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. In 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 tend to hibernate gre- 

 gariously. Most suitable hibernation quarters in the Southeast are 

 on wooded slopes where accumulations of leaves or pine needles offer 

 protection ana 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 suffi- 

 ciently toxic to kill larvae and some adults. Casemate 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 jshould 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 applied^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 beetle become numerous, usually at about the time the third 

 true leaf appears on the plant. From one to five applications are 

 required, depending on the degree of infestation, whether light or 

 heavy. 



