28 BULLETIN 1225, U. S. DEPARTMENT OF AGRICULTURE. 
SUMMARY. 
The camphor thrips first appeared in 1912 as an enemy to the newly 
developing camphor industry in Florida. At that time large acreages 
of camphor trees were being planted to produce a commercial supply 
of camphor gum. The tree was also being widely grown for its orna- 
mental value, both individually and in hedges. The thrips appeared 
in enormous numbers when the trees were cut back to obtain wood 
for distillation, and also when ornamental hedges were pruned back 
in conventional shapes. The injury is not confined to pruned trees, 
but much more aggravated cases follow such treatment. 
The thrips collect in large numbers on the stubs of the cut limbs 
and then attack the new shoots as soon as they appear. The buds 
are also attacked in the spring and at other times when new growth 
• appears. By feeding on the buds and tender tips the insects cause 
them to become blackened and die back. Feeding also takes place 
along the limbs, with the result that the bark becomes blackened 
and cracks. Later these injured areas become enlarged by the thrips 
working down into the wood, even causing deformed limbs at times. 
The camphor thrips probably is of Oriental origin, and not native 
to Florida, as was originally supposed. The bay trees of the genus 
Persea were believed for a time to be the native host of the pest, 
but the thrips which lives on the bay trees has been definitely shown 
to be a distinct species. Repeated efforts to rear and establish the 
camphor thrips on bay, avocado, and other closely related trees were 
unsuccessful. Its activities are confined entirely to camphor 
trees. The insect now occurs in practically all parts of Florida as well 
as in adjoining States where camphor trees grow. It reproduces 
rapidly, the generations requiring about 20 days in summer and 40 
days in winter. The adults lay an average of 463 eggs and often live 
for several months. 
The most practical method of control is a changed system of 
pruning the trees. Cutting the trees off at the surface of the ground 
rather than dehorning or cutting away part of the limbs eliminates 
most of the damage. Tins system removes all hibernating places 
of the thrips as well as their source of food. The trees later sprout out 
from the crown and the new growth resulting remains free from 
infestation for several months. 
If done at the proper time, good control can be obtained by spraying 
with the following solution: -| pound of 40 per cent nicotine sulphate, 
2 quarts of potash fish-oil soap, and 2 quarts of lime-sulphur solution 
in 50 gallons of water. Since the thrips have the habit of hiding in the 
cracks and lesions of the bark during cool or cloudy weather it is 
recommended that spraying be done on a bright, sunshiny day. 
The maximum number of thrips will then be found feeding on the 
leaves and buds and other exposed places. This method of control 
will be found practicable only where a few trees are being grown for 
ornamental uses, since the cost would be prohibitive on a commercial 
camphor farm. 
When it is desirable to cut back camphor hedges, a material such 
as shellac applied to the cut ends will prevent their dying back and 
will also prevent the thrips from ovipositing there. 
Infested nursery stock can be fumigated with sodium cyanid at 
