Effects of ultraviolet-B exposure of Arabidopsis thaliana on herbivory by two crucifer-feeding insects (Lepidoptera)

Larvae of Pieris rapae (L.) (Lepidoptera: Pieridae) and Trichoplusia ni (Hubner) (Lepidoptera: Noctuidae) were fed foliage from Arabidopsis thaliana (L.) Heynh. plants that had received a high dose of ultraviolet-B (UV-B) or from control plants. Treatments were compared using the Student independent t-test. P. rapae larvae consumed less of the foliage exposed to UV-B than control foliage. This difference was significant in older but not younger larvae, and the older P. rapae larvae fed foliage exposed to W-B weighed significantly less. For ?: ni, however, consumption and larval weights were approximately equal for UV-exposed and control foliage. No significant differences in grovvth rates per unit consumption on UV-exposed versus control foliage were found for either species. Chemical analysis showed that flavonoid levels increased in response to UV-B. Results suggested that UV-inducible flavonoids may act as feeding deterrents to P. rapae but not to T. ni.