THE ACTION OF METALDEHYDE ON THE SLUG AGRIOLIMAX RETICULATUS (MÜLLER)

Metaldehyde both as powder and in solution can act on slugs either by contact or as a 'stomach poison'. The characteristic effects of metaldehyde poisoning were immobilization broken by outbursts of unco-ordinated muscular activity and sliming which usually resulted in severe water loss. 24 hr. after treatment with moderate doses slugs were still abnormal and rarely fed within 30 hr. of treatment. It was not possible to determine the M.L.D. with the methods used, but 0·06 nig. solid metaldehyde taken orally could be lethal to slugs of 400–800 mg. body weight. Lethal effects were produced by contact of 1 hr. with concentrations equivalent to 0·0063 mg./cm.². Toxicity increased with rise in temperature and recovery from moderate doses was dependent on slugs being in a saturated or almost saturated atmosphere. No obvious gut lesions were found in slugs which had been dosed with or had eaten metaldehyde. Its action was not by depolymerization in the gut or body cavity. In the light of laboratory and small scale field trials it is suggested that broadcasting and spraying are the best methods of applying the material.