518 
and the acid arsenates. In those of the 
first group the ratio of lead oxide to ar- 
senic oxide is approximately 3 to 1. In 
those of the second group the ratio is as 2 
to 1. The neutral or ortho-arsenates are 
made by combining lead acetate and so- 
dium arsenate; the acid arsenates by us- 
ing lead nitrate in place of lead acetates. 
The insecticidal value of the various 
brands depends upon the actual amount of 
lead arsenate which is present. 
Concerning the relative value of neutral 
and acid arsenates no reliable experiments 
have demonstrated the superiority of 
either. It is commonly believed that the 
acid arsenates are more likely to burn 
foliage and we have received reports of 
injury from the use of Swift’s which 
would seem to support the inference. 
Manufacturers advise using 3 pounds ar- 
senate of lead to 50 gallons of water. We 
usually recommend 2 pounds, and Me- 
lander, of Washington, recommends to 
drench the trees with a weak solution of 
1 pound to 50 gallons. Recently there 
has been placed upon the market a prod- 
uct known as zinc arsenite, which is said 
to be cheaper and better than arsenate of 
lead. Several growers have reported in- 
jury from this spray and it does not ap- 
pear favorable. We have experimented 
with this spray during the past season 
and found it quite satisfactory. 
Cottony Maple Seale 
Pulvinaria vitis Linn. 
Pulvinaria innumerabilis Rathv. 
General Appearance 
This species can be easily recognized 
in early summer by the large white cot- 
tony egg-sacs which are posterior to the 
brown female bodies. 
Life History 
The eggs are very small, oval, and 
white to yellow in color. They are de 
posited in the large, loose, cottony sacs, 
which are secreted by the females. The 
young first settle on the leaves and later 
move to the limbs. The males appear 
late in the fall to mate and die. In the 
spring the females increase very rapidly 
and after egg-laying shrivel and die. 
There is but one generation a year. 
ENCYCLOPEDIA OF PRACTICAL HORTICULTURE 
Distribution 
Maine to California. 
Food Plants 
Maple, pear, apple, plum, peach, erape, 
sumach, linden, sycamore, locust, beech, 
elm, oak, orange, box-elder, spindle-tree, 
mulberry, alder, hawthorn, lilac, black- 
berry, willow. 
Control 
Kerosene and carbolic acid emulsions, 
or resin wash, applied when the young 
are hatching will aid in reducing the 
coming broods. 
Natural Enemies 
There are many natural enemies, in- 
cluding Rhizobius ventralis, Coccophagus 
lecanit and Encyrtus flavus, which prey 
upon this coccid. 
E. O. Essie 
Curculio 
Anthonomus quadrigibbus Say 
Conotrachelus nenuphar Herbst. 
Two species attack the apple The 
plum curculio and the apple curculio. 
Conotrachelus mnenuphar, Herbst. and 
Anthonomus quadrigubbus, Say. Doubt- 
less the curculio does more injury to the 
apple crop in some of the Central states 
than any other insect except the codling 
moth. It is a snout beetle about one- 
fourth inch long and of a dark grayish 
color. The snout is long and slender and 
may be folded under the body. The beetle 
winters under rubbish or in the soil and 
in early spring begins feeding on the 
opening leaves. After fruit sets it may 
gnaw little holes in the fruit, but it does 
most damage by laying its eggs in the 
fruit, cutting a crescent flap at the place 
where the egg is laid. 
This insect infests the plum, cherry, 
and peach, as well as the apple Com- 
paratively few of its larvae develop in the 
apple but they develop freely in the plum 
and sweet cherry. They develop less 
readily in the sour cherry and peach. 
Since damage to peach, cherry and plum 
often results from the fruit rot fungus 
entering through the wounds made by 
the cureulio. Orchards well cared for 
