Asynchronous Budbreak in Taxodium distichum L. Richard (Baldcypress) as a Mode of Resistance against Archips goyerana Kruse (Baldcypress Leafroller)

Abstract

Coastal stands of Taxodium distichum L. Richard (baldcypress) in Louisiana, USA, are in decline because of saltwater intrusion, prolonged flooding, and periodic defoliation by an insect herbivore, Archips goyerana Kruse (Lepidoptera: Tortricidae; the baldcypress leafroller). The objective of this study was to examine the potential for the use of variation in budbreak among half-sibling families previously evaluated for salt tolerance as a means of resistance to defoliation. Four half-sibling families were categorized as either early (FA7, SG2) or late (SW2, VE2) leafing during budbreak. Laboratory bioassays in 2002 found that larvae fed on foliage collected on the same date encountered foliage from early-leafing half-sibling families of an advanced age that was significantly lower in N, P, K, and moisture content and significantly higher in digestion-inhibiting compounds (phenolics) than foliage from later leafing half-sibling families. Insect pupal weights and relative growth rates were significantly lower on early-leafing half-sibling families. In 2003, the early and late-leafing families were experimentally synchronized with larvae by collecting foliage from family groups in order of budbreak. Foliar N remained significantly higher and total phenolics significantly lower in the late-leafing families; however, moisture content, P, K, and insect pupal weights and relative growth rates did not differ significantly between early- and late-leafing half-sibling families. Intraspecific budbreak variation in baldcypress can affect insect growth and, potentially, baldcypress leafroller populations and should be explored further. The success of coastal baldcypress restoration programs in Louisiana might be improved by capitalizing on separate traits that reduce damage from herbivory and salinity.