APHIDS 55 
BEET 
The Beet Aphis 
Pemphiqus betae Doane 
This is a robust greenish-white or 
white mealy louse infesting the roots of 
the beet on the Pacific coast. When in 
abundance it becomes very injurious, its 
presence being indicated first by wither- 
ing and stunted growth of the leaves. 
The lice attack first the small roots, later 
moving to the main root and causing it 
to become spongy. Agamic winged and 
wingless females occur on the plant the 
vear around and the sexed forms have 
yet to be found. This species also in- 
fests the roots of pigweed, dock and kin- 
dred plants. The only Known remedy is 
to discontinue for at least one year plant- 
ing beets on infested land and to de- 
stroy the wild host-plants. 
The Beet-root Aphis 
Tychea brevicornis Hart. 
This occurs in Colorado on the roots of 
beets and may be controlled by the dis- 
continuance of planting beets on infested 
land until such time as is required for 
the lice remaining in the soil to die of 
starvation. 
The California Beet-root Aphis 
Trifidaphis radicicola Essig 
The food-plants and control of this 
species are similar to that of the Beet 
Aphis. 
CUCURBITOUS CROPS 
The Melon or Cotton Aphis 
Aphis gossypii Glover 
This aphis inhabits a large variety of 
plants including cotton, orange, straw- 
berries and most of the Cucurbitacex. Its 
life history is yet imperfectly known. In 
early spring it migrates from various 
weeds and shrubs to cultivated plants. 
Later migrations follow during summer 
and fall. The progeny of the migrant 
lice settle in colonies on the under side 
of the leaves of the cucurbits and soon 
cause considerable curling. Control 
measures should be initiated as soon as 
the pest makes its appearance. Under 
spraying the foliage with oil emulsions 
or tobacco extracts is often satisfactory 
or the plants can be fumigated with 
carbon hbisulfid or tohacco paper. The 
carbon bisulfid should be evaporated un- 
der a tub or similar tight-fitting recep- 
tacle placed over the plant. A dram of 
liquid may be used for each cubic foot of 
space The plants can be fumigated suc- 
cessfully by burning tobacco paper under 
a canvas frame fitted over the plant. 
The amount of tobacco paper to be used 
varies with the cubic measurement of 
air space under the frame. If the leaves 
are badly curled fumigation is prefer- 
able to spraying. 
COTTON 
Two species of plant-lice occur on 
young cotton plants. These are the 
Melon or Cotton Aphis (Aphis gossypii 
Glover) and the Bur-clover Aphis (Aphis 
medicaginis Koch). Both are small black 
or dark brown species and inhabit nu- 
merous weeds, migrating thence to the 
cotton plant. The best means of con- 
trol lies in the prevention of the lice 
from reaching the cotton and this may 
be done by ridding the fields of weeds. 
If melons are planted near the cotton 
they will prove a continuous source of 
infestation. 
CORN 
The Corn-root Aphis 
Aphis maidi-radicis Forbes 
This aphis is a small bluish-green 
mealy species. Besides corn it infests 
sorghum, broom-corn, cotton and grasses. 
The eggs are laid in the late fall in ants’ 
nests, the egg-laying females having been 
earried thither by the ants. The young 
hatching in spring attack the roots of 
grasses, later migrating to cultivated 
plants. As the Corn-root Aphis is chiefly 
troublesome where corn has been planted 
on the same ground for several years in 
succession, a rotation of crops will greatly 
check its ravages. Fertilizing the land 
with barnyard manure will help the corn 
to withstand injury, and deep plowing and 
harrowing in winter will destroy the ants’ 
nests in which the winter eggs are stored 
besides getting rid of the ant protectors. 
The Corn-leaf Aphis 
Aphis maidis Fitch 
With the exception of the cotton plant 
this species has the same range of food- 
