Biomarker genes highlight intraspecific and interspecific variations in the responses of Pinus taeda L. and Pinus radiata D. Don to Sirex noctilio F. acid gland secretions.

Sirex noctilio F., a Eurasian horntail woodwasp recently introduced into North America, oviposits in pines and other conifers and in the process spreads a phytopathogenic fungus that serves as a food source for its larvae. During oviposition the woodwasp also deposits mucus produced in its acid (venom) gland that alters pine defense responses and facilitates infection by the fungus. A 26,496-feature loblolly pine cDNA microarray was used to survey gene expression of pine tissue responding to S. noctilio venom. Six genes were selected for further assessment by quantitative real-time polymerase chain reaction (qRT-PCR), including one that encoded an apparent PR-4 protein and another that encoded a thaumatin-like protein. Expression of both was strongly induced in response to venom, while expression of an apparent actin gene (ACT1) was stable in response to the venom. The pattern of gene response was similar in Pinus taeda L. and Pinus radiata D. Don, but the magnitude of response in P. radiata was significantly stronger for each of the induced genes. The magnitude of the biomarker gene response to venom also varied according to genotype within these two species. The qRT-PCR assay was used to demonstrate that the primary bioactive component in S. noctilio venom is a polypeptide.

Increased resin flow in mature pine trees growing under elevated CO2 and moderate soil fertility.

Warmer climates induced by elevated atmospheric CO(2) (eCO(2)) are expected to increase damaging bark beetle activity in pine forests, yet the effect of eCO(2) on resin production--the tree's primary defense against beetle attack--remains largely unknown. Following growth-differentiation balance theory, if extra carbohydrates produced under eCO(2) are not consumed by respiration or growth, resin production could increase. Here, the effect of eCO(2) on resin production of mature pines is assessed. As predicted, eCO(2) enhanced resin flow by an average of 140% (P=0.03) in canopy dominants growing in low-nitrogen soils, but did not affect resin flow in faster-growing fertilized canopy dominants or in carbohydrate-limited suppressed individuals. Thus, pine trees may become increasingly protected from bark beetle attacks in an eCO(2) climate, except where they are fertilized or are allowed to become overcrowded.

Use of systemic fipronil and imidacloprid to control regeneration pests of loblolly pine.

Regeneration pests of loblolly pine (Pinus taeda L.) threaten growth and survival in intensively managed loblolly pine plantations throughout the southeastern United States. The Nantucket pine tip moth, Rhyacionia frustrana (Comstock), in particular, often reduces growth of loblolly pine but has been difficult to control with traditional insecticides due to multiple annual generations and multi-year infestations which are difficult to predict in timing and location. Relatively new systemic insecticide products offer a solution in that their efficacy persists through multiple generations and years after a single application. Efficacy of systemic imidacloprid and fipronil were evaluated side by side across multiple sites in Virginia. Significant reductions in Nantucket pine tip moth damage were noted in trees treated with either the imidacloprid or fipronil product compared with check trees. After 2 yr, growth improvement of treated trees relative to controls was modest and not significant at all sites, but per acre volume indices were significantly greater in treated blocks as a result of higher tree survival. Reduced seedling mortality was attributed primarily to prevention of damage by pales weevil, Hylobius pales Herbst (Coleoptera: Curculionidae), by both insecticide treatments. Control of pales weevil in addition to pine tip moth suggests that systemic insecticide products with a long window of efficacy might control additional nontargeted pests.

Efficacy of two systemic insecticides injected into loblolly pine for protection against southern pine bark beetles (Coleoptera: Curculionidae).

We evaluated the efficacy of systemic insecticides emamectin benzoate and fipronil for preventing mortality of individual loblolly pines, Pinus taeda L., as a result of attacks by southern pine bark beetles (Coleoptera: Curculionidae, Scolytinae) for two consecutive years in Mississippi (2005-2006) and Alabama (2006-2007). Trees were injected once in the spring of 2005 (Mississippi) or 2006 (Alabama) and then were baited with species-specific bark beetle lures several weeks later. The southern pine beetle, Dendroctonus frontalis Zimmermann, was the target species but was changed to Ips spp. in Mississippi (but not Alabama) the second year because of few southern pine beetle attacks on baited trees. Single injections of emamectin benzoate were effective in reducing tree mortality caused by bark beetles compared with untreated checks. Although less effective overall, fipronil also significantly reduced tree mortality from southern pine beetle compared with the checks during the second year in Alabama. Tree mortality continued well after the lures had been removed. Evaluations of bolts taken from experimental trees killed in 2006 indicated that emamectin benzoate effectively prevented parent bark beetle gallery construction and that fipronil significantly reduced lengths of galleries constructed by adult beetles, brood development, and emergence, compared with checks. In contrast, neither insecticide treatment prevented the bark beetles from inoculating blue stain fungi, Ophiostoma spp., into treated trees.

Operational considerations for augmentation of Trichogramma exiguum (Hymenoptera: Trichogrammatidae) for suppression of Rhyacionia frustrana (Lepidoptera: Tortricidae) in Pinus taeda plantations.

Studies were performed to assess the operational feasibility of Trichogramma exiguum Pinto & Platner (Hymenoptera: Trichogrammatidae) augmentation for suppression of the Nantucket pine tip moth, Rhyacionia frustrana (Comstock) (Lepidoptera: Tortricidae), in commercial loblolly pine, Pinus taeda L., plantations. Single inundative releases containing two cohorts of encapsulated T. exiguum at a potential rate of 224,200 +/- 27,600 females per ha per cohort were made into two 4-ha plots during the second R. frustrana generation in 2000. Augmentation failed to increase parasitism rates above those occurring naturally; yet, 10% fewer shoots were attacked by R. frustrana, but not below acceptable levels. Quality control data suggest that low emergence levels and intense predation by ants upon developing T. exiguum lowered actual release rates to 13,000 +/- 900 females per ha per cohort. The effect of capsule distribution and microclimate on the discovery of capsules by predators (indicated by some E. kuehniella egg removal), parasitoid predation (percentage of eggs removed or destroyed), and subsequent parasitoid emergence was investigated. Uniformly distributed capsules experienced significantly higher predation levels than clustered capsules, and capsules exposed to field conditions for 5 d experienced higher predation than those exposed for 3 d, independently of distribution. Discovery of capsules by predators was unaffected by distribution or exposure period. Microhabitat significantly impacted average maximum daily temperature, the number of consecutive hours per day at or above 35 degrees C, and parasitoid emergence percentages. Parasitoid emergence declined significantly in response to increasing number of consecutive hours per day above 35 degrees C. Microclimate did not impact capsule discovery by predators or predation levels. Augmentation of T. exiguum for suppression of R. frustrana damage may not be practical within P. taeda plantations.

Resin flow responses to fertilization, wounding and fungal inoculation in loblolly pine (Pinus taeda) in North Carolina.

Resin flow is the primary means of natural defense against southern pine beetle (Dendroctonus frontalis Zimm.), the most important insect pest of Pinus spp. in the southern United States. As a result, factors affecting resin flow are of interest to researchers and forest managers. We examined the influence of fertilization, artificial wounding and fungal inoculation on resin flow in 6- and 12-year-old stands of loblolly pine (Pinus taeda L.) and determined the extent of that influence within and above the wounded stem area and through time. Fertilization increased constitutive resin flow, but only the younger trees sustained increased resin flow after wounding and inoculation treatments. An induced resin flow response occurred between 1 and 30 days after wounding and inoculation treatments. Wounding with inoculation resulted in greater resin flow than wounding alone, but increasing amounts of inoculum did not increase resin flow. Increased resin flow (relative to controls) lasted for at least 90 days after wounding and inoculation. This increase appeared to be limited to the area of treatment, at least in younger trees. The long-lasting effects of fungal inoculation on resin flow, as well as the response to fertilization, suggest that acquired resistance through induced resin flow aids in decreasing susceptibility of loblolly pine to southern pine beetle.