63G ANNUAL REPORTS OP DEPARTMENT OF AGRICULTURE. 



in the infested territory in a way to give the largest amount of 

 assistance to orchardists in the preparation and application of sprays. 

 A largo amount of spraying for the thrips was thus accomplished 

 under the direct supervision of the bureau, aggregating from 10,000 

 to 15,000 acres of orchards. The results indicate that this work has 

 been quite successful, and a large crop of fruit, it is expected, will be 

 harvested from the treated orchards. On the other hand, orchards 

 not sprayed are represented to have very little, if any, fruit on 

 account of the ravages of the thrips. 



In California the insect has not notably extended its range beyond 

 the general territory infested. It is, however, appearing in orchards 

 within this territory in which it was previously not known, and it 

 Avill soon doubtless be uniformly distributed throughout the decidu- 

 ous fruit-growing area in the San Francisco Bay region. 



Unfortunately, the pear thrips has made its appearance in other 

 parts of the country, as in. the Hudson Kiver Valley in New York 

 State, where it was found by the Geneva Agricultural Experiment 

 Station in the neighborhood of Germantown doing injury to pears. 

 The same institution has also determined that the insect occurs in 

 orchards at Geneva, N. Y., and the pear thrips has been discovered 

 by the Bureau of Entomology in several orchards in the vicinity of 

 North East, Pa. Its spread and injuries will be watched with care. 



GBAPE PHYLLOXEEA. 



Satisfactory progress has been made in the investigations in Cali- 

 fornia of the grape Phylloxera. The life-history studies in progress 

 in the laboratory at Walnut Creek, headquarters for the work, have 

 thrown light on several points in the biology of the insect, and some 

 of these have already been verified under vineyard conditions. Thus 

 it has been definitely determined that the winged migrant form of 

 This plant louse is developed in numbers under California conditions, 

 a fact heretofore disputed, which has an important bearing on its 

 dissemination in vineyards. The winged adults have frequently been 

 reared in the laboratory, and the nymphal stage of the winged form 

 has been taken in vineyards and subsequently reared to adult in 

 confinement. 



In the field investigations have been carried out principally along 

 two lines, namely, (1) the collection of information on the history 

 of the Phylloxera in the State and its injuries and spread in the 

 vineyards, and (2) the determination of the relative resistance to 

 the insect of roots of different varieties of grapes, the latter work 

 in cooperation with the Bureau of Plant Industry of this department. 



Under the first heading the inquiry relates to damage done by the 

 Phylloxera alone to vineyr.rds and damage resulting from the com- 

 bined influence of the Phylloxera and other causes, as improper 

 drainage ; the relative freedom from Phylloxera of vineyards grown 

 on various roots ; and the effect on Phylloxera abundance and injury 

 of different cultural methods. 



In the determination of the relative resistance to the insect of 

 the roots of various varieties of grapes, plants are grown in the 

 nursery and also in pots. The pot work permits of more accurate 

 observations of the condition of the vines and of the insects than 

 with plants grown under out-of-doors conditions, and is a valuable 



