12 



HOW TO CONTROL THE PEAR THRIPS. 



oil emulsion Avith commercial tobacco extract No. 1, added at the 

 rate of 1-60, and the cost of the three applications was $157.38, the 

 labor required in spraying being three men at $2 per day and one 

 team at $2.50 per clay, making a total of $8.50 per day, or a total of 

 $51 for the six days; gasoline for the engme cost $2.40; plowing and 

 cross plowing the previous fall, $26.65, making a total cost of $237.45 

 for the combined treatment of plowing and spraying the 5J acres, or 

 $44.54 per acre, an average of $0,449 per tree. 



The yiel4 from this plat was 45 tons of green prunes, making an 

 average yield of 8.44 tons per acre, or 155.17 pounds per tree. The 

 prunes when dried averaged 54 to the pound, giving a commercial 

 value for the plat of $1,710, or a value of $320.82 per acre, or an 

 average of $2,948 per tree, as the prunes were sold on a 2i-cent basis 

 for dried prunes averaging 80 to a pound. 



Plat II. — The rest of the orchard, comprising 10§ acres, and which 

 onlv had the plowing and cross plowing in the fall of 1908, at the cost 



Fig. 7.— Diagram showing yield in green prunes per acre upon the sprayed, plowed, and check blocks, 

 Landon prune orchard, 1909: a, Sprayed and plowed, 367.93 boxes, value $320.82 x)er acre; b, plowed 

 block, 85.65 boxes, value $74.85 per acre; c, check block, 7 boxes, value $6.65 per acre. (Original.) 



of $5 per acre, or $0,046 per tree, yielded 21 tons of green prunes, or 

 an average of 1.97 tons per acre, or 36.45 pounds per tree, giving a 

 commercial value of the plat as $798, or a value of $74.85 per acre, 

 averaging $0,692 per tree. 



Plat III, checlc. — This plat, embracing 5 acres of the prune orchard 

 belonging to Mr. F. Cottle, and immediately adjoining the Landon 

 orchard and of the same kind of soil and with similar trees in regard 

 to size and pre^dous care, received no treatment for thrips. The total 

 yield was 1,750 pounds of green prunes, or an average yield of 350 

 pounds per acre, or 3.24 pounds per tree, representing a commercial 

 value of $33.25 for the plat, or an average of $6.65 per acre or $0.06 

 per tree. The yield and value per acre upon the three plats is shown 

 diagrammatically in figure 7. 



The average gain per acre upon Plat I was obtained after adding 

 the total cost of treatment per acre to the value of the crop per acre 

 from the check plat, and subtracting that amount from the value of 



