1 7© 



THE CANADIAN HORTICULTURIST. 



i@TEi Aip eonniMTi 



Apple scab. 

 PLATE III 



B 



.'. '; .■ • Fig. 2297. 



A. Spores'(a:) in asci, B. Loose spores of scab 



{b) in ruptured ascus. 



Apple Scab [Fusicladium dentriticum) is 

 , one of the most serious hindrances of suc- 

 cessful apple growing". By the fruit marks 

 act, fruit so affected is virtually ruled out of 

 the market as No. i grade, and in many 

 orchards this will make seconds of nearly 

 one half the crop. This fungus has been 

 steadily increasing upon us, during the last 

 twenty years, and we must now face it with 

 faithful spraying or go out of apple growing. 

 Green, of Ohio, made experiments in 1897 

 showing an average of nearly seven bushels 

 of apples per treated tree and only, two and 

 one half per untreated ; and in the case of 

 Spy, and Baldwins the actuar average of 



profit derived from the 

 treatment was more than 

 $5.00 per tree ! 



The first application of 

 the Bordeaux should be 

 made soon after the leaves 

 begin to unfold ; the second 

 when the petals fall ; and, 

 if weather is wet, a third 

 should follow about two 

 weeks later. 



Clinton, of Illinois, found 

 the scab was preserved 

 over winter in the fallen 

 leaves of the affected trees, 

 and this stage of the life 

 history of the scab is 

 known by the name of 

 Venturia. Fallen leaves 

 gathered in October from 

 scab infested trees, show, 

 on the under side, small 

 black round, pustules, some- 

 times congregated in grey- 

 ish spots, which mark the 

 place of the winter scab colony. These 

 pustules are called perethecia, which is the 

 latin plural of perethecium. Figure 2298 C. 

 shows one of these which has been placed 

 fifteen hours in apple broth and the threads 

 are the mycelial growth from the spores 

 enclosed, which penetrate among the cells 

 of the leaf tissue. 



Figure 2298 D. shows some of these spores 

 separated, {a) spore not yet swollen, (d) a 

 germinating spore. 



Figure 2298 E. shows germination of spores 

 within 24 hours after placing them in water, 

 {a) being a spore and {b) a germ thread. , 

 Figure 2297 A. shows spores (a) asci, b) 



