John T. Nowak

The nantucket pine tip moth (Lepidoptera: Torticidae): a literature review with management implications

The Nantucket pine tip moth, Rhyacionia frustrana (Comstock), an important pest of intensively-managed loblolly pine, Pinus taeda L., was first noted in the scientific literature in 1879. This pest gained notoriety with the establishment of loblolly pine monocultures throughout the southeastern United States during the 1950s. Current intensive forest management practices have led to increasing interest in managing this insect. Herein we review all Nantucket pine tip moth literature (1879-2002) by addressing the following subjects: biology and life history, natural enemies, sampling methodologies, site and stand influences, economic impact, and management strategies. Further, we provide management recommendations in the form of a decision chart that is based upon the best available information to date and our collective experience.

Efficacy of Wing Versus Delta Traps for Predicting Infestation Levels of Four Generations of the Nantucket Pine Tip Moth (Lepidoptera: Tortricidae) in the Southern United States

Abstract The use of pheromone trap catches to reliably predict damage by the Nantucket pine tip moth, Rhyacionia frustrana (Comstock), in loblolly pine (Pinus taeda L.) plantations would provide forest managers with a valuable integrated pest management tool. At 17 sites throughout four states in the southern United States, in areas where R. frustrana has four annual generations, adult moths were monitored throughout the year (2002) using two types of pheromone traps, and subsequent infestation levels were determined for each tip moth generation. Cumulative wing trap catch tallies up to published spray dates for three of four adult emergence periods were highly predictive of top whorl damage during the subsequent generation using linear regression models. Multiple linear regression that included initial average tree height as a covariate did not significantly improve model efficacy. Cumulative delta trap catch tallies up to the spray date were not predictive of subsequent damage levels for any tip moth generation using linear regression models. Although multiple linear regression incorporating tree height as a covariate did greatly improve delta trap model efficacy, the power and significance of these models remained insufficient. Wing traps seem to be much more sensitive to tip moth population change than delta traps; however, both are useful for monitoring seasonal activity and initiation of spray timing models.

Irrigation and Fertilization Effects on Nantucket Pine Tip Moth (Lepidoptera: Tortricidae) Damage Levels and Pupal Weight in an Intensively-Managed Pine Plantation

The widespread application of intensive forest management practices throughout the southeastern U.S. has increased loblolly pine, Pinus taeda L., yields and shortened conventional rotation lengths. Fluctuations in Nantucket pine tip moth, Rhyacionia frustrana (Comstock), population density and subsequent damage levels have been linked to variations in management intensity. We examined the effects of two practices, irrigation and fertilization, on R. frustrana damage levels and pupal weights in an intensively-managed P. taeda plantation in South Carolina. Trees received intensive weed control and one of the following treatments; irrigation only. fertilization only, irrigation + fertilization, or control. Mean whole-tree tip moth damage levels ranged from <1 to 48% during this study. Damage levels differed significantly among treatments in two tip moth generations in 2001, but not 2000. Pupal weight was significantly heavier in fertilization compared to the irrigation treatment in 2000, but no significant differences were observed in 2001. Tree diameter. height. and aboveground volume were significantly greater in the irrigation + fertilization than in the irrigation treatment after two growing seasons. Our data suggest that intensive management practices that include irrigation and fertilization do not consistently increase R. frustrana damage levels and pupal weights as is commonly believed. However, tip moth suppression efforts in areas adjacent to our study may have partially reduced the potential impacts of R. frustrana on this experiment.

Colonization Dynamics of Subcortical Insects on Forest Sites With Relatively Stressed and Unstressed Loblolly Pine Trees.

Abstract Loblolly pine (Pinus taeda L.) is the most important commercial tree species in the southeastern United States. Since the 1950s, there have been reports of loblolly pines showing reduced growth and increased mortality, particularly in central Alabama and western Georgia, United States; the phenomenon is termed as southern pine decline (SPD). Recently, the role of rhizophagous (root-feeding) insects in loblolly pine health within the context of SPD has come under greater scrutiny. We investigated the impacts of subcortical insects, particularly rhizophagous weevils (Coleoptera: Curculionidae), on loblolly pine health in northeastern Georgia. We created plots—representing a gradient of increased relative tree stress—from ungirdled trees, ungirdled trees baited with ethanol and turpentine (ungirdled-baited), and girdled trees. In total, 10,795 subcortical insects from four families (Buprestidae, Cerambycidae, Curculionidae, and Siricidae) and >82 species were trapped in two years. Almost half of the insects trapped (46% of individuals and 11% of species) were nonnative to North America. Insect captures in plots with girdled trees were 61 and 187% greater than those with ungirdled-baited and ungirdled trees, respectively. Tree treatment impacted captures of native, but not nonnative insects. Relative feeding area by the rhizophagous weevils Hylobius pales (Herbst) and Pachylobius picivorus (Germar) on pine twigs placed in pitfall traps was 1, 17, and 82% in plots with ungirdled, ungirdled-baited, and girdled trees, respectively. Hence, there was a strong association of native subcortical insects, especially rhizophagous weevils, with relatively highly stressed trees, confirming that they are secondary instead of primary pine colonizers.

Previous tip moth infestation predispose trees to heavier attacks in subsequent generations.

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

Southern Pine Beetles in Central Hardwood Forests: Frequency, Spatial Extent, and Changes to Forest Structure

The southern pine beetle (SPB) is a major disturbance in pine forests throughout the range of southern yellow pines, and is a significant influence on forests throughout several Central Hardwood Region (CHR) ecoregions. At endemic levels, SPB colonizes individual stressed or lightning-struck trees, acting as a natural thinning agent. During outbreaks, tree mortality from SPB may impact CHR forests by indirectly converting stands to other species types, or changing the stand age and structure. Southern pine beetle can also create disturbance in stands by causing mortality in large clusters of pine trees or by hastening the succession from pine-hardwood forests to late-successional forest by killing single or groups of overstory pine trees. Populations are cyclical and have traditionally impacted CHR forests every 7–25 years, depending on location. The most significant outbreaks in this region in the past 65 years occurred 1974–1976 and 1997–2003, with the most recent impacting more than 405,000 ha, and caused an estimated economic loss of more than

The effectiveness of vegetation management practices for prevention and control of bark beetle infestations in coniferous forests of the western and southern United States

1 billion across six states. In this chapter we examine the spatial extent and frequency of SPB outbreaks in the CHR. We also discuss the severity of disturbance caused by SPB to forests in this region over the past 65 years; how this disturbance has altered the resultant forests; and the potential impacts of changes in climate and anthropogenic effects on preventing infestations and reducing levels of tree mortality attributed to SPB.