THE EFFECTS OF OZONE-EXPOSED SUGAR MAPLE SEEDLINGS ON THE BIOLOGICAL PERFORMANCE AND THE FEEDING PREFERENCE OF THE FOREST TENT CATERPILLAR (MALACOSOMA-DISSTRIA HBN.)

The effects of exposure of sugar maple (Acer saccharum Marsh.) to ozon e on the entire larval stage of a native insect have not been previous ly investigated. This study reports the effects of sugar maple seedlin gs exposed to different ozone concentrations on the relative performan ce and the feeding preference of the forest tent caterpillar (Malacoso ma disstria Hbn.). Three-year-old seedlings were set in nine open-top field chambers in the spring of 1992 and 1993. Three ozone concentrati ons were generated: charcoal-filtered ambient air (0x), ambient air (1 x) and three times ambient air (3x). In 1992, female and male larval d evelopment time did not differ among ozone treatments. In 1993, female larvae reared on 3x developed faster than those on 0x and 1x, while m ale larvae were not affected Ozone treatments did not influence pupal weights except for males in 1993 where pupae reared on 0x were heavier than 1x but did not differ from 3x. Larval and pupal survival rates w ere not affected by ozone in either year. Finally, 4th and 5th instar larvae showed a significant feeding preference for 3x foliage in 1993 but not in 1992. The response of the forest tent caterpillar to ozone exposed seedlings varied between years and could be more sensitive to annual climatic variations than ozone. (C) 1997 Elsevier Science Ltd.