50 BULLETIN 1243, U. S. DEPARTMENT OF AGRICULTURE. 
which soon dries. When beetles are abundant, beans are destroyed 
in two or three weeks. Since the larva consumes relatively greater 
quantities of leaf tissue than the beetle, the former is the more 
destructive stage. Im many sections of the South this insect has 
destroyed entire bean crops in the last two years, and has caused 
serious damage one year after it has reached a new locality. 
Winter is passed by the beetle in woodlands or sheltered places 
distant from the infested bean field; only a small proportion of over- 
wintered adults remain in the field. They bautls to hibernate gre- 
gariously. Most suitable hibernation quarters in the Southeast are 
on wooded slopes where accumulations of leaves or pine needles offer 
protection and relatively constant moisture conditions. 
The Mexican bean beetle, while primarily a bean pest, is able to 
reproduce on beggarweed, cowpeas, soy beans, and a few other plants. 
Where the bean beetle thrives, control measures are essential. 
The bean plant is very susceptible to injury from arsenicals, and 
care must be exercised in their use. Best results for its control have 
been obtained with magnesium arsenate, applied as a spray at 
the rate of 2 pounds to 100 gallons of water, or about 2 pounds per 
acre, on bush beans drilled in rows 3 feet apart. This arsenical 
is safe for application to bean foliage and at the same time is sufhi- 
ciently toxic to kill larve and some adults. Caseinate of lime may 
be used as a spreader at the rate of 1 pound to 100 gallons of spray. 
About 90 to 100 gallons of spray are required per acre when a large 
machine is used which directs three nozzles to each row. Two of 
the nozzles should be directed so that the spray will reach the under 
side of the leaves. The third nozzle should be directed to the tops 
of the plants. While this third nozzle is not absolutely necessary, 
best results have been obtained where three nozzles were used. 
The spray should be appled at 150 pounds pressure or higher. 
Where spraying is impracticable because of lack of water facilities 
or for other reasons, good results may be obtained by the thorough 
application of a dust consisting of 1 part of high-grade calcium arsenate 
and 9 parts of hydrated lime. On small acreages a knapsack bel- 
lows duster with a spout attached to a flexible hose is satisfactory. 
This dust should be applied to the under side of the leaves at the 
rate of about 15 pounds per acre. Similar results have followed 
the use of a mixture consisting of 1 part of dry calcium arsenate, 1 
part of fine dusting sulphur, and 4 parts of hydrated lime. Dust 
mixtures can be prepared on the farm more economically than they 
can be purchased. 
Heavily infested fields should be plowed under as soon as the crop 
is picked. The grower should not plant more beans than he can 
treat properly. Treatment should begin as soon as the eggs of the 
bean Pacts become numerous, usually at about the time the third 
true leaf appears on the plant. From one to five applications are 
required, departaiee on the degree of infestation, whether light or 
heavy. 
