406 REPORT OP STATE BOARD OP HORTICULTURE. 



prevented by adopting for it an entire4y new name. The name "canker" 

 is most commonly used in European works on plant diseases to designate 

 injuries to the bark which are caused by various species of Nectria. In the 

 Eastern United States it has been applied, by Mr. Paddock, to a disease of 

 apple bark which is caused by a Sphceropsis. To apply the same name to a 

 disease which is caused by a fungus entirely different from either of these 

 would only lead to confusion. ' ' Dead spot ' ' and ' ' black spot, ' ' the two other 

 names which are "sometimes used, applied not only to the disease under con- 

 sideration but also to diseased areas which are due to various other agencies, 

 such as sun-scald, the pear blight bacillus, etc. In view of these facts 

 and in order to avoid confusion, we shall propose for the disease the some- 

 what unwieldy name of "Apple-Tree Anthracnose. " Although somewhat 

 cumbersome the name seems appropriate from the fact that the fungus 

 which causes it, Glvesporium malkorticis, is closely related to numerous 

 other fungi of economic importance which have quite generally been 

 designated as anthracnoses. 



NATURE OF THE INJURY. 



Apple- tree anthracnose attacks principally the smaller branches — those 

 under two or three inches in diameter — although it also occurs upon the 

 larger ones and on the trunks of young trees. It appears first in fall, soon 

 after the autumn rains begin, as small, irregular, sometimes slightly 

 depressed, brown areas of the bark. During the fall and winter months it 

 spreads but slowly ; but, with the advent of warmer weather in spring, 

 growth takes place rapidly until, under favorable conditions, the disease may 

 invade an area several inches in diameter. Such areas under observation 

 at Corvallis the past season ceased to enlarge late in May, and early in June 

 the first evidence of spore formation was noted. At that time the diseased 

 areas were dark brown in color, markedly depressed, and in most instances 

 limited by ragged, irregular fissures which separated the dead from the 

 surrounding living tissues. These dead spots vai*y in size from those not 

 more than one-half inch in diameter to extensive areas two or three inches 

 wide by six or eight inches long. Occasionally a single area completely 

 girdles a branch, thus killing at once its distal portion ; but more commonly 

 only a dead spot occurs, from which in the .course of a few months the 

 bark sloughs off, leaving an ugly wound which requires several years to heal. 

 When these wounds are at all numerous the branches are exceedingly rough 

 and disfigured and are moreover greatly weakened. 



CAUSE OF THE DISEASE. 



Apple-tree anthracnose is caused by a fungus which belongs to the genus 

 Gloisporium. It is therefore one of the imperfect fungi — so-called simply 

 because the perfect form, if it has one, is not known. If a recently anthrac- 

 nosed spot be examined carefully, it will be seen to be covered by minute 

 projections. These are known as the acervuli and they contain the spores 

 of the fungus. At Corvallis the past season they began to appear early in 

 June. At first they were noted as small conical elevations of the epidermis, 



