Resource concentration and herbivory in oak forests.

Area of Science:

• Ecology
• Forestry
• Entomology

Background:

• The fall cankerworm (Alsophila pometaria) is a polyphagous insect that defoliates canopy trees.
• Larval emergence timing relative to host plant budbreak influences herbivory.
• Tree species composition in a stand can affect herbivore pressure.

Purpose of the Study:

• To investigate the herbivory patterns of fall cankerworm (Alsophila pometaria) in mixed oak stands.
• To determine if herbivory by Alsophila pometaria is influenced by host tree density or phenology.

Main Methods:

• Field observations in mixed stands of scarlet oak (Quercus coccinea) and white oak (Quercus alba).
• Monitoring of Alsophila pometaria larval populations and their host tree associations.
• Assessing defoliation levels on different oak species based on their relative abundance.

Main Results:

• In stands dominated by scarlet oak, scattered white oaks experienced higher defoliation by Alsophila pometaria.
• In stands dominated by white oak, scattered scarlet oaks experienced higher defoliation.
• The rarer tree species in each stand suffered greater herbivory, contrary to density-dependent herbivory models.

Conclusions:

• Alsophila pometaria herbivory is influenced by the relative abundance and phenological synchrony with host trees.
• The phenological asynchrony between larval hatch and budbreak of the rarer species drives increased herbivory.
• This study highlights an inverse relationship between host plant density and herbivore attack intensity for Alsophila pometaria.