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 UNIVERSITY OF CALIFORNIA 
 
 AGRICULTURAL EXPERIMENT STATION 
 
 E. W. HILGARD, Director 
 
 CIRCULAR 
 
 BROWN ROT OF STONE FRUITS. 
 
 By Frederic T. Bioletti. 
 
 Brown Rot is one of the most serious diseases with which fruit- 
 growers have to contend. It attacks principally stone fruits — peaches, 
 plums, apricots, and cherries, but occasionally does damage to apples, 
 pears, and quinces. It is widely distributed throughout Europe and 
 the United States. In some of the Eastern States it is considered the 
 most destructive disease with which the peach-grower has to contend. 
 In Delaware and Georgia it often destroys from 25% to 75% of the 
 crop. It is reported to destroy more peaches and cherries in Michigan 
 than all other diseases combined. In Kentucky it is said to be very 
 destructive to apples, and in Oregon it has been the cause of very 
 serious losses to the prune- growers for several seasons. In California, 
 though its occurrence has been noted for several years, no serious 
 damage seems to have been occassioned until last year, when it 
 appeared abundantly in several localities. Statements were received 
 from prune- growers in Napa County that 50% of the crop was rotting 
 in some orchards, and specimens of the diseased fruit received by the 
 Agricultural Station at Berkeley showed Brown Rot to be the cause. 
 In several large orchards in Alameda County the late varieties of 
 apricots were seriously affected; 25% or more of the crop being 
 destroyed in some cases. All the cases of this disease which have so 
 far been brought to the notice of the Station have been in localities 
 not far from the sea and therefore more or less under the influence of 
 the summer sea fogs. As there seems, however, to be a tendency of 
 the disease to spread in California, and as recent experiments in 
 Georgia and elsewhere show that it can be controlled with comparative 
 ease, the following brief description of the disease and of the method 
 of treatment is given. 
 
 Brown Rot is caused by a mould or fungus called Monilia fructigena, 
 which attacks various parts of the plant, leaves, blossoms, twigs, and 
 fruit. Its effects are most evident upon the fruit, but it does an 
 amount of damage that is hard to estimate, by attacking the other 
 
parts of the plant, but which some observers consider to be almost 
 equal to that of the rotting of the fruit. The fruit is usually attacked 
 after it has attained full size and just as it commences to soften. The 
 first symptom in the case of apricots and peaches is a brown spot on one 
 side of the fruit. This spot gradually enlarges and becomes covered 
 with small ashy-gray pimples which consist of myriads of the spores of 
 the fungus. Soon the whole fruit turns brown and the entire surface 
 becomes covered with spores. The fungus then passes from the 
 rotten fruit through its stem into the twig. Finally the disease 
 attacks the twig so severely that it dries up, loses its leaves and dies. 
 The accompanying illustration shows apricots and twigs in various 
 stages of the disease, and the gradual progress from the fruit to the 
 twigs is well shown. In the fruit on the left, by looking closely it 
 
 ■'..-: 
 
 Pacific Rural Press. 
 
 EFFECT OF BROWN ROT ON FRUIT AND TWIGS OF APRICOTS. 
 
 can be seen that the lower side is darker-colored than the upper, and 
 that the light-colored spores have commenced to appear. The middle 
 specimen is covered with a layer of the pimple-like masses of spores, 
 and the leaves have commenced to wither; while in the specimen on 
 the right the leaves are quite dead and the fungus has passed into the 
 
twig. The appearance of the disease on plums and prunes is some- 
 what different. In none of the specimens received at the station were 
 the spores formed when they arrived. The appearance of the diseased 
 plums was not at first very different from that of the normal ones, but 
 when they were cut open the inside was found to be discolored. When 
 placed in a moist warm place, however, the spore masses developed in 
 one or two days, and then the appearance was very similar to that of 
 the diseased apricots. 
 
 4 
 
 The attacked fruit, instead of becoming soft and falling off, as 
 with most other rots, gradually dries up and often remains firmly 
 attached to the tree until the following spring. In spring a new crop 
 of spores is produced by the mummified fruit, and, in the case of 
 peaches, the young growth and blossoms are attacked. The same 
 probably occurs in the case of apricots and other fruits. One of the 
 worst features of this disease is that the fungus may be in apparently 
 healthy fruit. Peaches which when picked and packed showed no 
 sign of the rot, may be completely spoiled when the boxes are opened 
 two or three days later. 
 
 Treatment. — As the fungus passes the winter principally upon the 
 mummified fruit, the most effective method of combatting the disease 
 is to remove and destroy thoroughly all the diseased fruit. The 
 diseased apricots should be gathered and destroyed as soon as the 
 appearance of brown spots indicates that they are attacked, and not 
 left on the tree until the fungus has penetrated the twigs. No fruit 
 should be left on the surface of the ground. Any fruit which falls 
 near the base of the trunk should be raked away in order that it may 
 be buried by the plow. These measures alone, thoroughly applied, 
 have been sufficient to produce a notable diminution in the amount of 
 fruit attacked ; but complete immunity can be obtained only by proper 
 spraying in addition. All orchards where there is reason to suspect 
 the presence of the rot, such as those where it appeared last year and 
 those in their immediate neighborhood, should be sprayed with 
 Bordeaux mixture one or two weeks before the blossoms open. This 
 will prevent the infection of the blossoms, and in the case of peaches 
 will also prevent curl-leaf. A winter wash with our ordinary lime- 
 salt- sulphur mixture would doubtless be nearly as effective against the 
 Brown Rot, and where used for destroying scale and other insects the 
 first spraying with Bordeaux might be omitted. In any case, where 
 the Brown Rot appeared last year the trees should be sprayed w T ith 
 Bordeaux as soon as the fruit has set. These measures will in 
 most cases be sufficient with early fruit; but for late-ripening varieties, 
 such as Moorpark apricots, a third spraying should be given about a 
 week or ten days before the fruit commences to color. As Bordeaux 
 would stain the fruit at this time it is better to use a spray of copper 
 acetate. 
 
Bordeaux mixture is a fungicide consisting of bluestone (copper 
 sulfate), lime and water, mixed in various proportions according to 
 the season and to the kind of tree to be sprayed. For the first 
 spraying, before the buds have started, the following formula can be 
 recommended : 
 
 Copper sulfate 5 pounds 
 
 Quicklime 5 pounds 
 
 Water 45 gallons 
 
 For spraying the trees when in leaf it is better to use less sulfate 
 and more lime, especially on peaches, in order to avoid danger of 
 injuring the foliage. For the second and any of the subsequent 
 sprayings the following should be used: 
 
 Copper sulfate 3 pounds 
 
 Quicklime 6 pounds 
 
 Water 45 gallons 
 
 Directions for mixing. — 1. Suspend the copper sulfate in a basket 
 or perforated wooden box, in a barrel containing half the water. The 
 box containing the sulfate should be just below the surface of the 
 water in order to dissolve quickly. 
 
 2. Slake the quicklime slowly and with great care to insure a 
 perfectly smooth paste free from grit. After the paste has stood for 
 twenty to forty minutes, with enough water to ensure it from drying, 
 dilute with the remainder of the water and strain through a wire sieve. 
 
 3. When the sulfate is dissolved and the milk of lime quite cool, 
 stir each mixture well and pour them together into a suitable 
 receptacle. 
 
 If large quantities of Bordeaux are needed it is more convenient to 
 make up two stock solutions as follows: 
 
 A.— Copper sulfate, 50 pounds; Water, 25 gallons. 
 B.— Quicklime, 50 pounds; Water, 25 gallons. 
 
 These should be made up in the way already described and separated 
 until needed. For use take half a gallon of solution A for every 
 pound of copper sulfate, and half a gallon of mixture B for every 
 pound of lime wanted; dilute each separately with a little less than 
 half the water; pour together and make up to the required volume 
 with water, stirring thoroughly. Never mix the lime and copper 
 liquids when hot. 
 
 The spray should be made as short a time as possible before using 
 and should be applied when the trees are dry and the weather calm. 
 Only the best quality of quicklime should be used. The spray for 
 use when the fruit is large is made by mixing six ounces of Copper 
 Acetate (dibasic acetate of copper) with forty-five gallons of water. 
 When the acetate is quite dissolved and mixed with the water it is 
 ready to be applied. 
 
 Berkeley, January, 1901.