THE CAMPHOR THRIPS. 25 



height of from 5 to 7 feet. They also appeared thrifty and vigorous. 

 During the first three or four months after pruning no thrips were 

 found nor any evidence of their presence. Very little damage was 

 done to either the buds or branches during the first six months after 

 pruning. After the expiration of more than a year there was some 

 evidence of their presence, but the injury from them was so slight as 

 to be of no importance whatever. Their presence in such small 

 numbers has not interfered with the development of the trees in the 

 least. 



On this 10-acre block a great variety of tree-wound paints, var- 

 nishes, grafting waxes, and wood preservatives were used. None of 

 these were of any value whatever in preventing reinfestation by 

 thrips or in assisting the tree to produce more vigorous sprouts. In 

 fact, the two rows treated with the wood preservative were 

 injured to a considerable extent and did not send out shoots until 

 several months after the untreated trees or those treated with other 

 materials. 



Additional experiments were conducted at Orlando to determine 

 the effect of pruning at different times of the year on the growth of 

 the trees and also to observe the relation of such pruning to the 

 increase of the thrips. Thirteen rows of camphor trees averaging 

 about 4 feet in height and planted in the form of a hedge were used 

 for this experiment. One row was left unpruned for a check. Each 

 month for a year, beginning in October and ending in September, 

 one row was pruned. One-half of each of the pruned rows was cut 

 on the level of the ground and one-half was cut exactly 1 foot high. 

 Observations made throughout the year showed very plainly that 

 those trees cut at the level of the ground during the winter months 

 put forth much more vigorous and extensive growth than those cut 

 the same way during the hot spring and summer months. The row 

 of trees pruned during December seemed to have better growth than 

 those cut during any other month of the year. At the end of a year 

 all those trees pruned during the previous winter months had attained 

 the same height that they were before being pruned to the ground 

 and looked as well as the check row which was unpruned. The trees 

 pruned during the summer did not attain the same height during that 

 year but they came back in reasonably good shape also. 



The half rows cut 1 foot from the ground gave results similar to 

 those cut to the ground. The experiment showed that the winter 

 months are unquestionably the best time to prune the trees. The 

 trees pruned in the winter put forth much more vigorous growth and 

 the growth came much sooner after the pruning than on those trees 

 pruned during the summer. In this case the rows pruned during 

 January and February were superior to those pruned during any 

 other month. On the rows pruned during the hot summer months 

 the sun scalded the exposed leaves and also killed the new shoots put 

 forth from the cut ends. Hence there was little new growth until 

 fall. 



Although there was an abundance of thrips on the unpruned 

 check throughout the year, except perhaps during March and April, 

 no insects or injury were ever observed on the young growth on any of 

 the trees cut at the level of the ground. The thrips, however, did 

 much damage to the trees pruned 1 foot high. The injury was most 

 severe on the half row pruned during the month of October, but there 



