Page 655 Advertisement 1

New Zealand Tablet, 13 April 1911, Page 655

The potato grub of ill-fame is (says the Oamaru Mail) remarkably tenacious of its caterpillar life, and may, not bo deprived of it by any mild violence. Hoping to discover a preparation which might be of practical use in exterminating the grub, Mr. C. B. Morris performed a series of experiments on caterpillars, but did not succeed in finding any preparation which" would kill the grub in 15 minutes—a practical time limit— even in a much longer period. A reporter who called on him was given some detailed results of the experiments. Mr. Morris first tried perchloride of mercury, known as ccrosive sublimate and recommended by the Agricultural Department. A solution of one in 1300, the strength recommended by the Department, failed, and the strength was then doubled, making it one in 650; but the grubs were perfectly healthy after 13 hours’ submersion. Formalin, which Mr. Morris had himself advised trying, proved to be quite incapable of producing the desired result, the caterpillars living after 13 hours’ submersion in a solution of 20 drops to the halfpint. _ Equally useless among other substances tried were chronic acid, acetic acid (solution equal to the strength of vinegar), and a saturated solution of alum. After six hours’ submersion in a solution of common salt, 26 grains to the ounce (about six teaspoonfuls to the pint), the caterpillars still lived. Stavesacre seeds, deadly to insect life, failed to kill after eight hours. _ As a result of these experiments Mr. Morris is of opinion that unless the pest is the product of the dry weather it will prove to be a plague such as North Otago has never yet experienced.