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46

Results of field treatments with granules

Results from the application of granular insecticides to a series of experimental field plots, in which a heavy earwig infestation had existed, are given as total active numbers in table 5 and in per cent control based on the check plots in figure 40.

In rapidity and degree of effectiveness, heptachlor and dieldrin were parallel as were aldrin and chlordane (figure 40). Heptachlor and dieldrin were more rapid to take effect, giving a 98 and 95 per cent control, respectively, on the fifth day. Aldrin and chlordane after the same period had effected on a 73 and 66 per cent control, respectively. All four chemicals tended to converge with respect to their degree of effectiveness on the sixth day and were thereafter essentially indistinguishable.

On the 28th day when the last counts were made, all chemicals have converged within a narrow margin of 96-99 per cent control. A glance at table 5 will show the small number of earwigs caught at this time in the treated plots.