496 INSECT PESTS OF FARM, GARDEN AND ORCHARD 



fly to neighboring vines. They lay from two to four eggs beneath 

 the loose bark on the old wood and soon die. " The eggs are of 

 two sizes, the smaller and fewer in number yielding males in nine 

 or ten days, and the larger the females of the only sexed generation 

 in the whole life round of the insect. In this last and sexed 

 stage the mouth-parts of both sexes are rudimentary, and no 

 food at all is taken. The insect is very minute and resembles the 

 newly hatched louse of either the gall or root form. After fertili- 

 zation the single egg of the larva-like female rapidly increases 

 in size until it fills the entire body of the mother and is laid within 

 three or four days, bringing us back to the starting point."* The 

 phylloxera has been distributed over the world by infested rooted 

 plants or cuttings bearing winter eggs, and is spread locally by 

 means of the winged females, by the escape of the young root- 

 lice through cracks of the soil and their migration to neighboring 

 plants, or by bits of infested roots being spread in cultivation, 

 and by the leaf-gall lice being spread to other plants by the wind 

 or by being carried by birds or insects. 



Control. The principal means of control lies in the use of 

 resistant vines. These may be varieties which have proven 

 successful in the eastern United States, where the insect is native, 

 or more commonly the stocks of grapes from the Eastern States 

 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 applied at the rate of 125 to 250 

 pounds per acre at a cost of $15 to $25 per acre. It may be 

 applied any time except during the blossoming and ripening of 

 * Quotations from Marlatt, 1. c. 



