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JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 17 
acre, and on the tenth day when 500 pounds per acre was used. The 
quantity toward the end of the period was extremely small in each case. 
These data indicate that the cyanide remains in the soil for only a short 
time, and that it will be perfectly safe to do the planting within a week or 
10 days after application. These results have been confirmed by field 
experiments. Seed potatoes planted immediately or the next day after a 
calcium cyanide application were all injured, but when planted a week or 
more after the application they showed no effect from the cyanide. 
The application of calcium cyanide to soil in which plants, such as 
potatoes, bulbs, and young seedling trees, were growing, demonstrated 
that when it was placed close enough to the plants or used in quantities 
sufficient to get a good killing of wireworms, injury to the roots or 
tubers resulted. 
On only one experimental plot are the plants sufficiently advanced in 
growth at this writing to show the effect of the treatment on the crop. 
A treated potato plot on badly infested soil shows a decidedly better 
stand and growth than the untreated adjoining areas. This not only in¬ 
dicates that the wireworms were controlled, but also that the calcium 
cyanide did not injuriously affect the soil for subsequent plant growth. 
Practically all plots have been planted to some crop, and examinations 
will be made during growth and at harvest to determine how effective 
the treatment has been in increasing the quantity or improving quality. 
The experiments so far have been intended primarily to determine 
whether calcium cyanide will kill a satisfactory proportion of the wire- 
worms when applied in moderate amounts. They indicate that 200 
pounds per acre if properly applied will kill 75 per cent, or more, of the 
worms at a cost of about $30 per acre. It should be borne in mind that 
the benefit of one treatment will extend over two or three years at 
least, 8 owing to the fact that it requires about three years for these wire- 
worms to reach maturity and a single brood may cause injury over this 
period. 
Experiments are now under way to discover means of reducing the 
amount of cyanide required per acre and thereby the cost of treatment. 
It is a well-known fact that wireworms collect in the rows of beans or 
other crops; therefore, if advantage is taken of this habit by drilling in 
split beans, rice bran, or other attractants, to induce the wireworms to 
concentrate in rows 2 or 3 feet apart, and subsequently treating these 
rows with a fairly heavy application of cyanide, a better killing may be 
8 In addition to controlling the wireworms, there is some evidence that the use of 
calcium cyanide increases the nitrogen content of the soil. 
