No. 6. DEPARTMENT OF AGRICULTURE. 369 



of general practicability. Varietal susceptibility influences very 

 much scab infection, and should influence our treatment of it. Bald- 

 win, York Imperial, JBen Davis and Jonathan are afl'ected little or 

 not at all, while Stayman Winesap, Mcintosh, Spitzenburg, and 

 Northern Spy are quite susceptible. Discrimination in the treat- 

 ment of varieties varying in susce})tibility Avill ptomote efficiency 

 and economv not onlv for scab, but for other troubles. A wet, cool 

 spring favors scab. Our climatic conditions, fortunately, are less 

 conducive to scab development than those farther north; and we 

 can for this reason safely omit, in the average season and on the 

 average variety, the early application, just before the blossoms 

 open. 



In the case of Cedar or Orange Rust, unprotected young leaves 

 and fruit of certain varieties are the endangered parts; the infec- 

 tive material in this case comes from red cedars that may harbor 

 the fungus in the familiar "cedai -apples;" and infection is favored 

 by periods of continuous wet weather for two or three days. When 

 these conditions occur together, which is only occasionally, we have 

 an outbreak of Cedar Rust. For this disease the removal of en- 

 dangering red cedars from the vicinity of orchards has proved more 

 constantly efl'ective than spraying. 



We were speaking of the si)ray applications, for us usually two 

 in number, made when the petals fall and two weeks later, that are 

 timed particularly for scab control. These, let us remember, will 

 also be more or less effective for Cedar or Orange Rust on leaves 

 and fruit, for blotch on leaves and fruit, for Sooty Mold on fruit, 

 and for Black Rot Spot (Sphaeropsis) and Frog Eye Spot (Tllos- 

 porium) on leaves. The diluted lime-sulphur material seems to be 

 satisfactorily efl'ective against these troubles, and is preferred to 

 Bordeaux mixture. Where blotch and Black Rot prevail, care should 

 be taken to cover twigs and limbs at one of the sprayings; and 

 as thorough as possible pruning out of affected woody parts should 

 be practiced. 



Sometimes, when cool, moist weather prevails, there may be a 

 midsummer outbreak of scab; and usually the leaf spotting fungi 

 and Sooty Mold and blotch of the fruit continue to cause infec- 

 tion until late in the season. Furthermore, Bitter Rot and Fruit 

 Spot usually begin their attacks after the fruit is half grown; and 

 such ripe rots as Black Rot, Brown Rot, and Yolutella Rot come on 

 in the latter part of the year. More efficient protection is afforded 

 against all of these if a fungicidal application is made in July, at the 

 time when spraying is done for the second codling moth brood. 

 Where blotch and Bitter Rot prevail, Bordeaux mixture must be 

 used in midsummer and the application made two or three times at 

 intervals of two weeks on varieties susceptible to these destructive 

 diseases. 



A word further about blotch and Bitter Rot may not be out of 

 place. Both of these diseases are among the most serious affecting 

 apples in the South. They occur in Pennsylvania to a small degree 

 only, but we must be on the alert lest they gain a greater foothold. 



Bitter Rot spots are brown and circular, and the rot extends 

 inward in a cone-shaped area quite rapidly, so that it may reach 

 the core by the time the surface area is the size of a half dollar. 



24—6—1911 



