36 BULLETIN 45, HAWAII EXPERIMENT STATION. 
POTATO DISEASES NOT KNOWN TO OCCUR IN HAWAII. 
There are a few very serious diseases and insect pests of the Irish 
potato and a number of rather minor importance which apparently 
have not yet become established in Hawaii. Among those which 
have not yet been observed are the following parasitic diseases: 
Black wart (which is one of the most destructive diseases of potatoes 
known), powdery scab, blackleg, southern bacterial wilt, silver scurf, 
Verticillium wilt, and leak; and the following supposedly nonpara- 
sitic diseases of unknown causation : Internal brown spot, net necro- 
sis, curly dwarf, leaf roll, and mosaic. Among the insects injurious 
to the potato not yet detected here are the Colorado potato beetle 
Fig. 6. — A potato affected with potato wart. (From U. S. Dept. Agr., Farmers' Bui. 544.) 
and species of flea beetles. The diseases above enumerated are de- 
scribed in order that they may be recognized promptly and be the 
better guarded against. It is quite possible that some of these dis- 
eases are already present in the islands but have not yet come to 
notice. In any cases where diseases are thought to be like these 
hereinafter described, specimens should be forwarded without delay 
to this station for determination. 
PARASITIC DISEASES. 
Black Wart (Chrysophh/ctis endobiotica) . 
The black wart disease was discovered upon potatoes in Germany 
less than 25 years ago. Since its discovery it has spread with great 
rapidity in Europe and has recently appeared in Newfoundland. It 
