308 MANUAL OF FRUIT DISEASES 



bacterial leaf-spot. The spots at the beginning are mere 

 specks, grayish in color, angular in form, and take on a water- 

 soaked aspect. Later, they become brown or purple-brown, 

 or even scarlet, although they are finally dark-brown. Ma- 

 ture spots ordinarily do not measure more than one-fifth of 

 an inch in diameter; many are smaller, but two or more 

 may coalesce so that large areas are involved (Fig. 81). In 

 later stages the affected tissue contracts, dries and falls away, 

 leaving a more or less circular hole (Fig. 81). Several such 

 holes in a leaf give it the appearance of having been riddled 

 with gun-shot, whence the name shot-hole (Fig. 81). Badly 

 diseased leaves fall prematurely ; in this way an infected tree 

 may lose from 15 to 75 per cent of its foliage by August. Not 

 all leaves fall at once, but one after another, until finally only 

 a few young leaves remain at the tip of each twig. In this 

 condition the affected tree is characteristic in its appearance. 



The lesions on fruits in their early stages are similar to those 

 described for the leaves. Soon, however, the skin is ruptured at 

 affected places, resulting in the production of numerous angu- 

 lar cracks. While the diseased areas are very small never 

 more than one-tenth of an inch in diameter they are often 

 so numerous that the crevices run together, thus forming a 

 network of fissures some of which may be an inch in extent. 

 Some growers speak of this condition as bacterial-crack. Black- 

 spot does not usually become evident on the fruit until about 

 the middle of May. 



The disease on the twigs shows itself in the form of black 

 spots or cankers; this phase has received the names black- 

 spot, black-tip and bacterial cankers. These lesions are found 

 abundantly in May and June, or even earlier. A single spot 

 develops as follows : surrounding a lenticel there first appears a 

 water-soaked area which bulges out somewhat. As the spot 

 enlarges it elongates, and at maturity extends from one-half to 

 two inches up and down the shoot and from one-half to two- 



