INSECTS INJURIOUS TO POTATOES AND TOMATOES 291 



destroyed wherever found. Seed potatoes must be free from the 

 larvae, or. they will soon give rise to moths which will infest a 

 whole field. When young plants are found wilting, the infested 

 stalks should be cut and destroyed as soon as possible to prevent 

 the further development and spread of the pest. Care should 

 be taken in cultivating to hill up the soil, or thoroughly cover 

 the tubers, so that they are not exposed. After digging, the 

 potatoes should not be left exposed in the field any longer than 

 is absolutely necessary and should not be covered with the tops 

 to shade them, as is often done, as this furnishes a shelter for the 

 moths and induces oviposition upon the tubers. Infested fields 

 should have the stalks and all rubbish and refuse thoroughly 

 raked up and burned as soon as possible, or sheep and hogs may 

 be turned into the fields to destroy the stages which may be 

 left in the vines or in the soil. Where fields have been flooded 

 for two or three weeks after the crop has been dug, they have 

 been entirely freed of the pest. For the treatment of stored 

 potatoes, fumigation with carbon bisulfide in a tight room 

 seems to be the only satisfactory method. This should be done 

 as described for grain insects (see page 57). The tubers should 

 be fumigated as soon as stored, and the treatment should be 

 repeated at intervals of two weeks, four or five fumigations 

 being recommended to entirely free the potatoes of all stages. 

 Obviously it will be important to sort over infested tubers and 

 remove all which are materially injured to prevent the increase 

 of rot in others. 



Colorado Potato-beetle * 



First and foremost among the enemies of the potato-grower 

 stands the Colorado potato-beetle the insect which in the early 

 seventies, on account of our ignorance of it, was made an entomo- 

 logical bugbear. But " there's no great loss without some small 

 gain," and we may be thankful that the invasion of this beetle 

 also brought about the use of Paris green, an insecticide which has 



* Leptinotarsa decemlineata Say. Family Chrysomelidae. See F. II. 

 Chittenden, Circular 87, Bureau of Entomology, U. S. Dept. Agr. 



