The resistance of Pteridium aquilinum (L.) Kuhn to insect attack by Trichoplusia ni (Hübn.).

Resistance of Pteridium aquilinum to insect attack was studied by incorporating air dried bracken leaf meal and extracts of bracken leaf meal into an artificial diet for Trichoplusia ni (Lepidoptera: Noctuidae). When larvae are reared on diets containing 6% bracken leaf meal, they do not mature past the second instar and after 16 days the average weight is approximately 1 mg compared to 70 mg for control larvae. Feeding initiation studies indicate that a feeding deterrent is present in bracken fern but feeding rates and food utilization efficiency studies suggest that either the deterrent or another compound also functions as a toxin. This toxin does not affect growth, feeding rates, or utilization efficiency for the first 4 days after third instar larvae are transferred to a diet containing the water extract of bracken leaf meal; thereafter growth is terminated and feeding is greatly reduced. The active factor is water soluble, heat labile, and non-volatile and this partial characterization indicates that neither the bracken ecdysones or the anti-thiamine factor of bracken is involved in the resistance of this fern to insect attack by T. ni.