POTATO INSECTS 165 



completion of the life cycle because of the lower temperature. 

 Under such conditions the egg stage^ requires a week or ten 

 days, the larva about six weeks and the pupa two weeks or over. 



Control. 



The injuries caused to the vines by the potato tuber moth 

 are not in themselves serious. The great loss comes from the 

 infested tubers« This may be prevented in large measure by 

 planting the potatoes rather deep and by keeping them care- 

 fully hilled so as not to allow any of the tubers to be exposed 

 on which the moths can deposit their eggs. Care should be 

 taken at digging time not to leave potatoes exposed overnight 

 while the moths are laying. Piles of potatoes should not be 

 covered with infested vines since the larva3 will leave the stalks 

 when they begin to wilt and enter the tubers. After the pota- 

 toes have been placed in storage, they should be examined at 

 frequent intervals and if any are found to be infested, they 

 should be fumigated with carbon bisulfid at the rate of 2 

 pounds to 1000 cubic feet of space, allowing the fumigation 

 to continue for about forty-eight hours. This should be re- 

 peated at intervals of about a week in summer or two weeks 

 in winter. Directions for fumigation will be found on page 380. 



Where the potato tuber moth is abundant, it is not advisable 

 to plant potatoes on the same land for two years in succession. 

 By practicing rotation of crops and by destroying all solana- 

 ceous weeds on which the insect may breed, much loss may be 

 avoided. 



References 



Cal. Agr. Exp. Sta. Bull. 135. 1901. 



Pieard, Ann. Service Epiphyties, 1, pp. 1Q6-176. 1913. 



U. S. Farm. Bull. 557. 1913. 



U. S. Dept. Agr. Bull. .59. 1914. 



U. S. Dept. Agr. Bull. 427. 1917. 



