436 INSECT TESTS OF FARM, GARDEN AND ORCHARD 



are grafted with the desired varieties. There is a marked varia- 

 tion in the resistance of different species and varieties and not all 

 of them can be successfully used as stocks for the desired scions, 

 so that the successful use of the method, which is fully outlined 

 by Quayle, I.e., requires a considerable knowledge of viticulture. 



Carbon bisulfide has been used very extensively for destroying 

 the root-lice, but is expensive and is only applicable on rich, deep, 

 loose soils. It cannot be used successfully on soils containing 

 much clay, or on dry rocky hillsides, or when the soil is saturated 

 with moisture, and is most effective on sandy soils where the 

 insect is least injurious. It is now seldom used and is considered 

 impractical by growers. 



One of the best methods of destroying the root-lice where 

 water is available is by submersion. In California the best results 

 are secured by flooding with at least six inches of water for a 

 week or ten days as soon as the vines have ceased active growth 

 in November. A little later two to three weeks' submersion will 

 be necessary and in winter thirty-five to forty days. Flooding 

 for a couple of days in midsummer seems to destroy some of the 

 insects, but its main value is in stimulating a vigorous growth 

 of new rootlets. Longer flooding in summer, when the aphids 

 might be most easily destroyed, injures the vines. 



On very sandy soils vines are uninjured by the phylloxera. 

 All sandy soils are unfavorable to the pest and vines on them die 

 more slowly, but to secure complete immunity there must be at 

 least 60 per cent of silicious sand. Sands containing clay or 

 which form lumps offer less resistance. 



JTheJjrapevine Root-borer * 



The larvae of the Grapevine Root-borer feed in the old roots at 

 some little distance from the base of the vine, and as there are 

 no indications of the pest, its presence may easily pass unnoticed. 

 Although not generally recognized as a serious one it has been 

 known as a pest of the grape for fifty years, and has been observed 

 to do considerable damage in Kentucky and West Virginia. 

 Although the vines are not killed, they are so enfeebled that they 

 make but little growth and the crop is much curtailed. All 



* Memythrus polistiformis Harris. Family Sesiidce. See Fred E. Brooks, 

 Bulletin 11CT, W. Va. Agr. Exp. Sta., and Bulletin 730, U. S. Dept. Agr. 



