'^' \ (HIjp i. 1. Mill IGtbrarg Nortlj (Earolina ^tat? Hmoerfiitg SB808 P5P5 ^ENS. Date Digitized by tine Internet Arciiive in 2009 witii. funding from NCSU Libraries. littp://www.archive.org/details/peachleafcurlitsOOpier :/ Bulletin No. 20. V. l'. P. -72. U.S. Dl^PARTMEN'r OF A( iRICUL'I URl^:. DIVISION OF VEGETABLE PHYSIOLOGY AND PATHOLOGY. B. T. GALL-OWAY, Chief. F'EACH leaf CURL: ITS NATURE AND TREATMENT. BY NE^VTO]S^ B. -ELEnOE, In Charge of Pacific Coast Laboratory, Santa Ana, California, WASHINGTON: (JOVKRNMENT PRINTING OFFICE, 1000 DIVISION OF VEGETABLE THYSIOUKa AM) PATHOLOUY. SCIENTIFIC STAFF. B. T. Galloway, ('///(/ oj Division. Albert F. Woods, Assistant Chief. ASSOCIATES. Erwin F. Smith, V. H. Dorsett, Merton B. Waite, Oscar Loew, Newton B. Pierce, Wm. A. Orton, Herbert J. AVebber, Ernst A. Bessey, M. A. Carleton, Flora W. Patterson, Marci's L. Floyd.* IN charge of laboratories. Albert F. Woods, J'huit Physiology. Erwin F. Smith, Plant Patltoh)(/y. Newton B. Pierce, Pacific Coast Lahoralory. Herbert J. Webber, Plant Breedimj. Oscar LoEW,t Plant Xutrition and Fcnncntalion. *Di'taik'cl ii.s tobacco expert, Divi.sion of Soils. +In charge of tobacco fermentation investigations, iJivisiun of Soils. LlHTIiR OF FRAXSMITTAL U. S. Department of A(;rk ultuhe. Division of Vegetable Physiology and Pathology, Washington, B. C, February W, 1900. Sir: I rospectfully transmit herewith a report on peach leaf curl, prepared by Mr. Newton B. Pierce, who has charge of the work of this Division on the Pacific coast, and recommend that it be published as Bulletin No. 20 of the Division. The report embodies the results of investigations and experiments carried on for a number of 3'ears, and shows conclusively that peach leaf curl can be controlled by com- paratively simple and inexpensive treatment. Respectfully, Hon. James Wilson, Secretary of Agriculture. B. T. Galloway, Chief (f Division. 3 LIHTER OF SURMITTAL Pacific Coast Laboratory, Santa Ajui^ Cal., Decemher 15^ 1899. Sir: I herewith .sul)init u report of investigations on the nature and treatment of peach leaf curl. The experiments described were con- ducted under the most varied conditions of soil, climate, etc., in all the leadinu- peach centers of the United vStates, and it is ])elieved that the recommendations for treatment here given are ecjually applicable wherever peaches are grown. Respectfully, Newton B. Piercp:, III Charge of PacljiG Coast Litlxiraton/. Mr. Vi. T. Galloway, Chief., Division <f Veijetahle Plajsiologij and Pafhalogij. CONTIiNTS. CnAITKR I. PkIMAKY CoNSII)P:K.\TIONS IflCI.ATIVi; to riCACII l.KAF ClKI 11 Introduction 11 General cluiract eristics of the disease 12 Geographic distribution 12 Origin of the disease 1 ,S Losses from the disease 1 !> Chapter II. ^Nature of Peach Leaf Curl 22 ~ ^ Physical conditions influencing the disease 22 The fungus causing the disease ?>\ H Relations of the fungus to the host 40 Chapter III. — ^History of the Treatment of Peach Leaf Ctrl 46 The European situation 4(3 ^ Development of the present methods of treatment 48 Chapter IV. — Plan of Preventive Spray Work Conducted hy the Depart- ment 67 Preliminary plans for the work 67 Sl)ray work conducted in 1894 70 Spray work conducted in 1 895 72 General consideration of sprays applied 75 Chapter Y. — Influence of' Sprays on the Vegetation of the Trees 77 +- Saving of foliage from injury by curl 77 Comparisons of weight and color of foliage from sprayed and unsprayed trees 88 -\- Growth of branches and leaf buds on sprayed and unsprayed trees 91 The development of new fruit buds and fruit spurs for the year following an attack of curl 95 Chapter VI. — Influence of Sprays on the Fruiting of the Trees lO."! Thinning the fruit of sprayed trees lO;? Gathering fruit of sprayed and unsprayed trees 1 OH -V- Comparative quantity, quality, and cash value of fruit from sDrayed and unsprayed trees 112 Comparati-ve value of sprays in relation to fruit 115 "Y- Comparative size of fruit on sprayed and uns2)rayed trees II li Color of sprayed and unsprayed fruit 1 20 Method of thinning and cost of picking peaches 121 Thinning ])y hand and by curl 121 Cost of picking peaches 1 22 The local action of curl on foliage and fruit 122 -^- Records of trees sprayed on one siile 122 Chapter VII. — Preventive Spray Work Conducted by One iiakdists 126 General consideration of the auxiliary work 126 Notes on the auxiliary experiments in Michigan 127 Notes on the auxiliary experiments in Oregon 135 Notes on the auxiliary experiments in California 140 Notes on the auxiliary experiments in New York, Indi.xua, and other peach-growing States 144 7 8 CONTENTS. Page. Chapter VIII. — Preparation, Composition, and General ('iiaracter.s of THE Sprays Used 146 Preparation of the copper sprays 146 Copper sulphate solution '. 147 Bordeaux mixture 1 49 Eau eeleste ] 52 Modified eau celeste 1 53 Ainnioniacal copper carbonate 1 53 i^Prei)aration of the 8uli)hur sprays 154 Preparation of combined copper and sulphur sprays and iKites on other sprays tested 1 61 Bordeaux mixture and snli)hur s^jrays combined 161 Miscellaneous sprays 161 General characters of the sprays tested 162 The enduring qualities of the sprays 162 The corrosive action of the sprays 164 Advantages of discernible and indiscernilile sprays 165 \l Sprays adapted to use in wet and in dry localities 166 Chapter IX. — The Application of Sprays 167 General accessories for winter spraying 167 Nozzles suited to winter work 167 Hose and extension pipes 169 Protection of the sprayer 1 70 Pumps for various sized orchaiils 171 Spraying tanks 175 ^-Applying winter sprays for curl 175 The time for winter spraying 1 76 Y The manner of applying winter spi-ays 1 7() Si>raying where other diseases a.re present with curl 1 77 Prune rust on the peach {Puccinia pnmi Pers. ) 177 Mildew of the peach {Podosphveva uxyacanthx De B.) 1 78 Brown rot of the peach {Monilid frudigena Pers.) 178 Black spot of the peach {Chtdos^porium mrpoph'dmn Thi'im. ) 1 78 Winter blight of the peach and other spot and shot-hole diseases, such as Phylloxttda rircumsrissd 3erk., Ccrcospora clr(niiiifiriK.s(i Sacc., etc.. 179 Sooty mold of the ])each 1 79 Animal parasites of the peach tree ISO Chapter X. — Nature and Source of the Sprayin(; Materials Used 181 Copper sulphate 181 Copper carbonate 183 Ammonia 1 85 Sodium carbonate 187 Sulphur 190 Chapter XL — Peach Varieties and Nursery Stock in Relation to Cirl. 194 Comparison of peach varieties 194 H Treatment of nursery stock 200 Suminarv _ 202 ILLUSTRATIONS. PLATES. Page. Plate I. Curl-iiifcstod peach shoot from Biggs, Cal 11 II. MyreHuiii of KruitKCHft defonnan — the fungus causing peach leaf cui-l 35 III. Fruiting stages of Exonscus deforniunts 36 IV. Germination of the ascospores of Eruascus deJoviiKWK. 38 V. Terminal peach twigs infested with peach leaf curl 42 VI. Sprayed and misprayed peach branches - 42 VII. Sprayed and unsprayed Crajvfords Late trees, Live Oak, Cal 77 VIII. Unsprayed trees in Lovell orchard. Biggs, Cal 89 IX. Lovell trees sprayed with Bordeaux mixture, Biggs, Cal 89 X. Fruit produced by row 15, experiment block. Biggs, Cal 107 XL Lovell trees sprayed with sulphur, lime, and salt. Biggs, Cal 112 XII. Lovell trees sprayed with sulphur and lime. Biggs, Cal 112 XIII. Lovell trees sprayed with Bordeaux mixture. Biggs, Cal 115 XIV. Lovell trees sprayed with eau celeste, Biggs, Cal 115 XV. Lovell trees sprayed with modified eau celeste, Biggs, Cal 115 ,.. wj TFig. 1, Manner of spraying trees on one side. Biggs, Cal \ ' iFig. 2, Action of curl on trees sprayed on one side, B>iggs, Cal ' 9'> XVII. Condition of trees sprayed on one side at maturity of fruit 124 XYIII. Fruit gathered from sprayed and unsprayed halves of tive 124 XIX. Showing fruitfulness of sprayed half of tree 124 XX. Sprayed and unsprayed Crawfords Late trees, Livi- Oak, C<i\ 142 XXI. Steam spray -cooking appliances for small orchards. 158 XXII. Steam spray-cooking appliances for large orchard.s 101 XXIII. Appearance of orchard at close of spray work, Biggs, ('al 176 XXIV. Unpruned trees, too late for spraying 1 76 XXV. An orchard properly pruned, but too late for si)raying 17(5 XXVI. An outfit for spraying small orchards - - - 204 XXVIl. An outfit for spraying medium-sized orcliards 204 XXVIII. Spraying eight trees at a time, Rio Bonito orchard, F.iggs, Cal 204 XXIX. A power sprayer in use at Santa Barl )ara, Cal 204 XXX. A power sprayer, San Diego, Cal 204 FIGURES. Fu;. 1. Cyclone nozzle, with direct discharge and dcgorgcr 168 2. Cyclone nozzle, with lateral discharge, for thin sprays 168 3. Heavy cyclone nozzle, with oblique discharge, for thick st)rays 168 4. Wire-extended suction hose 109 5. Bamboo extension pipe 109 6. Spray pump for use on barrel or tank 171 7. Spray pump for use on barrel or tank , 1 72 8. Spray pump for general orchard work, upright lever 173 9. Spray pumi) for general orchard work, upright lever 174 10. Pneumatic pump for general spraying 1 75 DESCRIPTION OF PLATE I. Cnrl-infe-«ted peach s^hoot from Biggs, Cal. Leaves of this character are badly infested with Exoascus deformans. The greatly broadened and distorted leaves, which are characteristic of this disease, are shown, and the whitened, spore-covered surface of. some of the more elevated portions of the upper surface may be distinguished. The petioles of the affected leaves are greatly enlarged, the branch is much bent and distorted, and the internodes of the diseased portion of the branch are greatly shortened. A branch thus badly diseased is apt to die during the year unless con- tlitions for growth are very favoral)le. It is in shoots of this character that the mycelium occurs in greatest abundance, but the hyphfe have been seen to spread only a short distance beyond the parts showing the hypertrophy. (Compare with Pis.' V and VI.) PEACH LEAF CURL: ITS NATURE AND TREATMENT. By Newton B. Pierck. CHAPTER I. PRIMARY CONSIDERATIONS RELATIVE TO PEACH LEAF CURL. INTRODUCTION. This bulletin has been prepared to place before the peach growers of the United States the results of experiments conducted during- sev- eral years past for the prevention of peach leaf curl. The losses arising from this disease frequently amount to several millions of dol- lars annuall}^ and it is believed that a wide dissemination of the results obtained b}' the experiments here outlined will lead to a large .saving to the peach industry. During the progress of the Department's work over one thousand six hundred peach growers in all peach-growing States have been requested to test the preventive measures here rec- ommended. A large number have done so, and some of the more important results of their work are also given. From conservative data it has been estimated that the experimental work thus widely set on foot by the Department has saved to the country in a single year the sum of three-fourths of a million dollars. This is but a fraction, however, of what may easily be saved in the future, when all growers have obtained a more thorough understanding of the disease and its prevention. The obscure views held by many growers in the past upon the true nature of peach leaf curl, and the total lack of preventive measures up to a recent date, make it desirable to thoroughlj^ consider the sub- ject at this time and to record the detailed work upon which the con- clusions reached are based. These conclusions are that peach leaf curl maybe prevented with an ease, certainty, and cheapness rarely attained in the treatment of any serious disease of plants, and that there is no longer a necessity for the losses annually sustained from it in the United States. 11 fltOnRTT LlBURr W. C. State C«lfc|« 12 PEACH LEAF CUKL: ITS NATURE AND TREATMENT. GENERAL CHARACTERISTICS OF THE DISEASE. The disease of peach trees here considered is variouslj^ known in diflE'erent regions and languages. In the United States it is commonl^v know as peach leaf curl, or curl leaf of the peach; in England and all British possessions, as leaf blister, leaf curl, or curly leaf; in France, as doque du pecher; in Germany, as Krauselkrankheit; in itah^, as Fillorissema, etc. Peach leaf curl is a disease which seriously aflfects the leaves, flowers, tender shoots, and fruit of the peach. Its action is most severe in the spring of the 3'ear, shortly after the leafing of the trees, and the greatest injuries are caused in wet seasons and in humid localities. The leaves become enlarged, thickened, much curled, and distorted. As the dis- ease progresses the healthful green of the foliage is changed to a yel- lowish, sickly appearance. The leaves soon fall, and the newh' formed fruit ceases to grow, yellows, wilts, and likewise falls. The total loss of foliage and crop is common in seasons favorable to the disease. A second growth of leaves develops more or less rapidly, according to the severity of the disease and the favora])le or unfavorable soil and atmospheric conditions prevailing at the time. If the soil and atmos- phere are drv and the temperature high, new foliage may appear slowly and much of the terminal growth may die throughout the orchard. In severe attacks young trees are frequentl}^ killed. The second crop of leaves, appearing on affected trees after the spring defoliation, u.simlh' remains comparatively free from curl for the rest of the season. The amount of disease which will appear upon this later crop of foliage depends largel}^ upon the humidity or dryness of the atmosphere, excessive moisture fuAoring a contiiuiance of the trouble. The action of the disease .upon spring branches causes them to enlarge, become curved and distorted in various ways, and often to dry up and die: GEOGRAPHIC DISTRIBUTION. Peach leaf curl exists in most peach-growing countries. Its distri- bution in the United States extends from the Gulf of Mexico to Can- ada and from the Atlantic to the Pacific. The centers of greatest prevalence, and where the greatest losses are sustained from this cause, are in the leading peach-growing districts bordering the Great Lakes, especially in Michigan and western New York; in the central, north- ern, and coast regions of California; and west of the Cascade Moun- tains in Oregon and Washington. The disease is less serious, or is of minor importance, in those peach-growing counties of New York most distant from the lakes, in Pennsylvania, Ohio, Indiana, Illinois, and in southern California. Still less injury is reported from New Jersey, Delaware, Connecticut, Rhode Island, Massachusetts, Mary-