A comparative trial of norbormide and zinc phosphide against Rattus norvegicus on farms

Norbormide has already been compared with zinc phosphide under laboratory conditions against normal and warfarin-resistant strains of wild rats by Greaves (1966). He found no significant difference in the response of the two strains to either poison and suggested that 0 5 °/O or higher concentrations of norbormide might give results in the field as good as those normally obtained with 2o5 or 5 0 °/O zinc phosphide, but refrained from drawing any firm conclusions until the two rodenticides had been tested under field conditions. The field trial, now described, was planned with the dual purpose of comparing norbormide and zinc phosphide aJnd of finding out to what degree of accuracy the laboratory results had predicted the effectiveness of the rodenticides in practice. Some of the methods, therefore, replicated those used in laboratory tests, while others were dictated by the inferences drawn from the results of those tests. The fact that normal and warfarin-reFsistant rats had responded similarly to the two poisons in the laboratory meant that there could be no objection to siting the trial in an area where warfarin-resistaUnt rat populations occurred and where, perhaps for that reason, a large number of infested farms were available. An added advantage wa.s that acute poisons were commonly used in this area, and farmers understood and accepted the risks involved. * 5-(a-hydroxy-oc-2-pyridylbenzyl)-7-(oc-2-pyridylbenzylidene) norborn-5 - ene - 2, 3 - dicarb