564 



Missouri Agricultural Report. 



APPLE SCAB. 



Scab is without question the most common and sometimes one 

 of the most destructive diseases affecting the fruit of Missouri 

 apple orchards. Fortunately it is only an occasional season that 

 serious general outbreaks occur. There are some orchards and 

 some localities, however, in which it appears almost regularly. 

 Some varieties, such as Arkansas Black, Winesap, Mammoth Black 



Twig, Little Romanite, Mink- 

 ler and White Winter Pear- 

 main are especially susceptible 

 to the disease and will invari- 

 ably need to be sprayed for 

 it. While no variety is entirely 

 immune, yet under ordinary 

 seasonal conditions splendid 

 crops of such varieties as York, 

 Grimes and Jonathan have 

 been matured with a reason- 

 able degree of regularity in the 

 southern part of the State 

 with little or no protection 

 against scab. In the north 

 ^PP'^ '"^^- part of the State, Jonathan in 



old orchards appears to be more susceptible to the disease and some 

 seasons scabs severely. The disease appears early in the spring 

 at the time the flower clusters and first leaves are coming out. Wet, 

 cool weather is most favorable for its development. It occurs on 

 both the foliage and the young fruit. Under favorable weather 

 conditions the infection may be so severe that the formation of 

 fruit buds for the following season's crop will be seriously inter- 

 fered with. The fungus carries over the winter, to a considerable 

 extent at least, on the fallen foliage. The following spring, at 

 about the time growth activities begin, enormous numbers of 

 spores are produced which are distributed by various agencies to 

 the new growth. During seasons of severe infection the trouble 

 is very difficult to control because the conditions which are most 

 favorable to the development of scab are the very conditions under 

 which it is most difficult to do effective spraying. The matter of 

 a few days in making the first application has much to do with its 

 efficiency. Scab may be prevented by using either lime-sulphur 

 solution or Bordeaux mixture. In cases of moderate infection 



