The Use of Metaldehyde Against Slugs

One part of metaldehyde in thirty parts of bran by volume is the minimum effective concentration for obtaining an economic kill of slugs under average weather conditions. For use against Milax gracilis Leydig. heaps of bait should not be normally more than 2 yd. apart and against Arion hortensis Fer. not more than 3 ft. apart. The mortality of slugs attracted to metaldehyde‐bran baits is dependent on the drying property of the soil and atmosphere around the baits. D.D.T. flea‐beetle dust and powdered pyrethrum flowers are sufficiently distasteful to slugs to prevent their consuming a lethal dose of the poison mixed with bran. The addition of 10%, by volume, of dried blood to metaldehyde‐bran bait increases the catch of some slugs under certain conditions but does not increase the mortality. The addition of 10%, by volume, of dextrose increases the mortality produced by metaldehyde but does not increase the numbers attracted to the bait. A metaldehyde‐bran bait compacted into ‘biscuit’ form with anhydrous calcium sulphate catches more slugs than an ordinary metaldehyde‐bran bait, but almost completely counteracts the effect of the metaldehyde. A metal‐dehyde‐bran‐casein glue bait in ‘biscuit’ form increases the catch and kill of Milax gracilis and Agriolimax reticulatus Müll., but not of Arion hortensis . Metaldehyde‐bran‐casein glue bait broadcast in ‘broken biscuit’ form is effective over a longer period, thus producing a greater kill of slugs, than a broadcast metaldehyde‐bran bait.