Previous Tip Moth Infestation Predispose Trees to Heavier Attacks in Subsequent Generations

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The Nantucket pine tip moth, Rhyacionia frustrana (Comstock) (Lepidoptera: Tortricidae), is a common regeneration pest of pine plantations in the southeastern U.S.A. The insect has two to five generations annually depending on climate (Fettig et al. 1999a, USDA For. Serv. Res. Pap., In press). Following oviposition and eclosion, first-instar larvae bore into needles and begin mining between the epidermal layers. Resin from this boring is the first visible sign of tip moth infestation but is often difficult to detect. Second-instar larvae feed at needle and bud axils and produce a web which becomes covered with resin and is the first readily visible sign of attack. Third through fifth instars enter the buds and shoots where their feeding severs the vascular tissue and kills the apical meristem. Pupation occurs in the buds or shoots killed by larval feeding (Berisford 1988, In A. A. Berryman, ed. Dynamics of Forest Insect Populations, Plenum Pub. Corp.). Tip moth infestations have been shown to reduce tree growth in young loblolly pine (Pinus taeda L.) stands (Nowak 1997, M.S. Thesis, Univ. of GA, Athens; Cade and Hedden 1987, South. J. Appl. For 11: 128-133; Stephen et al. 1982, Ark. Farm Res. 31 : 10). Chemical control of R. frustrana infestations usually consists of three insecticide applications per year in the Piedmont region of Georgia (Gargiullo et al. 1983, Ga. For. Comm. Res. Pap. No. 44). However, it has recently been shown that repeated insecticide applications within a single year may be unnecessary to protect trees from volume losses attributed to tip moth damage (Fettig et al. 1999b, South. J. Appl. For. In press). Fettig et al. (199913) found a 74.5% increase in volume yield when insecticide applications were limited to the first generation of the first two years following planting. They also observed that previous tip moth attacks appeared to predispose trees to heavier attacks in subsequent generations, and listed this observation as a potential cause or contributor to their findings To test this possibility we selected two sites in Oglethorpe Co., GA where three tip moth generations occur annually (Fettig et al. 1999a). As part of a larger study, 80