FUNGOUS AND BACTERIAL DISEASES 215 



killed by European bacteria than by bullets. Measles struck 

 the Fiji Islands like a deadly pestilence. So we inspect and 

 quarantine against the importation of such germs as those of 

 bubonic plague, Asiatic cholera, and foot-and-mouth disease, 

 but they slip by in spite of all precautions. The canker, or 

 chestnut-bark disease, appeared about ten years ago, coming 

 probably from Japan. Working as it does, between wood 

 and bark, it cannot be reached by sprays, and there are 

 not men enough available to prune and burn the diseased 

 trees. It is said to have destroyed over 130,000,000 worth 

 of chestnut trees, and predictions appear to be well founded 

 that it may not leave a single one alive in eastern North 

 America. 1 A third reason is that we are planting large areas 

 to the same crop, with field against field. This is like piling 

 up kindling for a fire, when a disease gets a start. 



Control measures. Methods are improving continually, and 

 the only safe course to pursue in this field is to correspond 

 with our nearest experiment station and secure their latest 

 spray calendars, take the monthly list of publications, and 

 keep abreast of discoveries. The underlying principles, how- 

 ever, should be generally understood. 



1. Be sure to plant healthy, uninfected, free-from-disease seeds, 

 tubers, bulbs, or nursery stock. This refers to germs of disease inside 

 the seed, tuber, or stock, and applies, of course, to buds and scions. 



Peach yellows, while the germ has not been discovered, is known to 

 be transmitted from diseased trees in seeds, buds, or scions. Wilt dis- 

 ease of sweet corn, or Stewart's disease, sometimes destructive to from 

 80 per cent to 100 per cent of the crop, is transmitted on, and prob- 

 ably in, the seed. Seed should not be saved, or distributed to uncon- 

 taminated land, from infected fields. The same is true of anthracnose 

 of beans and cotton ; bean blight ; bacterial blight, or wilt, of potato ; 



1 The species might be saved to the continent if nuts from sections as 

 yet uninfected could be sent to suitable places on the Pacific coast and 

 planted and reared beyond probable reach of infection. The United States 

 Bureau of Forestry would probably be glad to supply safe seeds to biology 

 classes that would agree to follow out directions for planting and culture. 



