FIRE-BLIGHT OF APPLE, PEAR, ETC. I TYPE 



367 



by means of a sponge. It is most easily applied on trees that 

 have been trained to a vase shape (Fig. 290). Those trees 

 trained to pyramidal form with a single central stem (Fig. 278) 

 are often killed by the first attack of fire-blight. 



^..i.- 



Fig. 282. — Fire-blight canker on apple (Waite's hold-over blight). Spring 

 condition — bacteria exuding and likely to be visited by bees and other pollen- 

 gathering and nectar-sipping insects. Bark discolored on the right side. After 

 Whetzel. 



Cause. — Pear blight or fire-blight is due to Bacillus amylo- 

 vorus (Burrill) Trevisan. The original name, Micrococcus 

 amylovorus, was given to it by Prof. Burrill, under the assump- 

 tion that it destroys starch but such is not the case. It is a 

 white, motile, peritrichiate-fiagellate (Fig. 291), non-sporiferous, 

 non-odorous, non-acid-fast. Gram negative, non-nitrate-reduc- 



