THE CAMPHOR THRIPS. 3 



between the nodes, the cut end invariably died back to the node. 

 In these dead ends injurious fungi and borers developed and often 

 their effect extended beyond the node. 



Plants thus treated are always stimulated to new growth. When 

 this occurred in late fall or winter the trees were not able to resist low 

 temperatures which an unpruned tree could withstand without the 

 slightest damage. The combined effect of the method of pruning 

 and the injury from cold was a great set-back to the growth of the 

 trees, resulting in the dying back of many large limbs and in some 

 cases the death of the trees. 



The camphor thrips was a third obstacle to camphor production. 

 This pest appeared in great numbers on the cut ends and on the new 

 shoots that follow pruning. This new growth appeared to furnish 

 an unlimited food supply for the thrips, which multiplied without 

 any apparent restriction. The effects of the thrips on trees thus 

 pruned was very marked. Plate IV, B, shows a tree attacked by the 

 thrips, following the usual pruning, resulting in the death of many 

 of the limbs. 



To discover means of controlling this pest, preliminary investiga- 

 tional work was carried on by Prof. J. R. Watson {3, 6'), 3 Florida 

 Agricultural Experiment Station, Gainesville, Fla. This work 

 showed that the insect was spread over the entire plantation at 

 Satsuma, Fla., and also indicated that it would be a difficult and 

 expensive pest to control by any artificial means. The seriousness 

 of the situation led Congress to appropriate funds with which to 

 work out some economical method for the commercial control of this 

 pest. The work began as a special project of the Bureau of Ento- 

 mology, with Professor Watson cooperating. After about a year the 

 project was placed under the Tropical and Subtropical Fruit Insect 

 Investigations, where it was continued over a period of two more 

 years. 



HISTORY AND DISTRIBUTION. 



The camphor thrips was first discovered at Satsuma, Fla., in 

 November, 1912, by William 0. Richtman (8), who found the pest 

 spread over the entire plantation and was very much alarmed by its 

 apparent ravages. It has since been found in many parts of Florida, 

 including Orlando, Clearwater, Oneco, Sebring, Daytona, Fort Pierce, 

 and Glen St. Mary, and no doubt may be found in all locations about 

 these places. In fact its range is now known to cover all of Florida 

 except the extreme southern part. Search has been made for it in 

 Dade County but without success, though very few camphor trees 

 are grown in that part of the State. The thrips also occurs on camphor 

 trees in Alabama, Mississippi, and Louisiana, and probably in Georgia, 

 since it has been found close to the Florida-Georgia State line. In 

 all probability the camphor thrips will be found throughout the range 

 of the camphor trees. Camphor trees grown as ornamentals will 

 probably not suffer to any serious extent from the ravages of this 

 pest, but it is quite certain that in hedges which are pruned back 

 at frequent intervals camphor will be severely damaged by the 

 thrips, a fact which may necessitate the abandonment of camphor 

 ^or ornamental hedges. 



8 Figures in parenthesis (italics) refer to "Literature cited," p. 29. 



