HOW TO CONTROL THE PEAR THRIPS. 



13 



the yield per acre upon Plat I. This gave a net gain of $269.53 per 

 acre as returns upon an investment of $44.54, or a gain of about 600 

 per cent. The gain upon this plat due to the spraying alone was 

 $199.88 per acre, or $1.85 per tree. 



Plat II, which received only the plowing and cross plowing, gave, 

 after adding the cost of the treatment to the yield per acre upon the 

 check plat and subtracting the total from the yield per acre upon 

 Plat II, a gain of $63.20 per acre for an investment of $5, or about 

 1,200 per cent on the investment. 



Owing to the lateness of the third application on Plat I, the larvae 

 caused considerable scabbing on the fruit, and the difference in 

 quality of the fruit from Plat I and Plat II was not as great as would 

 have been the case had the larval application been applied a few days 

 earlier. 



Results, 1910. 



During the fall of 1909 part of the orchard was irrigated and the 

 entire 1 6 acres were plowed to a depth of 8 inches in November. One 

 small block was cross plowed. The entire orchard was harrowed 

 several times after the plowing. 



Plowing Results. 



Soil samples were taken in similar cages as in the previous year and 

 yielded the following results: 



The average percentage of thrips killed by one plowing was 71 per 

 cent and the average number killed by plowing and cross plowing 

 98 per cent. 



No spraying was done in 1910, except a few trees for other experi- 

 ments. 



Results. — All of the trees on the 16 acres came into heavy bloom, 

 but only the 580 trees of Plat I and one block of about 80 trees which 

 was sprayed for larvae in 1909 set a heavj'^ crop, as many thrips were 

 present in the rest of the orchard. The trees sprayed in 1909 were 

 stronger, and so many of the thrips liad been killed by the treatment 

 that the accumulative results showed almost as great a difference in 

 the crop yield for 1910 as was the case in 1909, when the spraying was 

 actually done. 



