Issued June 22, 1910. U. S. DEPARTMENT OF AGRICULTURE. FARMERS’ BULLETIN 401. THE PROTECTION OF ORCHARDS IN THE PACIFIC NORTHWEST FROM SPRING FROSTS BY MEANS OF FIRES AND SMUDGES. i\ j. < >’( Scientific Assistant , Fruit-Disease Investigations , Bureau of Plant Industry . WASHINGTON: GOVERNMENT PRINTI NG OF FIVE, 1910. LETTER OF TRANSMITTAL. U. S. Department of Agriculture, Bureau of Plant Industry, Office of the Chief, Washington , D. C ., March 16, 1910. Sir: I have the honor to transmit and to recommend for publica¬ tion as a Farmers’ Bulletin the accompanying manuscript, entitled “The Protection of Orchards in the Pacific Northwest from Spring Frosts by Means of Fires and Smudges,” prepared by Mr. P. J. O’Gara, Scientific Assistant, Fruit-Disease Investigations. A great deal of interest has developed in the last two or three years among fruit growers in the subject of protecting orchards artificially from frosts. A good many attempts have been made, particularly in the Rocky Mountain States and on the Pacific coast, in both decidu¬ ous and citrus orchards to ward off the frost damage by fires. At the request of fruit growers in the Rogue River Valley, where he has been assisting in the eradication of pear-blight, Mr. O’Gara undertook to help in solving the problem of frost prevention. Notwithstand¬ ing the favorable results obtained, it must be acknowledged that there is still considerable doubt as to the possibility under varied conditions of warding off the damage from frosts by fires, and also some question about its practicability in open orchards. Nevertheless, it is thought desirable to publish Mr. O’Gara’s experiments and notes on this sub¬ ject at the present time. Respectfully, G. H. Powell, A ding Chief of Bureau . Hon. James Wilson, Secretary of Agriculture. 2 401 CONTENTS. Page. Introduction. 5 Preparation necessary for frost prevention. G Materials to be used for fuel. 7 Materials for starting fires. 9 Manner of distributing the materials in the orchard. 10 Quantity of material to be used for each fire. 11 Cost of materials for firing an acre. 12 Necessity of understanding weather conditions. 13 Meteorological data obtained in the Rogue River Valley. 17 Weather conditions producing spring frosts in the Rogue River Valley. 19 Injurious temperatures. 20 Results of the work. 20 Value of firing the orchards when the cost is compared with the value of the crop. 21 Practical suggestions on the use of the psychrometer and other meteorological instruments. 22 Conclusions. 24 3 401 ILLUSTRATIONS. Page. Fig. 1. Old fence rails used successfully for firing in saving the Bartlett pear crop of Mr. J. G. Gore in the Rogue River Valley, Oregon. 6 2. Old rails used for firing to save the crop of the 7-year-old apple orchard of Mr. J. G. Gore in the Rogue River Valley, Oregon. 7 3. View in the Hollywood Orchards, Medford, Oreg., at 5 a. m., April 21, 1909, showing the smudging used to prevent frost injury. 8 4. Paper sacks filled with shavings and sawdust saturated with crude fuel oil. 9 5. A supply of paper sacks filled with shavings and saturated with crude fuel oil to be used for starting fires. 9 6. Arrangement of cord wood in the Yellow Newtown apple orchard of Mr. W. Id. Brown in the Rogue River Valley, Oregon. 10 7. Arrangement of cordwood in the Esopus orchard of Mr. W. II. Brown in the Rogue River Valley, Oregon. 11 8. Arrangement of material on the outside borders of the pear orchard of Mr. A. C. Allen in the Rogue River Valley, Oregon. 12 9. Fir cordwood with dry prunings used for firing in the apple orchard of Mr. W. H. Brown in the Rogue River Valley, Oregon. 13 10. A homemade psychrometer showing the wet bulb extending below the frame, protected by a heavy wire loop. 16 11. Side view of a homemade psychrometer showing backs soldered to¬ gether 401 4 1G B P I .—505. THE PROTECTION OE ORCHARDS IN THE PACIFIC NORTHWEST FROM SPRING FROSTS BY MEANS OF FIRES AND SMUDGES. INTRODUCTION. The object of this bulletin is to give, in considerable detail, the results of successful experiments and the methods employed in pre¬ venting frost injury by means of fires and smudges in the apple, peach, and pear orchards of the Rogue River Valley in southern Oregon during the spring of 1909. This work was taken up by the writer at the earnest request of several growers, whose hearty cooperation made it possible to secure data of much value. It is believed that while every locality has its own peculiar factors and conditions, the results obtained in the Rogue River Valley will be of more or less interest generally. The practicability of protecting orchards from frost injury has remained more or less an open question. The preventable annual losses through¬ out the country from low temperatures during the blooming period and for some time thereafter amount to millions of dollars. This is no doubt due to the facts that sufficient practical data and actual orchard experience which would serve as a guide for the fruit grower are wanting. The excellent work done by the Riverside Horticultural Club," of Riverside, Cal., during the winter of 1897 and 1898 brought out many facts concerning frost prevention, but much of the apparatus used and many of the methods employed can not be adopted gen- erally. The important facts to be known by the grower arc how to prepare for frost prevention, what materials to employ for fuel and the man¬ ner of distributing them in the orchards, what to use in starting the' fires and the method of preparing them, etc. a Farmers’ Bulletin 104, U. S. Dept, of Agriculture, entitled Xoios on I ro.n. 401 6 PROTECTION OF ORCHARDS FROM SPRING FROSTS. PREPARATION NECESSARY FOR FROST PREVENTION. It should be understood at the outset that frost prevention requires considerable preparation. It is impossible to get the material for fuel on the ground and have it distributed, especially where the orchards are large, after frost warnings are given out, since these warnings can not be given sufficiently in advance of the time necessary for firing in the orchards. Whatever the material to be used may be, it should be so placed that it may be readily distributed, and a sufficient quantity of it should be on hand in case it may become necessary to fire for a considerable length of time or in case several Fig. 1.—Old fence rails used successfully for firing in saving the Bartlett pear crop of Mr. J. G. (lore in the Rogue River Valley, Oregon. firings are required during the season. Usually it is never necessary to fire more than once or twice during the season, but during certain seasons it may become necessary to fire four or five times. The material for building these fires, especially where brush and wood are to be the fuel used, should be piled up along the side of the field and, if necessary, covered to keep it dry so that it will ignite readilv. This work may be done at anv time during the summer or winter, whenever there is any spare time. Usually there are times when this work can be done without any real loss of time, 401 PROTECTION OP ORCHARDS FROM SPRING FROSTS. 7 since the men may not be able to do anything else with profit \ t any rate, one should have a plentiful supply of fuel on hand and bo sure that it, is near by where it can be readily distributed and that it is in a dry condition so that it can be readily ignited. The writer has known of failures in firing where the grower failed to keep his material in shape for immediate use. MATERIALS TO BE USED FOR FUEL. The materials which may be used for fuel depend largely upon local conditions. In some places the use of wood may be entirely out of the question. However, there is a choice in the use of coal, crude oil, straw, stable manure, or any rubbish which usually accu- Fig. 2.—Old rails used for firing to save the crop of the 7-year old apple orchard of Mr. J. G. Gore in the Rogue River Valley, Oregon. mulates around the farm. In the experiments in the Rogue River Valley, while there was some variety in the matter of fuel, wood was principally used. In some cases good fir and even oak cordwood was used. In other cases old rails from fences which had been torn down, small brush wood, and even primings from the orchard were used. In the Bartlett pear orchard of Mr. J. G. Gore the crops were saved for two years in succession by the use of old fence rails, as illus¬ trated in figure 1. Old rails were also successfully used in saving the crop of a 7-year-old apple orchard (see fig. 2). There are usually not enough primings in any one orchard to be worth anything except lor use in starting the fires quickly, for which purpose they are valuable if kept very dry. 401 8 PROTECTION OE ORCHARDS FROM SPRING FROSTS. Crude oil was used only to a very limited extent. The Southern Pacific Company very kindly gave a considerable quantity of their crude locomotive-fuel oil from their tanks at Ashland, Oreg., to the growers for experimental use. It was found, however, that since this oil contains a considerable quantity of water, due to the fact that it is pumped from the oil fields through pipes having a water jacket, it is very hard to ignite and even after igniting fails to burn well. This oil was used in different kinds of pots and burners with about equal success. In most cases the fires went out shortly after lighting or the contents exploded in the pots. Although the crude oil could not be used as a fuel, it was found very valuable for satu- Fig. 3.—View in the Hollywood orchards, Medford, Oreg., at 5 a. in., April 21, 1909, showing the smudging used to prevent frost injury. rating shavings or other fine materials which were used in starting the fires. This will be considered in detail later. Stable manure, straw, and rubbish were also employed, but only to a very limited extent. These materials were principally used for producing a dense smudge, with the idea of protecting the orchards from the direct rays of the sun in the early morning after it was known that there had been some freezing of the blossoms. The idea in nearly every case was not to raise the temperature of the air in the orchards, as was the case with the use of wood, but simply to form a heavy smoke blanket which would prevent the blossoms from warm¬ ing up too rapidly in case they were slightly frozen. Figure 3 repre¬ sents the smudging employed in the Hollywood orchards, Medford, Oreg., at 5 o’clock in the morning on April 21, 1909. Another valuable material which was used only in a few cases is the lignite coal which is mined near Medford. This coal, although 401 PROTECTION OF ORCHARDS FROM SPRING FROSTS not igniting very readily, was found to be of considerable value if used in connection with wood. In using the coal it was usually placed on top of the wood piles and was found to bo a good heat producer. Un¬ doubtedly it will be found very valuable where fires must be prolonged for some time during very cold nights. MATERIALS FOR STARTING FIRES. Fig. 4.—Paper sacks filled with shavings and sawdust saturated with crude fuel oil. In the experiments conducted by the writer the materials used for starting the fires va¬ ried about as widely as the materials used in maintaining the fires. These materials consisted of shavings or mill planings, sawdust, straw, crude oil, light brush, and rubbish or rakings from the adjoin¬ ing woods. One of the best materials was found to be mill planings, which were put into medium - sized p a p e r sacks and the whole saturated with crude oil or kerosene. A con¬ siderable n u m b e r of these bags were pre¬ pared beforehand and kept in a shed, where they were readily avail¬ able when it was nec¬ essary to build the fires. Sawdust mingled with tar was also used, but it was found to be harder to handle and not so easily made up as the bags of shavings. Figures 4 and 5 show the bags used in starting the fires. Pine leaves and other forest leaves may be used fur tins purpose. 38302—Bui. 401—10-2 Fig. 5.—A supply of paper sacks filled with shavings and saturated with crude fuel oil to be used for starting fires. 10 PROTECTION OF ORCHARDS FROM SPRING FROSTS. In some cases, instead of using shavings or very light material of any kind, kerosene was poured directly on the coarse material and then ignited with a match or a torch. This method, however, is more expensive than the former, and unless the wood or other mate¬ rial is very dry the fires will not start. One of the most important factors in firing is to get the fires lighted as rapidly as possible when the temperature begins to drop or approaches the danger point. Of course where there is only a small acreage this is not quite so urgent as where there is a considerable amount of ground to be gone over. With the use of kerosene torches and with the fires already laid, it was found that the fires for an acre could be lighted by one man in from seven to ten minutes. The use of a kerosene or gasoline torch Fig. G.—Arrangement of cord wood in the Yellow Newtown apple orchard of Mr. W. II. Brown in the Rogue River Valley, Oregon. is advisable for the reason that it does not readily blow out. With such a device one can light the fires almost as rapidly as he can run. MANNER OF DISTRIBUTING THE MATERIALS IN THE ORCHARD. The number of heaps or piles of material which should be distrib¬ uted in the orchard will vary somewhat, depending upon the kind of material used, about forty to fifty piles per acre being usually sufli- cient. In most cases a heap or pile was placed between every four trees—that is to say, a pile every other tree row in each direction in the orchard. The arrangement of cord wood in the apple orchard of Mr. W. H. Brown is shown in figure 6. Figure 7 illustrates a simi¬ lar arrangement in an Esopus (S pitzenberg) apple orchard. Gener¬ al PROTECTION OF ORCHARDS FROM SPRING FROSTS. ] ] ally it will be found that only half of these heaps will have to be lighted at one time, which of course allows a large amount of reserve material that may be used in case it is impossible to keep the temper¬ ature up with only half the fires lighted. It is also well to place heaps of fuel on the outer edges or borders of the orchard, since it is olten found that the outside trees may suffer where a slight bieeze tends to blow the heat away. These piles should be distributed outside the last row of the orchard, and in ease the temperature can not be kept up they should be lighted. Figure 8 shows the distribution of piles on the outside borders of the pear orchard of Mr. A. C. Allen, Medford, Oreg. In case the temperature can not be kept up to 28° F., a certain Fig. 7.—Arrangement of cordwood in the Esopus orchard of Mr. W. H. Brown in the Rogue River Valley, Oregon. amount of straw or stable manure, which will produce a dense smudge, should be placed upon these heaps before the sun rises in order to prevent the slightly frozen fruit or blossoms from thawing out too rapidly. These smudges should be started on the side or sides from which the wind is blowing and the material should be wet, so as to make it burn without any flame. QUANTITY OF MATERIAL TO BE USED FOR EACH FIRE. Experience has shown that the fires should not he large, since large fires tend to produce convective currents that are apt to bring in cold air; hence, the quantity of material for each heap need not be very great. Large fires also might scorch the blossoms. 401 12 PROTECTION OF ORCHARDS FROM SPRING FROSTS. four to five pieces of cordwood, or its equivalent in any other kind of wood or old rails, are sufficient for a single fire; very often when the low temperature is of short duration all of this material will not be consumed in a single firing. Figure 9 shows the piles of fir cordwood with dry prunings used in firing the apple orchard of Mr. W. If. Brown. In case stable manure or rubbish was used a larger number of heaps were placed, and the quantity of material to each heap averaged about a bushel or a bushel and a half. Fig. 8.—Arrangement of material on the outside borders of the pear orchard of Mr. A. C. Allen in the Rogue River Valley, Oregon. COST OF MATERIALS FOR FIRING AN ACRE. The cost of the material for firing varied greatly, depending upon how it was obtained. In some cases where good cordwood was used the cost of one firing was given as $2 per acre. Mr. W. II. Brown, who used good fir cordwood, states that when using from five to seven sticks in a pile every second row one way and every fourth row the other the cost per acre for three hours’ firing approximated 60 cents. However, it may be stated that generally the cost per acre for one night was between $2 and $2.50. In some cases the cost was estimated as high as $4, but it is quite possible that more material than was necessary was burned and that a higher price than usual was paid for it. Where stable manure and rubbish alone were used the cost for firing per acre was from 4 to 10 cents. This was because the material was on hand and the only element of expense was for distributing it. 401 PROTECTION OF ORCHARDS FROM SPRING FROSTS. 13 The cost of labor for firing an acre also varied, but a good general average would be about SI. Of course this item of expense varied with the type of material used as well as with the distance that it was necessary to haul it. NECESSITY OF UNDERSTANDING WEATHER CONDITIONS. Before efficient work can be done in frost prevention a thorough understanding of local weather conditions must be had. In other words, the grower should know when to smudge or fire in the orchards. Unless he knows beforehand that freezing temperatures may be ex¬ pected, the opportunity for firing at the right time may be lost. Fig. 9.—Fir cordwood with dry prunings used for firing in the apple orchard of Mr. W. II. Brown in the Rogue River Valley, Oregon. Again, unless he is reasonably certain low temperatures will occur during the night, he may waste a considerable quantity of costly material when there would be no real need of it. In order to carry on the work of frost prevention successfully, daily weather reports or the weather map, preferably both, should available. In many localities the use of a weather map would be out of the question, since it may be at least twenty-four hours old and of very little value when it is received. Especially on the Pacific coast there is very little gained by using a map that is so old. In case the map can not be used, telegraphic'reports should be received every day. During the time that the writer was at voik on frost prevention in the Pogue Piver \ alley, weather maps ve:e 401 14 PROTECTION OF ORCHARDS FROM SPRING FROSTS. received from the Weather Bureau station at Sacramento, Cal., through the kindness of Mr. N. B. Taylor, observer. Air. Taylor also gave valuable advice in regard to conditions on the Pacific coast, especially in the small, inclosed valleys which are sur¬ rounded by high mountains. The Weather Bureau office at Port- land, Oreg., kindly furnished telegraphic reports to the Medford Commercial Club, and weather signals were hoisted. The assistance from both of these Weather Bureau offices was of the greatest impor¬ tance in carrying out the work successfully. Of equal importance with the general forecasts given by the Sac¬ ramento and Portland stations were the local observations and fore¬ casts of the writer, made necessarv by the absence of a Weather Bureau observer. In a valley situated as is the Pogue Biver Valley, local conditions and surroundings influence to a considerable degree the temperature, air currents, relative humidity, etc. It was found that the most important thing to the grower was the immediate local forecast made every evening about sundown. An inspection of the record of observations made at Medford, Oreg., during the months of April and May, 1909, as presented in the following table, will show the nature of this work: Table I. — Record of weather observations at Medford, Oreg., during April and May, 1009. Readings referred to psy chrome trie tables for a barometric pressure of 29 inches. Wind. Date. Timeoi obser¬ vation. Sky. Direction. Velocity. 1909. Apr. 9 P. M. 7. 45 Partly cloudy... NE. Slight... 9 9. 10 Clearing. NE. Calming 10 8. 00 Clear. Calm.... 10 10. 00 ... .do. .. .do. 11 7. 25 _ do.. ...do.... 11 9. 00 .do.. .. .do. 12 9. 45 .do. NE. Slight... 13 7. 00 .do. NE. .. .do. 13 10. 00 .do. Calm.... 14 7. 15 .do. NE. Slight... 14 9. 45 .do. Calm.... 17 8. 45 .do. .. .do. 17 9. 30 .do. ...do. 18 6. 30 Partly cloudy. . N. Slight... 18 8. 30 .do. N. . ..do. 18 9. 30 Clear. Calm.... 19 6. 45 Hazy. N. Slight... 19 8. 30 Clear. Calm.... 19 9. 00 .do. ...do.. .. 20 7.30 .do... N. Slight... 20 9. 00 .do... N. ...do. 21 7. 30 .do. Calm.. 21 9. 15 .do. .. .do. 22 7.00 Hazy. NE. Slight... 22 8. 00 Clear. Calm.. 22 10.00 Ps jQ 3 rQ b a ychr read A 3 o> ome mgs. aJ O a CL) |> " (U| 1 ^ have been lost. The crop in this orchard has brought as 401 22 PROTECTION OF ORCHARDS FROM SPRING FROSTS. $1,000 per acre, and from all appearances the same price will be equaled this year. A number of similar statements from other growers who were just as successful might be given. It is quite possible that in many cases some of the growers fired and smudged more frequently than was really necessary. This was done early in the season before they felt confident that weather conditions could be pretty accurately predicted. At no time during the season did the writer fail to predict frost to within a degree or two of what actually occurred. The hour at which firing would be necessary was also given out. Another year, with a well-equipped station and a competent and zealous observer in charge, in whom the growers would have confidence, the cost of smudging might be considerably reduced should it be found necessarv to make use of it. 4 / PRACTICAL SUGGESTIONS ON THE USE OF THE PSYCHROMETER AND OTHER METEOROLOGICAL INSTRUMENTS. Wherever it is found necessary to protect orchards from frost injury, each fruit grower should provide himself with the following apparatus: (1) A psychrometer with tables for determining dew-point tem¬ peratures. This instrument may be purchased from a number of reliable concerns in the United States for from $4 to $5. Although it is advisable to purchase a high-grade instrument for making dew-point determinations, a very serviceable instrument may be made by the average person at a very moderate cost. An illustra¬ tion of this instrument is shown as figure 10. Procure two fairly good thermometers of the kind with the scale marked on a strip of metal which is attached to the tube by means of small wire clamps. The bulb and scale are removable from the tin protective shield. Slide one of the thermometers with its attached scale downward so that the bulb projects below the lower end of the frame. Fix the ther¬ mometers in the frame so that they will not slide out when the instrument is whirled. This may be done by drilling small holes through the frame and scale and binding the two together with wire. The two thermometers are now fixed together back to back by soldering or by small rivets, as illustrated in figure 11. A piece of heavy wire bent in the form of a U should be soldered to the lower end of the wet-bulb frame as a protection against accidental breakage. The pro¬ jecting bulb must now be covered with thin muslin cloth. A string or leather thong about 2 feet long should be tied in the rings, which are soldered to the top of the instrument. This string serves as a means with which to whirl the thermometers. After using the psychrometer a few times the linen cloth should bo changed. o 401 PROTECTION OF ORCHARDS FROM SPRING FROSTS. 23 In using the instrument, wet the covered bulb and whirl it rapidly so that evaporation will take place from the wet surface. The whirl¬ ing should be continued until the mercury is brought as low as pos¬ sible. When it can not be lowered any farther it should be read simultaneously with the dry-bulb thermometer. The temperature of the dry bulb, which is the air temperature, and the difference between it and that of the wet bulb should then be referred to Table II. It is best when using the psychrometer to take several readings and then take the mean before referring to the table. In this way greater accuracy will result. One point which should not be over¬ looked in the matter of selecting the thermometers is that the two instruments should read exactly alike for all temperatures, because it is the difference between the two thermometers that is of the greatest importance. (2) Several good thermometers, which should be placed at different points in the orchard at an elevation of from 4 to 5 feet from the ground. Temperatures near the ground are always much lower than those at 4 or 5 feet higher. It is the temperature of the air which surrounds the fruiting portion of the tree that we wish to know about. (3) A maximum and minimum thermometer. This instrument is not absolutely necessary, but it is very useful in serving as a check upon the observations made with the other thermometers. (4) An aneroid barometer. This instrument is rather costly, being worth from $18 to $20, but if a single grower does not desire to buy one, several might purchase the instrument together. This instru¬ ment indicates the air pressure and the highs and lows which may be seen marked on the weather maps. During a period of high pressure the chances are that frosts may bo expected, while during low pres¬ sure, which means that there is a considerable quantity of water vapor in the atmosphere, frosts are not so likely to appear. I Ins instrument would indicate the movement of the high and low pressure of the atmosphere and act as a check upon the psychrometer obser¬ vations. (5) It would also be well to get the daily weather maps and warn¬ ings from the nearest weather stations. these reports would indi¬ cate, at least in a general way, the kind of weather that would be likely to occur within a certain time and would give this information long enough in advance so that preparation might be made for fning in the orchards. For very small orchards preparation may be quickh made, but where the tracts are large it requires some time. A ithout doubt the small tracts of, say, 10 acres or less can be much nioie ea>il\ and successfully handled. 401 24 PROTECTION OF ORCHARDS FROM SPRING FROSTS. CONCLUSIONS. (1) There is no doubt that frost injury may be prevented by the use of fires and smudges. (2) Wood and coal have proved to be the best fuel. (3) Where the temperature drops to 20° F. it would seem that fifty fires per acre are necessary. Only half as many are needed when the temperature reaches, say, 25 to 26° F. (4) Shavings, chips, or other fine material in paper sacks saturated with crude oil or kerosene have been found best for starting the fires quickly. Kerosene torches for lighting the fires have also proved to be very serviceable as compared with matches. (5) Straw and stable manure are valuable for producing dense smudges, but are not effective in raising the temperature in the orchard. The value of the smudge, or dense smoke, is more to pro¬ tect the trees from the early morning sun where some slight freezing of the blossoms and the fruit has occurred during the night. (6) The cost of firing with wood and coal, including labor, should not average more than $3 a night per acre, even where it may be necessary to keep the fires burning five or six hours. In some locali¬ ties where wood can be had without expense except for the hauling, these figures might be reduced somewhat. However, in localities where wood is rather scarce they would probably be somewhat higher. (7) The results of the past season’s work in the Rogue River Valley have shown that many acres of crops valued at from $500 to $1,000 per acre have been saved at a total expenditure of not more than $15 to $20 per acre for firing. Very striking examples have been seen where unsmudged orchards adjoining those that have been smudged have borne no fruit. [A list giving the titles of all Farmers’ Bulletins available for distribution will be sent free upon application to any Member of Congress or the Secretary of Agriculture.] 401 o