Florida Agricultural Experiment Station


 There are several makes of "knapsack dusters" which cost
 ten dollars or more. These are best operated by a man on foot
 who can cover a strip about twenty feet wide by dusting on both
 sides. If there is any wind, it is better to dust only on the lee-
 ward side to avoid inhaling the mixture. It is better to walk
 across the field in a direction at right angles to the wind. A
 large acreage will justify the purchase of a dusting machine. Of
 course with a duster that will throw a sufficient amount one can
 do more efficient work.
 Dusting should be done in the early morning or after a
shower, while the vines are wet. The mixture sticks so well that
much of it remains after a heavy rain. It will be necessary to
redust every ten days or two weeks as long as the caterpillars are
abundant in order to cover the new growth which will have put
out. On the Experiment Station grounds we have never found
it necessary to make more than three applications.
 If half of the caterpillars can be poisoned their numerous
enemies can usually be trusted to destroy a good percentage of
those that escape. In fact these enemies are always the real
controllers of an outbreak. The farmer with his arsenate only
helps them a bit at a critical time. Except in especially favor-
ably located fields, such as small ones near woods, it will not do
to depend entirely upon these enemies. Such a policy may mean
the loss of an entire crop, and will usually mean a reduction in
yield, which will be much more costly than the application of
the insecticide.
 After one or two rains it will be perfectly safe to allow stock
to eat the poisoned vines. As stock is usually not turned in until
the pods are mature, months after the application of the poison,
there can be no possible danger of poisoning the animals even
if there has been no rain meanwhile. All the leaves which were
poisoned will have died and fallen, carrying the poison to the
ground where it soon loses its potency. Usually the pods will
not have appeared at the time the poison is applied and conse-
quently will carry no poison.

 CONTROL BY ENEMIES
 The caterpillars have many natural enemies. One of the
most important is the "rice-bird," also called "blackbird," or "red-
and-buff-shouldered-marsh-blackbird." These collect in great
flocks in infested fields. Other birds, especially mocking-birds,
eat many of the caterpillars. It is probably on account of birds