226 INSECTS INJURIOUS TO VEGETABLES 



finally succumbing to the combined injuries of insects and dis- 

 ease. Injury is three-fold to the plants above ground, and to 

 the tubers in the field, and again in store. The moths oviposit 

 on any part of a plant, on leaves, stems, on tubers in the hill and 

 when exposed in the field and after they are stored. 



Methods of Control. — It is impossible to reach the tuber 

 worms in their mines, in stalks or tubers growing in the field, 

 therefore we must proceed against this pest in other ways. 

 Several must be employed to insure success. First come clean 

 methods of cultivation, which implies that all infested plants 

 of potato and weeds of the vicinity must be destroyed, as 

 such material affords a breeding place for the insect and its 

 successful hibernation. Sheep and hogs can be utilized in the 

 destruction of the remnants merely by turning them into the 

 field. Crop rotation is desirable, and cooperation is practically 

 a necessity. Where potatoes are extensively grown in a given 

 region their cultivation might be discontinued for a year. Other 

 plants than tomato, eggplant and tobacco would answer as 

 alternates, and leguminous crops are particularly indicated, 

 owing to their value as soil restorers. Careful compact hill- 

 ing is an effective method in preventing infestation, especially 

 to the tubers. Carelessness in digging, which consists in leav- 

 ing potatoes in the field over night instead of promptly remov- 

 ing them to uninfested shelter, should be avoided. 



The remedy that has been used with best results consists in 

 placing infested potatoes in tight receptacles and treating them 

 with bisulphid of carbon. Several treatments are sometimes 

 necessary. 



The Potato-scab Gnat {Epidapus scahici Hopk.). — Some forms 

 of potato-scab are due to the attacks of minute whitish maggots 

 with blackheads which feed in decayed spots in tubers as 

 well as upon healthy portions. The detection of these as the 

 cause of scab is due to the investigations of Dr. A. D. Hopkins,' 



1 Special Bui. 2, West Virginia Agr. Exp. Station, 1895, pp. 97-111. 



