16 HOW TO CONTROL THE PEAR THRIPS. 



Plat A, which produced 16,254 pounds of green prunes from 300 

 trees, gave a crop value of S528.255, or $1.7608 a tree, or $190.08 an 

 acre. 



Plat B, which yielded 1,032 pounds of green prunes from 98 trees, 

 gave a crop value of $30.96, or $0,315 a tree, or $34.02 an acre. 



Plat C, which yielded 860 pounds of green prunes from 1 ,080 trees, 

 gave a crop value of $25.80, or $0,024 a tree, or $2,592 an acre. 



Cost of spraying. — As 3,800 gallons of diluted spray material were 

 used for all three sprayings upon Plat A, the total cost at $0.01625 

 per diluted gallon would be $61.75. The labor and gasoline cost 2 

 cents a tree, each application, for the 300 trees, or a total of $18. The 

 total cost of the spraying was $79.75, or $0,265 a tree, or $28.78 an 

 acre for the three applications. 



Gain due to spraying. — The gain due to the spraying would be ob- 

 tained by adding the value of the crop per tree on Plat B to the cost 

 of the spraying and subtracting the product from the value of the 

 crop per tree of Plat A. This gives a gain due to the spraying of $1.18 

 per tree, or $127.44 an acre. 



Other Demonstrations. 



In cooperation with or working under the advice of the Bureau of 

 Entomology, several fruit growers in Santa Clara, Contra Costa, 

 Solano, and Sacramento counties during 1910 gave thorough treat- 

 ment to portions of their orchards and left similarly infested areas 

 untreated without any protection from thrips injury. Many of these 

 demonstrations were highl}^ successful, but for lack of space only two 

 of these are recorded herein in some detail. These results show very 

 conclusively what can be done by the individual growers if the right 

 material is properly applied in time to kill the thrips before the buds 

 have been destro3'ed, and that the treatment will increase the yield 

 and value of the crop, frequently paj'ing several hundred per cent 

 on the investment. 



PEARS, CONTRA COSTA COUNTY. 



An orchard consisting of about 5^ acres of Bartlett pears belonging 

 to John Swett & Sons, in the Alhambra Valley, near Martinez, Cal., 

 had been badly damaged by tlirips for tliree years, causing almost 

 total failure of crop. 



In the spring of 1910 Air. Frank T. Swett had 550 of the trees 

 sprayed twice for adults, and a portion of these received a third 

 application or larval treatment. All spra34ng consisted of the rec- 

 ommended material (commercial tobacco extract No. 1 diluted 1 part 

 to 66 in 3 per cent homemade distillate-oil emulsion) put on the trees 

 with good pressure, using gasoline-power outfit with 8-foot tower, 

 thus enabling one man to cover thoroughly the tops of the trees and 



