46 MISC. PUBLICATION- 168, U.S. DEPT. OF AGEICULTUKE 



a knife blade or by moistening and wiping the apple. On Kieffer 

 pears the blotches are often surrounded by a zone of russet. 



The disease causes no decay nor even any browning of the tissues 

 under the spots, but affected fruits are sometimes badly wilted. The 

 chief loss is due to blemishing by the fungus and consequent reduc- 

 tion in the market value of the fruit. 



Sooty blotch is common throughout the central, eastern, and 

 northeastern apple-growing regions of the United States, but is 

 rare in the Northwest. All late summer and winter varieties may 

 be affected. 



The disease does not develop or spread in transit or in storage 

 and is of minor importance on the market. It is easily controlled 

 by the treatment for scab. (JfS, 100, lU, 161, 183, 195.) 



SPONGY DRY ROT 



(Vohitella fructi Stevens and Hall) 



Spongy dry rot has been reported as causing loss in North Caro- 

 lina, Massachusetts, New York, West Virginia, Pennsylvania, and 

 Indiana, usually on fallen fruits. It is rare on the market. 



In early stages the disease appears as small black spots scattered 

 over the surface of the fruit. Later, as these enlarge, they coalesce 

 to form black sunken areas half an inch to an inch or more in 

 diameter, which eventually become roughened by the fruiting bodies 

 of the fungus. Affected areas resemble those produced by the black- 

 rot fungus, but are firmer and drier and more uniformly black 

 throughout. 



The fungus grows very slowly at low temperatures and seems to 

 be unable to penetrate the uninjured skin of apples. {22, 100, llJi,, 

 218,) 



SPRAY INJURY 



There are several types of spray injury on the apple. Some of 

 them can be readily attributed to a particular spray material, 

 whereas others have various possible causes. 



Russeting is the most common form of spray injury. When it is 

 produced by Bordeaux mixture the skin is often decidedly rough, 

 showing evidence of extreme injury. When caused by arsenicals, 

 lime sulphur, or oils, the injury is likely to be less serious and usually 

 shows finer lines and markings. 



Russeting may be due to other agencies than spraying, but the 

 effects are usually somewhat different. Spring frosts often produce 

 a russeting, but the injury is usually found in definite bands and 

 lines around the fruit. Mild forms of russeting may be due to cold 

 spring rains and other unfavorable weather conditions and are some- 

 times difficult to distinguish from the milder cases of spray injury. 



Bordeaux russeting is most likely to result from applications made 

 early in the season (pi. 7, D). Late applications sometimes cause 

 injury in the form of small red or purple pimples, especially on 

 green or yellow varieties such as Yellow Newtown. Varieties most 

 susceptible to roughenino* and russeting by Bordeaux mixture are 

 Ben Davis, Grimes Golden, and Golden Delicious. 



