272 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 15 



injury in too many cases to make their recorrmendation general. Mag- 

 nesium arsenate, formerly a com^mercial product, was injurious to a 

 marked degree in only 2 out of 31 treatments; but since this arsenical 

 is not now available, and in view of the fact that it has been tested dirring 

 only one season, it cannot be generally recommended. As formerly 

 prepared, it is unsuitable for dusting. 



With present knowledge, wet sprays cannot be generally recom- 

 mended, and growers are advised to try them out under local conditions, 

 using the purest water available, preferably rain water collected from 

 buildings. Zinc arsenite is the safest commercially available arsenical 

 tested. It will effect efficient control if applied at the rate of three- 

 fourths of a pound to 50 gallons of water, or at the rate of one ounce to four 

 gallons. It should be applied to the underside of the leaves, at a high 

 pressure, with a nozzle set at right angles to the discharge tube. The 

 mixture must be continually agitated. An acre of bush beans in full 

 leaf requires from 50 to 75 gallons of liquid, the rows being sprayed from 

 each side with a small sprayer. 



Paris green, as is well known, cannot be applied to beans because 

 of the certain burning of the foliage. 



Dusts 



Successful dusting of garden beans for the control of the Mexican 

 bean beetle requires the application of the poison to the underside 

 of the leaves. This can be done best on a small scale with available 

 machinery by means of a bellows type of duster provided with a long 

 spout on a flexible hose, which makes it possible to direct the dust to 

 the underside of the leaves and to distribute it among the clusters of 

 hanging leaves. Care must be exercised to avoid distributing too much 

 dust per acre, and in heavy puffs at the stroke of the bellows. 



Cloud dusting in the early morning with various types of hand 

 machines was not thoroughly successful on bush beans, the force of the 

 air blast when directed against the ground being instifficient to carry 

 the dust thoroughly to the underside of the leaves. On large acreages 

 better results may be obtainable by the use of power machines. 



Arsenical dusts gave control in direct proportion to the percentage 

 of arsenical in the dust. No appreciable foliage injury was obtained 

 from any of the arsenicals used when these were diluted 9 times with 

 hydrated lime, but control was far from perfect. Applications must 

 be made every 5 or 6 days, where infestation is heavy, and must be 

 started as soon as the beans put out true leaves. 



Calcium arsenate is the best arsenical available to southern growers 

 for dusting purposes, but it will cause defoliation of beans in most cases 



