Return to Publications List ◄ Next Page►

52

chemicals that did not show maximum killing power in short exposures to have increased effectiveness with longer contact. Heptachlor was the only exception to this, indicating that the shorter exposure times

were sufficient for it to demonstrate maximum effectiveness. The length of exposure is an important factor in determining the degree of effectiveness of any one of these compounds. Also, an idea of the extent of repelling action of chemicals on earwigs may be indicated by higher mortality resulting from enforced contact with the insecticide than where an option exists.

The field experiment using granules showed that an excessive dosage of all chemicals was applied. However, due to difficulties involved in calibrating the application apparatus to a smaller output, it was impossible to obtain a dosage less than four pounds to the acre. It might be noticed, nevertheless, that the greatest differentiation among the chemicals took place in the first five days after treatment. The two chemicals showing most rapid control were heptachlor and dieldrin. These, in turn, were followed by aldrin and chlordane. It is noteworthy to mention that this order is not comparable to that obtained from laboratory experiments where heptachlor proved to be inferior to aldrin. However, the relative dosages in the laboratory experiments were different and thus an accurate comparison cannot made.