TRESS BULLETIN No. 62. January io, 19o7
Agricultural Experiment Station
SOME SUGGESTIONS ABOUT WHITEFLY.
BY DR. E. W. BERGER.
The exceptionally low temperature at Christmas time of 1906.
has resulted in a partial or complete defoliation of citrus trees in
some northern sections of Florida, and this fact again brings up ques-
tions of whitefly control under such circumstances.
In trees and groves where the friendly Fungi (the Red, Yellow
and Brown) parasitic upon the whitefly are found in abundance, it is
advised to collect large quantities of the dead leaves still clinging to
the trees, or fallen leaves, with plenty of fungus upon them. These
should be dried and stored, since the fungus may be useful for again
starting it in the trees and groves next spring. Methods for intro-
ducing the Fungi by spraying the spores suspended in water on the
leaves of trees infested with whitefly, or by pinning on leaves, have
been developed (see Bulletin 88, now in press. The Fungi when
dried have been found to retain their vitality for two months, and
further observations may extend this time. Should the leaves with
fungus collected prove useless by the time that they are required,
little labor will have been lost. Specimens sent to the Station at
the proper time will be gladly tested for their vitality.
LIFE HISTORY FACTS.
During December, January and February there are probably but
few if any unhatched eggs or adults of the whitefly; all are in the
young scale-like stages and live attached to the under surface of the
leaves. They are easily killed by spraying while in these stages,
provided, of course, that the spray comes in contact with them. Dry-
ing the leaves will kill them, hence all the young insects upon leaves
dropt by freezing will die, with the possible exception of those nearly
matured. For the latter reason all dead and dropt leaves should be
destroyed, plowed under or burned, excepting those wanted for the
Fungi on them.
COMPLETING THE WORK.
Now, in view of the fact that freezing has begun the work of
defoliating, it appears desirable to complete it, or to take advantage
of the reduced number of leaves and spray with the determination to
kill every remaining whitefly larva upon the tree; even going to the
extent of using a spray sufficiently strong to complete the defolia-
tion. One drastically thorough spraying at any time is bet-
ter than several less thorough ones. Spraying, furthermore,
cannot be made effective unless all co-operate. If but few green
leaves remain upon a tree it is advised to complete defoliation by
trimming. If, to complete defoliation, spraying is adopted, this
should be done at once before the new buds start.
While in the above the writer has emphasized spraying, yet he
does not for a moment desire' to leave the impression that he is an
unqualified supporter of spraying for the whitefly. On the contrary,
he considers spraying only in the light of an expedient, a makeshift,
and firmly believes that the solution of the whitefly problem is closely
bound up with whatever success we can achieve in devising sure and
ready methods for introducing the Fungi and other parasites. In
other words, the solution of the fungus problem will be the solution
of the whitefly problem, and it is believed that the solution of each is
at hand. The reader is again referred to Bulletin 88, which will be
ready for distribution in a few days.
For more complete spraying directions see Bulletin 76 of this
PLANTS TO CONDEMN.
It is also pertinent to the subject in hand to emphasize the ne-
cessity for destroying all unnecessary breeding places of the whitefly.
Under this head belong the following trees: Cape jessamine, privet
hedges, all useless and abandoned citrus, chinnberry and umbrella
trees, viburnum nudum, and the mock orange (cherry laurel) when
infested. Of these the cape jessamine may be defoliated, but the
work must be complete. All the others should be cut down and
burned. During summer these trees are such prolific breeding places
for the whitefly that the latter becomes scattered far and wide,
DEPARTMENT OF ENTOMOLOGY.
State papers please copy.