Photographic guide Ornamental to ornamental tree diseases Beginning with the top row and pro- ceeding from left to right, the photo- plant diseases and graphs illustrate Apple scab on crab- apple; Cedar apple rust on hawthorn; and Cytospora canker on mountain- their control ash. Proceeding from left to right on the bottom row: Verticillium wilt, show- by Roger Funk and Henry Gilbertson, Davey Horticultural Institute, ing streaking of sapwood; Wood rot The Davey Tree Expert Company and a shelf fungus associated with the wound; and Shoestring root rot show- ing rhizomorph fungus strands and whitish mycelial fan. An ornamental plant may be sources of inoculum is effective only if defined as diseased when its normal practiced on a wide area basis. The life processes are disrupted. These amount removed at a single site would disruptions are caused by both not significantly reduce the potential parasitic (living) and non-parasitic infection since the fungal spores are agents. windblow over great distances. Proper Parasitic agents of ornamentals are fertilization, pruning and watering principally fungi but also include bac- during droughts will not decrease teria, mycoplasms and viruses. fungal infection but will help the plant Many parasitic plant diseases can recover more quickly and remain be discussed according to the major vigorous. part of the plant infected. Rust Diseases Leaf Diseases That class of diseases known as Leaf Spot Diseases rusts should be included in a dis- Most deciduous ornamentals are cussion of leaf diseases since many of subject to leaf diseases to some the rust fungi cause serious leaf prob- degree. lems. One of the most common types of The characteristics of rust diseases disease is that caused by the leaf spot which sets them apart from the others fungi. These fungi overwinter in the is that most of the fungi that causes old leaves on the ground in the form of them require two hosts to complete spores which become windborne dur- the life cycles. In other words, the ing cool, wet spring weather. They spores produced by a rust fungus on produce diseased areas on the leaves one kind of tree cannot reinfect the which are more or less charateristic in same kind of tree. Instead they must size, shape and color for each species infect a second kind of tree or some of fungus. Such descriptive common other plant which is usually from an names as leaf blotch, tar spot and frog- entirely different genus. The fungus eye leaf spot indicate the distinctive then prduces spores on the second character of the injuries produced by host. These in turn cannot infect the many of these fungi. Some of the dis- second host but must return to the first ease organisms are specific to a partic- kind of tree or plant to grow to com- ular plant species; others may attack plete the cycle. In some cases both several species of trees or shrubs. hosts may be trees or other woody Leaf spot diseases are particularly plants. In other cases one host is a tree noticeable when they cause and the other some herbaceous weed premature leaf drop. However, partial or crop plant. Both hosts of some rusts defoliation is seldom serious unless it are herbaceous plants. Some of the occurs two or more years in succes- serious diseases of branches as well as sion. These diseases do not directly leaves of trees are caused by rust kill trees but rather predispose them fungi. The cedar-apple rust, which is a because of the long distance spores to other diseases or stresses which common disease of apple trees and may travel. Properly timed fungicidal may lead to decline and death. related ornamental species, may be applications have successfully con- Most leaf diseases can be sup- considered as typical of the rust dis- trolled most rust diseases on pressed or prevented with fungicidal ease. ornamentals. sprays applied at budbreak and The most effective preventative Stem Disease repeated twice at 7-to-10-day inter- measure for rust diseases would be to Canker Diseases vals. In wet years, additional applica- destroy the less desirable hosts within Canker diseases are common on tions may be necessary. Raking and carrying distance of the spores. Unfor- many ornamental trees and shrubs. disposing of leaves to reduce the tunately, this is seldom practical Some of the fungi which cause leaf diseases also cause a killing-back of destruction of bark is complete and a fungus destroying the cambium and the twigs for some distance from the wound results. In most cases, the conducting tissues of the phloem and end. For example, the fungus which cankered area is sunken and/or dis- outer xylem or as a result of infection causes a typical leaf disease known as colored and may be covered with the in the outdoor bark. This shuts off the anthracnose of sycamore also causes a fruiting bodies of the fungus. supply of water and minerals to the twig blight and canker stage on An individual canker may continue top of the tree and prevents the branches up to an inch in diameter. to grow until it girdles a large branch downward flow of prepared food Other fungi causing similar twig or a fair sized tree. Numerous small materials to the roots and other parts symptoms may not directly affect the cankers on a branch or trunk may below the cankered area. leaf tissue. Fungous injury on a trunk result in the same girdling effect in Cankers often go unnoticed until the or branch becomes a canker when less time. The damage is caused by the infected stem dies and the foliage turns brown. By this time, con- organisms is the result of phytotoxic lowing of a branch occurs near the siderable damage may have occurred substances produced by these top. and corrective pruning will drastically pathogens and by the clogging of Several vascular diseases caused by alter the appearance of the plant. water-conducting vessels with bac- fungi seriously menace some of our Vigorous plants usually are not af- terial or fungal growth. In some cases important shade and ornamental fected by cankers. Proper planting cells surrounding the vessels are trees. Verticillium wilt and Dutch elm procedures and cultural practices stimulated to form tyloses, extensions disease are two of our most important should minimize or eliminate many of the neighboring cells that grow into diseases and both are caused by problems caused by canker diseases. the vessels or tracheids, blocking ac- vascular wilt fungi. Some of the casual Since many of the casual fungi tive water transport. The wilt- organisms of wilt are limited to one invade plant tissues through breaks in diseased branch, in cross section, species or genus. Others may infect a the bark, care should be taken to avoid shows a discolored area in the number of species. Verticillium has unnecessary injuries. In general, sapwood. This may be confined to one been reported to infect over 50 chemical control measures have been annual ring or may be found in different species of trees and shrubs. unsuccessful in the treatment of several rings. Frequently the dis- Vascular wilt diseases are difficult cankers, while bark tracing and excis- coloration takes the form of a closed to control after serious infection has ing small trunk or branch cankers has or broken ring in one annual layer. occurred and preventative control has produced satisfactory results. When the stem is split lengthwise or not been entirely successful. Remov- Wilt Disease the bark peeled back, the diseased ing and destroying infected trees will Wilting is due to a deficiency of layers show as lengthwise streaks in reduce the sources of inoculum. water in the leaves and stems and can the sapwood. Where a disease organism such as ver- be caused by excess or insufficient Because wilt diseases are systemic, ticillium can spread from plant debris water in the soil, injury to the root they are usually more important, and remaining in the soil after an infected system or parasitic invasion of the harder to control than localized spots host is removed, susceptible trees and vascular xylem which conducts water or cankers. Often the fungus is present shrubs should not be replanted within throughout the plant system. near the base of a tree while the first the root zone of the diseased plant The wilting caused by disease symptom of flagging, wilting or yel- removed.

Brouwer MINNESOTA Canada R.L. Gould & Company Mower Dealers 3711 Lexington Ave. N. ALBERTA St. Paul, MN 55112 612/484-8411 Hauser Tractor & Equipment Ltd. 2619 - 7th Avenue NE CALIFORNIA Calgary, Alberta T2A 2L9 Tractor Equipment Sales NEW YORK 403/272-6686 705 Tully Road C.J. Perry & Son Inc. San Jose, CA95111 8401 Ridge Road 408/297-7422 Gasport, NY 14067 Hauser Tractor & Equipment Lts. 716/772-2636 11635- 156th Street Edmonton, Alberta T5M 3T8 COLORADO OHIO 403/452-0161 GM Turf Equipment Dravo Marks Route 1, Box 65 1310 Conant Street BRITISH COLUMBIA Berthoud, CO 80513 Maumee, OH 43537 Multi Turf Specialists Ltd. 303/535-4317 419/893-3339 6455 - 64th Street Delta, British Columbia V4K 3N3 FLORIDA Sharon Lawn Equipment 604/946-7011 Lake Equipment Company 11674 U.S. 42 Hwy. 715, Box 340 Sharonville, OH 45241 513/769-4061 MANITOBA Belle Blade, FL 33430 Mandem 305/924-5641 21 Murray Park Road Oviedo Tractor Company TEXAS ABM Company Winnipeg, Manitoba R3J 3S2 State Route 46, Box 257 204/885-4440 Oviedo, FL 32765 Box 364 305/365-3247 Needville, TX 77461 713/793-4600 ONTARIO KANSAS Brouwer Turf Equipment Limited WASHINGTON R.R. 2 Johnson County Equipment Valley Tractor & Equipment, Inc. Keswick, Ontario L4P 3E9 Box 242A DBA Redmond Lawn & Tractor Equipment 416/476-4311 Stillwell, KS 66085 P.O. Box 681 913/681-2781 Redmond, WA 98052 206/883-4444 QUEBEC MICHIGAN (parts only) O.J. Company Huron Sod Farms UTAH Rang St. PaulSud. 30877 Pennsylvania Rd. Johnson Tractor & Implement, Inc. Sherrington, Quebec J0I 2N0 Romulus, Ml 48174 Spanish For, UT 84660 514/861-5379 313/941-2730 801/798-8696 514/247-2994 Many cases have been reported commonly called conks, and are inhibits rot fungi would be useful in where maples infected with ver- among the most prominent of fungous preventing wood rot diseases. Pro- ticillium have "walled-off" the dis- growths. The under sides of these tecting ornamentals from mower ease by laying down new layers of fruiting bodies are divided into a great damage and other unnecessary tissue after being properly fertilized. many pores or have other types of wounds would also prevent rot Plants should be maintained in a openings on the inner walls from diseases. vigorous condition through pruning, which the-spores are produced. Root Diseases watering and fertilizing and sprayed, After the spore germinates, the Although the casual fungi of root where applicable, to control disease- growing mycelium branches again and rots are usually present in the soil, carrying vectors. again. As it advances into the wood, the most become aggressive on living Wood Rot Diseases walls of the cells that lie in its path are plants only when unfavorable growing The wood rots may be divided into dissolved or broken down and their conditions exist. those which infect the heartwood and substances used as food by the fungus. The main factors contributing to those which infect sapwood. The dis- The wood changes in color and weight such stress conditions are drought, tinction between the two is not always and becomes "punky" or "rotten". In altered drainage patterns, soil com- clear. Some of the fungi which cause addition to killing the living cells, paction, waterlogging of soil, landfill decay of sapwood are limited to the wood rots greatly weaken the struc- over roots, wounding of roots, nutrient older, non-living layers. Others may tural strength of trees and so make deficiencies and insect defoliation. attack the living outer layers which them more subject to being broken To prevent root rot diseases, both are actively engaged in water con- during storms. soil disinfection and removal of dis- duction. The rot fungi enter through unpro- eased roots or portions of roots have Infection takes place by the germi- tected wounds — either pruning cuts been tried, but with indifferent nation of a spore, this spore having or breaks due to mechanical or wind success. The most effective preven- been produced in a fruiting body injury. Although there is some ques- tion would be to maintain favorable which protruded from the surface of tion concerning the value of wound growing conditions. One cannot another diseased area. These fruiting dressings as a deterrent to fungal inva- overstress the importance of fertiliza- bodies are usually of the bracket type, sion, the addition of a fungicide which tion and proper watering.

How can you cut more grass per gallon? Get yourselfH ^ a Brouwer.

Run a 7 gang unit, cut up to 7 acres per hour with a 30 HP tractor. THE NEW BROUWER HYDRAULIC LIFT MOWERS ADD ANOTHER Brouwer's unique Positive P.T.O. TIME SAVING INNOVATION AT A Drive requires less horsepower than VERY LOW COST. conventional wheel drives, increases fuel economy, and successfully For complete details on the Brouwer operates in varying grass conditions. line of mowers, write for our free The lightweight, high-stress steel brochure. frame combined with the simple, "no- wheel and gear" mowers minimize flattening and avoid wheel tracks. Brouwer 3, 5, and 7 gang mowers are simple, easily transportable, re- markably maneuverable and excep- tionally economical and versatile. BROUWER The Turf Equipment People

Brouwer Turf Equipment Limited, Woodbine Ave., Keswick, Ontario, Canada L4P 3E9 Tel: (416) 476-4311 Write 120 on free information card