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 
