A TEST METHOD FOR FIELD STUDIES OF INSECTICIDAL BAIT FORMULATIONS AGAINST THE ANT LASIUS NIGER (HYMENOPTERA: FORMICIDAE)

Abstract:
In the early spring Lasius niger may be a nuisance indoors. These ants often originate from nests right next to the foundation, below the house or sometimes even directly under the floor. The ants raise the humidity, which may result in severe damage to the woodwork, due to rot. The same applies to an even greater extent to other species: L. umbratus and L. fuliginosus. The present method was developed for the evaluation of insecticidal bait formulations in the field. Special emphasis was put on maintaining the colony members' ability to communicate mutually. The study evaluated the response of L. niger to seven bait formulations, five containing azamethiphos, one containing chlorpyrifos, and a reference with no insecticide. The primary interest of the experiment was to develop a method where the palatability of the bait formulations, the ability of the baits to attract L. niger, and the ants' acceptance of the baits could be investigated. Thirty-four ant nests were used. When the number of ants on a jam bait indicated high activity, the test was initiated. A new jam bait was put into position for fifteen minutes and then replaced by the test bait for fifteen minutes. This was repeated three times. The number of ants visiting each bait was counted, and a small portion was collected by a sucking device when leaving the bait. The latter was observed for up to 24 hours to estimate the mortality. The results with the reference bait showed that the ants were only slightly affected by the method, while the palatability of the test baits ranged from as good as the controls to complete repellence. This result was confirmed by the percentage of ants killed. And both results indicate that the method could be used to establish comparable data for the efficacy of ant baits.