Page 4 



brella. as the cas< may be. When the 

 proper stage of maturity is reached the 

 containers are ruptured and the spores 

 are expelled. 



These "ascospores" are disseminated 

 the same as the spores on the ripe fruit 

 — by wind and insects, and, rinding 

 lodgement on a fruit or bud or blossom 

 in the presence of moisture, will grow as 

 in the other case described, thus pro- 

 ducing a rot or "blight" of the blossom 

 (fig. 3). Apothecia continue to appear 

 until after the blossoming season, and 

 so when weather ^conditions are favor- 

 able particularly a day or two of con- 

 tinuous wet or muggy weather at a time) 

 serious damage is done to the prospec- 

 tive crop. There is hardly a season but 

 what some loss occurs and actual obser- 

 vations of the writer have frequently 

 shown as high as 90 per cent of cherry 

 blossoms affected by brown rot. Or- 

 chardists have often attributed this dam- 

 age to the rainy weather preventing 

 pollination, to frosts, or to some other 

 more generally understood reason. 



WITH the rotting of the blossoms 

 the growth of the fungus follows 

 the same course as in the case of the 

 rotting fruit and the spores produced 

 are the same kind as on the ripe fruit. 

 Ascospores are produced only from old 

 mummies that winter over on the ground. 

 The other type, or summer spores, as 

 they may be called, are produced 

 throughout the growing season and are 

 visible over a considerable period. Blight- 

 ed blossoms with their store of spores 

 may be found attached to the trees as 

 late as June or July. Thus a supply of 

 spores is always at hand to infect the 

 young green fruits if weather conditions 

 are favorable, and the fungus is carried 

 over until the time of harvest the sec- 

 ond year, when the cycle begins over 

 again. Usually the seasons when great- 

 est damage occurs are at the time of 

 blossoming and at harvest, but if an ex- 

 tended wet period occurs serious loss 

 may be expected at any time. 



Considerable work has been done by 

 the Oregon Experiment Station relative 

 to limb cankers and it is possible that 

 they may be a source of infection in the 

 spring, but in general these cankers are 

 unimportant in the life economy of the 

 fungus. Twig blight sometimes occurs 

 when the fungus works back from in- 

 fected blossoms or fruits. This has been 

 observed especially on sugar prunes in 

 the Northwest and on peaches in the 

 East and South. 



Control Methods 



EXPERIMENTS on control methods 

 were carried on by the department 

 in Clark< county, Washington, and Ma- 

 rion county, Oregon, from 1915 to 1919, 

 and the recommendations below are 

 based on this work. 



BETTER FRUIT 



Effective control of the disease re- 

 quires attention to cultural and spray- 

 ing practices. Mummies should not be 

 allowed to hang on the trees over winter 

 and it would be beneficial if all the 

 rotted fruit should be gathered and de- 

 stroyed, but under large-scale opera- 

 tions this is impracticable. Resort should 

 be had, therefore, to thorough tillage 

 from the time the buds first show color 



April, 1921 



of application must be emphasized, for 

 if a fruit or a portion of a fruit is not 

 thoroughly covered there is a chance for 

 infection to take place on this area. 

 Finally, we must use an effective fungi- 

 cide or spray material. Of these there 

 are several that can be relied upon to 

 control brown rot, but mention will be 

 made of only three that may be re- 

 garded as standard. 



Fig. 2 Itali; 



nd shed 



une mummy with five apothecia attached. Apotl.^cia appear during the blossoming 

 yriads of spores which blight the blossoms and prevents them from setting fruit. 



until after the blossoms fall. This will 

 destroy large numbers of apothecia and 

 reduce the chance of infection at this 

 season. Heavy wet soils will seldom 

 permit of this practice so early in the 

 season, but where it can be followed 

 it will be found of distinct value. Prun- 

 ing the trees to admit air and sunlight 

 will also be beneficial since drying will 

 follow more quickly after rains and fa- 

 vorable conditions for spore germination 

 will thereby be curtailed. But these cul- 

 tural practices, while in themselves val- 

 uable, are only to be regarded as sup- 

 plementary to spraying, which must be 

 the main reliance of the orchardist in 

 combatting brown rot. 



In spraying for this, as for other 

 fungus diseases, the point to keep in 

 mind is that this treatment is preventa- 

 tive and not curative in nature. That is, 

 by applying a fungicide we cover sus- 

 ceptible parts with a material that pre- 

 vents the spore from germinating or de- 

 stroys the parasite before it can invade 

 the host. Once infection has taken place, 

 meaning that the tissues of the fruit 

 or blossom have been invaded by the 

 fungus it is too late to destroy it by 

 sprays. Hence timeliness of spraying is 

 a prime essential. Next, thoroughness 



BORDEAUX Mixture. 4-4-50, is the 

 old stand-by, and for effectiveness 

 can hardly be improved upon, but it is 

 not safe to use on peaches and some ten- 

 der plums. For cherries and Italian 

 prunes it is quate satisfactory, although 

 frequently causing more or less severe 

 foliage burning early in the season or 

 during wet weather. It is also more ex- 

 pensive than the other materials men- 

 tioned beltfw. 



Commercial lime-sulphur is safe to 

 use on cherries and prunes at a dilution 

 of 1 to 50, but must not be used on 

 peaches or Japanese plums at any dilu- 

 tion. Applied during late summer, when 

 hot weather prevails there is sometimes 

 severe foliage injury. It is, however, an 

 effective control agent for brown rot. 



Self-boiled lime-sulphur, 8-8-50 (8 

 lbs. lime, 8 lbs. sulphur, 50 gal. water), 

 is possible the safest and best all around 

 fungicide for use on stone fruits, and 

 may be used on peaches without danger 

 if properly prepared. It is best made 

 in lots sufficient for '200 gallons of 

 spray. Place 32 lbs. of good fresh stone 

 lime in a 50-gallon barrel and start 

 slaking by adding sufficient water for 

 that purpose. When the action is well 

 I ( 'ontinued mi page 15) 



