Armillaria mot rot. root rot, sometimes called shoeslring root rot, is one of the most destructive diseases affecting the mots and butts of most species, both wn- ifer and broad leaved. Infection by Armillaria can result in rapid mortality, reduced growth, or increased susceptibility to windthrow. Generally, decay is not extensive in living tm. but it spreads rapidly when the tree dies. Armillaria can infect and establish itself in the nonwounded mot systems of stressed and widespread death of large trees can oc- cur suddenly following severe stresses such as recurring droughts or severe defoliations. When the stress abates, many trees are able to wntain the funher spread of the while they recwer. Infection is most likely to occur where there are nearby infected stumps to serve as food bases for the fungus. The fungus spreads from diseased to nearby tm through mots or by means of fungal structures called rhizomorphs which penetrate intact bark of stressed trees. Rhizomorphs are black and wrd-like and grow freely in the soil so long as they remain attached to stumps or rods that serve as their food bases. After infec- tion, the fungus spreads in the cambial zone under the bark and produces a white mat of tissue (Fig. 96). When condi- Figure 97.-Rhiuomorphs (black wrd-like structures) of Ar- tions are favorable, the fungus spreads to other msand up millaria under the dead bark of a sugar maple tree. to the root wllar where it may girdle the tree. Usually, at this stage there has been little wood decay. Visible growth reduc- tion and crown symptoms (smaller and lighter wlored leaves or branch dieback) will appear only after onehalf or more of the root system is killed. When a tree dies, the mat of white fungus tissue beneath the bark is rapidly replaced by rhizomorphs (Rg. 97), and the active wooddecay stage sets in. The root system of dead trees or stumps can supply Armillaria with food energy for up to 10 years, enabling it to pmduce rhiiomorphs and infect nearby strwweakened trees.

Figure 98.-"Honey " of Armillaria

Management of Armillaria rwt mt entails keeping stands as vigorous as possible. Under most circumstances, controlling high populations of insect defoliators is warranted. However. little can be done to combat drought, which seems to be one of the major stress factors that increases susceptibility to infection. Mechanical injury to roots as well as soil wmpac- tion should be avoided. Experiments have shown that partial ly burning or debarking and chipping infected stumps ac- Figure %.-White fungus mat of Annillaria under the bark of celerates thsir decay. This rapidly reduces their potential as a diseased sugar maple tree. food bases for the fungus.

Hypoxylon mot and butt rot. The root and butt rot fungus This fungus produces an edible, honeycolored Hypoxylon deusturn (formerly UshlIina vufganis) infects trees 10 (Fig. 98). The central stalk is 2 to 4 inches (5 to cm) long through mechanical wounds on the butt and large mots. It and generally has a ring on its upper part. The yellowish also spreads from parent stumps to sprouts. While causing brown cap is I to 4 inches (3 to 10 cm) in diameter and in some root and bun decay in living trees, the fungus 10 late summer occurs in clusters of 5 to on dead stumps. becomes most active as a wooddecay organism in dead or Mushrooms also are found on roots of infected trees or downed trees. It forms large masses of tissue near the directly on the soil, but they are always attached to an orig~nalwound or on the cut surface of stumps. These undertying infected root. masses of fungal tissue are grayish and leathety at first, bul soon become black and brittle (Fig. 99). Minute fruiting bodies eventualiy develop in this tissue. H. deusfum affects sugar and red maples, ash, basswood, beech, , and many oaks.

This fungus is common though not serious in sugarbushes. Minimizing the number of large wounds at the base of hees or on large mots should limit its development in a stand.

Black mt rot. Another disease of sugar maple, black mot rot (Xylaria polymorpha) is sometimes confused with Hypoxylon root rot. Xylaria causes rod decay, especially of stressed trees. It is recognized by a black mycelial sheet that develops on decaying mots. In late summer or early fall, clusters of gray to black finger-like to club-shaped fruiting Figure 59.-Brown to black stromata (hard fungus tissues) of bodies, 1 to 2 inches (3 to 5 cm) tall, develop on large in. Hypoxybn deustum on a sugar maple tree. fected rods or butts (Fig. 100). The appearance of these structures has evoked the common name "dead man's fingers." Above ground, symptoms of infection include reduc- ed growth and sparse, chlordic, and dwarfed foliage. These appear when the infection is severe. A tree may show symp toms only on one side of the crown if only one large rod is infected.

Vascular Diseases

Verticillium Wilt (vetticilliurn albo-atrurn)

Diseases of the tree's vascular (waterconducting) system generally are not common in the forest or sugarbush. For example, Velticillium wilt damages mainly urban shade trees. The pathogen is a longlived, soil-bome fungus. Susceptible Figure 100.-Finger-like fruit bodies of XyMa polvmwpha. trees may become infected if they are planted where diseas- ed ones were removed. The fungus also can be transmitted Sapstreak Disease (Ceratocystis coerukscens (C. from tree to tree on pruning tools. It is unlikely, therefore. viescens) that Verticiilium will will constitute a significant forest p& lem. However, in the sugarbush, the pathogen could be car- Sapstreak disease can be a serious problem in the sugar- ried from diseased lo healthy trees during tapping, especially bush. The causal organism is one of the most common stain if infected trees near highways or homes are included fungi of northem hardwood logs and bolts. It can enter and among those being tapped. Because the organism is present kill wounded trees. The primary avenues of infection are mot in the soil, there also is the possibility that infection could oc- and buttress injuries made by skidding or sap hauling (Fig. cur through root and stem wounds. 103). Recent observations also suggest that trees can become infected through stumps created when sprout Foliage of diseased trees may suddenly win at any time dur- clumps are thinned (Fg. 104). Outbreaks of sapstreak always ing the gmwing season. A few branches, whole sections of have been associated with logging or with sugaring. There is the crown (Fig. 101), or the entire crown may show symp no evidence that broken branches, insect injuries, or even toms. Trees with only small portions of crown affected may tapholes are suitable sites for infection to begin. recover. Those with much or all of their crowns affected pr* bably will die, often rapidly. Stem cross sections show spds A sparse crown usually is the first sign that a sugar maple or partial to complete circular bands of dark green diswlor- tree has sapstreak. Leaves often are onehalf or less than ation involving one or more growth rings (Fig. 102). The normal in size (Fig. 105). Sometimes, trees die suddenly. In discolored streaks may be limited to the trunk or can extend fact, trees without symptoms during one year may fail to leaf even to the tips of wilting branches. out the next; others may succumb within a year or so. By contrast, some trees may linger for many years, showing progressive dieback before they die. Some may even recover. Figure 102.4reen discolored streaks of sapwwd are characteristic of Verticillium wilt (Cornell University photo).

Figure 101.-Verticillium wilt affects urban sugar maples and usually is not serious in sugarbushes. Portions of the af- fected tree's crown may wilt suddenly and die when the sap

Figure 104.-Trees can become infected by sapstreak disease through the stump "wound" created when a member of a sprout clump is removed.

Figure 103.-Injuries made to rods and lower stems during skidding or saphauling allow the sapstreak disease fungus to enter the sapstream of the tree. Figure 106.--Sapsteak disease gets its name from the distinctive stain it causes in the wood of roots and lower stems.

Figure 105.-Early symptoms of sapstreak disease are small leaves that result in a thin crown.

Wood of buttress roots and lower stems has a stain with a unique color and pattern. Freshly exposed stain is moist, and drill shavings from such wood will be "mealy" in consistency F~gure107.--Sapstreak sometimes affects trees in groups and discolcxed compared to clean, white shavings from Within this group near a sugarhouse, many trees were in- jured repeatedly during sap and wood hauling. healthy wood. The stain is yellowish-green, bordered by a thin dark green margin (Fig. 106). It contains flecks or streaks that are reddish when fresh. Soon after exposure to ground-inhabaing organisms (insects, millipedes, etc.), from air. the stain darkens and the red flecks become less wounding of groups of trees at specific times, or from in- distinct. The dark stain then fades to a light bmwn. In cross teraction with other root pathogens known to attack and kill sections, the stain appears to radiate outward toward the trees in groups. Nearfy all trees killed by sapsweak also are bark (Fig. 106). Cankws develop where the cambium comes severely attacked by one or more root fungi (Armillaria in contact with the spreading stain column. andlor Xylaria) (Figs. 108, 100).

Most trees affected by sapstreak are located along trails Because the sapslreak fungus often grows and produces where logs have been skidded or sap has been hauled. The spores on the ends of bolts cut from diseased trees, piling more heavily used the roadway, the more likely it is that wood from didtrees near the sugarhouse may serve to adjacent trees will be wounded. More diseased trees have build hioh- concentrations of inoculum lsoores, . and other been observed in sugarbushes where buckets are used than fungus materials that can spread disease). Since such where tubing is used. This reflects the greater number of buildups could increase the chances of lnfeciion in nearby wounds inflicted during the many trips to gather sap. trees, fuel wood from trees killed by sapstreak should be removed from the sugarbush promptly and used elsewhere Sapstreak rees often occur in groups, sometimes close to the sugarhouse (Fig. 107). Such localization could result from the pathogen being carried from diseased to healthy trees by ANIMAL DAMAGE

Wildlife

Wild animals may cause problems for sugarbush operators as some can injure maple trees or damage equipment, occa sionally causing significant losses in time and money. Sugar- bush managers frequently are concerned about the impact of deer on sugar maple seedlings and saplings that will make up the future stand, because the buds of such seedlings and saplings can be a major component of a deer's winter diet. Frightened deer running through a sugarbush can destroy tubing but generally they cause little damage to equipment.

Red and gray squirrel, snowshoe hare, cottontail rabbit, por- cupine, mice, and a variety of birds sometimes feed on sugar maple stem bark, buds, or twigs. This damage is rare ly serious, though significant damage by squirrels stripping bark from buttress rods has been reported. Also, squirrels and chipmunks can cause extensive and costly damage by puncturing and chewing plastic tubing (Fig. 109). It is not known what attracts these animals to tubing. Sweetness of maple sap and the salt that is imparted to the tubing when the plastic is manufactured-especially chlorine salt that is deposited by cleaning solul'ons--have been implicated. Chlorine salts can be removed by thoroughly rinsing tubing and using low concentrations of the cleaning sdution. New tubing produced by a variety of manufacturers (tubing that is salt free and that never has had sap in it) also attracts squir- rels. Perhaps squirrels, like most rodents, must wntantly use their teeth to prevent them from becoming too long. Curiosity alone may be enough to anract these pests to "foreign ob. iects." Once contact has been made, rodents ndonly gnaw Figure 108-White "fan" of Armillaria. Roots of sapstreak- on tubing but also on spigots, connectors, and couplings. diseased trees frequently are attacked and girdled by this fungus. Rodent damage may valy among regions and from year to year, but once the problem occurs it is difficult to control. Management of these vascular diseases should focus on Some operators coat tubing and fixtures near the tree with reducing injuries to rods, buttress roots, and lower stems, distasteful substances, such as a mixture of cayenne pepper and preventing an increase of the vascular pathogens and and varnish. Obviously, care must be taken to keep these the commonly associated rwt pathogens. materials out of the sap. Poison baits also have been used to control rodents. However, because the use of such For both sapstreak and Verticillium wilt it is of paramount importance to avoid injuring roots and lower stems when gathering sap, hauling wood, or skidding logs. Injuries can be reduced by using the same well-placed trails each year, the smallest machinery possible, and tubing systems rather than buckets. These measures are particularly impoltant on steep, slippely slopes. Because trampling injuries by mws or horses also have been associated with incidents d sapstreak, these animals should nM be allowed to graze the sugarbush. And, as mentioned earlier, prompt removal from the sugarbush of wood from sapstreak-infected trees will help reduce the buildup of infectious inoculum.

Figure 109.--Plaslic tubing damaged by squirrels or chipmunks.