104 MINNESOTA STATE HORTICULTURAL SOCIETY. 



THE TWIG BLIGHT" OR FIRE-BLIGHT" OF THE 



APPLE. 



A. F. WOODS. 

 From Report of 1893, Neb. State Horticultural Society. 

 During the month of October, 1892, the Botanical Department of 

 the Agricultnral Experiment Station sent out a list of questions with 

 the object in view of bringing- together the experience of Nebraska 

 horticulturists concerning "twig -blight" of the apple. There 

 vTQre. one hundred and three sets of questions sent out and fifty 

 sets were returned with most of the questions answered. While the 

 department regrets that there were not more answers received, still 

 it believes the results of the inquiry to be of practical value to the 

 fruit growers of the state and may at least serve as a foundation for 

 a more complete record. 



SUMMARY OF THE KNOWLEDGE OF THE DISEASE. 



Cause. — The disease is caused by a certain minute single-celled 

 plant, one of the "bacteria," named Micrococcus amylovorus'B., 

 and by no other. One or more of these bacteria gain entrance 

 into the young, succulent parts of twigs, increase rapidly in 

 numbers, and destroy the young growing cells of the twigs, 

 thus causing their death. 



Infectious. — The disease is extremely infectious, the bacteria being 

 carried rapidly from tree to tree by the wind. 



The Bacteria.— The bacteria remain alive in the twig long after it 

 is dead. They may dry up in the forin of dust and thus live in 

 a dormant condition indefinitely; they maj' grow in any dead 

 and decaying matter containing starch or sugar, and are not de- 

 stroyed by acid solutions, as are inany other bacteria. 



Species of Trees Affected. — The disease is most troublesome in the 

 pear, apple and quince, but affects many other near relatives 

 of these. The different varieties of apples are affected in differ- 

 ent degrees. 



Conditions. — It is generally held by investigators and those ac- 

 quainted with the disease that watery, succulent growth offers 

 the best conditions for the development of the disease. 



Remedy. — Removal and destruction bj'^ fire of the diseased parts 

 is, so far as known, the only retnedy. It is held bj'- some that 

 anj'-thing that will produce hardy growth, instead of watery, 

 succulent growth, aids the trees in resisting attack. 



KECORD OF ANSWERS TO QUESTIONS ONE AND TWO. 



(1.) What varieties of apples have you found least affected by this 

 disease, and (2) what varieties most affected? 



[Here follows a long list of varieties few of which are adapted to 

 our climate. ^Sec'j'.] 



Taking oitt those varieties that have at least six favorable reports, 

 witli verj' few or no unfavorable reports, we have in the order of free- 

 dom from disease: 



