THE PEAR THRIPS IN CALIFORNIA. 



15 



gained entrance into the bud cluster early in the season, and were left 

 unmolested, the entire cluster was sufficiently injured to prevent the 

 appearance of a single blossom. In 1909 there was greater evapora- 

 tion, comparatively little of the characteristic bleeding showed at the 

 tips of the buds, and far less of the blue molds appeared in any place. 

 Also the thrips came out of the ground more slowly than in 1910. The 

 latter year thrips were held back to a slight extent by cold wet weather, 

 but once the emergence from the ground commenced, thrips came very 

 rapidly. Then, too, they were more 

 numerous throughout the entire 

 section in 1910 than they were the 

 previous year. 



The serious nature of this insect 

 can be understood when it is re- 

 alized that in a badly infested pear 

 orchard it is far more usual to find 

 from 75 to 150 and often as high as 

 200 thrips to the cluster than only 

 10 to 15. Any spraying to be effec- 

 tive must be done before these thrips 

 have remained long, in numbers, 

 inside the bud clusters. A delay 

 of four or five days in spraying the 

 badly infested orchards in the spring 

 of 1910 meant the loss of the entire 

 crop, and in many cases a delay 

 of two to three days for the first 

 application meant a loss of more 

 than half the crop. 



In the ability completely to de- 

 stroy the crop the adult is of more 

 importance than the larva, and in 

 many large orchards the destruction 

 of the developing fruit buds by the 

 adults has been so complete that 

 by the time the trees would normally come into bloom there was left 

 no possibility for a crop of fruit. The larva, together with the 

 injury which has been caused by the deposition of the eggs by the 

 adult, can lessen the prospects of a good crop of fruit after it has appar- 

 ently set. To secure the best results it is always desirable first to 

 apply efficient treatment against the adult hi order to reduce the 

 early injury to a minimum so that the trees may bloom, and later, 

 to make additional treatment against the larva?. This will usually 

 result in increasing the value of the crop from 10 to 25 per cent for 



Fig. 3.— Work of the pear thrips on pear at San 

 Jose, Cal. (Original.) 



