10 MASS. EXPERIMENT STATION BULLETIN 226. 



.soiiiewliat later in the highlands of Worcester County and the counties to 

 tlie west, exclusive of the Connecticut Valley. 



Apple scab this year was on the whole of average, or perhaps slightly 

 less than average, severity, as indicated by the condition of the fruit on 

 unsprayed or poorly sprayed trees. Good spraying gave practically com- 

 plete protection even on Mcintosh and other susceptible varieties. West 

 of tlie Connecticut Valley there was a light infection on Baldwins. In 

 the Connecticut ^'allej, the disease became conspicuous later than usual 

 and in some orchards was regarded as severe on Mcintosh and Delicious. 

 There was evidence that the second post-calyx application on Mcintosh 

 gave some increased protection. In eastern Massachusetts some orchard- 

 i.sts h.id as mucli scab on Baldwins as on Mcintosh, or more. This was, 

 j^erhaps, flue to the fact that in many orchards the Baldwin received only 

 (Mie )ire-l)lossom application while the Mclntosii had two, and to the fact 

 that many of the Baldwins are old and tall trees and consequently more 

 difficult to spray well. In most orchards scab became conspicuous on the 

 fruit in July and continued to increase until into September. 



Spray Ix.iury 



The occurrence of spray injury is affected by the materials used, the 

 manner of application, the susceptibility of varieties, and the weather at 

 the time of and following the application. This being the case, it is not 

 surprising to find that there was serious spray injury this year in some 

 crchards and none at all in others. 



In some orchards there was considerable spray injury on the fruit of 

 Baldwin. But the most severe injury was on Mcintosh, fruit russeting 

 proceeding so far as to cause the fruit to crack. Leaf injury, in the form 

 of curling, yellowing, or burning of leaf margins was in some cases asso- 

 ciated with fruit russeting. This was easily confused with a condition 

 which occurred on the leaves of certain young and unsprayed trees where 

 the leaves showed a brown or blackened margin, probably caused by the 

 high temperatures and drying winds to which these leaves were subjected 

 during their period of development before the tissues hardened. 



Spray injury as it occurred this year has been ascribed to the use of 

 the spray gun, to the high temperatures which prevailed during the spray- 

 ing season, to the use of fungicides containing copper, and to arsenical 

 injury. The worst spray injury brought to our attention occurred in 

 orchards which received pre-blossom applications of Bordeaux mixture or 

 copper dust, with sulfur fungicides used for the calyx and post-calyx ap- 

 plications. Evidence was secured in 1924 that even for pre-blossom ap- 

 plications copper fungicides are less safe than are sulfur fungicides. As 

 recorded by the present writer in Massachusetts Agricultural Experiment 

 Station Bulletin No. 222, there was an average of 14. per cent russeted 

 Mcintosh apples on plots which received pre-blossom applications of Bor- 

 deaux mixture, and less than 1 per cent on plots which received pre-blos- 

 som applications of lime-sulfur. This year, there was of course some 

 spray injury in certain orchards where only sulfur fungicides were used. 

 Some of this may have been due to the use of a spray gun close to the 

 trees and to the unusually high lemperatures during the spraying season 

 During the first ten days of June the temj)erature was very high, with the 

 maximum above 90° F. for four days in the eastern half of the state. In 

 their study of foliage injury by arsenical sprays, Fernald and Bourne 



