Damaging Factors–Regeneration — Abstract of Paper


Insect-oak Interactions with Coast Live Oak (Quercus agrifolia) and Engelmann Oak (Q. engelmannii) at the Acorn and Seedling Stage
Connell E. Dunning,¹ Timothy D. Paine,² and Richard A. Redak²


We determined the impact of insects on both acorns and seedlings of coast live oak (Quercus agrifolia Nee) and Engelmann oak (Quercus engelmannii E. Greene). Our goals were to (1) identify insects feeding on acorns and levels of insect damage, and (2) measure performance and preference of a generalist leaf-feeding insect herbivore, the migratory grasshopper (Melanoplus sanguinipes [Fabricus] Orthoptera: Acrididae), on both species of oak seedlings. Acorn collections and insect emergence traps under mature Q. agrifolia and Q. engelmannii revealed that 62 percent of all ground-collected acorns had some level of insect damage, with Q. engelmannii receiving significantly more damage. However, the amount of insect damage to individual acorns of both species was slight (<20 percent damage per acorn). Curculio occidentis (Casey) (Coleoptera: Curculionidae), Cydia latiferreana (Walsingham) (Lepidoptera: Tortricidae), and Valentinia glandulella Riley (Lepidoptera: Blastobasidae) were found feeding on both species of acorns. No-choice and choice seedling feeding trials were performed to determine grasshopper performance on the two species of oak seedlings. Quercus agrifolia seedlings and leaves received more damage than those of Q. engelmannii and provided a better diet, resulting in higher grasshopper biomass.