Grantee Research Project Results

Don't Bug the Trees: Abiotic Factors Alter Paper Birch and Sugar Maple Resistance to Chewing Folivores

EPA Grant Number: U915146
Title: Don't Bug the Trees: Abiotic Factors Alter Paper Birch and Sugar Maple Resistance to Chewing Folivores
Investigators: Governer, Heather L.
Institution: Michigan State University
EPA Project Officer: Packard, Benjamin H
Project Period: January 1, 1997 through January 1, 1999
Project Amount: $68,000
RFA: STAR Graduate Fellowships (1997) RFA Text |  Recipients Lists
Research Category: Academic Fellowships , Ecological Indicators/Assessment/Restoration , Fellowship - Ecology

Objective:

The objective of this research project is to determine how light and nutrient availability affect constitutive and defoliation-induced resistance of paper birch and sugar maple to gypsy moth, whitemarked tussock moth, and forest tent caterpillar.

Approach:

Controlled field experiments were conducted at the Dow Gardens in Midland, MI. One paper birch and one sugar maple tree were planted in each of 48 1-m2 microcosms arranged in six rows of eight. The soil environment of each microcosm was isolated by a PVC liner extending 1 m below ground and 10 cm above ground. Two-year-old birch and 5-year-old maple saplings were planted in 1992, and established for two seasons before treatments were implemented. Light (main plot), nutrient availability (subplot), and defoliation (subplot) treatments were applied in a complete factorial split-plot design. Shade cloth was used to establish two levels of light: 20 percent or 100 percent of ambient in 1995, and 1996. Fertilization treatments were 0 or 225 kg/ha/yr 18:5:9 NPK, with one-half applied in May and one-half in October of 1994, 1995, and 1996. Two defoliation levels (0 and 50 percent for birch and 0 and 10 percent for maple) were established by inoculating one-half of the trees with forest tent caterpillar eggs. Treatment effects on tree resistance to herbivores was determined by insect bioassays. In 1996, survival, growth rate, development time, and pupal mass of gypsy moth and whitemarked tussock moth reared on detached foliage of experimental trees were recorded. In 1997, growth of second and fourth instar gypsy moth and whitemarked tussock moth, and fifth instar forest tent caterpillar were determined. Nutritional indices (consumption rate, digestibility of foliage, and percentage digested food converted to biomass) were measured on fourth or fifth instars in both years. Potential correlates of foliar phenolic concentrations with insect responses were examined by analyzing June foliage for total phenolic activity and condensed tannin concentrations.

Supplemental Keywords:

fellowship, light, nutrient availability, folivores, paper birch trees, sugar maple trees, soil, defoliation, insects, gypsy moth, whitemarked tussock moth, forest tent caterpillar.

Progress and Final Reports:

1997

Final