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DATE DUE DA'rsoyg DATE- DUE MSU lsAn Minn-five Maud Opportunky III-thatch mm: AN APPRAISAL 0F FUNGICIDES FOR THE CONTROL OF APPLE SCAB IN QUEBEC BY ROger Desmarteau Submitted to the School of Graduate Studies of Michigan State College of Agriculture and Applied Science in partial fulfillment of the requirements for the degree of MASTER.OF SCIENCE Department of Botany and Plant Path010gy 1952 :IHESIS ’v-I". /3 —*°"-“' 1 I TABLE OF CONTENTS INTRODUCTION.............. ...... ........Page 1 IMPORTANCE OF APPLE SCAB IN QUEBEC...... 3 The Apple Industry...... ......... ....... u Apple Scab in Quebec. ........ ........... 7 Fungicides in Use.. ..... ..... ........ ... 9 FIELD TESTS AGAINST APPLE SCAB IN QUEBEC 11 Method800......_o.o oooooooooooooo 0....... 11 Materials used in the Tests............. 15 SCheduleaoo...oooo ...... ..........oo.... 18 SEASONAL DEVELOPMENT OF APPLE SCAB...... 25 Determination of the Primary Infection Periods.... 25 Periods of Ascospore Liberation......... 28 Scab Deve10pment........................ 34 RESULTS or THE EXPERIMENTS.............. #2 Results for the Year 19h8............... 42 Ebsults for the Year 1949............... 46 Results for the Year 1950............... 53 Results for the Year 195l............... 57 SUMMARY AND CONCLUSIONS................. 68 LITERATURE CITED... ...... ...... ...... ... 7O cTfiFWQig , . '1 ' P . - e . aw" .I V I (.1 'n ACKNOWLEDGEMENTS The writer wishes to express his sincere thanks to Dr. George Gauthier and Professor Donald Cation for their help in making this thesis possible. Thanks are due to Dr. Gauthier for his cooperation in permitting the use of the material collected from experiments conducted by the writer as a part of his regular duties vith the Plant Protection Service, Quebec Depart- ment of Agriculture. Professor Cation's advice and criticism during the preparation of the manuscript were invaluable. Thanks are also due to the generous aid the writer has received frcn.assistants and workers at the Orchard Protection Station of Quebec dur- ing the course of these investigations. .1, u. .. in I f 5'. LR. w tn..| .. F.. . Ij‘OI ail-fir I’ll! L... . INTRODUCTION Since the early develOpments of the apple industry in America, apple scab caused by Venturia inaequalis (Cke.) Winter, has been recognized as one of the most important . diseases affecting that crop. On control alone, a great deal of research has been done since the nineties of the past century when Goff start- ed the first experiments in United States for control of apple scab (13). Even today, a number of plant pathologists, extension workers and horticulturists devote their time entirely or partly to control measures alone. Each.year reports of field tests on spray materials are issued from.all over United States and Canada. During the past 15 years, new deve10pments in the fungicide field have supplied new ammunition for the con_ trol of apple scab. The use of the organic fungicides is becoming more and more general among apple growers. How- ever, further development is needed before these synthe- tic materials will displace the sulphurs as the main comp bat arm.against apple scab, partly because the synthetics are more expensive but also because they are rather selec- tive and may be inconsistent in their performances. Most recently, a revolution in spray equipment and technique of applying materials to fruit offers new possibilp 2 ities for control of this disease. This new development, concentrate spraying, when equipment is adequately adjust- ed to particular orchard needs, or trees modified by prun~ ing or cultural methods to meet equipment deficiencies, should not only effectuate a much needed reduction in cost of the spraying Operation, but will possibly provide a better control of apple scab. Despite the efforts of experimental workers and others, losses due to apple scab are still high. High losses appar- ently result from.poor timing, difficult to achieve in some years because of excessive rainfall and rapid growth, imp proper use of old standard materials as well as inexperience with the new ones and poor coverage which may be an impora tant factor with new fungicides and spraying machinery. Recently,.McNew, McCallan and Miller hare reported, for 1920 to 1939, compilations of loss from the most impor- tant diseases affecting apple in United States (1%). For a 20byear average covering the period 1920—1939, it was estimated that 10% million bushels of apples a year have been lost on account of apple scab. According to these writers, this would mean, at present prices, a loss of 25 to 30 million of dollars a year. In 19fl5, a severe epidemic struck the northeastern states. No exact figures are available but it was report— ed as the worst blow in two decades in New York'by Burrell (2) and no doubt the loss ran into millions of dollars, though frost and poor pollinating conditions also took a toll in that disastrous year. 3 IMPORTANCE or APPLE seas IN QUEBEC The apple industry in Quebec is concentrated in the southwestern part of the province. By far the greatest number of orchards are situated south of the St. Lawrence River in the Montreal Plain and the Appalachian Region. In the vicinity of Montreal a.number of orchards are located on the north shore but most are planted in an area south and east of the metrOpolis. To the east, most or- chards are concentrated around the Monteregian Hills, a series of small elevations of volcanic origin scattered in the plain. The five hills, St. Bruno Mount, St. Hilaire Mount, Rougemont, St. Paul Mount and St. Gregoire Mount are all centers of apple production. South of the city other orchards lie on gently undu- lating ground in the valley between the St. Lawrence and its tributary, the Richelieu river. Chateauguay, Huntingdon, Hemmingford and Franklin are the most important centers of that district. Further east from.Montreal, beyond the Richelieu.river, other orchards are planted on the edge of the plain and on the lepes of the Appalachian Mountains. The Frelighsburg district in the Mississiquoi county is the most important one in the Appalachian Region. It is a new producing area, the first trees having been planted in 1927 and it now includes around 250 thousand trees. A.most recent survey of the Horticultural Service of the Provincial Department of Agriculture and compilations u by the Department of Commerce and Industry gives statis- tics regarding the nember of trees of bearing and non— bearing ages for the leading varieties in the province. This information is summarized in table 1 for the Hon- treal and the Appalachian Regions. The apple industry also extends in the east of the province, lower in the St. Lawrence Valley. In this third area the Eastern Quebec apple region, small orchards are distributed on both shores around Quebec city. On the south shore orchards extend cast into Kamcuraska county. A.num- ber of trees are planted on Orleans Island, one of the oldest apple districts situated a few miles below the city. Compilation of statistics is not finished for Eastern Quebec but it is estimated by the Horticultural Service, that there are 250 to 300 thousand apple trees in the area. 50 to 60% of these are the McIntosh variety. In Southwestern Quabec there is a little over 1 million trees with 55% of the McIntosh.variety, an apple of the fin, est quality and high market value but also very susceptible to scab. Table 2 gives the annual yield of apples in Quebec from 1933 to the present and.the average price obtained for McIntosh and Fameuse, the two leading varieties. These figures give an idea of the importance of the crop in the province. P Heao# mum. Re. H 3n. n2. Rm. men cum. Ra RE. mm R». R 8a. R mum. me :33 umm.mn nma.m ~ma.mu mms.m~ enaaanon mom. em Rm. m mm”. a” m? . m one..— canonsamasn mom. on man. in man. 3 man. in Beam pm. 3 #2.. in So. am out ma 35$ m8. mm was. an «mm. 3 mum. m Boas; new. on mam. mm «mm. m mac. n 8.325— mam.~mn Hmm.mm mnn.mm m:m.nn 0.90353 mam.o~m ~:~.mmm -~.ama mm~.maa enopsno Hench - mmmummmmh a. H o a .o a. ma can» once eao Hush ma unmonncoo no «Hoop we me up no .03 soon» no .0 a. canned zen—$538 B was Sun: .3 33.2. :..-H 393.. TOTAL YIELDS OF APPLES IN Table 2--- QUEBEC AND AVERAGE PRICES PER.BUSHEL Years . N33351: 12f fggeicaggtgzic 3181a Fameuss 1933 986,850 --- 1935 504.339 --— 1936 32n,870 --- 1937 561,990 --- 1938 uu5,200 2.7a 1939 . 1,066,305 2.51 19u0 1,030,980 2.28 19|+1 726 ,15k 3 .31; 19n2 1,170,000 3.27 19u3 911,000 3.81 19kt 900,000 3.57 191.5 80 ,000 ~- 19u6 1,000,000 3.92 191*? 1 .300 .000 3.39 194-8 1 ,005 A50 3 . 0t 19h9 2,250,000 2.52 1950 1,900,000 1.75 1951 3,110,000 1.75 (about) 7 A la Scab in ebec There are no statistics available for apple scab in Quebec. waever, each year the Canadian Plant Disease Survey issues an annual report in which plant pathologists from all the provinces give an acCount of their observations on plant diseases of economic importance. In the province of Quebec, observations on apple scab have been reported from year to year since the start of the Quebec Spray Service in 1929. Though some of the reports are fragmentary, often referring only to particular locations or orchards, they do give an idea of the prevalence and losses from apple scab in Quebec for the past 20 years. For most of the years from 1929 on, conditions were favorable for scab development. An appreciable loss was reported each year except for 1939, l9hl, and l9fl8 when scab was of little importance. The approximative percentages of infected fruits in some of the poorly sprayed orchards reported on, may give an idea of the losses that occurred. These percentages ranged from.30 to 60 in the years 1929, 1931, 1935 and 1939. Reduced yields that accompany such heavy infections were not considered in these estimations. ‘ An example of such losses that do occur, is shown in counts by the writer in 1999 in an orchard where sprays were poorly timed. M5% of the fruits of the McIntosh variety were found scabbed, most of them badly. In addi- tion, the setting that had been excellent was reduced S considerably by the disease and also there was only a small crop the following year though scab was under control. No figures were given in the other years for orchards of this type in which most of the losses from apple scab are likely to occur. Of course, in well-sprayed orchards, scab was much less important and when reported, it ranged from "slight" to 10%. Though during epidemic years the percentage of scabby fruits must have been higher, in general. 1931 and 1932 are mentioned in the reports of the Canadian Plant Disease Survey, as years where scab was “especially prevalent“ (3)(h) and 1933 was worse when orchards 'usually free from scab, did not escape'(5). Again in 1937, scab is reported as “very destructive“(6). Apparently, 19“} was one of the worst years for apple scab in Quebec when “scab was usually severe throughp out Quebec'(l7). A severe outbreak occurred in 19u5 when scab was “exceptionally severe and widespread“; “most of the orchards showed infections, often with almost complete defoliation“(7), Petch states, for the province,that “the greatest epidemic in the history of apple growing" occurred that year (18). Again in 19M7, scab struck hard in Quebec. Scab is reported in the Canadian Plant Disease Survey as having caused “great losses in Southwestern Quebec" and “few growers secured clean cr0ps“ (18). For the following years, seasonal scab develOpment "4 9 is reported later by the writer and need not be described here. One point that stands out in reviewing the reports on apple scab in Quebec, is the many times late infection has occurred. Late scab has been a real problem in many years. The relatively frequent heavy precipitation during August and early September results in considerable late infection, causing appreciable losses to apple cr0p fairly or exceptionally free from early scab. Fu icides in Use ainst A la Scab n uebec Most of the growers in Quebec use Lime-Sulphur and elemental sulphurs to control apple scab. The sales of the main spray materials in Quebec for the past few years are presented in table 3. There is a pr0gressive decrease in the use of Lime- Sulphur, and when used, it is frequently applied as an emergency for eradicative purposes, though a number of growers are still on a straight Lime-Sulphur schedule. Elemental sulphurs came into use around the late thirties in Quebec. Kolospray, a pr0prietary formulation of wettable sulphur, was the first to be generally used. Other prOprietary brands of sulphur have been used since. Magnetic 7O sulphur paste was introduced in 1948 and has gained in favor and use by growers. Organic fungicides have yet to be used extensively, except possibly Ferbam, the iron salt of dimethyl dithiocarbamic acid. Ferbam.was not used in appreciable Table 3--- SALES OF THE MAIN span MATERIALS In QUEBECI Materials . 199 1950 . 1951 Lime Sulphur 138,600 128,700 112,200 gals. gals. gals. Iolospray --- --- 30,000 lbs. Magnetic 70 160,000 £100,000 #110,000 lbs. lbs. lbs. Crag 3’41 C -- -—- 600 gals. Ferbam --- --- 200,000 lbs. I--These figures have been Obtained from the 000perative Federee de Quebec. ll amounts before 1950 but is now becoming more p0pular. Crag 3910, a glyoxalidine formulation, was used for the first time in 1951. The organic mercuries are also of recent appearance and have been used only in isolated cases as emergency spray. FIELD TESTS AGAINST APPLE SCAB IN QUEBEC The experiments here reported have been conducted at the Orchard Protection Station, a summer laboratory of the Plant Protection Service of the Quebec Department of Agriculture. This work has been done in the Frelighsburg district in.Mississiquoi county at two different locations. A first series was completed in the years 1948, 1999, and 1950 at Dunham and another series not yet completed was‘begun at Farnham in 1951. Methods At Dunham, the tests were made on 20 year old McIntosh trees while at Farnham, Melba trees were also included in the experiments. In the first series, each treatment was replicated n times in plots arranged in randomized'blocks. Trees were uniform in size and planted in diagonal rows. Each block was bordered by rows of Fameuse and Melba. Each plot con. sisted of 9 trees so that 36 trees were sprayed for each treatment. 12 In the second series triplicated plots of 9 trees were used. The trees are planted in the square system and are about the same size giving fair uniformity. The plantation was set 18 years ago and trees are bigger than those in the first series at Dunham. Two of the blocks contained a row of Melba trees that are included in the counts. Data collected from.Me1ba are thus Obtained from duplicate plots. The application of material was done with an ordinary hydraulic sprayer, a small machine manufactured by the John Bean Company. This sprayer has a ZOO—gallon tank capacity and a possible discharge of about 15 gallons per minute. The treatments were applied with a "Spray Master de Luxe Gun“, the Operator spraying from a tower on the upper» atus. Pressure was kept at about 550 pounds per square inch. All treatments were applied by the same Operator except in 1950 when, under uncontrollable circumstances, the last 3 cover sprays were applied by another worker. Timing of the sprays was based particularly on close observations of the rate of development of the trees, state of the weather and several other factors. Thus, the daily expansion of cluster leaves and growth of new shoots was Observed to determine the development of uncovered leaf area; the prediction of rainfall, the amount of weathering resulting from previous precipitation, temperature, the humidity (which indicated the rapidity of drying) were all taken into consideration. 13 Except for 2 cases in 1998, all the protective treat- ments have been completed the same day. For the materials applied for the express purpose of eradication in 1950 and 1951, the treatments were made only after infection periods. Within limits, fairly uniform.gallonage was attained. Checking was done on this point at frequent intervals dur- ing spraying. Wind in general was not a factor in hindering applicap tions. No spraying was done under really adverse conditions. At Farnham in 1951 where windy conditions prevailed, most of the spraying was done at night under conditions of quiet air. Data were collected at sometime during the summer on the foliage and on the fruits in the trees, on the windfall apples and again immediately after harvest. The harvested apples were brought inside and classified under the differ- ent categories for amount of scab and russeting, more or less according to regulations of the law of commercial classification in Quebec. These comparative categories were as follows: 1) severe scab: individual spots more than i inch in diameter or any cracked Open scab or several coalesced spots that cover more than 5 inch in diameter. Apples having that type of infection are considered as “culls" in the commercial classification. 2) light scab: total surface covered, less than i inch and no cracking. Apples in this category may be accepted in grade "C". The categories of scab described above have not been 14 closely followed at all times and early infections and late infections have sometimes been distinguished and are defined later. The categories for russeting were: 1) light russeting: a few streaks any place on the fruit or in most of the cases, light russeting in the cavity (depression around the stem). This category is not consid- ered in commercial classification. 2) medium russeting: russeting covering 1/8 to i of the surface of the fruit. Such apples are classified as grade '0“. t 3) severe russeting: involves over i of the surface of the fruit. Severe russeted apples are culls. Foliage data were collected by counting the number of scabby leaves around the tree in a.peripheral zone of chest height from the lower limbs and for a distance of arm length of about 3 feet into the trees. The number of scabby fruits in the trees during the summer was also determined in that zone. Trees chosen for the counts were approximately of the same shape, spread and height. Always the same Operators (2, 3 or M men) did the counts in a particular season. The same number of men were not always engaged in the Operation but once a count was begun, the same Operators stayed on the 30b until it was finished. Care was taken to make the counts during a dry, warm spell when there was no scab development or just a few days 15 after the appearance of the first scab spots in.June and then the counts were made in a single day. Materials Used in;gge Test;_ The following fungicides were used in the tests: 1) somergiai pipe-31mm was used only in 1911.8, at the strength of 2% gallons (imp.) in 100 gallons of water in the first 2 sprays and at 2 gallons in 100 for the rest of the season. 7% pounds of hydrated lime was added to the mixture in all the sprays. 2) A mixture of Lime-Sulphur at the strength of 1 gallon (imp.) and Kolosprgy, at the concentration of 9.6 pounds in 100 gallons (imp.) Of water, were used in 1998 and 1949. 3) Kolosprgy (85% sulphur) was used 3 years at a concentration of 9.6 pounds per 100 (imp.) gallons of water. Kolospray is an elemental sulphur manufactured.by the Eiagara Sprayer and Chemical Company. According to the manufacturer, it consists of a mixture of 33% "Bentonite Sulphur“ (fused sulphur absorbed into bentonite) and an elemental sulphur. u) Mulsoid (93% sulphur) is a.micronized sulphur produced by the Sherwin-Williams Company. The Micronizer process yields very fine particles of sulphur but neverthe- less not more so than the pastes and sulphur obtained by the Grinrod process (9). Mulsoid was used only in 19h8. 5) Magnetic,19 (not less than.69$ sulphur) is a 16 sulphur paste obtained by the Grinrod process. The parti- cles of this product are among the smallest ones of the elemental spray sulphurs. Magnetic 70 sulphur paste must not be confused with the so—called "Flotation sulphur pastes“ which also have very fine particles but are Obtain- ed by an entirely different process, being a by-product of the artificial gas industry. Flotation sulphur pastes have a low sulphur content that varies with impurities but generally are around 50% sulphur. Magnetic 70 has been used during the four years at the concentratiOn of 9.6 lbs per 100 (imp.) gallons of water. This product is manufac— tured by the Stauffer Chemical Company. 6) Ferbam has been used since 19h9 as Fermate, a product of the Dupont de Nemours Company. Fermate contains 70% ferric dimethyl dithiocarbamate as the active ingredient. It was used at the rate of 1.8 lbs per 100 gallons (imp.) of water. It is a black powder with the characteristic smell of urae. 7) Tag Fppgicide No, 331 an organic compound containing 10% phenyl mercury acetate was used during 3 years. It is a product of the California Spray Chemical Corporation. It is claimed to be a protective and eradicative material for the control of apple scab. In 19h9 and 1950 it was used on a protective basis while in 1951 it was tested as an eradicant. Tag Fungicide has been employed at the recommend— ed concentration of % pint to 100 gallons (imp.) of water. 8) Puratgged Agricultural Spray manufactured by the 17 Gallowhur Chemical Corporation was used in 1950 and 1951. It is also a mercury compound, consisting of 5% phenyl mercuri triethanol ammonium lactate. It has been tried as an eradioant at the rate of 1 pint in 100 gallons (imp.) of water. 9) Crag Fruit Fupgicide 341 C, a mixture of glyox- alidines in isoprOpanol, was used for the first time in 1951. It was tried at the rate of only 1 pint in 100 gallons (imp.) of water. This product is manufactured by Union Carbide and Carbon Corporation. 10) Merthon.6u2, a relatively new combination, was used only in 1951. This product is manufactured by the Eastern Chemical Corporation. It is claimed to be a fung— icide-insecticide material effective against apple scab, aphis and “red mites”. According to the company, the composition of this product is as follows: 10% mercurated pentaethyl triphosphate, 5% mercury as metallic, and 89% pentaethyl triphosphate and other related organic phos- phoric esters. This liquid material is suggested to be used as a supplement ot a sulphur or Ferbam program. Claimed to be eradicative, it is applied in the critical period of the early sprays. In the 1951 schedule it was employed at the rate of i pint to a mixture of 3/5 lbs Fermate in 100 gallons (imp.) of water. l8 Scpgduies .9 - Adequate protection against insect pests was provided each year in addition to our experimental scab sprays. To prevent an infestation of the Eur0pean red mite, in 1948, a superior type 011, Sovaspray, was applied to all plots at the concentration of 2%. This treatment was followed on May 7 by an application of Bordeaux mixture 2.u.1oo that constituted the first preventive treatment against scab at delayed dormant. Again, in 1949, a superior type 011, Sun Superior 0i1 No. 11, was applied but was combined with Bordeaux mixture 2§.5.1oo in the first spray at the delayed dormant stage. At Farnham, in 1951, the fruit tree leafroller and the European red.mite were threatening and a semi-dormant spray consisting of 3% Sun Superior 011 was given on April 27. Later in the season, 2 lbs of DDT 50 W were applied on June let to get rid of the larvae of the fruit tree leaf roller that had survived in spite of the oil application to kill the eggs in the spring. At any time during thefOur years, lead arsenate was added to the tank in the prOportion of 3-3/h lbs per 100 gallons (imp.) of water, when necessary and especially in July for apple maggot in accordance with the law. However, lead arsenate was never used in conjunction with incompati- ble materials such as Puratized Agricultural Spray. Straight-protectant schedules are often inadequate in years favorable to heavy infections. Timing is often 19 difficult to achieve with rapid growth and frequent rains. In the past, during such years, good control was easier to achieve in general with the use of Lime—Sulphur which has both protective and eradicative prOperties. However, when long periods of rain occurred, even Lime-Sulphur) applied within 50 hours after the beginning of the rain, failed to give adequate control at most favorable temperatures. With the advent of the organic mercury materials that eradicate scab if applied up to 72 hours or more after an infection period, it seemed more desirable to work out split-schedules for emergencies. Thus when the trees are not adequately covered with protective materials before an infection period occurs, it appears possible that an eradi— , cative material can be applied within sufficient latitude of time to prevent or stOp the infection. With this purpose in mind, Puratized Agricultural Spray, in 1950 and 1951, and Tag Fungicide No. 331 in 1951, were applied only after infection periods. Because of their mercury content both materials were replaced by Magnetic 70 after the second cover spray. In the early critical periods no other material was sprayed on so that no protection.was given to the trees before infection periods in order to determine the eradicative possibilities of the materials. In 19%, the following materials and their concen- trations in 100 gallons (imp.) were used: Lime-Sulphur, first two sprays ......... 2% gallons others. ..... ...2 ” 20 plus hydrated lime. ....... .75’1bs. Kolospray. .......... .......9.6 lbs. Kolospray ........... .......9.6 ' . plus - Lime-Sulphur ............. ..1 gallon Magnetic 70..... ....... ....9.6 lbs. Mulsoid. .............. .....9.6 ' Table 4 refers to schedule followed in 1948. The following fungicides were used in 19h9 at the concentrations per 100 gallons (imp.) mentioned below: Tag Fungicide No. 331......1/2 pint Kolospray ............ ......9.6 lbs. Fermate. 00000000000 000.00.01.8 u Magnetic 70. ............. ..9.6 ‘ Lime-Sulphur. ..... .........1 gallon plus Kolospray. ....... ..........9.6 lbs. Table 5 refers to schedule followed in l9h9. In 1950, the following fungicides were tested at the concentrations listed to make 100 (imp.) gallons: Tag Fungicide No. 331......1/2 pint KOlOBprayoo oooooo 000......0906 lbs. Fermate ........ ............1.8 ' magnetic 70.. ..... .........9.6 i Puratized Ag. Spray........1 pint Table 6 refers to schedule followed in 1950. The fourth year, 1951, the following products and their concentrations in 100 gallons (imp.) were used: Tag Fungicide No. 331......1/2 pint L 003.30 0033300 003.30 0033.30 3330a Hag—”0m H0093 00.336 00.3 00.3 00.3 00.3 00.3 00.3 05M 00.3 00.3 00.3 003 003 003 00.... 00.3 033 ha.“ 0 00.3003M haunuoflou 00.3003M 0H3 Quezon 000000H0M 50.3003 50000030M 2. 2. 2. 2. 2. m2. em“. 00 03003 0.300 0.3.00.3: 0.3003 0.3250! 0.3.0 030 a 0.3050: 843311415144; 030.800 00000000 or 03000 00000000 030 0000 0300000 0300000 0» as .300 00.3 0000 003 .033 00.3 0000 00.3 H000 00.3 0000 003 0000 003 .0003 00.3 0000 H00 I003 I30 I003 IH00I0 IH00 I003 I30 I003 130003 400003 400 I003 hammoaou 000000.30 00300.30 0.030300 00.300.3L 00.3033 00.30033 00.30300 21 6.30.35 04.0035 0.30.33 6.30.25 64003: 0.30.33 6.30.3.3 6.30.3.2 00.00 00:. m3: 00:. «A has «a 2.2. an .3. 00.00 .3. ma as: 3 so: 0050 0250 0030 0030 0003. 30.3 00.3 0030.3 .03 0.0m .000 .0: i .200 -unsE .. 33 050130 003 00... 0000000000 00004000 000 00 00000000 ...... a 303. .9 22 . __ all-.330 00.”. on 040300.30 . _ Hdudl0 00..n..0._.u..#._ .30 [Odom . . .__II.Nm.0..mn0.0.n.mw, 00.3 0030 00.3 00.3 00.3 300000 83 00003 2:0 050000 83 000000 33 0000000 3.3 .2. 03300: 2. 23803. 00 03300: 2. 033000 2. 30300: 0000000 0000000 0000000 0000000 0000000 000000.00M 00000000H 00000000M 00000030 000000000 303003 8030000 0330000 033003 3030000 02. was 000 03. 08. m 32. 2.0 000 00 3. 00 3. m 3. 0260 .000 i 0260 .30 . 00000 ._. 0000 33 . 050.30 33 $00 000 3000000000 00004000 00m 00 00000000 Inn. 00000 23 33V ad 569nm hammm hame hummm non capo: canon capo: canon .w4 . . . um»: um»: um; um»: .32 can: can: 683 you: naamm. udanm udnsm lansm capo: caved canon canon canon canon edema canon canon canon swan awn: um; um»: awn: um»: um»: :9... um... :93. oadnfioh cassava oaaauoh oudauoh cadanoh oadauoh opdanoh updanoh opdanoh updanoh opaanoh 33. 5% 33» ~39. 73a beam 33.. .223» 9.3.. .83» noaou noaom uoaou noaoM aoaou aoaou IoaoM Ioaom noaou noaou adflfllfilfiflmflndfifllfifl capoa canon capo: capo: capo: uwanh smash Jmnsh umqah awash :92 um; uwua um; .3: was was mus m3. was $9 5% 3w. cam ma mung. 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Aw“ V .an j .BNL in. 18m r 3.39. 628:9 on? mo.— mafiamafia 952% amp .3 Epsom :....m 328 0.3m can can 0 0H 0H can on can 0H wane mduo mama mm“... wuuw 24L mama wawfl mama yum“ d.” on: 0:8 an 3: 2: 5: 0.30: 0.300 0.30: K 00.03 human 3.26 has um»: :3 :03. ”and 04 839.3 03E .2 02: II 10.25 Lana Lon 03.00 0300 0.30: 032" 0.32 0.33 0309 0.30 030: 0.30J 21L :3. .0»: -47.. .03 09% -41.. .091 3.030..“ onwauoh coda—Huh opuauoh opdflnoh opus—nob guano.- 3390 3.8:: 3030.3. wagon 309.35 00033 093.35 3.03.": Eugen ova—anon 3.033 opaach onto: nonouoa n05.” cognac: 3.08.“: .H.H.__o§3_ 3m Hm: a Wm: 03.00 0.300 353 03253. 036.“V 003a A: 030w awn: awn: awn: 2. oaswmw. $0an nwwua nmawwm m b. l a HH 03:. .n 23h 9.. a! 3 had. wm 32. ma 2:5 N 036 on 3 mm has ma has .z." 3 0H 3 n has Timo>00 no>00 JMo>00 .350 4260 3....00.._.H_.9.J._; gig“ ulna—IN...“ Iolndu 93598, .03 . .5: . .03 v .08 , .93 . 33 . 33 , ~08 . 3.80 . 09258 f $9 m8 aaumumxn 02333 a: .8 Shannon :....N 03a.“ 25 Merthon 6h2.. ........ .......1/2 pint plus Fermate.. ....... ............3/5 lbs. Magnetic 70, until 3rd cover spray. ....... ..8 lbs. from 3rd. cover spray on...‘......... Puratized Ag. Spray.........l pint Crag Fruit FungiCide 3410...l pint plus Hydrated Lime. ............ ..3/5 lbs. Fermateoo 0000000000 0000000001/8 . Table 7 refers to schedule followed in 1951. SEASONAL DEVELOPMENT OF SCAB Previous investigators have shown the importance of. climatic factors upon the seasonal deve10pment of scab. In conjunction with the field tests, temperature, rainfall and humidity were also recorded to get a better comprehensive knowledge of the behavior of scab and a more accurate determination of fungicide performance. Temperature and humidity were obtained with hygro- thermographs and maximum and minimum precision thermometers. Two rain meters were used, a simple rain gauge that serves to record the amount of rain and an automatic rain recorder to give duration and intensity of the rain. therminatign og_the Primagz Infection Periods In 1950 and 1951, primary infection periods were closely followed. Determination of the periods were made according to.Mills on the basis of hours of wetting of the foliage and the mean temperature prevailing during that time (15). ' 2.6 The approximative length of a wetting period was determined.by considering the duration of the rain (re- corded by the automatic rain meter) and such factors as the time at which the rain had occurred in the day, ob- servations on humidity, sunshine, wind velocity and partic- ularly by observing the foliage in relation to its wetness. The mean temperature during a wetting period was calculated from the thermOgraph diagram. Once Obtained, it was then compared with the computations of Hills which gave the length of the wetting period necessary for an infection to occur at that temperature. This indicated whether or not infection had taken place. An example is given here to illustrate that point. On May 11, 1951, a rain started at 7 p.m. and ended on.lay 12 at 2 p.m.; the sky remained covered after the rain and there was no wind that day; the leaves did not dry up before 5 p.m. According to nillc' table, 16 hours of wetting is required for infection at 48°F during that period: the leaves had been wet during 22 hours, indicating an infection had taken place. In several cases it was possible to check the occurrence of the infection periods with the date of appearance of scab spots. Rate of foliage and fruit development, espec- ially of the clusterébud leaves and the first leaves of the terminal shoots, was closely followed in order to distinguish the dates at which lesions became apparent. These dates were compared with the interval necessary for scab to become visible at the preceding temperatures. 27 The incubation period given by Hills (20) was followed for this determination after the mean temperature for the 5 days following the infection had been calculated. For the rain period of May 11-12, 1951, it was cal— culated that infection started 16 hours after the beginning of the rain and that there was an interval of 15 to 17 days before scab spots would appear on the foliage. Scab spots did appear after this interval and in that case, it was possible to check the occurrence of the May ll—lZ in— fection period. From the rain period of May 23, 1951, it was also possible to check the incidence of infection after cal- culation of the incubation period and the fact that scab spots appeared on the fifth and the sixth leaves of the terminal shoot that were not expanded when the first infec- tion (May ll-l2) occurred. Applications of the eradicants were timed on these determinations wholly'based on Hills' indications. The eradicant materials were applied within a number of hours after the start of infection periods indicated according to Mills' tables. Some of the final primary infection periods could not be checked definitely as secondary infections were also possible toward the end of ascospore discharge. Nevertheless, it is believed that the calculated primary infection periods of lbv'and of the early days of June were delimited and the calculations were of value in timing the organic mercury treatments. 28 Peripds of_§scospc;e Liberations No attempt was made to follow closely ascospore dis- charge but work has been done in connection with that point and may be of some value here. Over-wintered leaves were gathered from different places in the orchard and only those bearing numerous per- ithecia were chosen for the work. Leaves were placed side by side in the bottom of a rectangular box of one foot long by five inches wide and five inches high. This box was provided with a fine-wire bottom so that leaves deposited in it had some contact with the soil. The box was open at the tap and exposed to rains in the orchard when in Operation. Vaseline—coated slides were used as spore traps. They were placed face down about t inch above the leaves on narrow wood supports. ‘ Tables 8 and 9 show data obtained from examinations of the coated slides at various intervals after periods of exposure to the shooting asci. The exact amount of rain fallen during the exposure is shown in relation to the dates of liberation and the comp parative number of ascospores discharged. Number of spores emitted at the different dates is not strictly comparable as no effort was made to examine all microscopic fields after spores were once found. Nevertheless, dates of first effective emission of ascospores are probably accurate since slides were exposed'before buds had expanded and were examined following each rain. 29 The tables also give an idea of the intensity of the spores liberation though they do not indicate the exact dates of heavier emission. The extent of ascospore dischange cannot be determined accurately by spore traps. If spores were not collected on the slides, it does not preclude liberation as there were indefinite numbers of perithecia in the orchard. This would be especially true for late spore discharges. However, as the leaves exposed were selected for numerous and mature perithecia, it is believed that the earliest effective emiss- ion of ascospores has not been missed. Spore traps alone were not considered reliable in tim— ing the sprays and determining the infections. In no case, was a rain period considered a non—infection period because no spores were caught on the traps. In 1950, the first liberation of spores recorded, occurred during the rain of May 16. Apparently heavy dis- charge occurred with succeeding rains from that date until the first days of June. Correspondingly, that period of heavy spore discharge was also the most critical for ra>id develOpment of leaf growth and fruit bud expansion. This is indicated in table 10. Thus in 3 days, leaves expanded rapidly, increasing in number from 2—3 to 5-6 in each cluster, and in two more days, all leaves were expanded. From.Hay 16 to Kay 22, dur- ing which apparently most of the ascospores were expelled, the vegetation developed from the Early Prepink to Pink 30 stage, or from a tight close cluster of blossoms to well separated blossoms with pedicels well exposed. No rains were recorded from May 20 to May 30 but from then on, rain fell each day for a week except on June 5. As a result, more spores were ejected and further primary infections occurred. In 1951, the growth started earlier and also devel— Oped at rapid rate (see table ll). The first emission of spores was recorded during the rain of May 11 and 12 when the trees were at the Prepink stage. However, heavy dis- change took place several days after the Opening of blos- soms which occurred on May 21. Many of the trapped spores on the slides examined on June 15 (1951) had been expelled apparently several days previous. Some were dessicated and many were already germinated but many more were fresh and plump showing recent ejection. Thus in 1951, heavy liberation of ascospores seems to have occurred mainly during the rains falling in the last days of May and the whole month of June. Rain was recorded on In days during that period. There is little doubt that ascospore discharge extended over a wide period of time in 1951, at least from.May 11 to June 27 when the last ascospores were trapped. A grower in the neighborhood of the experimental orchard, who stopped dusting in the middle of June because of excell- ent control, found his trees heavily infected at the end of the month. 31 Table 8—- ASCCBPOIE DISCHARGE FOR THE SEASON 1950 Dates of . No. of (No. of 1 Hundreth . Dates examin- hours of Spores inch of this at ion exposure rain record-1 rain was ed during recorded egpoEre Kay 5 20 O 0 .. " 6 2’1- 0 o .... " l2 -- 3 Kay 8 8 " 10 l '_' 11 I' in as 0 n6 '3 1n " 17 ha 125 x Z " 16 u 17 “ 19 48 50 x 7 " 18 3o 2 19 u 20 an 17 x 3 i 20 June -- 10 x l ' 30 3 24 '.' 31 1|- June 1 51 " 2 16 ' 3 " 7 95 2 39 " it 3 L‘ 6 9 ' 7 " lit -— 0 5 " 11 w 1'3 .. o 12!; i 18 Table 9--- 32 ASOOSPORE DISOHARGES FOR THE SEASON 1951 Bites of 1 No. of . No. of finndrethfl} Dates examina— hours of spores inch of this run tion exposure rain reco was ded duri recorded . ,l m - __ Kay 8 21’. O 2 May 8 Kay 9 2h 0 o ..... lay ll 60 O .5 Kay 11 key 12 24 l 23 Key 12 Kay 17 2M 2 35 Kay 17 Kay 23 21+ 2 2+ Kay 23 may as 72 3 65 Hey as 162 O 45 me}!!- June 15 -- 100 x 11 June 5 "-7 June 7 1 June 1‘1- 5 June 15 l 6 J 1 June 16 72 5 x 6 :32: I; 97 June 22 June 25 -- 26 88 June 23 91 June 25 June 27 ll»! 4 1 June 28 39 June 30 July 2 - 0 11 July 1 37 July 2 33 mm $2 Hm saw. NH. _ “ma. .#:.H.__.wa ma um: 2 as: N Nu: m E H & 7mm. wmw do TdeQKo IdeQNm qumeo d III III III III III moaned mopwoa mm>woa Idnwmx II Imwm In .mwm “and anus paws Moan Inod IHOd and scan Mada snag Iona .Hod .Hod Inc thdo BOOHm HamhI IOHMI mmmdm oamn mama dohmao Hmma.m0h mama gamm< nma so mau4em m>Ha IIIHH nanny H mm :m mm H H H Ha m mm“ do»d do do do , do [ammooa Induce qudnuo 1dqwnxo quwmno Idnunuo do mudpom dud Ado: Have Ham: . ado: poo mama nodded Idsdnxo Fad 359 M53 0253 350..” mobdoa @263” no .3} A mauve souooam aomuoam sommoam HH< Im MIN NIH I m In, ”I, IIL ends adds a undo Inca used a shame aoofim 2 mean uaam has“. Iona .H00 .H06 .90 2 Hana Y r .oam, r sauamw,f opus . opamu. comma» 0mm” m8 name 5%: a: .3 32$ EZZEE 3.2 £98 34 Scab DeveIOpment For 19H8, no data were collected for correlating climatic factors with scab develOpment. However, gen- eral notes taken on weather during the season, show that June was relatively dry and followed by a dry and very warm spell in July. Hay, though rainy, was rather cold. As a result, little or no scab deve10ped and 1948 was a very minor scab year in Southwestern Quebec. In.;3&9, primary infections were not closely followed but presumably occurred after'bloom since the first scab spots appeared June 6 and development of growth started very early, calyx arriving on May 20 (see table 12). First ascospore discharge occurred Kay 13 but rains were scattered and occurred in showers. Presumably, from rain data, one infection took place on.Kay 22-23. To give an idea of scab develOpment during that season, data obtained from counts of the number of scabby leaves are given briefly here. On June 16 and 17, 78 scabby leaves per tree were found for the least successful treatments. June and July were relatively dry (see table 13) and scab infections increased.but they were still relatively few in the third week of July. The least successful treat- ment gave 476 scabby leaves per tree while data for the best treatment showed only 72, though the last application was made June 9. 0n the other hand, August and the first half of Sep- tember were very wet (5.70 inches and 3.63 inches of rain respectively) and scab develOped freely at the end of the 35 Table 12-“ VEGETATIVE STAGES OF THE APPLE TREE FOR 19MB Eelayed. [Fre- 4 Kate . ull Full 4 malt pink pi; Pink pink loom Calyx April27llay2 Mayh- llayé’llay7klaylh Hay20 I “A! TEMPERATURE Table l}--- AND RAIN DISTRIBUTE}! FOR THE SEASOB 1911-9 Month I lean . Rain in I Days Fighest aunt. in tempera hundreth rain 3 le r ature inch recorded Amount } _Date April (26-30) #3.9 .50 --- I-.. -__ lb: 55.h 307 l2 (0 22-23 30 hrs.) * J me 65.“ 281$ 9 7113 21-22 (19 hrs.) l July 69.8 368 9 162 10 (29 hrs.) August 69.} 570 7 ?88 28-29-30 38 hrs.) Sept. 59.3 363 10 117 in (1-16) ‘# #:==.-.=: [Total Amount ziagg 36 season. _ Tables 1% and 17 give primary infection periods of 1950 and 1951. Both seasons were humid and had lower mean temperatures than in 1949. Consequently scab was rather severe in those years. In 1950, heavy infection occurred during Prepink when massive liberation of ascospores occurred. Timing was difficult because of frequent rain periods and rapid growth. On May 31, the first scab spots appeared on the foliage and increased considerably in number during the following days. Except where the eradicant materials were applied after the infection periods of May 16 and Kay l8- 19, the counts showed between 589 and 816 scabby leaves per tree on June 1%. Scab further deveIOped with the least effective treat- ments during rains of July August and early September (rain was recorded on 35 days during that period of time) (see table 15). Counts at the end of July showed 1,622 scabby leaves per tree with the least effective spray. It was more difficult to delimit secondary infection periods but at least 13 were possible,in 1950 the first one occurring with the rain of Ray 31. 195; was also favorable for apple scab develOpment and a few growers in the neighborhood of the station who failed to give adequate protection, found their crap ruined literally. Rains were recorded on 27 days during May and June. 37 w." .r :a 05:. mu m scam an I m 03:. Manon : ma .. m 23s on i: noon R .. 3 hi Agatha m 05:. _ .. R an: 3 S beam 3 ma. .3: “.596.” a _ hand dozen 2.33 9:32. 8:3 mafia»: note V 23 9:32. do dengue." manned on» 95946 was dogmas mason no magnet 93¢.» mean no comedies.“ Inoaobo 30.80..” a .o: 3.3 no 930a Incas: Apondfifi noupoemsa ozpdpome n33 Axons ._ no .02 noon 7. 3 5mm no 3.3 a no omdvm omma .833 a: mom 83mg n3 8:5 amass Ill...” ado—mu. 38 p503 Hmaom :....Av mm manna «ma m mmn 9mm .pdom m; a... am a as as teas up 9: mum mm 9” mos m.$ h .33. I... S and ma Rm 2mm 83. H a ll! SHIN.” OH MH M . Nm AHMlmv m: w a 3 33a no even #5584 dedaooon £05.. cusps _ mason .o .i 4 adds £90.32 Incas» . Annou— i Egon EM 9505 33 and I a.“ 5am 1 5mm omma .833 a5 «2 noHBmHmamHn BE 8: amassing.“ .35 :..-9 can: 39 (see table 16). Moreover, as previously mentioned, ascospore discharge was extended over a long period in 1951. As a result, possible primary infection periods occurred (see table 17). The first infections established themselves on May 11-12 with at least 22 hours of contin- uous wetting of the foliage, and, as previously calculated, scab appeared on May 27-28-29. It was possible to check the ocurrence of the second infection period of May 23 by recording the date of q>pearance of soap spots (June 5) but the following primary infection periods could not be verified since they intermingled with the secondary infec- tions. The first scab spots appeared early that year and rains came close together. As in 1950, numerous scab spots appeared on the foliage during the summer, where only the protectants had been applied. Rain was recorded for 12 days in July, 14 in August and 7 from September 1 to 15. Nevertheless, infection‘was confined to the leaves and the fruits were free from scab during the summer. A count in the first week of July showed only 1.77% of infected fruits in the McIntosh plots. Counts in the.lelba.plots when the fruits were harvested on the 22nd, 28th and 29th of August gave a range of infections from 0.33 to 5.u#%Ishowing that scab was under control to date. However, considerable late infections were present on 40 MEAN TEMPERAT URI Table 16».— AND mun DISTRIBUTION FOR TH]: SEASON 1951 lo Kean Rain 2:.” t 3183128; nth . tempera in . in ., mm in . ours _ t hund - rd— Am't. } 15 t“? 'W a n" th 1:21: 1:30 a hgur: of g rgin . lav 55.7 325 12 1.62 29 5 June 62.3 } 507 15 97 22-23 9.5 July 68.3 500 12 1.05 L5 12. August 6u.2 S5} in 1.07 16 11 Sept . 60.2 363 7 1.26 6-7 9 t1-15) lI-l ma am on m.~m mm .aa onus noses .enm ma .2 9mm 5 m 35s Hose .96. .2 m fimm am a onus 38° .93 3 3 11m mm" mm 3. .880 .93 D” 3 finm mm mmafi 2: sang a. Imum 83. ma 2 2mm mm mm .2: 283 a mm . Immasm .3. mm 3 mt? mm «.73 .2: “SHIPS definIIMo I l A: .2: m5» 333 mass: .833 I92. 3» mafia: _ no mason don «sacs 95.36 25. $5.26 fies descends no .0: magnet Page on.“ as no 028305 Imouobod unease.” 059.95 no mason Iaonaop Apondnsn seasons opdpmpowob move : Iuonmnd . no .on _. among -. a.“ mama . no came a we own; $2 3838 a: mom 802E noHSEaH #363 III: 62.8 42 McIntosh fruits at harvest (September 15). The first lesions of this type appeared in the last days of August and increased in number so that the qaples were badly affected in some plots. The last spray was made July 11. RESULTS OF THE EXPERIMENTS Results for the Year lQES Results for 19146 are reported in tables 18 and 19. Nine sprays were applied that year including Bordeaux mixture at delayed dormant. The last one was put on July 27-28. Scab was not prevalent that year and all treatments gave excellent control. However, results on the leaves give some indication of the relative value of the mater— ials used. Trees sprayed with Lime-Sulphur and those spray- ed with the Kolospray-Lime-Sulphur mixture showed practically no scab at all While in the Kolospray plots, there was an average number of 120 scabby leaves per tree on August 2. On the fruits, all materials gave similar amount of scabby fruits except Kolospray with .72%. Idght russeting that was followed in that year should not be considered as commercially important here. However, the relative amounts recorded gave an indication of greater causticity when compared to Mulsoid and Kolospray, which were milder in their effects and gave slightly better finish. 1*3 Table 18-- NUMBER or SGABBY LEAVES DETERMINED IN 19kg FOR McINTOSH 1 “1 'fi_ lst.count Mulsoid Kolospray Lime- Magnetic Kolospray 7-13 July sulphur 7O lime Hydrated sulphur I499 Total' 532 896 17k 463 219 Mean number 44.} 7h.7 1%.5 39.0 18.3 per tree _ 2 2nd.oount 2.} Aug. Total 1H2 #80 12 189 .23 lean number 35.5 120 3 #7.} 5.3 per tree 1 l Data.obrained from 12 trees per treatment distributed in 2 replicata of the plots. 2 Data Obta.ned from h trees per treatment distributed in u replicata of the plots. 44 SCAB CONTROL AND RUSSETING Table 19...- EFFECTS OBTAINED m 1948 FOR. McINTOSH later- No. of Sound Scabby light Medium Severe No. of ials trees a les apples russetv russetq russet- apples used treated pg ing 7‘: ing % ing 73 examined Hul- soid 2h 49.5 .#0 37.2 1.12 .53 22,537 Kolo— spray 32 53.4 .72 33.7 .98 .62 28,326 Lime Sulphur H drat— e3 lime 29 15.7 .31 1.11.2 1.66 .73 13,177 £476 30 was .33 um 1.1m .51 20,235 1010- spray Ldme Sulphur 25 n7.9 .35 33.7 .96 .65 17,630 45 Another point of interest is the reduced number of apples harvested from the trees sprayed all through the season at the usual strengths of 2% gallons and 2 gallons in 100 gallons (imp.) of water. Only 13, 177 fruits were harvested from 29 trees sprayed with Lime-Sulphur as comp pared with.22,537 from 24 trees sprayed with Kolospray that allowed the largest crap. Although.there may rightly be some some doubt in comparison of yields for one year of experimentation, the difference was so great, the trees so uniform and well distributed over the orchard and as all had received similar cultural and spray treatments in previous years, there is no doubt that Lime-Sulphur affected the yield in this instance. Moreover, as is shown later for 19u9, the reduction in yield resulting from Line-Sulphur sprays held over another year, even though another material, 'Iermate, notable for its mild effect on the tree, was sprayed on the following year. Burrell (l), Rasmussen (l9) and others have well dem- onstrated that Lime-Sulphur used in a straight schedule year after year was responsible for a considerable reduc- tion of yield. These results confirm their observations. Considerable damage was done to the foliage by Lime- Sulphur. Yellowing and shedding of numerous cluster leaves after the two first sprays with 2} gallons in 100 gallons (imp.) of water, prompted a change in the concen- H6 tration to 2 gallons in 100. Despite this lower con— centration, foliage during the summer was thin with much crinkling and curling present. The mixture Kolospray-Lime-Sulphur sprayed through- out the season also damaged the foliage but much less. Thinner foliage was Observed in the trees sprayed with the mixture when compared with those sprayed with Kolo— spray and.Mulsoid. Results For the Year 1949 In 1949, 6 sprays were applied including the Bordeaux mixture treatment at delayed dormant. The last spray was on.June 9. In tables 20 and 21, results show the protection of the foliage against apple scab during 19%9. In 4 counts, Kolospray and Tag Fungicide No. 331 tried as a protect- ant that year, showed much less protection than Fermate, Magnetic 70 and the mixture Kolospray-Lime-Snlphur. Fermate was the best of all with an average of 87.5 scabby leaves per tree in the final count on August 30- 31. The mixture Kolospray-Lims~Sulphur came next in effectiveness with 1h6.5 scabby leaves, while Magnetic 70 and Xolospray gave 3 to 8 times less control than.Fermate with 289 and 638 scabby leaves respectively. It should be noted for Fermate that the number of scabby leaves per tree did not greatly increase from the first aaunt to the last one as compared with Magnetic 7O In Table 20... NUMBER or SCABBY LEAVES DETERMINED IN 19kg FOR nomToss lst. . Tag . Kolo— Fermate Mag- . Kolo— Uount Fungi- Spray netic 7O Spray June 16- side Lime 1? Sulphur Total 31h 237 i as 58 1 lean nump 78.5 59.2 7.0 15.5 0.25 ber per tree June 28— July 1 Total sons 16 02 1151+ #74 83 Mean number 170.7 133.5 37.8 39.5 6.9 per tree 1 Data obtained from h trees per treatment distributed in # replicates of the plots. 2 Data Obtained from 12 trees per treatment distributed in H replicates of the plots. Table 21--- NUMBER OF SCABBY LEAvES DETERMINED IN 1949 FOR.McINTOSH (continued) i1. I 3rd. Tag Kolo— Fermate Magnetic Kolospray Count Fung- spray 70 Lime July 20— icide sulphur __. 22 l Total 4837 5714 847 1848 874 Mean ’ L number 403.1 476.2 70.6 154.0 72.8 per tree { 2‘ 4th, Count Aug. 30- Total 1715 2552 350 1156 586 Mean number 428.8 638.0 87.5 289.0 146.5 per tree ' 1 Data obtained from 12 trees per treatment distributed in 4 replicates of the plots. 2 Data Obtained from 4 trees per treatment distributed in 4 replicates of the plots. 49 and the mixture Kolospray-Lime-Sulphur that were about equal or better in the initial determination. On a basis of the initial number of scabby leaves, scab devel— Oped considerably in the other treatments, even with Magnetic 70 and the mixture that had a small number of scabby leaves in the first count. It seems then, that Fermate served to check the de— velOpment of scab that year, especially following the rains of long duration occurring in August. In estimating the results on fruits for 1949, we have made the following distinction: infections of the first part of the season or ”early and midsummer infection" and infections that appear toward the end of the season or “late scab infection“. According to rain records, the "early and midsummer infections" would have resulted in the latter part of May until the middle of July. Rains during August (5.70 inches) would be reaponsible for “late infections“. The distinction was made because it gives a better comp prehension of the actual performance of the materials since the last spray was applied on June 9 and consequently the trees were not well protected.against the unexpected attacks during August. It was rather easy to distinguish the “late infections“ on the fruits. Lesions were recOgnized as the so—called ' I'pin paint“ type or they gapeared as distinctly visible spots g As appl the ate acistu: or tea: Cc Septerl: since 1 are 2;“. fruits the wi: were In I . A the f :- Occur 1- Maénet equal 1? (se '71 50 spots grouped mostly near the cavity or around the stem. As apples approach harvest stage, they hang downward from the stem and the stem area is in a position to retain more moisture and received a greater number of spores falling or washed from above. Counts made on windfall apples (see table 22) on September 2, 9, and 15, seems to justify that distinction since the percentages of "early and midsummer infections” are approximately the same as those Obtained on the picked fruits. Percentages of “late scab infections” are lower on the windfall apples than on the picked qaples since counts were made later on the latter. All materials were nonpsatisfactory ih 1949 if only the fruit late infections are considered. But for infections occurring during the first half of the season, Fermate, Magnetic 70 and the Kolospray-Lime-Sulphur mixture did equally well with 1.4, 1.8 and 1.4% scabby apples respective- ly (see table 23). Tag Fungicide No. 331 and Kolospray gave less satis- factory results in the control of both early and late infec- tions. Russeting was more prevalent than in 1948, probably because of cooler and more humid conditions. Except for Fermate that shows a slight difference, all materials gave the same amount of russeted qaples. It is of interest to note the lower yield obtained in 1949 from.Fermate-sprayed plots. In these, the trees had 51 Table 22--. SCAB 00NTR0L OBTAINED 0N WINDFALL APPLES1 IN 1949 - EoINTOSB aterials } Scab Scab ' Number of sed Early and Late apples midsummer infection examined infection 3‘; _ Eng 151 151 2241 ungicide 6.7 6.7 EOIOBPIay 302 268 3768 8.0 9.8 Lermate 7E 60 2983 2. 2.0 hagnetic 70 41 141 2515 1.6 5.6 kplospray 53 164 3102 ime Sulphur 1.8 5.3 1 Data obtained from 16 trees per treatment distributed in 4 replicates of the plots. Apples were collected on September 2, 9 and 15. 52 Table 23--- SCAB 00NTNDL AND RDSSETING EFFECTS1 OBTAINED IN 1949 - MOINTOSH Iaterials Sound Scab J Scab Basset- Risset- Number—— used ap les Early Late ing ing of ; infectio Infec- Radium Severe apples $ tion ¢ f examin- T 12 211 1,61 ,9 6 1, 6 s 21, 6 Faggicide 56.6 . 7 527?:3 6.3 364 58 Iolospray 13,012 2,099 7,399 2,14 852 24,56 53.0 8.5 30.2 8. 3.5 3 r rmat 11 as 211 2, 09 s 6 1 , 1 c a 76.55 1.4 13.3 260 2. 5 53 lagnetic 15 ,8 5 408 3 260 1 ,833 704 21 ,647 70 73.1 1.9 16.3 8.5 3.3 Iolospray 15,136 294 3,652 1,876 747 21,279 Lime 71.1 1.4 17.2 8.8 3.5 Sulphur “m 1 Data obtained from the entire crap of 16 trees per treatment distributed in 4 replicates of the plots, except for Kolospray—Lime-sulphur treatment for which 15 trees were selected. tll'tlr. I , 53 received Lime-Sulphur at the usual recommended strength the previous year. Though blossoming was abundant in these trees, fruit setting was poor compared to other trees in the orchard. By actual count it was found.40% less fruits remaining on August 16 in those trees Sprayed previously with Lime-Sulphur, than on trees having received different previous treatments. As previous workers have reported bad after-affects from Lime-Sulphur (1)(19) and as the Fermate-Sprayed trees recovered in 1950 by more flowering, 61%, when compared to the other trees that showed 30% in the case of KoloSpray and 21% in the case of Magnetic 70, it is apparent that Lime—Sulphur rather than Fermate was responsible for the low yield in 1949. Results For the Year 1950 In 1950 Puratized Agricultural Spray was included in the experiments. It was used to test its eradicative value and as such was applied only after the infection periods calculated as previously mentioned. Puratized was applied on May 17, 34 hours after the beginning of an infection rain; 52 hours, on May 20; 21 hours, on May 31, and 54 hours on June 3. Later in the season this material was replaced by'Mmgnetic 70 on account of its mercury content. Thus in the split-schedule of 1950, Puratized Agricultural Spray was Sprayed on 4 times and followed by Magnetic 70 in 5 applications. 54 In the straight-schedule, the protectants were applied 11 times in the season. The last spray was put on August 6. In 1950,Tag Fungicide No. 331 was applied at the same time the protectants were put on. But as weather condi- tiOns prompted frequent treatments, some of which were applied soon after infection periods, it is probable that the material also acted in an eradicant capacity. Because of its mercury content which might leave a poisonous residue and as late treatments were foreseen because of scab prevalence and frequent rains, Tag Fung- icide No. 331, as well as Puratized, was replaced by Mag- netic 70 after the first cover spray. Infections of the leaves were determined in two counts in 1950 (see table 24). The first count was made after the heavy infections resulting from the rain period of ‘ May 16-17-18-19 had shown. The count at that time showed Tag Fungicide No. 331 and Puratized Agricultural Spray gave outstanding results as eradicants for the control of foliage scab. Kolospray-sprayed trees resulted in an average number of scabby leaves per tree Of 816. Tag Fungicide with 18 was not only much better than the protectants but showed indication of more effectiveness than Puratized Agricultur- al Spray. Magnetic 70 and Fermate gave equivalent protection of the foliage in the experiments that year. 55 Table 24--- NUMBER OF SCABBY LEAVES DETERMINED IN 1950 FOR McINTOSH 1st. CountT Tag Kolo— Ferm- V Magnetic Puratized June 14 Fung- spray ate 70 Ag.S. igide Magnetic Magne- 7O tic 70 Total 73 3266 2356 2134 165 Average number 18.2 816.5 589.0 546. 41.25 per tree 2nd.‘fiount2' July 24—26 Total 304 19,464 5,385 7,214 848 Average number 25.3 1.622 448.7 601.2 I 70.7 per‘tree 1 Data obtained from.4 trees per treatment distributed in 4 replicates of the plots. 2 Date Obtained from 12 trees per treatment distributed in 4 replicates of the plots. 56 The second count, on July 24-26, showed that Magnetic 70 and Fermate checked develOpment of scab on leaves while Kolospray—sprayed trees showed many spots with an average number of 1,622 scabby leaves. Both Tag Fungicide No. 331 and Puratized Agricultural Spray showed the least foliage scab in the second count and the results were considered outstanding. Fermate was found particularly good in checking leaf scab in 1950. Thus, for this material, the second count showed fewer scabby leaves than the first. Only live scab spots were counted in all cases and many of the early spots were dead at the time of the second count. There was an average of 589 scabby leaves in the first count and 448 in the second count. Investigators of Fungitoxicity in laboratory tests (10)(11)(l6) have found a fungistatic effect of Ferbam against the conidia of Venturia inaequalis. The material was found to have an inhibiting effect upon germination when Spores had been exposed to it for a period of time. On the other hand, many workers in the field (12) have reported the odd fact that Ferbam gave better protection to the fruits than to the foliage. Similarly, in these exper- iments, deepite the fact that considerable infection was present on the leaves, only 4.5% were scabbed 1n the middle of July while 10, 11, and 13.6% scabbed fruits were found for Magnetic 70, Tag Fungicide No. 331 and Puratized Agri- cultural Spray respectively. 57 From this fruit count, data reported above on foliage scab, and other results in 1951, this work gives further evidence that the small amount of fruit scab is correlated with the fungistatic effect of Ferbam demonstrated by Cuba and others. I The colnts on the harvested fruits (see table 25) showed Fermate gave excellent commercial control with 1.9% severe scab and 3.4% light scab. KolOSpray failed in 1950 to give adequate protection as thec:ounts showed 25% severe scab while Magnetic 70 was fairly good with only 4.5% severe scab. Despite outstanding control of foliage scab obtained With Tag Fungicide No. 331 and Puratized Agricultural Spray, results on fruits were not satisfactory as shown in table 25. Results fg£_the Year 1951 The 1951 experiments were conducted at Farnham in triplicated plots. Melba as well as Holntosh were included in these tests. Crag 341 C and Herthon 642 were added to the list of materials used. In 1951, Tag Fungicide No. 331 as well as Puratized Agricultural Spray were employed after calculated infection periods only. However, they have not been applied after all infection periods: for those occurring in the middle of June, it was too late to use these eradicative materials on account of their mercury content. 58 Table 25—-- SCAB CONTROL AND RUSSETING EFFECTS OBTAINED IN 1950 — McINTOSH laterials Sound Severe Light Severe ) Number of used ap 1es scab scab and Apples medium examined russeting Tag F - icideung 26,149 3,016 5 014 2,646 36,369 followed 71.2 8.3 13.8 7.2 by Magnetic 7O Kolospray 18,449 9,125 6,842 2,488 36,447 50.6 25.0 18.8 6.8 Fermate 40,102 897 1,275 3,593 45,851 87.5 1.9 3. .8 Magnetic 30,048 1,684 2,542 2, 76 ,16 70 80.8 4. 6.8 6.4 37 7 Puratized Aso Spray 25.197 3.985 2.897 2.100 34.481 followed .1 .6 8.4 6.1 by MagnetJ ' io 70 1 Data Obtained from the entire cr0p of 16 trees per treatment distributed in 4 replicates of the plots, except for Puratized Ag. Spray for which 15 trees were selected. 59 Tag Fungicide No. 331 and Puratized Agricultural Spray were applied 75 hours after the beginning of an in— fection rain on May 14; 71 hours, on May 25; 61 hours, on May 30 and 86 hours on June 7. It should benoted that the applications were made later after the start of infec- tion periods than in 1950. In the split-schedule of 1951, the eradicant materials were applied 4 times and followed by Magnetic 70 in 4 addi- tional cover sprays. The protectant materials used in a straight-schedule were sprayed on 10 times during the season. The last Spray was put on July 11. In a combined schedule, Merthon 642 was applied with Fermate only in the early season treatments: at Early Pre— Pink, Pink, Late Pink and Late Bloom. In the other 6 appli- cations, Fermate alone at the regular concentration was used. 1951 was also favorable to scab develOpment as would be expected in considering weather conditions and primary infection periods. It was more difficult that year to make suitable counts on foliage scab as there was an intermingling of primary and secondary infection periods. For this season only one foliage count was made on July 17-19. In that count, Tag Fungicide No. 331 and Pura- tized Agricultural Spray, gain showed good eradicative properties. As in the previous year, Puratized was a little less effective than Tag. (see table 26). Magnetic 70 exhibited abalt the same protective value as formerly with 671 scabby leaves per tree while Crag 341 C 60 Table 26".. NUMBER OF SCABBY LEA DETERNINED IN 1951 FOR uoINTOSN Block Tag Ierthon Fermate —ll.agne- Puratiz- Crag Fungi— plus tic 70 ed Ag. 341 o . cide Fermate Spray 1"; .. 15"". (T... tic ‘70 erma e 370 o 1 33 2047 7074 470 78 393 L 2 51 1310 1901 622 62 823 3 23 1632 968 921 92 395 Total 107 4989 9943 2013 232 1612 Average number 35.7 1663 3314.3 671 77.7 537.3 per tree 1 Data obtained from 3 trees per treatment distributed in 3 replicates of the plots. Date: July 17-19. 61 used at 1 pint in 100 gallons (imp.) of water was a little better with 537. Fermate, in 1951, did not show the same behavious as in previous years. There was not only an average of 3314 scabby leaves in the trees Sprayed with.Fermate but new infections arose from week to week until the middle of the season. The combination Merthon 642-Fermate, with an average of 1633 scabby leaves, gave the same result as Fermate alone, if we except the anomalous count Obtained in one Fermate-Sprayed tree which had 7074 scabby leaves. These inferior results on leaves from the combination may possibly be attributed to the Fermate ingredient in the mixture. In fact, Merthon 642, as a supplement of Fermate, did not play an eradicative role since the applications did not follow infection periods except in one Spray (Kay 25). Counts made on the fruits during the summer showed they were free from scab for a time deSpite frequent rains and considerable foliage infection. (see table 27, 28 and 29). Crag 341 C was outstanding in the control of fruit Scab during the sunmer with only 0.37% scabby apples in early July and 0.32% on August 13, in the McIntosh counts, and 0.33% on picked Helba at the end of August. Fermate still exhibited good fruit protection despite very prevalent foliage scab. 0n McIntosh, in early July, there was only 0.74% scabby fruits and on August 13, 1.3% 62 Table 27--.. FIRST COUNT: t SCABBY APPLES DETERMIN DURING THE SUMMER FOR McINTOSH - 1951 t Materials Number of % Scabby Number of used scabby fruit 8 apple 8 fruits examined Tag Furg- icide 8 0.34 2382 .——— t Hagnetic 70 Herthon plus l'erllte l2 0. 50 2392 Femate Fermate 16 0.74 2165 Magnetic 70 43 1.77 2,433 Puratized Ag. Spray 40 1.64 2432 Hagnetic 70 Crag 341 0 8 0.37 2167 r—( 1 Data obtained on July 4, 6 and 7 from 3 trees per treatment distributed in 3 replicates of the plots. 63 Table 28-— SECOND COUNT: % SCABBY APPLES DETERMINED DURING _ THE SUMNER FOR NoINTCSH - 1951 iv. _, laterials Number of % Scabby Number of fruits used scabby fruits fruits examined 1‘88 Fungicide 23 1.2 1924 Magnetic 70 [ Eerthon plus Fermate 13 0.70 1832 Fermate Fermate 22 1.3 1611 E Iagnet 10 70 42 2.3 1785 Purat 12 ed Ag . Spray 42 2.1 2022 E's-.gnetic 70 i l Crag 341 o 6 0.32 1863 1 Data obtained August 13 from 3 trees per treatment distributed in 3 replicates of the plots. 64 Table 29--. % SCABBY APPLES DETERMINED FOR.MELBA;- 1951 Haterials Number of % scabby Number of used scabby fruits fruits apples examined Tag Fungicide 97 2.84 3410 Eggnetic 70 Merthon plus Fermate 34 1.16 2926 Egrmate Fermate 50 2.49 2012 Magnetic 7o 68 i 2.22 3057 P‘Irat 123d Age Spray 161 5 .44 2958 Magnet lo 70 Crag 341 C 10 0.33 3038 1 1 Data obtd ned from 3 pickings on 4 trees per treatment - distributed in 2 replicates of the plots. Dates: August 22, 28, and 29. circus .. 1". 55 and in the Melba counts in last August, only 2.5%. Magnetic 70, with much less foliage infection also gave good protection to the fruits with 1.77%, 2.3% and 2.2% in similar counts. Though the eradicants gave outstanding results against foliage scab, they did not Show more effectiveness than - ”.1 1.3“ i. the other treatments on the control of fruit scab during 2 the summer. Puratized Agricultural Spray was the least 'm.‘ 1'3), ‘1 ‘A' "-. 4 successful of all the treatments with 5.4% scabby Melba fruits. When compared to Tag Fungicide No. 331, it was less successful in all the counts. The combined schedule Merthon 642-Fermate gave ex- cellent control to fruits during the summer as seen in tables 27, 28 and 29. Fermate again played a role in re- tarding fruit scab deSpite the numerous infections on the leaves. In the determination of fruit scab on picked.McIntoah for the 1951 experiment, samples of apples were examined instead of the entire cr0p of individual trees as done in preceding years. 6 bushels of fruits were taken at diff- erent points in each of the 12 trees Chosen per treatment. When McIntoSh fruits picked on September 14-18, numerous late infections were present. These apparently resulted from rainy periods in August. It should be pointed out that in all treatments except Crag 341 0, “light scab" for that year was of the "pin point” type in most cases. 0n the other hand, for 66 Crag 341 0, late infections were so numerous and so well developed that most of the fruits affected c011d only be commercially classified in “C” grade. With Crag 341 C at the concentration of 1 pint in 100 gallons (imp.) of water, practically all scabby fruits or 37.82%Iresu1ted from late infections while the early control had been outstanding with only 0.43% (see table 30). The other materials gave more satisfactory results for late scab. Where Magnetic 70 was applied, in a straight schedule or following the eradicative treatments in the cover Sprays, the total amount of scab averaged only 6.5%. Fermate, considering the abundant foliage infection, gave satisfactory control in the end with 8.24% scabby fruits, all in the “light“ category. . The mixture Merthon 642-Fermate and Tag Fungicide No. 331 followed by Magnetic 70, were the best treatments for both types of scab infections giving less than 7% scabby fruits. Puratized Agricultural Spray, when compared to Tag Fungicide was only a little less effective in the counts on picked McIntosh fruits with 9.21% scabby apples. There is little to state for russeting effect of the materials except that Crag 341 0 gave a few more russeted apples than the others. As this is the result of only one years trial with that material and since other factors may also account for russeting, no conclusions can be drawn. l... 67 Table 30--— SCAB CONTROL AND RUSSETING EF ECTS OBTAINED IN 1951 - MCINTOSH Materials Sound Severe Light Russeted Number used apples scab scab apples of T ‘% apples examined Tag Fungicide 6682 64 446 399 7456 7 --- 39.6 0.85 5.98 5.35 Magnetic 7O Merthan . plus 6637 56 438 41 7527 .-_H Fermate 88.2 0.74 5.81 5. 8 TSTmate r ‘t 641 616 8 46 erma 6 85.3 1.25 8.24 5.16. 7 9 .Magnetic 6755 160 473 228 7594 70 89.0 2.10 6.22 3.02 Puratized Ag.Spray 6299 122 550 291 7236 -"'. 87.0 10 1 7060 I"002 Magnetic 70 c 41 c 42 8 2 2 o 4 6 rag 3 5830 6.43 3;?82 6?19 737 1 I Data obtained from 12 trees per treatment distributed in 3 replicates of the plots. 68 SUMMARY AND CONCLUSIONS Fungicides were tested for their comparative value in controlling apple scab during the years 1948 to 1951 in the province of Quebec. Seasonal apple scab develOpment as related to weather conditions is discussed in a study of aSCOSpore discharge, primary infection periods, rain and temperature records I and develOpment of foliage scab during the summer. Lime-Sulphur caused a reduction in yield in 1948 and also in 1949 as an after-effect of the damage done to 5 the trees. Elli“ A mixture of Lime-Sulphur and KolOSpray, applied in 1948 and 1949, caused some dammge to the trees but much less than Lime-Sulphur alone. It gave satisfactory control of apple scab but was not better than the other treatments. From 1948 to 1950, KoloSpray was the least effective of all the treatments. Fermate and Magnetic 70 gave sat- isfactory control except in 1949 when a relatively high percentage of late infections occurred through all the experimental block. Even that year, both materials were superior to Kolospray. Fermate gave better protection to the fruits than the foliage. In 1951, Mbgnetic 70 gave slightly better control of fruit scab than Fermate. Fermate was much less success- ful than.thnetic 70 in controlling leaf scab of that year. The mercury fungicides Tag Fungicide No. 331 and 69 Puratized Agricultural Spray gave outstanding control of foliage scab when applied in an eradicant capacity with Tag showing some superiority. However, for the control of fruit scab, both materials did not give better results than Magnetic 70 and Fermate. In fact, Tag and Puratized were non-satisfactory in 1950 for control of fruit scab. Tag fungicide No. 331 gave inferior results when used in a protectant capacity. Crag 341 C and the combination Merthon 642-Fermate were used only in 1951 in a new series of tests and it is too early to draw conclusions. It was apparent from these tests as well as observa- tions on seasonal scab develOpment and data collected on weather occurrence, that spraying must be continued late into the summer to prevent late fruit infection. 2. 7O LITERATURE CITED Burrell, A. B. A six-year Comparison of Lime-Sulphur and Flotation Sulphur as to Yield and Growth of Young MacIntosh Apple Trees. (Abst.) PhutOpath. 33: 2. 1943. f , Field Testing of Fungicides for the Control of Scab. In 59th Ann. Rept. Coll. of Agr. and Cornell Exp. Sta., Ithaca, N. Y. 1946. I " Godbout, F. In 11th Ann. Rept. of the Can. P1. Dis. ' Survey, Bot. and P1. Path. Division, Sci. Service, Dept. of Agr., Ottawa, Can. 1932. , In 12th Ann. Rept. of the Can. P1. Dis. Survey, in; a,” Bot. and P1. Paht. Division, Sci. Service, Dept. of Agr., Ottawa, Can. 1933. , In 13th. Ann. Rept. of the Can. Pl. Dis. Survey, Bot. and P1. Path. Division, Sci. Service, Dept. of Agr., Ottawa, Can. 1934. , In 17th Ann. Rept. of the Can. P1. Dis. Survey, Bot. and P1. Path. Division, Sci. Service, Dept. of Agr., Ottawa, Can. 1938. , In 25th. Ann. Rept. of the Can. Pl. Dis. Sur- vey, Bot. and P1. Paht. Division, Sci. Service, Dept. of Agr., Ottawa, Can. 1946. , and Cinq Mars, L. In 27th Ann. Hept. of the Can. Pl. Dis. Survey, Bot. and P1. Path. Division, Sci. Service, Dept. of Agr. Ottawa, Can. 1948. Groves, A. B. The Elemental Sulphur Fungicides. Tec. Bul. 82, Virg. Agr. Exp. Sta., Blacksburg, Vir. 10. 11. 12. 13. 14. 15. 16. 17. 18. 71 Cuba, E. F. Interrelation of Wettable Sulfurs, Lead Arsenate and Lime in Apple Spraying. In Ann. Rept. Mass. Agr. Exp. Sta. Bul. 346. 1945-46. , Eradicating Apple Foliage Scab with Summer Sprays. PhytOpaht. 37: 848 (Abst.) 1947. Hamilton, J. M. Report of the Section on Fungicide Tests for the Control of Apple Diseases, 1948. In E Second Annual Report of the Special Committee on the Coordination of Field Tests with New Fungicidal Sprays and Duets, with Reference to the Results ob- tained in 1948. P1. Dis. Reptr. Supplement 183. 1949. Large, E. 0. Advance of the Fungi, New York, Henry Holt 8 00., Inc. 1940. McNew, G. L. et al. The Control of Fruit and Veg- etable Diseases. Reprint No. 694, Boyce Thompson Inst. of P1. Res., Inc., N. Y. Mills, W. D. Efficient Use of Sulfur Ducts and Sprays during Rain to Control Apple Scab. Cornell Ext. Bul. 630, N. Y. State Coll. of Agr. Cornell Univ. Ithaca, N. Y. Newton, W. Fungistatic Value of the Dithiocarbamates and their Significance. Proc. of the Can. PhytOpath. Soc. (Abst.) No. 17. 1950. Perrault, C. In 22th Ann. Rept. of the Can. P1. Dis. Survey, Bot. and P1. Path. Division, Sci. Service, Dept. of Agr., Ottawa, Can. 1944. Patch, C. E. Elemental Sulphurs in Apple Orchards. 30th. Ann. Rept. Quebec Soc. for the Prot. of Plants. 1946. 72 19. Rasmussen, E. J. et al. Effect of Spray Treatment on Foliage Injury, Pest Control, and Yield and Quality of Apple. Mich. Agr. Exp. Sta. Special Bul. 347. 1948. 20. Rasmussen, E. J. and Galahan, C. L. 1951 Vermont New Hampshire Orchard Spray Handbook, Brieflet 616, Coop. Ext. Work in Agr. and.Home Econ. Univ. of Vermont and U. 3. Dept. of Agr. 000perating, 1951. 144.3%; . . rubs! 1‘1118‘.‘ vii-v: . . . .7 -l. - it ‘4! r: gfifvfltiilévlflawnw 1 . n t L .c .l 4‘. . . I wont . u. 1‘ t . ‘ .11“: , 1 ll HICHIGQN STATE UNIV. LIBRRRIES llsll IN I llHlllllll llllllll III 312 3008758744