BUAKD OF HORTICULTURE 



115 



learned the game or have failed to equip themselves with spray outfits adequate 

 for the work, for the U:)sses from scah aloue, not to meiition codling rnoth, have 

 ruii up iuto mauy thousaiuls of doUars, au average of 50 per ceiit cuUs haviiig 

 been reported from some districts of considerable size. That this could have been 

 prevented is showu hy the fine results from systematic spraying obtained by 

 certain individual orchardists in these same sections. Perhaps some explauatiou 

 of the requirements for successful scab control might be helpful to growers who 

 do not want to repeat the experiences of the past. 



Hood River growers, in a climate favorable for scab, have adopted a spray 

 program of four to five spring sprays for scab control, two of these being combi- 

 nation sprays for codling moth prevention. The reason they put on so many 

 scab sprays and follow up with the number of codling moth sprays which they 

 regularly give, is that they have proved to their own satisfaction that it doesn't 

 pay to omit any step in this schedule of applications. They have come to feel as 

 though the Omission of one application would lie much like hanging out a sign 

 in front of the orchard reading "Welcome Apple Scab." There was a time wheu 

 Hood River growers had not learned the secret of successful fruit protection. 

 Enormous losses were sustained from scab in some seasons. Then along came 

 the Oregon Experiment Station at its Hood River bi-anch, studying the Situation 

 through several years of investigation under the direction of Winston and 

 Childs. As a result of this work it was discovered that the Pacific Slope fruit 

 sections require one more spray application for succesful control than other 



sections of the United States were giving. This 

 extra application is the one put on at the begin- 

 ning of the growing season, just as soon as the 

 tiny leaves surrounding the blossom Clusters 

 have turned back far enough so that the spray 

 can reach the little, close-packed. undeveloped 

 group of flower buds in the center. This has 

 been called the delayed-dormant or early Cluster 

 application. It is the spray tliat nips scab in 

 the bud. 



In the early days of plant disease investiga- 

 tions it was found that apple scab was carried 

 over from year to year on the old apple leaves 

 of the previous season, and practically only in 

 this way. It was formerly the general scien- 

 tific opinion that the spring discharge of scab 

 spores from the old leaves on the ground began about the time the blossoms 

 opened, Init several years ago I found that under the climatic conditions existing 

 in Western Oregon these spores were discharged from the old leaves as early as 

 February, and this was confirmed by the Hood River Station where Childs found 

 that spore discharge started as soon as the snow was gone, and that it continued 

 right along at every rainy spell until June. Spores, therefore, are in the air of 

 the apple orchard even before the tender leaf tips begin to poke out from the 

 bud scales, ready to infect the emerging parts whenever a wet spell makes it 

 possible. 



These facts explain why it was that apple scab could get a serious Start in the 

 orchard before the usual "pink" or pre-blossom spray was applied, and it is easy 

 to understand why immediate improvement in control occurred when, after this 

 discovery. the growers began with the early Cluster (or delayed-dormant) stage 

 and followed with the other usual sprays. Western Oregon growers who are 

 getting tlie best results are putting on two separate applications before the 

 blossoming period. Then they follow with two or three more through the moist 

 spring weather. Of course summer applications for codling moth rust must be 

 given besides. 



RIGHT STAGE FOR FIRST 

 APPLE SCAB SPRAY 



