The role of phytoecdysteroids in bracken fern,Pteridium aquilinum (L.) Kuhn as a defense against phytophagous insect attack

Analysis of green bracken fronds collected during July, August, and October, 1975, for phytoecdysteroids showed that these compounds occur in only trace amounts (0.25–0.53 g/kg fresh weight FW]). The effect of ecdysteroids on the feeding behavior of seven species of insect showed that four species were deterred at ecdysteroid concentrations at or above 60 mg/kg FW diet; one species of insect at 6 mg/kg or above, and two species which were not affected at the higher concentrations. It was concluded that the levels of phytoecdysteroids in bracken would not deter insects from feeding on the plant. The previously published data relevant to the possible role of phytoecdysteroids as defense compounds are also discussed.