ipi8 



BETTER FRUIT 



Page 7 



the re-heading of a tree due to the 

 presence of so many canker covered, 

 practically functionless, scaffold limbs. 

 The permitting of infection of the main 

 branches of the tree, even though con- 

 trol of the disease is eventually accom- 

 plished by proper spraying, gives the 

 tree a very unsightly appearance. These 

 cankers remain open, shredded wounds 

 for many years, offering complete over- 

 wintering protection to such apple 

 pests as the codling moth and the 

 woolly aphis, the presence of which in- 

 creases the chances of losses from these 

 sources. In older orchards the large 

 limbs seem to be the object of the 

 greatest amount of infection; the main 

 trunk suffering to a less extent. In 

 young orchards the trunk is quite often 

 attacked and completely girdled, result- 

 ing in the immediate killing of the tree. 

 The fruit is also attacked by this fun- 

 gus, which causes a brown storage rot, 



The Apple Tree Anthracnose and How to Control It 



By Leroy Childs, Entomologist and Plant Pathologist, Hood River (Oregon) Branch Experiment Station 



resulting often in the loss of much 

 fruit after it has been packed. The 

 spores are liberated by the first rains 

 before the fruit is picked, upon which 

 they lodge, germinate and cause decay. 

 The only way to avoid losses from 

 fruit infection is to keep the orchard 

 free from cankers. 



The disease is caused by a fungus 

 which attacks apples for the most 

 part, though occasionally cankers of 

 this disease are found upon the pear 

 and quince, and cankers have been pro- 

 duced by investigators, by inoculation, 

 on peach, cherry and prune. Natural 

 infections in the case of these latter 

 fruits have never been found. Infec- 

 tion occurs during the fall soon after 

 the rainy weather sets in. This prob- 

 ably occurs most extensively during the 

 months of November and December, 

 though rains occurring before this time 

 permit some infection. The fact that 

 during some seasons rather extensive 

 rains occur before the fruit is har- 

 vested has led many rochardists to 

 wonder if benefits would result in 

 applying a spray following those rains. 

 The answer to this query should be — 

 by all means spray. It is more than 

 probable that only a very small fraction 

 of the spores have been liberated by 

 the first of November and a large 

 amount of protection can be gained 

 by spraying even as late as the first of 

 November. 



The fall rains cause a disruption of 

 the small pimple-like sacks which can 

 be found on the surface of an anthrac- 

 nose canker, liberating countless num- 

 bers of spores which are therein con- 

 tained. These spores are either washed 

 down onto other parts of the ti'ees or 

 carried by wind, insects or birds to a 

 favorable location, where they germi- 

 nate much as a seed would do. The 

 little rootlet-like projection which is 

 thrown out usually enters a lenticle or 

 pore-like opening in the bark and soon 

 establishes itself in the healthy tissue 

 of the plant. After the penetration of 

 the host plant the application of a spray 

 to the surface of the plant will do no 

 good. The spray must be applied to the 

 limb of the tree before the spore is de- 

 posited upon it. When the spray coat- 

 ing is present the germinating spore 

 sends its little rootlet out, strikes the 

 spray coating before reaching the 

 plant tissue and is immediately killed. 

 The spray, therefore, acts only as a 

 preventive coating and the essential 

 point to bear in mind is that it must be 

 there ahead of the spore if control is 

 to be obtained. 



Young cankers can be found develoi)- 

 ing on infected trees during the latter 

 part of November. At this lime these 

 ai)pear as small reddish-brown spots. 

 Tiic bark and cambium beneath will be 

 found wet and discolored, extending 

 down to the woody portion of the twig 

 or branch. During the winter these 

 spots grow little, if any, but during 

 March and April extend rapidly, becom- 

 ing elongated in shape when mature, 



IN many sections of the Northwest 

 the most pernicious invader of the 

 apple orchard at the present time is 

 apple-tree anthracnose or canker. The 

 cause for this invasion is not due to the 

 fact that control measures are unknown 

 or impossible to attain, but are due 

 entirely to carelessness or neglect on 

 the part of the orchardist. Anthracnose 

 is a disease of no great moment to the 

 competent and thorough-going orchard- 

 ist. Its control is easily and readily 

 attained if proper methods of procedure 

 in spraying are practiced and followed 

 year after year. 



Anthracnose, or apple canker as it is 

 commonly called, is a most serious dis- 

 ease to tolerate in the orchard. Unlike 

 losses resulting from codling moth and 

 aphis infestations, or those resulting 

 from an apple-scab epidemic, the losses 

 caused by this disease are more funda- 

 mental. The injury resulting from the 

 presence of the former pests detract 

 from the orchardist's net returns for 

 the season, while those resulting from 

 the latter cut into the capital invested 

 through the loss not only of trees but 

 to the reduction of the bearing area of 

 the trees. 



War-time shortage of labor and high 

 costs of materials tend to influence the 

 grower toward the omission of a spray 

 now and then. The last spray, the one 

 for the control of this disease, is more 

 likely to be object of neglect as its 

 application comes at a time when har- 

 vesting and packing of the crop is at 

 its height. Disagreeable weather also 

 must be contended with. Regardless of 

 these facts the growers should plan 

 their work that spraying may follow 

 harvesting at the earliest possible 

 period that control be obtained. 



This particular canker disease of the 

 apple is confined chiefly to apple- 

 growing sections west of the Cascade 

 Mountains, and its development reaches 

 its height in sections of abundant rain- 

 fall. Certain varieties apparently suffer 

 more severely from this disease than 

 do others. In the Hood River Valley 

 the Spitzenberg is much more subject 

 to infection than other varieties grown. 



The economic losses resulting from 

 the occurrence of this disease are diffi- 

 cult of estimation; it is considerable, 

 however, and in badly-neglected or- 

 chards have depreciated in value fully 

 one-half to two-thirds their original 

 valuation. The direct injury to the 

 tree consists of a partial to a comiilete 

 reduction of the functioning or fruit- 

 producing area of the tree. This re- 

 duction is usually gradual; at first a few 

 cankers appear on flic main branches. 

 As the number of infections increase, 

 these cankers, which have killed all of 

 the living bai'k beneath them, eventu- 

 ally become so numerous as to join one 

 another. A girdling of the branch oc- 

 curs and its death results. The disease 

 proceeds in this manner until nothing 

 remains but a framework of dead, 

 scarred limbs. Two or three seasons 

 of neglect will often make necessary 



I'liniu Oregon Experiment SlaUoii 



Fir.URK l^Anthracnosf t-nnkoi* on apple l)raiifh. 



Note the characteristic pustules on the 



bark surface. 



