This research addresses possible adverse ecological effects of insects introduced for biological control of weeds. The cinnabar moth, Tyria jacobaeae, was released in Oregon in 1960 to control tansy ragwort, Senecio jacobaea. Prior to release larvae were shown to feed and develop on other Senecio species in laboratory tests. Since release, they have been shown to use two native species, S. triangularis and S. pseudaureus, in the field. This study examined the non-target impact of the cinnabar moth on native Senecio in Oregon.
We compared overlap in the geographic distributions of Tyria jacobaeae and non-target native Senecio to determine which species were likely to be exposed to the cinnabar moth. We conducted a regional survey of a representative sample of sites selected for their potential exposure to cinnabar moth to assess frequency and severity of attack. We also sampled local sites where cinnabar moth attack was recorded to characterize variation in frequency and severity of attack.
Nine of the 23 native Senecio have been exposed to the cinnabar moth in Oregon. Preliminary results show damage to two species, S. triangularis and S. pseudaureus. Attack frequency ranged from 0% to 80% of stems attacked in S. triangularis and 28% in S. pseudaureus, and was negatively associated with stem density in both species. Average damage per stem was 10% to 53% in S. triangularis and 8% in S. pseudaureus.
Two native Senecio were used infrequently by Tyria jacobaeae in Oregon. These data suggest that cinnabar moth feeding has limited negative impact on native plants.
The ESA 2001 Annual Meeting - 2001: An Entomological Odyssey of ESA