FLORIDA STATE HORTICULTURAL SOCIETY. 
61 
sible, there will be no risk from that 
source. I hope to spray some grove 
this fall, late, and determine this point. 
Some grower may do that himself. 
Mr. Temple: I would like to ask 
Mr. Yothers, and also Dr. Berger, if 
he is here, as to the latest opinion as 
to what percentage, or in what multi¬ 
plication each brood of whitefly in¬ 
creases over the parent brood; that is 
to say, originally we were informed 
that each brood of the whitefly was 
multiplied in the next brood by two 
hundred. In other words, the female 
laid two hundred eggs. That was aft¬ 
erwards cut down until the latest they 
were figuring on was a multiplication 
of twenty-five to one in each brood, 
and that there was at least four well- 
defined broods, and two scattering 
broods, with an average of about five 
to one. What is the multiplication, 
and what power have you raised it to? 
Mr. Yothers: So far as I know, we 
note only three well-defined broods in 
Orlando. Of course there are adults 
all the time that are laying eggs inter¬ 
mittently. This year there will be 
adults from the first of June until prob¬ 
ably the first of September. I think 
we have it about right when we say 
each female lays from 150 to 200 eggs, 
but nearly all of these die before ma¬ 
turity. I should say about twenty-five 
reach maturity. 
Because the fly does increase so 
enormously is the reason why I stated 
it does not mean very much to kill 95 
or 96 per cent, where there is a bad 
infestation. Consequently, I predict 
all these groves we have sprayed, if 
nothing more is done, in September or 
October will be just as black as though 
they had not been sprayed. This is 
rather a sweeping statement. They 
may not be so bad, but I feel that they 
will. Consequently, if anybody expects 
to spray I do not see how they could 
get along without two sprayings, es¬ 
pecially if one is done in winter or early 
spring. They might get along with 
one spraying done late in the summer. 
Mr. Temple: Your Orlando figures 
show about twenty-five raised to the 
third power. That is a good many 
from one fly. 
It seems to me the most excellent 
agent for the extermination of the 
whitefly is some spraying material that 
will remain effective for three or four 
months on the leaves and during that 
time will be working towards the ex¬ 
termination of the fly. The great trou¬ 
ble with fumigation is that unless you 
kill 100 per cent, of the fly, you might 
just as well let it alone, because, with 
twenty-five raised to the third power, 
if you kill 99.9 per cent, with fumiga¬ 
tion, with that one-tenth left alive, and 
multiplied to that extent, you are go¬ 
ing to be worse off in the fall than you 
were in the spring. 
One of my groves was fumigated in 
February, and it was the smuttiest 
grove I had in the fall. While we were 
supposed to have killed ninety-nine and 
a fraction, that little fraction, owing 
to its rapid multiplication, gave us 
more fly in the fall than we had in Feb¬ 
ruary. 
Mr. Yothers: I do not think, Mr. 
Temple, that you can ascribe the entire 
