48 BULLETIN 1243, U. S. DEPARTMENT OF AGRICULTURE. 



Spraying has certain disadvantages, compared with dusting. 

 Initial expenditures for equipment are greater in some cases, and 

 more time per acre is required on account of refilling the machine, 

 preparing the spray, and cleaning the nozzles. 



Spraying has the distinct advantage that it makes the most efficient 

 and economical use of magnesium arsenate, which is not especially 

 adapted to dusting. 



Magnesium arsenate has been found by several investigators to be 

 injurious to the foliage of fruit trees. It will not, therefore, fill the 

 place of an arsenical for general use. A high-grade material, however, 

 will undoubtedly be safe for many uses. 



Because of the availability of calcium arsenate and its superior 

 dusting properties, it will be much used, and is recommended as a 

 dust where no better material is at hand. Only a very high grade 

 should be employed, and it should not be stronger than 1 to 9 parts 

 of hydrated lime (or plasterers' lime) . 



When fine dusting sulphur is available, the 1-1-4 mixture of cal- 

 cium arsenate, dusting sulphur, and hydrated lime is recommended. 

 If injury to foliage results, the hydrated lime content should be 

 doubled. 



Lead arsenate and zinc arsenite should never be used on beans 

 in the Southeast. 



MIXING DUSTS. 



Dusts may be mixed on the farm with very little trouble. Ingre- 

 dients should be weighed. Quantities up to 100 pounds may be 

 mixed with a steel drum which can be tightly covered. The drum 

 should be filled not more than two-thirds full, covered tightly, and 

 rolled about for a distance of approximately 50 feet. It should then 

 be tipped up on each end and this process of rolling and tipping 

 repeated 15 or 20 times. When ingredients are lumpy from standing, 

 they should be sifted through at least a 50-mesh sieve before mixing. 

 For large quantities, a ball mill or a baker's sifter and mixer may be 

 used. 



SUMMARY OF CONTROL RECOMMENDATIONS. 



Magnesium arsenate, at the rate of 2 pounds to 100 gallons of 

 water, is an effective spray. Caseinate of lime as a spreader may be 

 used with this mixture at the rate of 1 pound to every 100 gallons 

 of spray. Using three nozzles to the row on bush beans drilled in 

 rows 3 feet apart, about 90 gallons of spray are required per acre with 

 a power machine drawn by a team. About 2 pounds of the poison 

 per acre is the proper dosage. Two nozzles should be directed to the 

 under side of the leaves, and a pressure of 150 pounds or more is 

 essential for good results. The nozzle over the top of the row need 

 not be used in cases of light infestation or when pressure can not be 

 maintained. 



The spray should be applied when the eggs of the bean beetle 

 become numerous, usually when the beans begin to send out their 

 first trifoliate leaves; i. e., the third and fourth leaves. 



Under conditions of heavy infestation, four applications are neces- 

 sary at intervals of from 7 to 10 days. Spray may be applied until 

 the first bean pods are 2 or 3 inches long. 



When spraying is impracticable, magnesium arsenate may be used 

 as a dust diluted with from 1 to 5 parts of hydrated lime, depending 



