REPORT OP COMMITTEE ON PUBLICATION 175 



larger acreage of vines planted. In addition to the two insects mentioned, 

 there are some half dozen other species which do injury in some sections 

 and in certain years. 



THE PHYLLOXERA. 

 Phylloxera vastratrix, Planch. 



The phylloxera which is an insect native to the United States east of the 

 Rocky Mountains, was introduced from that section into France and from 

 France into California. Since it is in California that most of the vinifera 

 vines occur, it is here the phylloxera has done greater damage than elsewhere 

 in the United States. This damage has occurred chiefly in the Coast counties 

 as its spread has been much more rapid there than in the interior valleys. 

 This difference in the rate of dispersion is due, no doubt, to the fact that in 

 the interior valleys the winged form seldom, if ever, occurs, while in the 

 Coast sections the winged form is common. The spread is also more rapid 

 in heavy soils than in sandy soils, and in soils having a high percentage of 

 sand the vines may be much more resistant or practically immune. 



The phylloxera is a minute sucking insect which does injury by feeding 

 upon the roots of the grape. The injury, however, is not due so much to the 

 nourishment taken from the vine as to the decay which follows the feeding. 

 This decay occurs much more seriously on the vinifera vines than on the 

 wild or American vines. 



The life history of the phylloxera is somewhat complex where all the 

 forms of the insect occur. In the Eastern States the most evident indication 

 of phylloxera infestation is represented by the galls on the under side of the 

 leaves. 



These leaf galls seldom, if ever, occur in California. A colony may arise 

 from a single egg which has over-wintered on the rough bark of the two-year- 

 old wood. While this winter egg has not been actually observed in Cali- 

 fornia, the much more rapid spread of the insect in the coast sections, where 

 the winged form occurs, can scarcely be accounted for unless the winter 

 eggs are laid. Upon hatching, the insect makes its way to the leaves, and 

 becomes a gall maker where it gives rise to a new generation of egg-laying 

 root-feeders. In California, where the gall form is not found it is 

 probable that, in case the winter egg actually occurs, that the insect arising 

 from this egg goes directly to the roots. Generations of this form follow one 

 another throughout the growing period of the vine until there is a total of 

 probably seven or eight. In the interior valleys, this root-feeding form is 

 practically the only form which occurs. In midsummer and later, some of 

 the eggs deposited by the root-feeding form develop into nymphs which 

 finally acquire wings, emerge from the soil, and form new colonies from 

 eggs deposited on the under side of the grape leaf. The eggs from a single 

 individual number from three to six and they are of two sizes, the smaller 

 of which produce the males. The females arising from the larger eggs, after 

 fertilization, move to the rough bark of the two-year-old wood and deposit 

 the single winter egg already referred to. 



There have been four principal methods adopted for the control of the 

 phylloxera, namely: 1, injection of carbon bisulphide; 2, flooding; 3, planting 

 in sand; 4, planting vines grafted into resistant stock. The T^st of these 



