Effects of Pterophoridae carduidactyla (Riley) seed predation on Cirsium palustre (L.) Scop. and Cirsium muticum Michaux, control and invasive implications.

Abstract

Cirsium palustre, native to western Europe, was first collected in Marquette County, Michigan in 1934. This invasive has spread quickly and reached the mainland of Michigan's lower peninsula causing concern. Cirsium palustre establishes in areas of high disturbance like along roadsides. Cedar swamps like Reese's Swamp in Cheboygan County Michigan harbor both C. palustre and the native swamp thistle Cirsium muticum. The purpose of this study is to compare the effects of Platyptilia carduidactyla seed predation on C. palustre and C. muticum in Reese's swamp. Flower heads of both thistles were collected to compare infestation. The plum moth larvae found were used in head and seed choice tests between C. palustre and C. muticum. Results show no significant difference between heads infested of C. palustre and C. muticum. However, results showed that there was a significant difference between the infected plants of the Cirsium species. Both preference tests were limited in sample size and scope. The larvae showed no preference for heads of the two thistle species. However, there was a seed preference shown for C. muticum over C. palustre. It was concluded that the female plume moth shows no preference for C. muticum or C. palustre in this study. This study also suggests that a plant of C. palustre is more likely to be oviposited in than C. muticum due to chance rather than preference. However, due to plant structure this study suggests that if infected C. palustre is impacted less than C. muticum.