FLORIDA STATE HORTICULTURAL SOCIETY 
53 
preference of feeding grounds is some¬ 
what different from that of the young 
thrips. They require about two weeks to 
complete their growth. 
CONTROL 
The most efficient insecticide, all things 
considered, is a combination of lime sul¬ 
phur and tobacco. Soap and tobacco will 
kill the thrips fully as well, but because of 
its greater value against rust mites and 
red spiders, which are often beginning to 
increase about blossoming time, the lime 
sulphur is preferable. 
Lime sulphur alone is not an efficient 
insecticide for the Florida flower thrips. 
I want to emphasize that point, for not a 
spring passes without some one breaking 
into print with a recommendation of 
straight lime sulphur for this thrips. This 
idea originates, I think, from the publi¬ 
cations on the California orange thrips. 
The latter is not only a different species 
from ours, but belongs to a different 
genus as well, and is a smaller and more 
delicate insect. 
On the other hand, tobacco alone is not 
an efficient agent unless used at a con¬ 
centration which makes it very expensive. 
As to the amount of tobacco, we have 
found that in combination with lime sul¬ 
phur solution at the ordinary rust mite 
strength, i. e., 1165 or 70, a full pint (13 
oz.) of nicotine sulphate is necessary for 
efficient killing. By increasing the 
strength of the lime sulphur to 1140 the 
tobacco can be cut to 10 oz. And this is 
a cheaper formula as well as a more ef¬ 
fective one against citrus scab. 
As to the best time to spray, the ex¬ 
perience of the past two years has 
strengthened our former recommendation 
to spray into the full bloom, i. e., when the 
maximum number of blossoms are open. 
It is, however, better to be a day or two 
early rather than a day or two late. 
Our experience has been that in the 
hands of most spraying crews better kill¬ 
ing is secured by the use of a spray gun 
than with a rod and nozzle. The driving 
force of the discharge from a spray gun 
is more likely to force the liquid into the 
interior of the blossom, behind the column 
of stamens where thrips are most numer¬ 
ous. 
DUSTING 
In co-operation with Mr. W. W. Moth¬ 
ers some experiments were started this 
spring to test the practicability of control- 
ing thrips by the use of dusts consisting 
of lime impregnated with nicotine sul¬ 
phate. Three different strengths were 
tried containing respectively 2.2, 5 and 
10% of nicotine sulphate. Wherever this 
material was driven into the blooms with 
sufficient force to penetrate behind the 
column of stamens the thrips were killed. 
The killing was fully as thorough as with 
spraying and as high with the 2.2% ma¬ 
terial as with the 10%. But in blossoms 
exposed only to the drifting cloud of dust 
the penetration was not as thorough as 
could have been desired and a large pro¬ 
portion of the thrips escaped. It was es¬ 
timated that between 50% and 60% of 
the thrips were killed as compared with 
85% or 90% in the case of thorough 
spraying. It is as yet too early to form 
any reliable conclusions as to the practi- 
