Dec.. 1909.] 



SOME APPLE DISEASES. 



129 



the unaided eye. They eoutain numerous two-celled spores borne 

 in asci or sacs. 



Treatment. All cankered limbs should be destroyed. Wounds 

 should be thoroly coated with Bordeaux or paint. Spraying 

 may serve to disinfect the smaller wounds produced by insects, 

 hail storms, etc. (See page 138.) 



BLISTER CANKER. 



Nunimularia discreta Tul. 



The disease is sometimes known as 

 "Illinois Canker," since it was first 

 observecl as particularly destructive 

 in that state. It is of quite common 

 occurrence in New Hampshire, but 

 seems to be less destructive than the 

 black rot and European cankers. It 

 has a characteristic appearance that 

 readily distinguishes it from either 

 of these diseases. (See Fig. 27.) 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 attacks 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 known as 

 stromata develop on the diseased area. 

 They are formed beneath the bark, 

 but soon break through to the surface, 

 furnishing the most characteristic 

 feature of the disease. The stromata 

 are firmly fastened to the wood by 

 means of a hard ring of fungous tis- 

 sue, so that they remain attached to it even after the bark has 

 fallen away. Summer spores are produced on the surface of the 



Fig. 27.— Blister Canker of apple. 

 The bark has been removed from 

 the upper portion showing the cir- 

 cular markings produced in the 

 wood. 



