FIRST INSTAR MORTALITIES OF 3 NEW-ZEALAND LEAFROLLER SPECIES (LEPIDOPTERA, TORTRICIDAE) EXPOSED TO CONTROLLED-ATMOSPHERE TREATMENTS

Mortality-responses of first instar Cnephasia jacratana (Walker), Cten opseustis obliquana (Walker) and Planotortrix octo Dugdale on artifici al diet to various controlled atmospheres at different temperatures we re determined. At 20 degrees C, reducing the O-2 concentration through the range of 3.85-0.4% greatly reduced the mean estimated time for 99 % mortality (LT(99)). An O-2 concentration of 0.4% combined with a CO2 concentration of 5% resulted in the lowest LT(99)s for each of the sp ecies (18.8, 31.5 and 31.6 h respectively). At this temperature, C. ja ctatana was more susceptible to atmospheres with greater than or equal to 1% O-2 than C. obliquana and P. octo. Although LT(99)s were greatl y decreased by the same reduction of O-2 concentration at 30 degrees C , the mortality responses to atmospheres with concentrations less than or equal to 1% O-2 were similar. In contrast, changing the CO2 concen tration of the atmosphere over the range of 1-20% had a minor effect o n the mortality responses of the three leafroller species at both 20 a nd 30 degrees C. When treatments were applied at 40 degrees C, the LT( 99)s were short (less than or equal to 4.6 h) and comparatively homoge neous regardless of either the O-2 or the CO2 composition of the atmos phere.