killed when the tree again be- bark. On older thick-barked trees comes dormant in the autumn. the diseased bark is usually 12 AGR. HANDBOOK 211, U.S. DEPT. OF AGRICULTURE

FIGURE 12.—A, Nectria canker (X Vz) ; B, wood invaded by Nectria (X %); C, perethecia of Nectria galligena in recently killed or dying bark (X 4). not sunken. Moist areas in the dark discoloration occurs in the bark commonly secrete a blood- wood beneath the canker and may red or black fluid (fig. 13). Be- extend several feet upward from neath the surface of the canker the canker and downward into the bark tissue is reddish brown, the roots. surrounded by an olive-green Leaves of trees affected by border at the transition between bleeding canker are often small healthy and diseased tissue. A and foliage may appear to be DISEASES OF SHADE AND ORNAMENTAL MAPLES 13 Excising diseased bark and correcting adverse conditions under which the affected tree may be growing are recommended. In excising the diseased bark remove all discolored tissue plus a narrow margin of healthy bark around the edge of the canker. Then shape the resulting wound so that it is oval or elliptic and the margin is smooth and regular, with the bark adhering tightly to the wood. Dis- infect wounds by swabbing or brushing several times with de- natured alcohol and then paint with shellac. After the shellac has dried, coat the wound once or twice with an asphalt tree-wound dressing. However, excision or treatment of the cankered area often fails to control the disease unless adverse growing conditions are corrected and the tree is brought into good vigor. Young diseased trees have recovered without treatment of the cankei-s when the trees were exposed to full sunlight. BASAL CANKER A canker developing at the base of the trunk and caused by the FIGURE 13.—Bleeding- canker of maple. fungus Phytophthora cambivora (X Vi.) (Petri) Buis, was reported on Norway maple in New Jersey. In sparse. Dieback of tops may oc- the United States the fungus has cur, and the trees may produce not been found elsewhere or on excessively heavy crops of seed. any other host. It is widespread Bleeding canker has been re- in Europe and is the cause of the ported on black, Norway, red, su- serious ink disease of chestnut. gar, and sycamore maples. Trees Basal canker is characterized are especially susceptible to bleed- by reddish-brown discoloration ing canker if they have been dam- of the bark, cambium, and outer aged or weakened by earth cuts sapwood near and below the soil or fills, frosts, wind, or soil com- paction. These cankers commonly line. No pink or red exúdate is develop around bark injuries pro- present. Crowns of affected trees duced by frost, storms, or me- are thin. Diseased trees may die chanical impact. within a year or two. Control measures for bleeding No control measures are known canker are not always successful. for this canker disease. 14 AGR. HANDBOOK 211, U.S. DEPT. OF AGRICULTURE SCHIZOXYLON CANKER ing to the genera Sphaeropsis, Schizoxylon canker is caused Leptothyrium, and Phacidium. by the fungus Schizoxylon micro- Pruning affected parts, fertiliz- sporum Davidson & Lorenz. This ing, and maintaining good cul- disease occurs in the Lake States tural conditions will often control on suppressed red and sugar these parasitic fungi. maples less than 3 inches in diam- TRUNK SPLITTING, FROST eter. It is of little economic im- BEAKS, AND BARK portance. The catface cankers re- FREEZING semble those caused by Nectria. The cankers are shallow and Deep winter cold may freeze sunken. The wood is often ex- fluids in the wood. Trunks may posed in older areas and often crack vertically, sometimes with a partly decayed. White mycelial loud report. The cracks serve as fans form beneath the bark at entrance ports for fungi and bac- the margin of the canker. teria. Callous tissue forms on The fungus grows on 2Vä-per- both sides of the crack and may cent malt agar, in which it pro- develop into frost beaks, or ridges, duces a white mycelial mat with commonly seen on maple (fig. 14). occasional light-brown patches in In some areas frost cracks are older cultures. This mat is tufted common on Norway maple. and wavy with numerous globose Treatment consists of cleaning bunches of mycelium, which ap- and smoothing the bark along the pear to be pycnidial primordia. frost crack and covering with an- The margin of the mat is thin and tiseptic asphalt paint. Split trunks irregular. may be drawn together with bolts. The light-gray globose pycnidia Bore one or more holes through are embedded in shallow, cuplike the trunk. Use washers on both depressions. The spores are rod ends of each bolt. Countersink shaped and 2 to 5 microns by 1 the washers and bolt head and micron. Ascospores are filiform, tap into the wood. Cover the bolt multiseptate, 1 micron in diam- ends and surrounding exposed eter, and up to 170 microns long. wood with an antiseptic asphalt They finally break into slightly paint. curved segments or short rods Bark may be killed by freezing, from 2 to 3 or 4 to 8 microns often in small patches on upper long. or exposed surfaces of small limbs OTHER CANKERS or branches. Damage becomes Fungi of the genera Hypoxylon evident in midsummer, when the and Diatrype cause cankers, par- killed or weakened bark dries. ticularly on winter-injured trees. Leaves on parts distal to the in- The cankers are frequently elon- jured bark may suddenly dry. gate and have callous beaks, or Weakly pathogenic or saprophytic ridges. They probably are pro- fungi soon appear on the damaged duced annually. They are of rela- parts, and the presence of their tively minor economic importance fruiting bodies confuses the diag- on maple. nosis of the cause. Weakened boxelder and other Exposure to full sunlight by maples are attacked by weakly pruning previously shaded limbs pathogenic canker fungi belong- predisposes to freezing damage DISEASES OF SHADE AND ORNAMENTAL MAPLES 15 roughly horizontal rows of holes in the bark (fig. 15). Transfer of food materials downward in the bark is reduced. Injured bark dries and dies, and the injuries serve as entrance ports for fungi.

FIGURE 14.—Frost beak on silver maple. (X 1/15.) and sunscald of thin bark. To minimize this damage, avoid extensive pruning of the crowns of heavily shaded trees, such as those in woodlands. Gradual thin- ning of crowns reduces danger of damage from both freezing and sunscald. SAPSUCKER DAMAGE FIGURE 15.—^Section of maple branch Sapsuckers sometimes seriously severely damaged by sapsuckers. injure maple. The birds peck (X 1/2.) 16 AGR. HANDBOOK 211, U.S. DEPT. OF AGRICULTURE ROOT DISEASES ROOT-KNOT NEMATODE Gills of the lower surface are Root knot, caused by Meloido- whitish and attached to the stalk. gyne sp.," was reported on bigleaf The fungus Ganoderma luci- maple in Oregon. Roots swell, be- dum (Leyss. ex Fr.) Karst, causes come stubby, and produce galls a root rot of maple and decay of when attacked by this nematode. the bole. The corky fruiting No cure is known, but soil in nur- bodies develop annually at the sery seedbeds may be disinfected base of affected trees or later on before planting if previous ex- stumps. The upper surface of perience indicates that root knot new conks is red and shining as is likely to be a serious prob- if varnished. The fungus can lem. Under experimental con- enter through wounds. Avoid / ditions Meloidogyne incognita wounding roots and the base of Chitwood produced galls on roots the trunk. of Japanese maple."* No practical method of control- , ling the root rots caused by A. ROOT ROTS mellea or G. lucidimi is known. The fungus Phymatotrichum However, they are more likely to omyiivorum (Shear) Dug. causes aifect trees in poor vigor. The a serious and often lethal root following practices should help rot of many species of plants. It prevent these root rots : Applying i has been reported on silver maple fertilizer, correcting unfavorable in Texas and on boxelder in Texas soil conditions, watering during and California. No cure is known. droughts, and treating wounds on Avoid planting maples on sites in- exposed roots at the base of the fested with this fungus. trunk. Armillaria mellea Vahl ex Fr. may cause a root rot. It is some- ROOT DAMAGE FROM times called shoestring root rot ADVERSE SOIL CONDITIONS because of the long, commonly Young, recently transplanted flattened strands of mycelium that trees that fail to grow and have the casual fungus produces be- small leaves that turn red or yel- neath the bark of affected trees. low prematurely may have defec- The fungus is also known as the tive root systems. honey mushroom from the color Poorly drained soil is a com- of its fruiting bodies. A. mellea mon cause of poor root develop- may kill weakened trees. The ment and defective root systems. fruiting bodies of the fungus are Roots need oxygen. In clay soil usually produced in clusters at retention of too much water ex- the base of dead or dying trees or cludes air. In such soil water may on the ground from infected roots. collect in a planting hole filled The stalk of the fungus is 3 to 10 with porous soil. Even though the inches tall with a broad, honey- site may be on a slope, it is ad- yellow to brown cap with scales. visable to check drainage in the hole. Dig a hole 10 to 15 inches " Reported as Heterodera marioni deep. Fill it with water in the (Cornu, 1929) Goodey, 1932. This spe- spring or fall. The water should cies has been divided and placed in Meloidogyne, drain from the hole overnight. If ' Personal communication from R. it does not, provide drainage or Schindler, Crops Research Division. slightly elevate the planting site. DISEASES OF SHADE AND ORNAMENTAL MAPLES 17 In sandy or gravelly soil or in Maples that grow slowly and areas with low rainfall maples have light-green or small leaves may need to be watered during or leaves with various abnormally droughts. Wilting of leaves and colored spots may need fertilizer. drying and browning of their A standard garden fertilizer is margins are symptoms of water satisfactory. A minimum dosage deficiency. The sugar maple is is 2 pounds per diameter inch of particularly sensitive to drought. trunk measured at breast height. GENERAL INFECTIONS SLIME FLUX AND WETWOOD The characteristic symptom of slime flux is a persistent or inter- mittent flow or oozing of sap from cracks or other injuries in the bark and wood of maple. This infection is usually associated with a water-soaked and more or less discolored condition of the wood known as wetwood. Often the fluid exuding from wetwood is so copious that it will flow down the trunk to the ground in a glis- tening stream, particularly in the spring. Often less fluid may be exuded. It may gradually seep down the trunk or limbs and evaporate before reaching the ground. However, moist streaks or whitish deposits remain on the bark. The exuded fluid frequently thickens until it becomes viscous and sticky. If the flux dries, a light-gray to brown deposit may be left in a more or less vertical streak on the bark (fig. 16). The clear sap that runs for a short time from fresh wounds is similar to the sap obtained when maples are tapped for sirup and should not be confused with slime FIGURE 16.- -Slime flux on maple trunk. flux. However, if injuries do not (X 1/4.) heal, slime flux may develop later in them. Invasion of the wood by bac- The cause of slime flux of elm teria may be limited to relatively is a bacterium, Erwinia nimipres- small areas or may be extensive suralis Carter. Although the cause in the trunk and ¡branches. The of slime flux of maple has not been infected wood becomes more or investigated thoroughly, it is less discolored and water-soaked, probably caused by a bacterium. and considerable gas pressure 18 AGR. HANDBOOK 211, U.S. DEPT. OF AGRICULTURE may develop in it. The pressure the trunk. The pipe always should is instrumental in forcing fluids be long enough to conduct the out of the affected tissues. toxic sap away from the trunk Injurious compounds are pro- and the base of the tree. The sap duced in affected trees. They will sometimes kill grass when it spread to the smaller branches drops on it. Pipes one-half to 1 and may discolor and wilt the inch in diameter may be used. leaves and cause dieback of twigs After the gas pressure is re- and small branches. Bark over duced and the flux has ceased ex- which the toxic sap flows may be cept for drainage through the killed, and wound healing often is pipe, the wounds from which the retarded or prevented. Badly af- flux issued can be cleaned and fected trees may eventually lose painted with a wound dressing. most of their smaller branches Sometimes the wood around the and become stag headed. Healthy flux point remains so wet that sapwood of Norway maple is paint will not adhere to it. slightly acid ; diseased sapwood is As a supplementary treatment alkaline. apply fertilizer to help keep af- Not all trees with wetwood re- fected trees vigorous. lease toxic sap through injuries, VERTICILLIUM WILT pruning wounds, or other chan- nels from the interior to the out- Verticillium wilt affects Nor- side of the trunk. IMany such way, sugar, red, hedge, silver, trees grow poorly and show symp- Japanese, bigleaf, and sycamore toms of decline, such as small maples and boxelder. Character- leaves, dying leaf tissue, and die- istic symptoms of this fungus dis- back of shoot tips. ease are dying of one or more Control or alleviation of slime limbs and progressive dying of flux and wetwood can often be the crown. Sometimes trees wilt obtained by inserting drain pipes suddenly, but more often the into the infected wood. This pro- disease develops slowly. Leaves cedure does not cure the disease, wilt and dry, sometimes remain- but much of the toxic fluid is re- ing on the twigs and sometimes moved from the wood and often dropping. Wilting and dying are the tree benefits. more prevalent in late than in Drain pipes should be inserted early summer but may occur at into the trunk and branches near any time. Affected trees are pre- where the flux issues. Sometimes disposed to winter freezing and a single pipe installed near the slime flux is common on them. Maples affected by this wilt often base of the trunk is sufficient. have sparse foliage throughout Galvanized pipes with a driv- the crown. ing fit should be inserted into each hole to a depth of 2 to 4 inches. Diseased ti'ees develop a green- A tight fit is necessary to prevent ish discoloration in the infected the pipes from becoming loose sapwood. The green streaks may and falling out. Sometimes it may be found in leaf petioles, twigs, be desirable to run the pipe down and larger woody parts, especially the trunk to the ground or to a in the lower trunk. Maples also surface drain. Other times the develop greenish stains in wood pipe may extend from several around wounds in the absence of inches to a foot or more out from this fungus disease. Such a lo- DISEASES OF SHADE AND ORNAMENTAL MAPLES 19 i. calized stain development is con- extent in sapwood of all woody Î fusing in the diagnosis of verti- parts. The light- to dark-red Î cillium wilt. stain is commonly present in box- 1 Trees with a trunk diameter of elders, but very little is known s 1 to 2 inches may be killed in a about its relationship to tree Id year by the disease. Larger trees growth. The fungus probably is may live many years after symp- a weak pai-asite. , toms appear, but they may decline i progressively or remain unattrac- SAP STREAK i tive. Sap streak is caused by the fun- t Maples can be inoculated by in- gus Endoconidiophora virescens ¡_ serting the causal fungus Verti- Davidson. This disease of sugar r cillium albo-atrum Reinke & maple occurs in a national forest Í. Berth, into holes bored into the in North Carolina. The fungus ; wood and into wounds. The fun- also causes a sap stain of hard- gus commonly invades through wood lumber throughout the East. the roots. Leaves of affected trees are ,; The recommended treatments smaller than normal and often for maples affected by verticillium slightly chlorotic. The foliage ap- wilt include pruning the dying or pears to be sparse because of the dead parts, pollarding severely small leaves. Dieback of the affected trees, improving soil fer- crown progresses until some trees tility, using fertilizers containing die after 3 or more years. Oc- ammonium sulfate as the nitrogen casionally affected trees in full source, and watering during foliage die suddenly, but the dead drought periods. leaves usually do not fall. Sap- Pruning tools should be steri- wood of affected trees appears lized with wood alcohol or other water-soaked and has green disinfectant after use on such streaks at the margins of the trees. These treatments are not water-soaked areas. The water- always effective, but they are the soaked sapwood has a pH of about best known. No method is known 8.5, whereas normal maple sap- of treating trees internally for wood has a pH of about 5.5. this internal disease. Some af- SILVER LEAF fected trees recover without treat- The fungus Stereum purpur- ment. eum Pers. ex Fr. has been re- RED STAIN OF BOXELDER ported as the cause of silver leaf Red stain of wood of living box- of maple in South Dakota. The elders is caused by the fungus fungus invades woody parts. Dis- Fusarium reticulatum Mont. var. eased trees have small leaves and negundinis (Sherb.) Wr., which are stunted. Very little is known grows in heartwood and to a less about this disease. WOOD DECAY All species of maple are subject limbs and branches as well as the to damage by wood-decaying trunk. Fungi causing decay of fungi. Some of these fungi de- heartwood invade the older and cay sapwood, some heartwood, larger limbs and the trunk, even- and some both. Those causing tually weakening them so seri- sapwood decay attack the smaller ously that they may break in 20 AGR. HANDBOOK 211, U.S. DEPT. OF AGRICULTURE

FIGURE 17.—Wuod-decaying fungi on maples: A, Sporophores of Fames applanatiis I Va) ] B. soft, creamy-white svorophore of Stecchei-inuiyi septentrionale (Xyio). wind, snow, or ice storms. In gen- Fungus Decay' eral, heartwood decay is more Hericittm erinaceus (Bull, ex Fr.) serious than sapwood decay. Pers H-W Hericium laciniatnm Leers ex Some of the fungi causing de- Banker .. -W cay of maple are as follows : Peniophora sp B Fungus Decayó Pholiota adiposa (Fr.) Kumm H-B Pleurotiis ostreatus (jacq. ex Armilîaria 7nellea (Vahl ex Fr.) Fr.) Kumm ._. S-W Kumm S-H-W Plenrotns nbnarius (Bull, ex Collybia velutipes (W. Curt. Fr.) Kumm S-H-W ex Fr.) Kumm . ... S-W Polyporu.s adustus (Willd.) ex Fr. S-W Corticinm vellereum Ell. & Crag . W Polyporas glomeratiis Pk S-W Daedalea miicotor (Bull.) ex Fr H-W Polyponis hirsutns (Wulf.) ex Fomes applanatiis (Pers. ex Fr S-H-W S. F. Gray) Gill H-W Polyporus pargamenus Fr H-W Fomes connatus (Weinm. ex Fr.) Polyporus pubescens (Schum.) Gill - ..H-W ex Fr S-W Fomes everhartii (Ell. & Gall.) Polypoi'HS resinosits (Schrad.) Sehr. & Spauld.. H-W ex Fr .....S-H-W Fomes fomentarius (L. ex Fr.) Polyporus suiphureits (Bull.) Kickx H-W ex Fr _ H-B Fomes fraxineus (Bull, ex Fr.) Polyporus tulipiferus (Schw.) Cke - H-W Overh ...... S-W Fomes igniarins (L. ex Fr.) Polyponis versicolor (L.) ex Fr S-W Kickx ___H-W Schizophyllum coniviune Fr S-W Ganodermu applanatum (Pers. ex Steccherinum septentrionale (Fr.) Banker H-W S. F. Gray) Pat..... H-W Stereunimurraii (Berk. & Curt.) Ganoderma lucidum (Leyss. ex Burt W Fr.) Karst ...... S-W Ustiilina vulgaris Tul W Gymnopilus spectahilis (Fr.) Sing H Valsa leucostomoides Pk S sapwood, H — heartwood, W = white or light colored, B ^ brown. DISEASES OF SHADE AND ORNAMENTAL MAPLES 21 Identification of fruiting bodies of the wood-decaying- fungi re- quires specialized knowledge. The sporophores, conks, or other spore-producing structures may be sent to your State agricultural experiment station or to the U.S. Department of Agriculture for identification. The spore-producing structures may be hard and woody (fig. 17, A), corky, leathery, or fleshy like a mushroom (fig. 17, B). Some persist for years, some are an- nuals, and some last only a few days or weeks. Recognition of the fruiting bodies of some fungi is useful in estimating the extent of probable decay in a diseased tree. The fruiting bodies of Fomes connatus indicate limited decay of not more than 3 to 4 feet, and often less, above and below them. Those of Steccherinum, septentrionale suggest extensive decay from 6 feet below to 13 feet above them. Conks of Fomes igniarius indicate that decay may extend 5 feet below and 9 feet above them. Fruiting bodies of Ustulina vulgaris indicate that decay may ex- FIGURE 18.—Decay starting at a prun- tend about 9 feet above them. ing wound on sugar maple. (X %.) This fungus enters through the roots or at least at the base of to 160 years old. Increasing di- the tree. On the other hand, fruit- ameter of the trunk is associated ing bodies of Pleurotus ostreatus with increased decay. In the suggest that decay may extend Canadian study sugar maples 10 only a short distance from them. inches in diameter at breast Older trees are more likely to height had one or more decayed be attacked by wood-decaying areas and 80 percent of the trees fungi than young trees. One in- were infected, whereas those vestigator in Canada reported "' more than 10 inches in diameter that decay occurred in 67 percent had decayed wood and 90 percent of sugar maples 81 to 120 years of the trees were infected. old and in 85 percent of trees 121 Wounds that break through the protective bark and expose wood " NORDIN, V. J. STUDIES IN FOREST are points of entry for fungi PATHOLOGY. XIII. DECAY IN SUGAR MAPLE causing sapwood and heartwood IN THE OTTAWA-HURON AND ALGOMA EX- decay. Frost cracks, pruning TENSION FOREST REGION OP ONTARIO. scars, lightning scars, sapsucker Canad. Jour. Bot. 32: 221-2.58, illus. 1954. punctures, dead stubs of branches, 22 AGR. HANDBOOK 211, U.S. DEPT. OF AGRICULTURE cankers, fire scars, broken tops, that sugar maple is reaching its and the parent stump of sprout northern limits in Ontario. reproduction serve as invasion Valsa leucostomoides is re- routes for wood-decaying fungi ported ' to be the principal cause (fig. 18). of decay and discoloration asso- One investigator in Canada ciated with tapping of sugar stated " that in sugar maple, frost maple. The fungus fruits during cracks were the access points for July and August in Vermont. The about .35 percent of the decay or- discolored zone the fungus pro- ganisms, and branches and stubs duces in the wood is light yellow- for 3.3 percent. Armillaria mellea, ish green in the center and deep Ustulina indgaris, and Pholiota olive or greenish black at the usually enter through the roots. margin. In the Canadian study Poly- The cause of a black stain in porus glomeratiis, Corticiiim vel- the heartwood is not known. lereum, Armillaria mellea, and Decayed wood can sometimes be Fom.es connatus accounted for gouged out of limbs and large slightly over 65 percent of the in- branches, but if it is extensive, fections and 62 percent of the removal of the member may be volume of decay of sugar maple. necessary. Decayed wood can also Ustulina vuUiaris, although pres- be removed from tree trunks. The ent in only 3.8 percent of the in- resulting cavity may be filled with fections, caused 13.1 percent of concrete or left open. Cavity fill- the volume of decay. P. glomera- ings are usually unsatisfactory in tiis was present in 36 percent of silver and red maples and box- the infections. It should be noted elder. COMMON AND SCIENTIFIC NAMES OF MAPLES amur Acer ginnala Maxim. bigleaf ____ - — _ macrophyllum Pursh bigtooth._ , - - grandicJp^^frifiim Nutt. black nigrum Michx. f. boxplder.___ — - _ negundo L. devil diabo^icJim Blume ex K. Koch hawthorn _. crataegifo^hfm Sieb. & Zuce. hedge camnesfre L. Japanese —_ palmatuw Thunb. mountain ^ spicatum Lam. Norway plafanoides L. red __ - )ïib)nm L. redvein rufinerve Sieb. & Zuce. Rocky Mountain _ - - - - glabnim Torr. siebold sieboldianitm Miq. silver __ saccharinimi L. striped pensylvanicum L. sugar saccharum Marsh. sycamore. ___ - pseudo-platauus L. trident -- - hnergerianinn Miq. vine -— _-. circinatnm Pursh '^ See footnote 5, p. 21. ' SPROSTON, T., JR., and SCOTT, W. W. VALSA LEUCORTOMOID^.S, THE CAUSE OF DECAY AND DISCOLORATION IN TAPPED SUGAR MAPLES. PhvtopatholoR-V 44: 12-13, illus. 1954.

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