Bulletin 232, Truck and Garden Insects


 In the spring of the year, when the aphids are most apt to
 be injurious to watermelons and the vines are small, wind is
 apt to interfere with dusting. To get good control at that season
 it is necessary to construct a hood to cover the plants. This is
 best made with a wire framework over which light muslin cloth
 is stretched. The hood should be of a size to cover the largest
 watermelon plants, and so constructed that when placed over a
 hill it fits closely to the ground. The hood is fastened securely
 to the end of the discharge pipe of the duster. With this hood
 one is independent of the wind, and gets a much better kill of
 aphids with much less dust than when dusting in the open. If
 the watermelons are attacked by aphids when they have reached
 considerable size, such a hood arrangement will not be practical.
 Spraying.-If one does not have a suitable dusting machine
or if it is desirable to spray with bordeaux mixture for fungus
diseases at the same time, he will probably find that the most
satisfactory method of dealing with an outbreak is to spray with
a nicotine compound in bordeaux. He will probably find it cheap-
er to buy the nicotine extract already made, but if a supply can-
not be quickly had when the first signs of aphids appear, it is
better to make his own than to delay action. Tobacco stems and
refuse are placed in enough water to cover them well and kept
at a temperature just below boiling for an hour, or allowed to
soak over night. The solution should then have the color of
strong tea. To keep this more than a day or two, add an ounce
of salicylic acid to each four gallons. Before use it is diluted
with 10 parts of bordeaux.
 A newer insecticide which is used for killing aphids is a
compound of derris. This is used in the same manner and at
about the same strength as 40 percent nicotine sulphate. It is
somewhat cheaper than nicotine sulphate but kills more slowly.
In mixing it with bordeaux it is very important that the con-
centrated liquid be not poured into the tank of bordeaux. Al-
ways dissolve the derris compound in a few gallons of water and
pour this diluted solution of derris into the bordeaux.
 If the grower wishes to spray but does not care to use bor-
deaux mixture he should place a little soap in the nicotine solu-
tion to act as a spreader (see page 11). Derris compounds do
not need a spreader unless the water is very hard.
 In applying the spray use a nozzle of the Vermorel type
with an elbow, and be sure to spray the under sides of the
leaves, because it is there that the aphids are located. For this