Evaluating the benefits of doseresponse bioassays during aerial pest eradication operations

Abstract

Between January 2002 and May 2004 a series of aerially applied sprays of Btk (Bacillus thuringiensis var kurstaski) were made to areas of Auckland and Hamilton New Zealand The purpose of the sprays was to eradicate the painted apple moth (PAM; Teia anartoides) from Auckland and the Asian gypsy moth (AGM; Lymantria dispar) from Hamilton In both operations bioassays were used to test the effectiveness and consistency of spray applications Bioassays were undertaken by placing foliage samples (Acacia mearnsii) at a selection of locations in the spray zone next to cards on which spray deposition was measured After spraying PAM larvae were placed on each plant and mortality recorded Results indicated that there was a strong relationship between droplet density on cards and PAM mortality on plants Once this relationship was determined further bioassays were of limited additional value to simply measuring deposition on cards