DISEASES OF CULTIVATED PLANTS 434 
POPLAR 
Anthracnose. Species of poplar or cottonwood are at times attacked by 
anthracnose (Warsonia populi Hals.). It produces similar effects to those of an- 
thracnose upon sycamore. 
Rust. The leaves of poplars are frequently attacked by the rust (Welampsora 
populina (Jacq.) Lev.) which disfigures the leaves by the spots caused through its 
development. The thrifty growth of poplars usually overcomes these foliage 
diseases under favorable conditions. 
POTATO 
Bacterial Blight. This is a serious disease of the potato; it also’attacks the 
tomato, tobacco and egg-plant. It has been referred to a microbe (Bacterium 
solanacearum Smith). The parts of the stem attacked die off suddenly and the 
tubers from the affected plants have a dark discoloration of the tissues in a 
distinct ring at a slight distance from the exterior of the potato. Fungicides 
are practically useless for this disease. Such diseased tubers should not be 
planted nor should potatoes follow a diseased crop of tomatoes, egg-plants or 
potatoes. (Div. Veg. Path. B. No. 12, U. S. Dept. of Agric.) 
Black-Leg. In much of Europe and in America the bases of potato stems are 
often attacked in the early season by a basal stem-rot which causes serious 
check to the growth of the plants. The diseased parts show well-marked lesions 
due to the work of a bacterium (Bacillus phytophthorus Appel.). Dr. Smith has 
recently investigated the disease in this country and has found it widely dis- 
tributed. In Ohio it occurs to a certain extent and is at times quite similar in 
its effects to those referred to rosette. Measures of control will largely consist 
in rotation of the potato crop. See Bulletin Maine Expt. Station 174 (1909). 
Fig. 81. A potato destroyed by Dry-Rot. This shows the characteristic appearance 
of the rotted potato.—From a photograph by T. F. Manns, 
