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; MEXICAN BEAN BEETLE IN THE SOUTHEAST. 49 
on the numbers of beetles present and the damage done. Another 
effective dust is composed of a high grade of calcium arsenate diluted 
with 9 parts of hydrated lime. A mixture of high-grade calcrum 
arsenate 1 part, fine dusting sulphur 1 part, and hydrated lime 4 parts 
also is effective and may be substituted for magnesium arsenate when 
the ingredients are readily available to growers. 
On bush beans drilled in rows 3 feet apart, dust should be applied 
at the rate of 15 pounds or a little less per acre. Dust should be 
applied when there is no wind blowing and to the under surface of 
the leaves. Dew is not essential, but best atmospheric conditions 
usually occur when dew is on the plants. 
On small plantings up to 8 acres in size a knapsack type of hand- 
bellows duster with tube attached to a flexible hose gives best results. 
On larger plantings up to 5 to 10 acres, a 2-row duster with nozzles 
arranged to direct the dust to the under surface of the leaves should 
be used. One dusting to the row is sufficient except in very heavy 
infestations, when each row should be dusted from both sides. On. 
larger plantiags a power or traction 4-row duster is necessary. Beans 
should be planted in straight rows and at equal distances apart for all 
control operations where two or more rows are treated at once. 
Where the beetle is numerous, bush beans should be planted. 
Pole beans mature too slowly and require too many applications to 
make control practicable. | 
ae = - —~ 
SUMMARY. 
The Mexican bean beetle is the most serious insect enemy of edible 
beans in the portions of the United States which it inhabits. It has 
long been present in the Southwest, and within the last few years 
has made its appearance in the Southeast. At the close of 1922 the 
infestation included portions of seven States in that section, including | 
Alabama, Georgia, Kentucky, North Carolina, South Carolina, 
_ Tennessee, and Virginia. It is spreading northward rapidly and, as 
it is capable of long flights, may, in the course of a few years, extend 
its range over the whole central and eastern part of the United States. 
The adult insect, or beetle, is copper-colored, bears eight black 
spots on each wing cover, and is about one-fourth of an inch long. 
The female lays orange-yellow eggs in masses of from 40 to 60 on 
the lower surfaces of the leaves, and in from 5 to 7 days during summer 
_ these hatch into small spiny orange-yellow larve, which when full- 
grown are about one-third of an inch long. The larval period is 
from 16 to 20 days long in summer. The larva transforms to pupa 
on the lower surface of a leaf, or on near-by weeds or other objects, 
and emerges as a beetle in 6 or 7 days, requiring in Alabama a total 
from egg to adult of 27 to 33 days during summer. 7 
The Mexican bean beetle is extremely prolific. A maximum of 
four generations from first egg to first adult in each generation 
occurred in 1921 and 1922; that is, the earliest progeny of each 
generation was reared and four generations were produced. * Two. 
generations annually, with a possible third, may be considered the 
rule in the field, with the peak of the infestation during July and 
early August. 
The beetles and larve feed on the under surface of the leaves of 
_ beans and other legumes, leaving a characteristic network of tissue, 
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