20 CIRCULAR 6 5 9, U. S. DEPARTMENT OF AGRICULTURE 



as commonly recognized that apples with bad bruises should be culled 

 out. Bad bruises not only detract from the sales appeal of the fruit 

 but are also potential avenues of blue mold infection to almost the 

 same extent as are skin punctures. 



Physiological Diseases 

 bitter pit 



Bitter pit, Baldwin spot, or stippin, as it is variously called, is a 

 physiological disease that is found all over the world where apples are 

 grown. It occurs as brownish spongy or corky spots or pits in the 

 flesh just under the skin and usually is most prevalent at the blossom 

 end (fig. 5, C). Occasionally the pits are deep-seated and are not evi- 

 dent without cutting the apple. The affected part often has a some- 

 what bitter taste, which accounts for the name "bitter pit." Bitter 

 pit does not impair the keeping quality of the apples, but since the 

 affected parts have to be pared away it reduces the value of the fruit 

 and of course detracts from its appearance. 



No variety is entirely immune, but bitter pit is particularly prevalent 

 in Baldwin, Gravenstein. Arkansas (Mammoth Black Twig), De- 

 licious, Yellow Newtown, Rhode, Island Greening, and Northern Spy. 

 The disease is most likely to occur in light-crop years, and apples 

 grown on young trees are particularly susceptible. Susceptibility to 

 the disease is also increased when late-season growth is stimulated 

 by heavy irrigation or rains, fertilization, heavy pruning, or other 

 means. Bitter pit may begin to appear before the apples are picked 

 and seems to develop to the greatest extent if they are picked before 

 they reach proper maturity, but as the disease is seldom fully mani- 

 fested by the time of harvest it is impossible at that time to sort out 

 all of the apples which will show the pitting. Ordinarily, however, 

 the diseased apples can be detected within a month or 6 weeks after 

 they are picked, and if susceptible crops are held until then before 

 sorting and packing the pitted fruit can be eliminated. If this pro- 

 cedure were more generally followed, there would be less likelihood of 

 having to repack affected lots or suffer heavy market losses because of 

 bitter pit. 



JONATHAN SPOT 



Jonathan spot is a superficial skin disease characterized by small 

 black or brown spots resembling "freckles" scattered over the apple, 

 particularly on the well-colored part (fig. 5, D). In later stages 

 these spots may become sunken and the flesh immediately beneath 

 becomes brown and spongy as the tissue dries out. This disease 

 affects the appearance and sales value of the fruit rather than its 

 keeping quality. Jonathans are very susceptible, but the disease 

 occurs also on many other varieties. The same kind of spot or one 

 closely resembling it often seriously detracts from the appearance 

 of Rome Beauty apples. Jonathan spot is only skin deep except in 

 late stages when underlying flesh tissue becomes brown and dried. 



Jonathan spot is a physiological or functional trouble. It occurs 

 to some extent on highly colored apples left on the tree until they 

 become overripe, but primarily it is a storage disease that is most 



