TENTH REPORT OF TEE STATE ENTOMOLOGIST 447 



One Form, of the Scab may be Caused by Bacteria. 



It was believed a few years ago that Prof. Bolley, now of the North 

 Dakota Agricultural Experiment Station, had demonstrated that at 

 least one form of potato scab was produced by bacteria, but later 

 studies favor the idea that the bacteria observed merely accompanied 

 the fungus disease, and that it rarely, if ever, becomes parasitic under 

 mature conditions. 



A Potato Scab Caused by Fungus Gnats. 



Quite recently the studies of Prof. A. D. Hopkins, Entomologist of the 

 West Virginia Experiment Station, on the connection of species of 

 Sciara (small flies) with scabby potatoes and the potato rot, have 

 resulted in his showing that one form of scab may be caused by species 

 of these flies, commonly known as " fungus gnats." He concludes a 

 paper* on the subject read before the Entomological Society of Wash- 

 ington in these words: 



While I admit that one or more forms of the so-called potato scab 

 may be due to the action of fungi and that the true potato rot is a 

 fungous disease, I am conBdent that there are forms heretofore recog- 

 nized as scab and rot which are not due to fungous disease, but are the 

 direct result of the attack of insects belonging to the family Myceto- 

 jyhilldcn and to the genera Sciara and Epidapus. 



The species that he found especially instrumental in producing the 

 potato scab blemish was a new and interesting, Epida^yus which he has 

 described, named and figured as Epidapus scabies. The fly is so 

 minute, being only from 1 to 2 ram. in length, that it would escape 

 observation in ordinary examination of potatoes affected with the 

 scab. 



How to Prevent Potato Scab. 



Replying to the important inquiry of how to prevent the scab, Dr. 

 Thaxter, while not able from the results of his experiments to indicate 

 any remedy for it, has named the following as preventive measures: 

 1. The seed must be free from scab. 2. Land where scab has prevailed 

 must not be planted to potatoes. 3. Scabby potatoes should not be fed 

 to live stock unless they have been first thoroughly cooked. 4. Use 

 any other fertilizer in preference to barnyard manure. 5. If a crop is 

 found to be infested with scab, dig it as soon as possible in order to 

 stay its increase. 



The following treatment, it is claimed, will almost insure a crop 

 against the scab, if planted in soil not already infested. It is known 



* Notes on the Habits of Certain Mycetophilids, loith Descriptions of Epidapus scabies sp. 

 nov. 



