1042 



THE FRUIT INDUSTRY IN XKW YORK STATE 



over cankers on body or limb or even in infected twigs. They 

 may die out in many such places, and in cankers they are 

 alive only at the margins and often there only in isolated 

 pockets. During warm days in spring the bacteria, nourished 

 by abundant sap, becomes active and begin to invade the adjoin- 

 ing healthy tissues. They increase rapidly in number, and dur- 

 ing warm rainy weather may ooze out with the sap through cracks 

 in tissues or through broken down lenticels in viscid milky drops 

 (Fig. 323). This sweet sticky ooze is attractive to insects and 

 is visited, among others, by wasps, bees, and flies. They become 

 smeared with it, and later, in visiting blossoms, leave behind in the 



nectar some of the bacteria 

 that cling to them. Then 

 every blossom visited by these 

 insects becomes inoculated in 

 the same manner. The bac- 

 teria increase rapidly in the 

 sweet nectar; other bees vis- 

 iting it become contaminated 

 and carry the organism to all 

 other blossoms visited by them. 

 In this way the organism may 

 become widely distributed 

 from a single source of infec- 

 tion. One can readily im- 

 agine how 7 extensive this dis- 

 tribution would be with 

 numerous sources of infection 



and with many insects flying. 

 FIG. 323. CANKERED LIMB SHOWING r , - /?, o.'M* 



EXUDING MILKY DROPS Tne bacteria left m the blos- 



soms of susceptible plants 



easily penetrate the tender tissues of the flower, where they move 

 about among the cells and absorb the nutritive sap that is needed 

 for the development of the young fruit. The blossoms die after 

 nine or ten days, and the disease shows as blossom blight so com- 

 monly observed on apple and pear trees. The bacteria may prog- 

 ress down the spur to the limb where they spread in the tissue about 

 the base of the spur. This infection later shows as a canker ( Fig. 



