BUREAU OF ENTOMOLOGY. 525 



THE PEAB TURIPS. 



The results of the Bureau's studies and experiments in the control 

 of the very destructive enemy of deciduous fruits in California 

 known as the pear thrips were set forth in the last report. It was 

 found possible to destroy a large percentage of the total thrips in a 

 given orchard by spraying with a tobacco and distillate spray in the 

 spring, before the opening of the blossoms. Excellent results were 

 also obtained in the destruction of the helpless pupse in the soil by 

 deep plowing and cross plowing in the fall. 



In the fall of 1909 special attention was given to demonstrating 

 on a large scale the benefits of plowing in the control of this insect, 

 and in the spring of 1910 spraying operations were carried out in 

 several parts of the infested territory. The Bureau's agents had full 

 charge of several orchards or parts of orchards, and in addition 

 acted in a supervisory manner over the work done by a considerable 

 number of orchardists. In this way a large amount of remedial work 

 was accomplished, and the active interest of many orchardists in 

 Santa Clara, Contra Costa, Solano, Sacramento, and other counties 

 has materially strengthened the Bureau's work. Thus, in the terri- 

 tory adjacent to Walnut Creek there were sprayed about 220 acres 

 of pears, 100 acres of prunes, and 30 acres of cherries; in the Suisun 

 territory 200 acres of pears, 190 acres of cherries, and GO acres of 

 prunes; and in the Courtland district 200 acres of pears and 20 acres 

 of cherries; a total in the district to the north of San Francisco of 620 

 acres of pears, 160 acres of prunes, and 240 acres of cherries. 



In the Santa Clara Valley the Bureau's work proper included thor- 

 ough plowing of about 100 acres and the spraying of about 70 acres 

 of orchard. There were plowed, however, under the advice of the 

 Bureau, about 1,650 acres, and in a similar manner 540 acres of 

 orchard were sprayed. This work on the whole has yielded about as 

 successful results as were obtained the year previous. However, the 

 benefits have been somewhat obscured on account of the serious injury 

 to the prune crop by late spring frost. There is, unfortunately, often 

 a tendency on the part ot orchardists to attribute to any injurious 

 insects that may be present the losses resulting from unfavorable 

 weather conditions. It is proposed to take the yield of fruit from 

 sprayed and un^prayed blocks in the orchards under treatment and 

 thus secure definite figures as to the benefits of the work which may 

 be expressed in dollars and cents. 



Along with the demonstration and experimental field work, a con- 

 siderable number of other sprays have been tested as they were sent 

 in by persons believing tliem to be of value or which have been made 

 according to formulas suggested. None of these, however, has proven 

 equal to the tobacco and distillate oil spray mentioned, and this has 

 become the main reliance. Attention has also been given to obtaining 

 additional information on various points in the life history of the in- 

 sect, especially in orchards, as to its migration and ground habits, and 

 its distribution in different types of soil. It seems possible that in the 

 deeper alluvial soils, as in (he Courtland district, the value of thor- 

 ough plowing will be materially lessened for the reason that the 

 larvaj are able to penetrate to a considerable depth and below the 

 reach of plows. Our knowledge of the insect, however, is now very 



