228 INSECTS INJURIOUS TO VEGETABLES 



more destructive than the fungus, on account of their pene- 

 trating while in the larval stages deep into the substance of 

 the tubers, thus rendering them worthless for market. 



Methods of Control. — Preventive measures that will at the 

 same time be effective against the scab fungus apply quite 

 as well to the gnats and their maggots. Dr. Hopkins recom- 

 mends the following measures for protection against injury: 



"Select sandy or other soils of a dry character in which a 

 crop of surface growing vegetables or grain has been grown 

 the previous year, and from which the refuse has been thor- 

 oughly removed in order that the soil may be as free from 

 vegetable matter as possible. Do not use as fertilizers animal 

 manures, lime, ashes, and like substances. If a fertilizer is 

 necessary, use only a ground bone, phosphate, kainit and other 

 commercial fertilizers of ?, like character. Select smooth and 

 healthy tubers for seed. . . . When the potatoes are dug, 

 and before they are stored, carefully sort out all tubers showing 

 the least indication of decay, as well as those which are seri- 

 ously affected with scab. Do not plant the same land in pota- 

 toes for at least three years after a potato crop is taken 

 from it." 



Soak seed potatoes in a solution of corrosive sublimate or 

 formalin according to directions furnished in the chapter on 

 insecticides. In case a piece of land is especially favorable 

 for the production of potatoes of excellent quality, if the pre- 

 caution is taken to remove and burn all rubbish, such as potato 

 tops, weeds, refuse tubers, etc., the same land may be, by 

 judicious fertilizing, planted in potatoes every alternate year. 



