April, 1912.] SOME APPLE DISEASES — TREATMENT. 



23 



produced, the first small and unicellular, the second sickle-shaped 

 and having three or more cells. The latter are probablj^ largely 

 responsible for the spread of the disease during the summer. 

 In the spring compact clusters of red lemon-shaped perithecia 

 may be found near the edge of the 

 canker. These may be seen with 

 the unaided eye. They contain 

 numerous two-celled spores borne 

 in asci or sacs. 



Treatment. All cankered limbs 

 should be destroyed. Wounds 

 should be thoroly coated with 

 paint. Spraying may serve to dis- 

 infect the smaller wounds produced 

 by insects, hail storms, etc. (See 

 page 32.) 



BLISTER CANKER. 



Nummularia discreta Tul. 



The disease is sometimes known 

 as "Illinois Canker," since it was 

 first observed as particularly de- 

 structive in that state. It seems to 

 be less destructive in New Hamp- 

 shire than the black rot and Euro- 

 pean cankers. It has a character- 

 istic appearance that readily dis- 

 tinguishes it from either of these 

 diseases. (See Fig. 28.) It is 

 usually found on the larger limbs, 

 and sometimes attacks the trunk. 

 Old cankers are often a foot or 

 more in length. The fungus at- 

 tacks the wood as well as the bark. 



In the early stages of the disease the bark is brown and slightly 

 sunken and usually set off from the healthy bark by a distinct 

 boundary. As the season advances circular fungous masses 

 kno-^Ti as stromata develop on the diseased area. They axe 



Fi§. 2S. — Blister Canker of apple. 

 The bark has been removed from the 

 upper portion showing the circular 

 markings produced in the wood. 



