MEXICAN BEAK BEETLE IN THE SOUTHEAST. 31 



however, was so low that entirely satisfactory results were not 

 obtained under conditions of severe infestation. Magnesium arsenate 

 was therefore recommended because it was the only arsenical known 

 which could be used without dilution and not cause plant injury. 



OTHER INSECTICIDES. 



Experiments were also conducted with materials other than 

 arsenicals. Nicotine dusts were thoroughly tried. Various strengths 

 of dust were used, ranging from 0.38 per cent nicotine content to 

 4 per cent nicotine content. The insecticidal properties of these 

 dusts against the Mexican bean beetle were nil. 



A number of experiments were performed with pyrethrum powder, 

 used undiluted as a dust and combined with various diluents, such as 

 cornstarch and hydrated lime. Decoctions of pyrethrum powder 

 were also used. It was found that pyrethrum powder and certain 

 decoctions thereof were very toxic .to the adult of the Mexican bean 

 beetle, less toxic to the larvae, and almost ineffective against the eggs 

 and pupae. Because of the high cost of the material, however, and 

 the frequent applications required, pyrethrum is absolutely 

 impracticable for field control. 



A number of new compounds were tried in an experimental way 

 in cooperation with Dr. William Moore and C. M. Smith. While 

 some of these materials may be of value, not one of them has as yet 

 warranted recommendation over some of the better known available 

 arsenicals. 



INVESTIGATIONS OF 1922. 



The problem presented in the 1922 experiments in artificial control 

 was the use of an arsenical which would not be injurious to bean 

 ? oliage and at the same time would be sufficiently toxic to the Mexican 

 3ean beetle to insure satisfactory control, the former requirements 

 Deing the more limiting. 



Since magnesium arsenate and calcium arsenate with an excess of 

 lime were the most promising arsenicals tested in 1921, these, as well 

 as basic lead arsenate, were used on a larger scale than others. 



A few experiments were performed with lead arsenate and zinc 

 arsenite in order to check the results obtained the previous season. 

 A number of other compounds were also the subject of experiment. 



SPRAYING AND DUSTING MACHINERY USED IN EXPERIMENTS. 



The power sprayer (figs. 11, 12) referred to is a 150-gallon capacity, 

 triplex-pump, high-pressure potato sprayer, equipped with a high- 

 speed 5-horsepower engine, and was used in experiments as a 4-row 

 sprayer, 3 nozzles per row, at 250 pounds pressure. 



An arrangement was improvised to permit the driver to raise and 

 lower the boom with one foot when turning around ,or driving over 

 uneven places. 



The wheelbarrow sprayer (fig. 13) is a 15-gallon capacity, hand- 

 operated outfit, capable of maintaining 150 pounds pressure at two 

 nozzles. It was mounted on a narrow slide and pulled by one horse. 

 Two men were required — one to pump and one to spray. The 

 arrangement of the nozzles on a U-shaped pipe attached to the spray 

 od made it possible to spray a row at the speed the horse walked. 



