PARENT SESSION
Oral Session #72: Herbivory: Herbivore Response to Plants.
Presiding: C. Mitchell
Wednesday, August 7. 1:00 PM to 4:45 PM. Mesquite Room, Radisson.

Competitive release of cambial herbivores in response to experimental removal of a stem-boring moth on pinyon pine.

Welton, Cody^*,1, Cobb, Neil¹, ¹ Northern Arizona University, Flagstaff, AZ

ABSTRACT- The stem-boring moth, Dioryctria albovittella, has been systematically removed for the last 18 years from susceptible pinyon pines (Pinus edulis). Feeding by this moth has important effects on pinyon growth, reproduction, and architecture as well as on many other species dependent upon pinyon. In this study we examined the effect of moth removal on cambial-feeding vertebrate and invertebrate herbivores, including the boring moth, Dioryctria ponderosae, and the porcupine, Erethizon dorsatum . We measured cambial herbivory by quantifying wounds on a whole-tree basis for three groups of trees, moth-resistant, moth-susceptible trees where moths have been removed annually for 18 years, and moth-susceptible trees that have been allowed to stay infested. Moth removal lead to significantly increased levels of porcupine and insect herbivory compared to both resistant and susceptible trees. This was true for density and absolute area damaged. These results strongly support the notion trees that are resistant or susceptible to moths also show the same degree of resistance/susceptibility to cambial herbivores, although this increased susceptibility of moth-susceptible trees to cambial herbivory is only realized when moths are removed. Thus, stem-boring moths reduce cambial herbivory through indirect competition, probably by reducing resources available to both vertebrate and insect cambial herbivores.

KEY WORDS: pinyon , herbivore, release, keystone