126 



companiment of drought in Florida, part of the damage may un- 

 doubtedly be ascribed to the effect of the dry weather. 



The remedies are the same as for the rust of silver mite. The 

 bisulphide of lime is also an effective wash. It can be made very 

 cheaply by boiling together in a small quantity of water equal 

 parts of lime and sulphur. Five pounds of lime and 5 pounds of 

 sulphur, dissolved by boiling, should be diluted to make 100 gal- 

 lons of spray. Gassing is ineffective. (Farmers' Bui. 172; U. S. 

 Dep. of Agr.) 



The Orange Thrips. This insect, a small, yellow, active insect 

 belonging to the order Thysanoptera (popularly known as thrips), 

 scars the fruit and curls and distorts the leaves of the orange. At 

 the present time its control constitutes the chief insect problem con- 

 fronting the citrus growers of the San Joaquin Valley orange belt 

 of California, which winds along the Sierra Nevada foothills, from 

 east of Fresno to south of Delano. This insect, the work of which 

 was first noticed 15 or 16 years ago, has increased in numbers with 

 the growth of the citrus industry and recently has assumed serious 

 economic importance. 



Injury to citrus trees and fruit is caused directly by the feeding 

 of both adults and larvae upon the surface of the parts attacked. 

 This feeding may be on the young fruit, the nearly mature fruit, 

 or the new, tender foliage, and generally takes place on all of these. 

 The injury to foliage is generally on young leaves, but may also 

 occur on the axillary buds. 



The manner of feeding of both the adult and larva of the thrips 

 is identical, and consists in piercing the plant tissues with the sharp 

 mouthparts with which both stages are equipped and then rasping 

 the wound by a rooting motion of the head. The vegetable juices 

 thus liberated from the plant cells are sucked into the alimentary 

 canal of the insect. The characteristic marking or scabbing of the 

 fruit so noticeable at picking time, is started when the fruit is very 

 small just after the petals have fallen from the blossoms. This 

 scabbed area is small at first, but as the fruit grows and the thrips 

 continue to feed the markings deepen and at the same time the area 

 of injury is enlarged. The continued feeding of a large number of 

 thrips results in the scabbing of nearly the entire surface of the fruit. 

 Often the marking is so large and deep over a portion of the orange 

 that it causes the fruit to be misshapen and aborted. Frequently the 

 entire surface is scarred while the fruit is still small, with the result 

 that it ceases to grow and falls from the tree. 



The orange thrips passes the winter in the adult state, and it is 

 generally the adult form which first becomes conspicuous upon the 

 orange trees in the spring. Although no large number of adults 

 has been collected in hibernation, these undoubtedly pass the winter 

 in sheltered places, such as the dead leaves and twigs forming the 

 trash under most orange trees ; they are occasionally found on living 

 plants and on citrus nursery stock in midwinter. 



In view of the success attained in reducing injury to fruit and 

 foliage by the orange thrips, it is believed that it will be possible to 



