conspectus: prevalence and distribution 55 



loss estimated at $10,000,000 for the five years preceding the 

 efforts for its restriction begun in 1905 by the United States 

 Department of Agriculture. This is a very conservative esti- 

 mate considering the number of trees destroyed. In the San 

 Joaquin Valley in California, "in the short space of three years, 

 from 1900 to 1904," according to O'Gara, ''almost half a million 

 pear trees were lost by blight. Practically no attempt was made 

 to check the disease and one of the greatest industries of the 

 San Joaquin Valley vanished hke a dream." Very serious 

 losses from this disease are experienced every year in the East, 

 or were until growers became generally familiar with methods of 

 control. In certain seasons bacterial diseases of barley and oats 

 injure these crops to a considerable extent. 



In our southern states the wilt disease of tobacco and the 

 tomato, due to Bacterium solanacearu^n, has made it impossible 

 to grow these crops on many fields. In the northern United 

 States the cucurbit wilt is wide-spread and destructive, but 

 cucurbits are, of course, a minor crop. Blight of beans due 

 to Bacterium phaseoli is another common and troublesome dis- 

 ease. In certain seasons and on some varieties the angular 

 leaf-spot injures cotton very seriously (see Part III, No. X). 



The wide prevalence and destructive nature of the bacterial 

 black chaff of wheat in the United States west of the Mississippi 

 River in 1915, and since, adds another to our serious bacterial 

 diseases. This blights the leaves, shortens the head and shriv- 

 els the kernels (Fig. 38). In the study of this disease in my labo- 

 ratory during the last three years we have discovered a second 

 bacterial disease of wheat previously confused with the ''black 

 chaff," the basal glume rot (Figs. 39, 40), due to Bacterium 

 atrofaciens McCulloch, a green fluorescent organism which causes 

 a black rot at the base of the kernel. 



The walnut blight has done much damage in California and 

 recently it has been reported from New Jersey (Cook) and from 

 other parts of the Eastern United States (McMurran, Bull. 

 611, U. S. Dept., Agric). This disease occurs also in Chili, 

 South Africa (Miss Doidge: Letter to the Author), New Zealand 

 and Tasmania. 



The bacterial disease of alfalfa has been serious in parts 



