SUMMARY. 



i Potato rot, or late bligJit, is caused by a fnngiis which may 

 develop with extreme rapidity under favorable circumstances ; it 

 may cause the decay of all parts of the potato plant, including the 

 tubers. (Page 297.) 



2. The conditions favoring the growth of the parasite are a tem- 

 perature of about 70° F. and a moist atmosphere. Few sections 

 of New York are every year seriously troubled by the disease. 

 (Page 298.) 



3. A leaf affected by late blight normally shows distinct brown and 

 mostly large areas of varying form, but usually not circular spots ; 

 these may enlarge very rapidly, the under surface of the leaf show- 

 ing a frost-like growth in the parts first attacked. Unaffected 

 portions of the leaves retain their healthy green color. (Pages 

 299, 300.) 



4. Tubers affected with potato rot assume a dark color where the 

 fungus is found. Where decay takes place slowly, the dead por- 

 tions become dry and shrivelled ; during rapid invasions consider- 

 able moisture may be present in the rot. (Page 301.) 



5. The early blight of potatoes does not cause the tubers to rot. 

 A more or less rdpid drying and curling of the leaves and stems 

 mark the presence of the disease. The edges of the leaves are first 

 visibly affected ; the color changes to yellowish brown, while the 

 central parts of the leaflets gradually become lighter green or even 

 yellow and more or less spotted. Eventually all portions above 

 ground turn brown. (Pages 302, 305.) 



G. Young, vigorous potato plants do not appear to suffer from 

 early blight. (Page 306.) 



7. The proliable causes of early blight, as found in New York, 

 are the following : A fungus, this having the power of attacking 

 only such tissues as have become weakened to a certain extent ; 

 unfavorable conditions of soil or atmosphere ; mechanical injuries 

 to the foliage, commonly produced by flea- beetles or other insects. 

 (Pages 307, 309.) 



8. Potato scab, as commonly found upon the tubers, is due to the 

 presence of a fungus. Similar blemishes have also been ascribed 

 to the work of bacteria, and to insect injury. (Pages 309, 312.) 



