4 DECIDUOUS FRUIT INSECTS AND INSECTICIDES. 



well along before enough thrips have appeared to become especialh' 

 injurious. Many instances can be cited where thrips were especially 

 numerous on almond trees, often as many as 25 or 50 inhabiting a 

 single blossom, and yet the trees set and matured a full crop of nuts. 

 The insects did not have an opportunity to attack the opening buds, 

 and after blossoms were open they preferred the nectarv' glands on 

 the inside of the calyx cups. They did not, apparently, relish any 

 other parts of these particular blossoms, and the pistil, stigma, and 

 young fruits were not attacked. Stamens were weakened, for they 

 arise from the rim of the calyx just above the place where the insects 

 find their enticing food, but the pollen had already ripened and had 

 been shed. Thrips can be found as numerously on almonds as on any 

 •other variety of affected trees, but there is a large, newly exposed leaf 

 and blossom surface, and the greatest danger period is passed before 

 the insects arrive. For these reasons the trees are able to support 

 many thrips without the amount or the quality of their fruit being 

 appreciably affected. 



The peach, especially the Muir and the Nicols' cling varieties, 

 suffers as much as other fruits, but the acreage in the Santa Clara 

 Valley is not large as compared with that of the prune, for instance; 

 consecjuently the damage has not been so marked. The period of 

 opening buds and blossoms occurs just at a time to permit of thrips 

 entering them from their earliest development. The swelling bud 

 pushes apart its outer winter protecting scales and thrips immediately 

 force a way in. The insects feed on the tender, closely plaited tips 

 of petals, wdiich are readily killed. They force an entrance between 

 calyx lobes and petals, feeding as they go, and soon reach and attack 

 the very small and fragile blossom stem. This is soon destroyed. 

 Later the blossoms wliich may have escaped the early injury are 

 attacked from witliin, the thrips feeding on the inner flower parts. 

 The piercing and rasping manner of feeding is very disastrous to ten- 

 der plant tissue, and fatal injury can be effected by a very few move- 

 ments of the powerful mouth cone with its armed tip. The writer 

 has often examined peach trees which had but recently been attacked 

 by thrips and found that almost every blossom would fall out from 

 its cluster of scales when the limbs were gently tapped. Badly 

 infested peach trees do not bloom at all. 



Apricot blossoms are similar to those of the peach and are injured 

 in the same way. 



The thrips is at its worst on trees of the second group, which 

 includes the pear, prune, cherry, and apple. These fruits bloom 

 later, which permits the gathering of thrips in numbers before 

 buds are at all advanced. The writer has found thrips on cherry and 

 prune trees waiting, as it were, for. the buds to open, and he has found 

 as many as 75 individuals in a single blossom which opened prema- 

 turely early. A thrips enters a prune bud through the tip and forces 



