, HOW TO CONTROL THE PEAR THRIPS. 19 



In the letter giving the results upon which these itemized figures 

 are based, ^Ir. Swett continues: 



The results from sprajdng on prune trees were very marked. Owing to cross limbs 

 we could not use the tower in sprapng the prune orchard. The crop was protected 

 only up to the distance from the ground that could be reached by the spray rods. 

 We wet the tops of the trees as best we could, but could not drive the spray into the 

 bud and flower clusters directly from the nozzles. Anyone can tell where the rods 

 reached, for above the line there is no crop, and below that line the limbs mostly 

 have to be propped. 



CHERRIES, SACRAMENTO COUNTY. 



A good demonstration showing the possibility of control and the 

 commercial advantage by spraying cherries was given by Ish. T. W. 

 Dean, near Courtland, Cal. Mr. Dean has about 1^ acres or 180 trees 

 in bearing, which were sprayed upon an average four times in the 

 spring of 1910 (some of the trees sprayed five times and the remainder 

 onh' three times). The cost of tlie spraying was approximately $90, 

 or 50 cents per tree. !Mr. Dean shipped 1,362 boxes of cherries from 

 the 180 trees, or 7.56 boxes per tree, which, at a net value of $1,196 per 

 box, gives a return of $1,619.95, or $8.99 per tree. 



Sixty-five trees belonging to ^Mr. I. G. Doty and immediately 

 adjoining the above orchard were not sprayed. The 65 trees gave a 

 yield of 43 boxes, a\^eraging practically two-thirds of a box per tree, 

 or a cash value of $0,798 per tree. Adding this to the cost of spray- 

 ing, 50 cents per tree, gives $1.30 as the amount to be deducted 

 from the value of the crop per tree in the sprayed orchard. The 

 difference is $7.49 per tree, or approximately $898.80 per acre, 

 the net gain due to spraying paying over 1 ,400 per cent on the 

 investment. 



RECOMMENDATIONS. 



Spraying is by far the most satisfactory means for controlling the 

 pear thrips on all classes of deciduous fruit trees in C'alifornia. 

 However, to spray successfidly involves an entirely different concep- 

 tion of the operation than as ordinarily practiced against other orchard 

 insects. Only the most efficient spray materials should be used, 

 namely, the combination of distillate-oil emidsion and tobacco extract 

 or distillate-oil emulsion and nicotine solutions. The spraying must 

 be thoroughly done and put on the trees wdien the thrijis appear in 

 numbers, not waiting till many buds have been destroyed. It is 

 strongly advised to use power machines, and growers are urged to 

 use them for all the spraying, and to have a tower platform elevated 

 over the tank so that one man can thoroughly drench the tops of the 

 trees. Figures 6 and 1 1 show two good types of power outfits at 

 work. It is absolutely necessary to use high pressure — from 150 to 

 200 pounds — and only angle nozzles should be employed, and these 



