201 



from perfect, while the mosaic disease remained unchecked. Prelimi- 

 nary tests of the efficiency of the spray used showed only about 26 

 per cent, mortality of the beetles. 



A series of tests with various insecticides was then conducted in 

 large cages, the results being shown in a table. The average of two 

 season's results showed for zinc arsenite an efficiency of 24 per cent. ; 

 lead arsenate, either sweetened or not, 17 per cent. ; Paris green, 16 per 

 cent. ; zinc arsenate, 14 per cent. ; Bordeaux lead arsenate, 14 per 

 cent. ; lead arsenate dust, 9 per cent. ; cobalt arsenate, 4 per cent. ; 

 calcium arsenate, 1 per cent. ; arsenic bisulphide (Realgar), per cent. 

 Zinc arsenate is too unstable, in its present commercial form, to be 

 of importance. Arsenic bisulphide is too heavy to stay in suspension 

 and does not spread well. 



It is evident from these results that Diahrotica vittata is difficult to 

 poison. In cases where Bordeaux mixture is of value in controlling 

 plant diseases it may be used to advantage wath lead arsenate or zinc 

 arsenate. Under the conditions prevailing in the cucumber-growing 

 sections of the north central States, its value as a control of the insect 

 does not warrant the expense of application. 



Wilson (H. F.) & Gentner (L. G.). The Imported Cabbage Worm 

 in Wisconsin. — Jl. Econ. Entom., Concord, N.H., xi, no. 1, 

 February 1918, pp. 79-81, 2 plates. 



The investigations recorded in this paper were made with the object 

 of convincing Wisconsin growers that cabbages sprayed with arsenicals 

 for the control of the imported cabbage worm [Pieris rapae] are not 

 rendered dangerous for use as food. 



Life-history studies of this butterfly during two seasons have shown 

 that there are three distinct generations in a year and sometimes a 

 partial fourth. There is usually some overlapping of the generations, 

 especially toward the end of the season. Adults emerge chiefly during 

 the first two weeks of May, from the pupae that have hibernated ; 

 those of the first generation appear in the first half of July ; those of 

 the second generation during the first half of August. In the southern 

 half of the State both early and late cabbages are grown, while in the 

 northern sections generally only the late variety is cultivated. The 

 early cabbage generally matures without much injury, but the late 

 variety is often seriously attacked. 



The tests showed that while Paris green gives efficient control its 

 cost is too high for economical use. Lead arsenate and calcium 

 arsenate at the rate of 1 lb. powder or 2 lb. paste to 50 U.S. gals., 

 with the addition of 1 lb. or more of common laundry soap, give 

 efficient control and are the most economical to use. Zinc arsenite 

 failed to control the caterpillars, contrary to expectations, and further 

 experiments will be made. Tobacco dust and lime apparently had 

 no effect upon the insects. 



No trace of arsenic was found to be present on heads prepared for 

 cooking, even when these had been sprayed as late as a week before 

 picking. The outer leaves may however carry enough arsenic to 

 poison stock and it is therefore dangerous to use them for feeding. 



