2 BULLETIN 534, U. S. DEPAETMENT OF AGEICULTUEE. 



orchard, in other sections it is only locally severe. The former is the 

 case in the Ozarks of Missouri and Arkansas and in the commercial 

 apple-growing sections of Kansas, while the latter is true in Virginia 

 and Maryland. 



On account of the above-mentioned facts it is very difficult to com- 

 pute the amount of damage caused by the disease, but it is probable 

 that $2,000,000 would be a conservative estimate of the annual loss 

 due to it. 



In orchards in which blotch has not been placed under control by 

 spraying, the entire crop of susceptible varieties may succumb to the 

 disease and the trees themselves may be severely injured, in extreme 

 cases even killed. Losses of 50 to 75 per cent of the entire crop are 

 common in some sections. 



The disease is ( found in practically all the eastern and middle- 

 western apple-growing regions from Pennsylvania, Ohio, Indiana, 

 Illinois, northern Missouri, and Nebraska southward. It is most 

 serious and widely prevalent in Kansas, southern Missouri, northern 

 Arkansas, Tennessee, and Kentucky. It is also a serious disease in 

 fruit-growing sections bordering on or near the Ohio Eiver. In Vir- 

 ginia and Maryland it is only locally severe, but it has become much 

 more prevalent during the last two years. Blotch has been gradually 

 extending farther north, but should not become serious in properly 

 sprayed orchards. In those sections which have been free from the 

 disease and in which a fungicide such as lime-sulphur solution or 

 Bordeaux mixture is annually applied to apple trees about three 

 weeks after the petals have fallen, blotch should not be able to gain 

 a foothold. 



DESCRIPTION OF APPLE BLOTCH. 



Blotch occurs on the fruit, foliage, and twigs of the apple. 



On the fruit it first appears as small dark, somewhat raised spots, 

 which later enlarge slowly. Usually these spots have in midseason 

 a dark fringed or stellate appearance, though on some varieties, such 

 as Maiden Blush, the center of the spots may be somewhat more 

 raised or blisterlike in appearance and of rather light color, due to 

 the raised cuticle (PI. I, figs. 2 and 3). 



A later phase of this disease on the fruit is the coalescence of sev- 

 eral spots, a general homogeneous darkening, with complete elimina- 

 tion of the stellate configuration typical of earlier stages. On some 

 varieties, notably Ben Davis, a cracking open of the fruit often in 

 three directions from a central point, is very common in orchards in 

 which the disease is at all serious (PI. I, fig. 1). 



A characteristic spot is raised, glistening black, with margins 

 so deeply cut in and so irregular as to give the spot its commonly 

 noted stellate appearance (PI. I, fig. 4). The tissues beneath the epi- 



