THE PEAR THRIPS IN CALIFORNIA. 



17 



1910, and they did not accomplish much injury in the Santa Clara 

 Valley, but larvae were present in large numbers everywhere and 

 riddled the foliage (fig. 4) and weakened the fruit stems, making the 

 financial loss amount to about half as much as in 1910. 



In regard to varieties, Imperial prunes seem to be attacked first 

 and injured, on the whole, more severely than French prunes in the 

 Santa Clara Valley. This may be explained in several ways: For 

 one thing, the acreage of this variety in the Santa Clara Valley is 

 much less than that of the French prunes and the blossoming period 

 is usually about a week or more earlier; then, too, the small develop- 



Fig. 4. — Prune foliage riddled by pear thrips larvae. (Original.) 



ing fruit stems of the Imperial prunes seem to be more tender and 

 not so able to withstand the attacks of the thrips as are those of the 

 French prunes. Sugar prunes, which blossom at a period interme- 

 diate between the blossoming periods of Imperial and French prunes, 

 are, from a financial standpoint, not injured so greatly as are either 

 of the other varieties. This is partly due to the fact that this variety 

 sets an unusually large amount of fruit and is therefore able to with- 

 stand the loss of a considerable portion of it and still produce a fair 

 crop. The scabbing of the prunes on this variety, however, is often 

 so deep as to cause a large exudation of gum and to render a large 



73390°— Bull. 173—15 3 



