EB 0668 Why Cherry Trees Die Rugose Mosaic Verticillium Wilt Cherry Rasp Leaf Bacterial Canker COOPERATIVE EXTENSION -~ Washington State University CONTENTS INTRODUCTION . 1 NURSERY STOCK AND CULTURAL PRACTICES ............... 1 Nursery Stock . 1 Time of Planting . 2 Poor Planting ................................................... 2 Lack of Pruning . ...............................................· 2 Heat Canker ................................................... \ 2 Mechanical Injury . 2 Fertilizer Injury ........................ ....................... 2 Lack of Sufficient Water . 3 Too Much Water ............................................... 3 VIRUS DISEASES . 3 Black Canker . 3 Cherry Mottle Leaf . 3 Cherry Rasp Leaf . 4 Cherry Twisted Leaf . 4 Little Cherry ... ; . 4 Necrotic Rusty Mottle ........................................... 4 Rugose Mosaic . 5 Rusty Mottle . 5 Sour Cherry Yellows . 6 MYCOPLASMA DISEASE . 6 X-Disease . 6 BACTERIAL DISEASES . 6 Bacterial Gummosis or Canker . 6 Crotch Gummosis . 7 Crown Gall . 8 FUNGUS DISEASES . 8 Verticillium Wilt . 8 Crown Rot .................................................... 9 Cytospora Canker .............................................. 10 Armillaria Root Rot ............................................ 10 Wood Rots ... ...... ... ..................................... 11 Insects ...................... ................... .... ........ 11 Winter Injury .................................................. 12 Rodent Injury .................................................. 12 Deer Damage .................................................. 14 Incompatibility ................................................. 14 Herbicide Damage .............................................. 14 Arsenic Residues ............................................... 15 Fire Damage ................................................... 15 Heating Oil Damage ............................................ 15 Spray Oil Damage .............................................. 15 WHY CHERRY TREES DIE By Earle Blodgett, Ph.D., formerly Plant Pathologist, Washington State University and Washington State Department of Agriculture, Prosser, Washington Revised by D.A. Johnson, Ph.D., Extension and Associate Plant Pathologist, Washington State University, IAREC, Prosser, Washington and G. G. Grove, Ph.D., and E.H. Beers, Ph.D., Assistant Plant Pathologist and Extension Entomologist, Washington State University, TFRC, Wenatchee, Washington INTRODUCTION standard black cherry. Natural mutations of sweet cherry which develop into varieties are rare. Rainbow Cherry growing in the Pacific Northwest is not only Stripe is one example. Mutations giving rise to the an interesting and sometimes profitable endeavor but undesirable kinds such as crinkle and deep suture are one attended by many problems. This publication dis­ fairly common in Bing and Black Tartarian. cusses several factors that lead directly or indirectly to the untimely death of cherry trees. It is likely there With rare exceptions sweet cherry varieties are self­ may be other factors that have not yet been recogniz­ sterile; this gives rise to cross pollination problems. ed. Nevertheless, the known problems are numerous and many are serious. The sweet cherry has become a favorite orchard tree of Western United States. Favored locations for The Sweet Cherry large plantings are found in Washington, Oregon, Utah, Idaho, Montana, British Columbia, and Early literature on cherries comes from the writings California. Although cherry growing is beset with of Theophrastus in Greece about 300 B.C. It is believed, many uncertainties, attractive returns in some years however, that cherries were cultivated even before this have maintained grower interest in the crop, and in period. Propagation by grafting has been known since recent years plantings have greatly increased. Part of very early times. Perhaps one reason for the early this has been on a renewal or replacement basis, such recognition of the cherry, even more important than as after the 1955 freeze which killed or severely damag­ the use of its fruit, was the value of the trees as wood. ed thousands of trees. Many large, new orchards have been planted in Washington, not only in the Yakima The presently cultivated sweet cherry is known Valley but near Wenatchee and especially in the Col­ Prunus avium L. Its wild ancestor, alsoP. avium, is umbia Basin. now known commonly as Mazzard. At present this is one of the two favored rootstocks. The other is While the sweet cherry is characteristically a large, Mahaleb (Prunus mahaleb L.), a small, black strong-growing, long-lived tree, it does have problems. (sometimes red) fruited kind which originated in about With domestication and concentration of orchards this the same region and now grows wild over most of tree is subject to a long list of ailments or weaknesses, Europe. Both Mazzard and Mahaleb are native and some of them perplexing as well as serious. Complaints abundant in the Black and Caspian Sea regions and from both new and experienced growers about trees occur in great numbers and variations in northern dying or declining have been more frequent the last Turkey and eastward. few years. It recalls the philosophy of an orchardist friend in Idaho years ago who remarked, "Sweet cherry Until comparatively recent times sweet cherries were trees just can't wait to die." grown mostly in backyards, on estates, and in small semi-commercial plantings. Their culture now extends The following discussions may be helpful in deter­ to temperate climates throughout the world. The sweet mining the causes and possible control of some of these cherry is one of the most delicious of fresh fruits. ailments of sweet cherry trees. Domestication of the sweet cherry over the cen­ NURSERY STOCK AND CULTURAL turies has brought great changes in varieties and culture PRACTICES and in its use in a rapidly expanding commerce. Development in Oregon the last hundred years has seen Nursery Stock three seedlings become popular and important One of the most important items in growing cherries varieties: Black Republican, Lambert, and Bing, the is the quality of the nursery stock. A Nursery Improve- 1 ment Program has been in operation in Washington Approximately half the top should be pruned away for over 40 years, and has upgraded the stock material­ at planting time. If a lower-headed tree is desired, even ly. And, since 1962, a Certification Program has made more of the top can be removed. available stock that is true to name and essentially free from all known virus and virus-like diseases. Heat Canker Any trees, especially those that are slow in start­ By using certified stock, an orchardist can avoid ing or are planted late, may develop heat canker. This the risk of planting a new orchard with poor trees. The is a brown, dead area near the soil line caused by heat best is none too good and certified trees are better than injury to the bark from exposure to the sun. any others. Heat canker can be prevented by placing a large Practices used in growing, handling, and storing chunk of sod against the south side of the trunk at nursery stock have improved during the past few years. planting time (Fig. 1). This will provide shade. A Most trees are in good condition when they leave the shingle or a short board is also effective. nursery. They should be transported under good con­ ditions and planted promptly. If this cannot be done, Mechanical Injury they should be kept from freezing or drying out. Many young cherry trees are injured, disfigured, or killed during cultural operations. Sometimes weed Time of Planting growth is so thick and tall that the young trees are not Trees should be planted as early in the spring as easily visible. Most of the damage from mechanical the ground can be worked. Chances of tree survival equipment can be prevented. (and good growth) diminish rapidly if hot weather ar­ rives before the active root system is re-established. Fertilizer Injury Generally, fertilizers should not be applied to Poor Planting cherry trees the first year. Under good cultural condi­ Holes should be large (18 to 24 inches across) so the tions trees may not need applications of nitrogen un­ roots can be spread out evenly and deep enough so the til they start to bear. bud union can be set I to 2 inches below the soil line. The soil should be firmly packed around the roots and, if moisture is low, the trees should be watered. Lack of Pruning Unless trees are pruned back at planting time, they have little chance to do well. The newly planted root system will not be able to support the original top. Fig. 2. Young tree dying due to high water table. Fig. 1. A clump of sod placed at the base of a newly planted Note that some peach and cherry trees are still tree will prevent injury by heat canker. alive. 2 Putting too much fertilizer too close to the trunks and roots has damaged or killed many young trees. Leaf yellowing and scorching and shoot die-back are characteristic symptoms. Lack of Sufficient Water Young cherry trees are vulnerable to lack of water and to competition from weeds, especially during the first two seasons. This is particularly true of replants. Poor or indifferent orchard care accounts for weak growth or death of many cherry trees. Replants in established orchards need special care and more fre­ quent watering. Too Much Water Cherry trees usually do poorly or die outright in heavy soils with poor drainage. A high water table, standing water, or excessive water will normally kill