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Aggressive bark beetles colonize and kill healthy conifers through pheromone-mediated mass aggregation. In several species, the focal point of aggregation moves progressively from mass-attacked ‘focus trees’ to adjacent, unattacked ‘recipient trees’, resulting in infestation growth. This process, termed ‘switching’, is hypothesized to be mediated in whole or in part by antiaggregation pheromones released by beetles as colonization intensifies on a focus tree. We tested this hypothesis with the southern pine beetle, Dendroctonus frontalis Zimmermann (Coleoptera: Curculionidae: Scolytinae), by using a windvane apparatus that maintained an unbaited, black, cylindrical trap (surrogate for a recipient tree) continuously 4 m downwind from an identical trap baited with synthetic aggregation attractant (surrogate for a focus tree). In two of three replicated trials, addition of pheromone components with antiaggregation activity, endo-brevicomin or verbenone, to the upwind trap caused a significant but small (

Semiochemical background in the environment can influence insect orientation to release points of the same or different semiochemicals. endo-Brevicomin is a pheromone component of the tree-killing bark beetle Dendroctonus frontalis Zimmermann (Coleoptera: Curculionidae: Scolytinae) that has a biphasic dose–response curve, enhancing attraction at low release rates but reducing attraction at high rates. We investigated the effect of artificial manipulation of background levels of endo-brevicomin on D. frontalis responses to sources of aggregation attractant in the field. Traps baited with the aggregation pheromone component frontalin and the host odor alpha-pinene were deployed either with or without a background of endo-brevicomin produced by three surrounding dispensers of this semiochemical each located 20 m away. Two tested levels of endo-brevicomin background caused catches to increase by an order of magnitude above those in the absence of background. Presence of background also altered the beetles' biphasic dose–response when endo-brevicomin dispensers were added to traps. Background reduced or concealed attraction-enhancement otherwise observed for low-release dispensers added to traps, and it decreased the release rate necessary to produce reductions in catches. We propose that spatial variability in abundance of natural, background sources of endo-brevicomin in the environment (i.e., infested trees) is a cause of the observed variability in effects of endo-brevicomin dispensers on southern pine beetle behavior in the field. Furthermore, our results illustrate the potential complexity of the density-dependent effects of biphasic pheromone components on bark beetle mass attack and colonization behavior.

The southern pine beetle, Dendroctonus frontalis Zimmermann (Coleoptera: Curculionidae: Scolytinae) is a major destructive pest of Pinus L. In the southeastern United States, numbers of this species and a major predator, Thanasimus dubius (Fabricius) (Coleoptera: Cleridae), captured during an annual springtime trapping survey are used to make forecasts of the likelihood and severity of an outbreak during the following summer. We investigated responses by both species to six lure formulations to evaluate their suitability for the survey and allow integration of historical data sets produced with differing lure compositions. Trapping trials were performed at four locations across three states (Louisiana, Mississippi, and Alabama) during spring, and at these and one additional location (North Carolina) in fall 2016. All lures included the pheromone component frontalin. Southern pine beetle preferred lures that additionally included the pheromone component endo-brevicomin and turpentine as a source of host odors (rather than a 7:3 mixture of monoterpenes alpha- and beta-pinene). Thanasimus dubius displayed little discrimination among lure compositions. Lure preferences by southern pine beetle did not differ significantly among locations in spring but were influenced by season. Gas chromatography (GC)-electroantennographic detection analyses with southern pine beetle and GC-mass spectrometry identified numerous known and potential semiochemicals that distinguished volatiles released by the tested host odor devices. The lure combination that included endo-brevicomin and alpha/beta-pinene is recommended for the trapping survey because of its high sensitivity for southern pine beetle and potential for greater data integrity resulting from its reproducible composition.

Invasive plants have the potential to affect decomposition both directly, by introducing novel substrates that may differ from native species in key structural or chemical properties, and indirectly through changes to soil properties and microbial communities. The relative importance of these two mechanisms is unclear, especially with regard to wood decomposition. To explore these questions, we used a novel method to rapidly assess the wood decay rates of 11 native and 11 invasive non-native angiosperm species. The study was repeated at three pairs of sites, each consisting of an invaded and a relatively uninvaded forest. The invaded sites had either been colonized by a non-native grass (Microstegium vimineum (Trin.) A. Camus), a non-native woody shrub (Ligustrum sinense Lour.) or by multiple invasive species. After one year in the field, mass loss varied more than two-fold among the 22 wood species (24.2–52.3%). Wood origin (i.e., native or non-native) was only important at the Microstegium sites, with non-native species decomposing marginally faster than native species. Wood decomposed faster at both the Ligustrum-invaded and multiply-invaded sites than in their respective uninvaded sites but there were no differences between sites invaded or not by Microstegium. We detected positive relationships overall between mass loss and pH, K, P and NO3−, but invasion had no consistent effects on these soil properties. The results from this study show that the differences in wood decay rates between native and non-native species and the effects of invasion are highly idiosyncratic, with effects depending greatly on species and ecological context.

Management options are needed to limit sweetpotato yield loss due to weeds. Greenhouse studies were conducted in 2018 in Greensboro, NC, and in the field from 2016 to 2018 in Clinton, NC, to evaluate the effect of bicyclopyrone on sweetpotato and Palmer amaranth (field only). In greenhouse studies, Covington and NC04-531 clones were treated with bicyclopyrone (0, 25, 50, 100, or 150 g ai ha−1) either preplant (PP; i.e., immediately before transplanting) or post-transplant (PT; i.e., on the same day after transplanting). Sweetpotato plant injury and stunting increased, and vine length and shoot dry weight decreased with increasing rate of bicyclopyrone regardless of clone or application timing. In field studies, Beauregard (2016) or Covington (2017 and 2018) sweetpotato clones were treated with bicyclopyrone at 50 g ha−1 PP, flumioxazin at 107 g ai ha−1 PP, bicyclopyrone at 50 or 100 g ha−1 PP followed by (fb) S-metolachlor at 800 g ai ha−1 PT, flumioxazin at 107 g ha−1 PP fb S-metolachlor at 800 g ha−1 PT, flumioxazin at 107 g ha−1 PP fb S-metolachlor at 800 g ha−1 PT fb bicyclopyrone at 50 g ha−1 PT-directed, and clomazone at 420 g ai ha−1 PP fb S-metolachlor at 800 g ha−1 PT. Bicyclopyrone PP at 100 g ha−1 fb S-metolachlor PT caused 33% or greater crop stunting and 44% or greater marketable yield reduction compared with the weed-free check in 2016 (Beauregard) and 2017 (Covington). Bicyclopyrone PP at 50 g ha−1 alone or fb S-metolachlor PT resulted in 12% or less injury and similar no. 1 and jumbo yields as the weed-free check in 2 of 3 yr. Injury to Covington from bicyclopyrone PT-directed was 4% or less at 4 or 5 wk after transplanting and marketable yield was similar to that of the weed-free check in 2017 and 2018.

Field studies were conducted in 2016 and 2017 at Clinton, NC, to quantify the effects of season-long interference of large crabgrass [Digitaria sanguinalis (L.) Scop.] and Palmer amaranth (Amaranthus palmeri S. Watson) on ‘AG6536’ soybean [Glycine max (L.) Merr.]. Weed density treatments consisted of 0, 1, 2, 4, and 8 plants m−2 for A. palmeri and 0, 1, 2, 4, and 16 plants m−2 for D. sanguinalis with (interspecific interference) and without (intraspecific interference) soybean to determine the impacts on weed biomass, soybean biomass, and seed yield. Biomass per square meter increased with increasing weed density for both weed species with and without soybean present. Biomass per square meter of D. sanguinalis was 617% and 37% greater when grown without soybean than with soybean, for 1 and 16 plants m−2 respectively. Biomass per square meter of A. palmeri was 272% and 115% greater when grown without soybean than with soybean for 1 and 8 plants m−2, respectively. Biomass per plant for D. sanguinalis and A. palmeri grown without soybean was greatest at the 1 plant m−2 density. Biomass per plant of D. sanguinalis plants across measured densities was 33% to 83% greater when grown without soybean compared with biomass per plant when soybean was present for 1 and 16 plants m−2, respectively. Similarly, biomass per plant for A. palmeri was 56% to 74% greater when grown without soybean for 1 and 8 plants m−2, respectively. Biomass per plant of either weed species was not affected by weed density when grown with soybean due to interspecific competition with soybean. Yield loss for soybean grown with A. palmeri ranged from 14% to 37% for densities of 1 to 8 plants m−2, respectively, with a maximum yield loss estimate of 49%. Similarly, predicted loss for soybean grown with D. sanguinalis was 0 % to 37% for densities of 1 to 16 m−2 with a maximum yield loss estimate of 50%. Soybean biomass was not affected by weed species or density. Results from these studies indicate that A. palmeri is more competitive than D. sanguinalis at lower densities, but that similar yield loss can occur when densities greater than 4 plants m−2 of either weed are present.

We investigated geographic variation in the semiochemistry of major disturbance agents of western North American pine forests, Dendroctonus brevicomis Le Conte and Dendroctonus barberi Hopkins (Coleoptera: Curculionidae: Scolytinae), species separated by the Great Basin in the USA that until recently were synonymous. At 15 sites in the western USA and northern Mexico, beetle populations were examined to determine (1) pheromone production by solitary, mining females, (2) male electroantennogram amplitudes in response to known semiochemicals for the genus, or (3) relative attractiveness of two female-produced pheromone components (endo- and exo-brevicomin) and two host odors (alpha-pinene and myrcene) to beetles in the field. Compared to female beetles collected east of the Great Basin (D. barberi), western females (D. brevicomis) produced a consistently higher proportion of, and male antenna were correspondingly more sensitive to, the exo- than the endo-isomer of brevicomin. With the exception of one sampling location (where no preference was observed), beetles west of the Great Basin were more attracted to exo- than endo- brevicomin trap lures, whereas eastern beetles displayed the reverse preference. In contrast, there was not a consistent difference between these populations regarding relative attraction or olfactory response to myrcene or alpha-pinene, although some geographic variability was evident. These data show that the semiochemical systems of D. brevicomis and D. barberi have diverged and corroborate genetic and morphological evidence that they are distinct, allopatric species.

Field experiments determined the critical period for weed control (CPWC) in grafted and nongrafted watermelon [Citrullus lanatus(Thumb.) Matsum. & Nakai] grown in plasticulture. Transplant types included ‘Exclamation’ seedless watermelon as the nongrafted control as well as Exclamation grafted onto two interspecific hybrid squash (ISH) rootstocks, ‘Carnivor’ and ‘Kazako’. To simulate weed emergence throughout the season, establishment treatments (EST) consisted of two seedlings each of common purslane (Portulaca oleraceaL.), large crabgrass [Digitaria sanguinalis(L.) Scop.], and yellow nutsedge (Cyperus esculentusL.) transplanted in a 15 by 15 cm square centered on watermelon plants at 0, 2, 3, 4, and 6 wk after watermelon transplanting (WATr) and remained until the final watermelon harvest at 11 WATr. To simulate weed control at different times in the season, removal treatments (REM) consisted of two seedlings of the same weed species transplanted in a 15 by 15 cm square centered on watermelon plants on the same day of watermelon transplanting and allowed to remain until 2, 3, 4, 6, and 11 WATr, at which time they were removed. Season-long weedy and weed-free controls were included for both EST and REM studies in both years. For all transplant types, aboveground biomass of weeds decreased as weed establishment was delayed and increased as weed removal was delayed. The predicted CPWC for nongrafted Exclamation and Carnivor required only a single weed removal between 2.3 and 2.5 WATr and 1.9 and 2.6 WATr, respectively, while predicted CPWC for Kazako rootstock occurred from 0.3 to 2.6 WATr. Our study results suggest that weed control for this mixed population of weeds would be similar between nongrafted Exclamation and Exclamation grafted onto Carnivor. But the observed CPWC of Exclamation grafted onto Kazako suggests that CPWC may vary with specific rootstock–scion combinations.

Field studies were conducted in 2016 and 2017 in Clinton, NC, to determine the interspecific and intraspecific interference of Palmer amaranth (Amaranthus palmeri S. Watson) or large crabgrass [Digitaria sanguinalis (L.) Scop.] in ‘Covington’ sweetpotato [Ipomoea batatas (L.) Lam.]. Amaranthus palmeri and D. sanguinalis were established 1 d after sweetpotato transplanting and maintained season-long at 0, 1, 2, 4, 8 and 0, 1, 2, 4, 16 plants m−1 of row in the presence and absence of sweetpotato, respectively. Predicted yield loss for sweetpotato was 35% to 76% for D. sanguinalis at 1 to 16 plants m−1 of row and 50% to 79% for A. palmeri at 1 to 8 plants m−1 of row. Weed dry biomass per meter of row increased linearly with increasing weed density. Individual dry biomass of A. palmeri and D. sanguinalis was not affected by weed density when grown in the presence of sweetpotato. When grown without sweetpotato, individual weed dry biomass decreased 71% and 62% from 1 to 4 plants m−1 row for A. palmeri and D. sanguinalis, respectively. Individual weed dry biomass was not affected above 4 plants m−1 row to the highest densities of 8 and 16 plants m−1 row for A. palmeri and D. sanguinalis, respectively.

The southern pine beetle Dendroctonus frontalis Zimmermann (Coleoptera: Curculionidae: Scolytinae) is attracted to an aggregation pheromone that includes the multifunctional pheromone component endo-brevicomin. The effect of endo-brevicomin on attractive lures varies from strong enhancement to reduction of beetle attraction depending upon release rate, lure component spacing, and proximity of beetle infestations. Anecdotal observations have further suggested that the effects of endo-brevicomin vary during the year. We investigated this possibility under nonoutbreak conditions in southwestern Mississippi where for two-and-a-half years we monitored traps baited with frontalin and the host odor alpha-pinene either (a) alone, or with an endo-brevicomin release device either (b) located directly on the trap, or (c) displaced 6 m away. The endo-brevicomin devices in our tests increased D. frontalis catches during all times of year, and 6 m displacement of the endo-brevicomin release device from the trap did not significantly alter responses except during the spring flight peak when displacement increased catches. Our data suggest that flying D. frontalis have a stronger tendency to avoid the immediate proximity of a release point of endo-brevicomin during their springtime dispersal flight when catches are greatest. Catches of Thanasimus dubius (F.) (Coleoptera: Cleridae), a major predator of D. frontalis, were not altered by endo-brevicomin, and ratios of D. frontalis to T. dubius changed over the course of the year. We discuss the possible effects of intra-annual variation in D. frontalis response to endo-brevicomin both on beetle attack behavior and use of endo-brevicomin as a lure adjuvant in D. frontalis population monitoring.

Soybean (Glycine max) is an important food stock, and also considered an allergenic food with at least eight well characterized allergens. However, it is a less prevalent allergen source than many other foods and is rarely life-threatening. Soybean is incorporated into commonly consumed foods, and therefore, the allergens pose a potential concern for individuals already sensitized. The protein profile of soybean can be affected by several factors including genetic and environmental. To investigate how soybean allergen content may be affected by genetics and/or environment, nine soy allergens were quantified from three commercial soybean varieties grown at nine locations in three states within a single climate zone in North America; Iowa, Illinois, and Indiana, United States. Quantitation was achieved using liquid chromatography-selected reaction monitoring (LC-SRM) tandem mass spectrometry with AQUA peptide standards specific to the nine target allergens. Quantitation of allergen concentration indicated that both genetics and location affected specific allergen content. Seven of the nine allergens were significantly influenced by genetics, with the exceptions of glycinin G4 and KTI 3. The allergens P34, Gly m Bd 28k, glycinin G3, and KTI 1 showed statistically significant impact from location as well, but at a lower threshold of significance compared with genetics (cultivar/variety). This dataset contributes to our understanding of the natural variation of endogenous allergens, as it represents a sampling of soybeans grown in a controlled, distributed plot design under agronomic conditions common for commercial soybean food and feed production. The aim was to build upon our recent understanding of how allergens are expressed as part of the overall soybean proteome.

The non-native emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), threatens extirpation of susceptible ash (Fraxinus species; Lamiales: Oleaceae) in North America. Cerceris fumipennis Say (Hymenoptera: Crabronidae), a ground-nesting wasp that preys on Buprestidae in eastern North America, is used as a survey tool for the emerald ash borer in the northeastern U.S. and Canada. The recent detection of the emerald ash borer in Louisiana provides an opportunity to complement trapping surveys with the use of C. fumipennis, but knowledge of C. fumipennis in the region is lacking. From 2011 to 2014, we conducted searches at 155 sites and located C. fumipennis aggregations at 25% (n = 39) of these sites; 36% (n = 14) of these were located at forest harvests, an aggregation habitat not previously reported in the literature. We collected 1,559 buprestids representing 35 species from 2 aggregations in Louisiana between May and Aug 2012. Buprestid collections at these aggregations and...

Since 2003, the Southern Pine Beetle Prevention Program (SPBPP) (a joint effort of the USDA Forest Service and Southern Group of State Foresters) has encouraged and provided cost-share assistance for silvicultural treatments to reduce stand/forest susceptibility to the southern pine beetle (SPB) (Dendroctonus frontalis Zimmermann) in the southeastern United States. Until now, stand- and landscape-level tests of this program’s efficacy were nonexistent. In 2012, SPB outbreaks occurred in the Homochitto and Bienville National Forests (NFs) in Mississippi. Parts of each NF were treated (thinned) using SPBPP management recommendations, whereas other areas were untreated (unthinned). In the Homochitto NF, 99.7% of SPB spots occurred in unthinned stands, whereas all SPB spots occurred in unthinned stands in the Bienville NF. Unthinned stands in both NFs had higher basal area, higher stocking, and lower growth rates over the last decade. Burning also resulted in a lower incidence of SPB infestation. Our retrospective study results validate the effectiveness of SPBPP treatments for reducing stand- and landscape-level susceptibility to SPB, which encourages proper silvicultural methods that increase tree spacing, growth, and vitality, while effectively altering the in-stand atmosphere enough to interfere with SPB pheromone communication, thus reducing susceptibility to SPB spot initiation and spread.

An integrated management approach is needed to maintain eastern hemlock (Tsuga canadensis (L.) Carriere) in eastern North America and to minimize tree damage and mortality caused by the invasive hemlock woolly adelgid (Adelges tsugae Annand). This study examined the hypothesis that chemical control with low rates of insecticide and biological control can be combined in the same stand to impact adelgid populations, prolong crown health, and allow predator proliferation. Sixty T. canadensis trees in northern Georgia were individually treated via soil injection with 0%, 10%, or 25% of the label rate of imidacloprid insecticide, and the biological control predator Laricobius nigrinus Fender was released in the stand, two and four years later. By year seven, hemlocks treated with the 25% imidacloprid rate lost their insecticide protection, had significantly better crown health and higher adelgid densities than untreated trees, and supported as many Laricobius predator larvae as untreated trees. In year seven, no residues of imidacloprid were detected in Laricobius larvae feeding on previously-treated hemlocks. Most (77%) of the predators collected on study trees were identified as L. nigrinus, 12% were the native congener Laricobius rubidus LeConte, and 11% were hybrids between the introduced and native species. The hybridization rate remained stable over time. The density of undisturbed A. tsugae ovisacs was twice as high on branches protected from predators as compared with branches exposed to predators. Results suggest that chemical and biological control of A. tsugae can be successfully integrated to help prolong hemlock health, although additional predators may be necessary to protect hemlock trees in the southern Appalachians.

The redbay ambrosia beetle (Xyleborus glabratus Eichhoff) is an invasive pest and vector of the pathogen that causes laurel wilt disease in Lauraceous tree species in the eastern United States. This insect uses olfactory cues during host finding, but use of visual cues by X. glabratus has not been previously investigated and may help explain diameter-related patterns in host tree mortality. The objective of this study was to determine whether X. glabratus females visually detect silhouettes of tree stems during host finding and are more likely to land on large diameter stems than smaller ones. Three field experiments were conducted in which stem silhouettes (black cylinders or standing nonhost pines) of varying diameters and identical capture surface areas were baited with essential oil lures. The Log10-transformed number of X. glabratus trapped per week increased as a function of silhouette diameter in 2011 and 2012, using artificial silhouette diameters ranging 2-18 and 3-41 cm, respectively. When lures and capture surfaces were attached to standing pines ranging 4-37 cm in diameter, a positive relationship between Log10(X. glabratus trap catch) and stem diameter was modeled using nonlinear quadratic plateau regression and indicated a diameter above which visual attraction was not enhanced; however, there was not a maximum diameter for enhanced X. glabratus attraction that was generally consistent across all experiments. These results 1) indicate that X. glabratus incorporates visual information during host finding, 2) help explain diameter-related patterns of redbay (Persea borbonia (L.) Sprengel) mortality observed during laurel wilt epidemics, and 3) are applicable to the management of this forest pest.

We compared pheromone production and response for populations of western pine beetle, Dendroctonus brevicomis LeConte, from sites in northern Arizona and northern California. Volatiles were collected from individuals of both sexes that had mined as a pair in a Pinus ponderosa log for 1 d, and they were subsequently analyzed by gas chromatography coupled to mass-spectrometry. Principal component analysis of quantities of Dendroctonus pheromone components indicated strong site-associated clustering of blend composition for females but not males. Much of the clustering in females evidently was due to differences in the production of endo- and exo-brevicomin, which occurred in average ratios of 0.1:1 and 19:1 for populations in the California and Arizona sites, respectively. In the California site, exo- was better than endo-brevicomin in enhancing trap catches of both sexes to lures containing the host-tree odor α-pinene and the male-produced aggregation pheromone component frontalin. In an identical test in the Arizona site, endo- was a better adjuvant than exo-brevicomin for male attraction, whereas females did not show a significant preference. At neither location were the isomers antagonistic to one another in activity. Thus, one aggregation pheromone has apparently diverged between these populations, concurrent with published evidence that D. brevicomis on either side of the Great Basin are genetically distinct and are possibly different species. Furthermore, production of and response to the isomers of brevicomin by flying Dendroctonus frontalis Zimmermann in the Arizona site were similar to those of sympatric D. brevicomis. This interspecific signal overlap is likely sustainable since joint species mass-attacks may assist both species in overcoming host defenses, thereby increasing host availability.

We propose a novel likelihood method for analyzing time-to-event data when multiple events and multiple missing data intervals are possible prior to the first observed event for a given subject. This research is motivated by data obtained from a heart monitor used to track the recovery process of subjects experiencing an acute myocardial infarction. The time to first recovery, T1, is defined as the time when the ST-segment deviation first falls below 50% of the previous peak level. Estimation of T1 is complicated by data gaps during monitoring and the possibility that subjects can experience more than one recovery. If gaps occur prior to the first observed event, T, the first observed recovery may not be the subject’s first recovery. We propose a parametric gap likelihood function conditional on the gap locations to estimate T1. Standard failure time methods that do not fully utilize the data are compared to the gap likelihood method by analyzing data from an actual study and by simulation. The proposed gap likelihood method is shown to be more efficient and less biased than interval censoring and more efficient than right censoring if data gaps occur early in the monitoring process or are short in duration.

Dendroctonus frontalis Zimmermann (Coleoptera: Curculionidae: Scolytinae) is a major economic pest of pines in the United States, Mexico, and Central America. We report biochemical investigations relevant to the taxonomic status and semiochemistry of two distinct morphotypes of D.frontalis recently detected in the Central American region. Morphotype A beetles (pre-episternal area of prothorax of both sexes smooth, bulging callus on anterolateral margin of prothorax of females) and morphotype B beetles (pre-episternal area of prothorax of both sexes with fine ridges, reduced female callus) collected in infestations in Chiapas, Mexico differed significantly in their production of 10 behaviorally-active compounds occurring in the genus Dendroctonus, including the major pheromone components for D. frontalis. Notably, host-attacking morphotype B females produced hundreds of nanograms of both endo-brevicomin and frontalin, whereas morphotype A females produced similar amounts of frontalin but subnanogram quantities of endo-brevicomin. Reanalysis of a published D. frontalis trapping study in Chiapas indicated that both morphotypes responded in greatest numbers when frontalin and endo-brevicomin baits were both present. In addition, we quantified 18 different cuticular hydrocarbons (the methyl-branched alkane components) from both morphotypes collected in Belize and Chiapas as well as morphotype A beetles from the southeastern United States, and principal component analysis revealed nonoverlapping clusters associated with either morphotype. This evidence of two distinct, complex phenotypes coexisting in the same sites and host trees supports the hypothesis that the D. frontalis morphotypes represent separate species and consequently indicates that the taxonomy of D. frontalis should be re-evaluated in the Central American region.

Where a female places her eggs can have a major impact on the fitness of her offspring, especially for insects in which the winged adults are far more mobile than the neonates. Larvae of Heliothis subflexa (Guenee) (Lepidoptera: Noctuidae), a specialist moth phylogenetically nested within a generalist clade, feed only on fruit of some Physalis species. Field observations of the oviposition behavior of H. subflexa revealed that 1) females laid most of their eggs on leaves of the Physalis plant, despite the larvae's frugivorous diet, and 2) females laid nearly 20% of the eggs on nonhost plant species. Most eggs oviposited on nonhosts were placed close to the host plant-88% were within 15 cm of the Physalis plant. However, in a study of neonate movement, we found that a distance of 2 cm from the hatch site to the host plant significantly decreased the ability of neonates to establish on the host plant. The estimated fitness cost, quantified as reduced neonate survival, for females ovipositing on nonhosts is 8-17%. Many ecological and evolutionary factors could result in oviposition on less suitable host parts and on nonhosts. One possibility is that specialization on Physalis has recently evolved in H. subflexa, and females have not fully optimized their oviposition behavior. However, the fitness cost of oviposition on nonhosts may be balanced by fitness benefits of such behavior, such as faster decision-making and reduced predation.

Ophiostomatoid fungi are important components within the highly damaging insect-fungal complexes attacking trees in North America. This group includes the disease agents responsible for Dutch elm disease and laurel wilt, as well as a number of associates of tree-killing bark beetles. While systemic fungicides have been applied against ophiostomatoids in certain fungus-host systems, the breadth of their utility and their management implications for a wide array of fungus and host species remain uncertain. To evaluate the impact of commercially available fungicides against the bluestaining fungus Ophiostoma minus, an associate of the southern pine beetle, researchers conducted two experiments with loblolly pines (Pinus taeda; mean dbh 14.2 and 18.5 cm, respectively) in central Louisiana, U.S. The first experiment screened three fungicides (Alamo®, Arbotect® 20-S, and PHOSPHO-jet) for their systemic impacts on O. minus, and the second further evaluated the best performing product (Alamo) alone and in combination with Arbotect 20-S. In all cases, loblolly pines were stem-injected basally and challenged with inoculations of cultured O. minus at time periods ranging from 28 days to 738 days post-treatment. In both experiments, treatment of loblolly pines with Alamo produced the smallest lesion areas, indicating that this treatment was the most effective for limiting the within-tree growth of O. minus. This effect was still present more than two years post-treatment. The study authors conclude that Alamo is the most effective product of those evaluated for prophylactic treatment against O. minus, and suggest that evidence is building for the effectiveness of this product generally against ophiostomatoid fungi.

Entomopathogenic nematodes (EPN) in the families Steinernematidae and Heterorhabditidae occur naturally in the soil and are produced commercially for the management of soil-dwelling pests. EPN infected cadavers also represent a potential resource for other soil organisms. We examined the short-term (24 h) response in abundance, diversity and community composition of localized soil microinvertebrates to the presence of EPN-infected insect cadavers in no-till and conventional-till maize. We hypothesized that the response of soil microinvertebrates to the EPN-infected cadavers would vary by soil management practices and EPN species. We expected to observe greater numbers and diversity of arthropods in no-till compared with conventional-till soil, and in the vicinity of steinernematid-infected insect cadavers compare to what would be found in the vicinity of heterorhabditid-infected cadavers. 45,606 invertebrates were collected and identified to 134 morphotaxa. Tillage regime accounted for the majority of the variation observed (84.6%), whereas nematode treatment accounted for 7.5%. Taxonomic richness of invertebrates was greater in treatments with Steinernema carpocapsae -infected cadavers than with Heterorhabditis bacteriophora -infected cadavers. Some invertebrates increased in abundance where EPN were applied whereas others decreased, regardless of tillage practice. Applications of Galleria cadavers infected with steinernematids elicited positive responses from two mite taxa, Galumnidae and Scheloribates spp., while negative responses were elicited from three mite (Histiostomatidae, Scheloribates spp., Eupodes spp.), taxa and Entomobryidae (Collembola) in response to applications of Heterorhabditis -infected cadavers.

The male-produced bicyclic acetal endo-brevicomin is a component of the pheromone blend that mediates colonization of host pines by the bark beetle Dendroctonus frontalis Zimmermann. Efforts to identify its behavioral function have been complicated by contrasting reports that it either enhances or reduces attraction of flying beetles. Our studies failed to support the hypothesis that this published variability is due to differences in release rate and/or the enantiomeric composition [i.e., the beetle-produced (+)-enantiomer vs. the racemate] of the endo-brevicomin used in the experiments. In trapping trials within active D. frontalis infestations, racemic and (+)-endo-brevicomin did not differ from each other in behavioral effects when tested at seven different release rates ranging from 0.005 to 3 mg/d. At the highest release rates, racemic and (+)-endo-brevicomin similarly reduced catches in traps baited with an attractant (frontalin and turpentine), but neither enhanced catches at any release rate. Furthermore, the activity of racemic endo-brevicomin baits depended on trap proximity to D. frontalis infestations. Addition of these baits to attractant-baited traps located inside active infestations reduced catches, but they enhanced catches at traps located either 100 or 200 m outside these infestations. The contrasting responses may reflect differences in host-seeking strategies by either aggregated or dispersing D. frontalis, and may be elicited by differing abundance of natural sources of semiochemicals or differing responsiveness of beetles inside vs. outside of infestations. We suspect that much of the published variability in D. frontalis responses to endo-brevicomin is attributable to differing proximity of experimental field sites to infestations.

Natural vegetation occurring on farms in field margins, fallow fields, ditch systems and neighboring forests, provides increased biodiversity, structural diversity, habitat for wildlife and beneficial insects, and can act as a protective buffer against agrochemical drift. Nevertheless, farmers frequently view these areas as non-productive and as potential sources of weeds, insect pests and diseases. Weed species richness and abundance were examined in crop fields in 2002–2003 at the Center for Environmental Farming Systems near Goldsboro, NC to determine if crop field weed infestation was associated with field margin management (managed versus unmanaged). Weed species abundance and richness were measured over two growing seasons on four occasions in crop fields along permanent transects that extended from the field edge toward the center of the field. The presence/absence of data for all plant species in the field margin was also recorded. For both margin types, managed and unmanaged, more weeds were found near the field edge than in the center of the field. Weed species richness was slightly higher in cropland bordering managed margins than in cropland along unmanaged margins. Several significant interactions led to an examination of nine dominant weed species in each field margin type and their distribution in crop fields. When all sampling dates were pooled, only 42 (40%) of 105 species identified in the field margins were observed in the crop field. Managed margins had lower species richness than unmanaged field margins—less than half the mean number of species (15 versus 6 species, respectively). Contingency table analysis did not reveal any association between plant species occurring in the margin and those found in the crop field. Furthermore, margin type and weed presence in the field margin were not effective predictors of weed occurrence in the crop field as determined by logistic regression.

1. Insect oral secretions are important for the induction of a number of plant responses, but the relative role of mechanical damage in the induction of these responses is often not well understood. Damage from the frugivore Heliothis subflexa, a specialist on Physalis species, causes herbivore-induced fruit abscission. In this field study, we examined the separate and combined effects of mechanical damage and H. subflexa oral secretions on Physalis fruit abscission. 2. To determine the relative role of mechanical and chemical factors, the following treatments were administered to fruit: (1) three levels of mechanical damage, (2) natural herbivore damage by control larvae and by larvae surgically treated to inhibit saliva secretion, and (3) injection of H.subflexa oral secretions and a water control. Abscission of mechanically damaged fruit with and without the addition of oral secretions was also compared. 3. Mechanical damage was sufficient to cause fruit abscission, and the addition of oral secretions to mechanically damaged fruit did not cause an increase in fruit abscission. Normal caterpillars and those treated to inhibit saliva secretion caused similar abscission rates. 4. Though most studies examining the effects of insect oral secretions on induced plant responses find these chemical stimuli to be important or essential, the results of the present study showed that oral secretions are not necessary for fruit abscission. Future work is needed to determine the relative importance of mechanical damage in herbivore-induced plant responses in other systems.

No-tillage (NT) organic vegetable production presents several economic opportunities for growers in the southeastern United States while promoting natural resource conservation. This study was conducted to determine if removal of sorghum sudangrass (SS) cover crop biomass as hay, frequency at which the cover crop is mowed, and tillage affect weed suppression and head weight of transplanted organic cabbage. Sorghum sudangrass [Sorghum bicolor(L.) Moench×Sorgum sudanense(Piper) Staph.] was planted in May 2004 at Reidsville and Goldsboro, NC, preceding the planting of organic ‘Bravo’ cabbage (Brassica oleraceaL. Capitata group) in August and September 2004, respectively. SS management systems included: low-frequency mowing with hay removed following the first mowing operation (LFM-H), low-frequency mowing with hay not removed (LFM), high-frequency mowing with hay not removed (HFM) and a no cover crop control. Two tillage treatments were applied within each management system: conventional tillage (CT) and NT. Under NT conditions, SS mulch generated by LFM offered broadleaf weed control in cabbage similar to that achieved under CT, regardless of whether cover crop biomass was removed as hay. Mowing with higher frequency reduced SS cover crop biomass by 18–33% and reduced weed suppression in NT cabbage. Mowing frequency did not influence the quantity of SS that re-grew in the cabbage crop. SS re-growth contributed to lower head weight in NT compared to CT cabbage in Goldsboro, and crop failure of NT cabbage in Reidsville. Cabbage head weight was highest when the crop was not preceded by SS in both CT and NT systems (1.6 as opposed to 1.3–1.4 kg head−1). Our findings suggest that the potential for growers to manage a cover crop also as a hay crop does exist; however, SS may not be a compatible cover crop species for organic fall cabbage production due to high amounts of re-growth.

The watershed of the Neuse River, a major tributary of the largest lagoonal estuary on the U.S. mainland, has sustained rapid growth of human and swine populations. This study integrated a decade of available land cover and water quality data to examine relationships between land use changes and surface water quality. Geographic Information Systems (GIS) analysis was used to characterize 26 subbasins throughout the watershed for changes in land use during 1992-2001, considering urban, agricultural (cropland, animal as pasture, and densities of confined animal feed operations [CAFOs]), forested, grassland, and wetland categories and numbers of wastewater treatment plants (WWTPs). GIS was also used together with longitudinal regression analysis to identify specific land use characteristics that influenced surface water quality. Total phosphorus concentrations were significantly higher during summer in subbasins with high densities of WWTPs and CAFOs. Nitrate was significantly higher during winter in subbasins with high numbers of WWTPs, and organic nitrogen was higher in subbasins with higher agricultural coverage, especially with high coverage of pastures fertilized with animal manure. Ammonium concentrations were elevated after high precipitation. Overall, wastewater discharges in the upper, increasingly urbanized Neuse basin and intensive swine agriculture in the lower basin have been the highest contributors of nitrogen and phosphorus to receiving surface waters. Although nonpoint sources have been emphasized in the eutrophication of rivers and estuaries such as the Neuse, point sources continue to be major nutrient contributors in watersheds sustaining increasing human population growth. The described correlation and regression analyses represent a rapid, reliable method to relate land use patterns to water quality, and they can be adapted to watersheds in any region.

Misidentification of animals is potentially important when naturally existing features (natural tags) are used to identify individual animals in a capture-recapture study. Photographic identification (photoID) typically uses photographic images of animals' naturally existing features as tags (photographic tags) and is subject to two main causes of identification errors: those related to quality of photographs (non-evolving natural tags) and those related to changes in natural marks (evolving natural tags). The conventional methods for analysis of capture-recapture data do not account for identification errors, and to do so requires a detailed understanding of the misidentification mechanism. Focusing on the situation where errors are due to evolving natural tags, we propose a misidentification mechanism and outline a framework for modeling the effect of misidentification in closed population studies. We introduce methods for estimating population size based on this model. Using a simulation study, we show that conventional estimators can seriously overestimate population size when errors due to misidentification are ignored, and that, in comparison, our new estimators have better properties except in cases with low capture probabilities (

Fruit abscission as a response to herbivory is well-documented in many plant species, but its effect on further damage by mobile herbivores that survive fruit abscission is relatively unstudied. Physalis plants (Solanaceae) abscise fruit containing feeding larvae of their main frugivore, Heliothis subflexa Guenee (Lepidoptera: Noctuidae), a specialist moth. We tested the ability of H. subflexa larvae placed under the plant canopy to find and climb onto two architecturally different Physalis species. Physalis pubescens L., a low, shrub-like, spreading plant, abscises its fruit at a higher rate than Physalis angulata L., a tall arborescent plant. As a result, small larvae are more often dropped from P. pubescens . Third and fifth instars located P. pubescens faster and with a higher probability than P. angulata . Although fifth instars outperformed third-instar caterpillars at finding P. angulata , P. pubescens was located equally fast by the two instars. Heliothis subflexa located Physalis plants more successfully and more quickly than a close relative, the generalist Heliothis virescens Fabricius. The higher fruit abscission rates in P. pubescens may be an evolved response to its greater susceptibility to searching caterpillars.

Plant growth regulators are routinely used in cotton (Gossypium hirsutum L.) production to reduce plant height and hasten maturity. The objective of this research was to determine the response of several cotton cultivars to mepiquat pentaborate (MPB) application in environments accumulating different levels of heat units. Four MPB application regimes were imposed on three cultivars in Virginia and South Carolina in 2005 and 2006. Total MPB season rates of 0.0, 54.9, 85.3, or 121.9 g ai ha -1 applied at the five-leaf stage, pin-head square, match-head square, and early bloom were used. The cultivars were: Deltapine (DP) 444 BG/RR, an "early-maturing" cultivar; Fibermax (FM) 960 BR, a "medium-maturing" cultivar; and DP 555 BG/RR, a "late-maturing" cultivar. In South Carolina in 2006, FM 960 BR July plant height was reduced by 25% with MPB application compared to only 12 and 13% for DP 444 BG/RR and DP 555 BG/RR, respectively, although actual plant height reductions were not different among cultivars. Mepiquat pentaborate applications decreased plant height at harvest by 8 to 34%, height-to-node ratio by 10 to 32%, enhanced maturity as measured by nodes above white flower for all cultivars, and decreased lint yield by 3.7 to 8.5% compared to untreated cotton. Higher seasonal totals and earlier initiation of MPB application resulted in the greatest decrease in lint yield.

Oleate content is important for the nutritional value and oxidative stability of soybean [Glycine max (L.) Merr.] seed oil. Response to selection for higher oleate content depends on its heritability in breeding populations, and correlated responses of other fatty acid and agronomic traits to selection for oleate content depend on their genetic correlations with oleate. The objective of this study was to estimate the heritability of oleate content and to determine the correlation of oleate with other fatty acid and agronomic traits in three soybean populations segregating for major and minor oleate genes grown in multiple environments. One of the populations consisted of 721 lines, providing excellent precision for estimation of the genetic parameters. The results of this study indicated that heritability for oleate content was suffi ciently high that early generation selection can be effective when practiced on unreplicated lines grown at a single environment. Signifi cant negative correlations were observed between oleate and linoleate, oleate and linolenate, as well as oleate and palmitate in all three populations. Signifi cant positive correlations were detected between palmitate and stearate in one population segregating for oleate genes and fap nc and fap1 alleles, which reduce palmitate content. In the same population we also observed a signifi cant negative correlation between yield and oleate content, and positive correlations between yield and linoleate, and linolenate and palmitate contents.

Water level time series records from the Neuse and Pamlico River Estuaries were statistically compared to local and distant wind field data, water level records within the Pamlico Sound and also coastal ocean sites to determine the relative contribution of each time series to water levels in the Neuse and Pamlico Estuaries. The objectives of this study were to examine these time series data using various statistical methods (i.e. autoregressive, empirical orthogonal function analysis (EOF), exploratory data analysis (EDA)) to determine short- and long-time-scale variability, and to develop predictive statistical models that can be used to estimate past water level fluctuations in both the Neuse Estuary (NE) and Pamlico Estuary (PE). Short- and long-time-scale similarities were observed in all time series of estuarine, Pamlico Sound and subtidal coastal ocean water level and wind component data, due to events (nor'easters, fronts and tropical systems) and seasonality. Empirical orthogonal function analyses revealed a strong coastal ocean and wind field contribution to water level in the NE and PE. Approximately 95% of the variation was captured in the first two EOF components for water level data from the NE, sound and coastal ocean, and 70% for the PE, sound and coastal ocean. Spectral density plots revealed strong diurnal signals in both wind and water level data, and a strong cross correlation and coherency between the NE water level and the North/South wind component. There was good agreement between data and predictions using autoregressive statistical models for the NE (R2 = 0.92) and PE (R2 = 0.76). These methods also revealed significant autoregressive lags for the NE (days 1 and 3) and for the PE (days 1, 2 and 3). Significant departures from predictions are attributed to local meteorological and hydrological events. The autoregressive techniques showed significant predictive improvement over ordinary least squares methods. The results are considered within the context of providing long time-scale hindcast data for the two estuaries, and the importance of these data for multidisciplinary researchers and managers.

Solidago verna M. A. Curtis ex Torrey & A. Gray (spring-flowering goldenrod) [Asteraceae] is threatened in North Carolina, a species of federal concern, endemic to fire– adapted longleaf pine flatwoods in the Carolinas, and is in the Center for Plant Conservation's National Collection of Endangered Plants. Highway construction threatens the largest known population of S. verna. We conducted a transplant study to provide information for the plan being developed to mitigate for the impact of the highway. Plants of the threatened population were transplanted into study plots on seven Coastal Plain soils varying in wetness. Half of the plots on each soil were controls with unclipped neighbor vegetation; the others were experimental plots with clipped vegetation. Soil was the most important factor affecting transplant survival. Survival was lowest on soils that experienced ponding or flooding. Neighbor vegetation clipping tended to improve survival, with the greatest improvement on soils of intermedia...

Current methods for estimation of age- and year-specific instantaneous mortality rates based on multiyear, multiple-age tagging studies assume that it is feasible to tag fish in a wide range of ages. For some species, however, only the youngest one or two age-classes are readily available for tagging. Given the practical advantages of tagging young fish only, an important question is whether such studies would provide the information needed for estimation of age-dependent mortality rates. We investigated three designs: tagging only the youngest available age-class, tagging the two youngest age-classes, and tagging the first five age-classes. We carried out simulation studies to assess estimator performance under these three designs, in each case assuming the same total number of tagged fish. Data were generated assuming fishing mortality rates to be age and year dependent and natural mortality rates to be constant or with limited age dependence. Estimator performance is best when fish are tagged ...

Tag return studies play an important role in providing estimates of mortality rates needed for management of many fisheries, but current methods of estimation do not allow age dependence of instantaneous mortality rates. We present models that allow age-dependent fishing and natural mortality rates, an important advance, because there is often substantial variation in age (and size) of fish at tagging. Age dependence of fishing mortality is modeled by assuming that availability to the fishery, that is, selectivity, depends on age but is constant over years. We assume that all age classes are tagged each year, and allow for incomplete mixing of newly tagged fish and for fisheries that are year-long or limited to a fishing season. We investigate parameter redundancy and estimator performance using analytic and simulation methods, and show that estimator properties are poor if the tag reporting rate is estimated (without auxiliary data such as planted tags). We analyzed multiple age class tag return data from a 13-year study on striped bass (Morone saxatilis) and saw clear evidence that selectivity increases with age. Assuming that the tag reporting rate is constant and known, results also demonstrate age dependence of natural mortality rates, and an increase in natural mortality rates from about 1999 coinciding with observation of a bacterial disease in the fish.

Catch-and-release fisheries have become very important in the management of overexploited recreational fish stocks. Tag return studies, where the tag is removed regardless of fish disposition, have been used to assess the effectiveness of restoration efforts for these fisheries. We extend the instantaneous rate formulation of tag return models to allow for catch and release as well as harvest. The key point of our methods is that, given an estimate of the tag reporting rate, the fishing mortality rate (F) is separated into two components: the mortality on harvested fish and the “mortality” on tags (because the tags are removed) of fish released alive. The total fishing mortality rate for untagged fish is the sum of the Fs due to harvest and hooking mortality suffered by fish released alive. Natural mortality rates can also be estimated. Both age-independent models and age-dependent models are constructed, and the age-dependent models are illustrated by application to data from a study of striped ...

Timber plantations have the potential to catalyze regeneration of natural forest on degraded land. However, effective management methods to restore native tree diversity and wildlife habitat in areas planted with non-native timber species are needed. Our study investigated the effectiveness of creating artificial canopy gaps within timber plantations to increase germination, growth, and survival of native tree species that may be important food plants for the Puerto Rican Parrot (Amazona vittata). Seedling growth increased significantly in gaps; however, there were no differences in percent germination or survival between gap and closed (control) plots. Percent cover of grasses, shrubs, and vines increased in gaps, but the increased growth of competitors did not prevent tree seedlings from growing significantly more rapidly in gaps. Removing leaf litter at time of sowing had no effect on germination, growth, or survival of direct seeded species. Creation of canopy gaps by girdling timber trees reduced basal area of non-native tree species to levels comparable with those of native trees. Both local and landscape level diversity were predicted to increase in canopy gaps; however, plantations will continue to be dominated by non-native and timber tree species because advance regeneration of these species is common in plantation understories. Our results suggest that restoration of native tree diversity and wildlife habitat in plantations will require continued management to remove non-native species and to promote growth of tree species with high wildlife habitat value.

Demand for goat (Capra hircus) meat in the southeastern USA is steadily increasing as a result of preferences exhibited by ethnic communities. Feeding systems that include fodder trees can be developed to take advantage of the natural preference of goats for browse. Data were collected for 2 years on a 5-year old stand of Robinia pseudoacacia L. to evaluate growth characteristics for goat browse and to develop allometric relationships in a randomized complete block design (intra-row spacing 0.5 or 1 m and coppice height 0.25 or 0.50 m) replicated six times. Allometric equations were derived from destructive harvests of 68 trees. Main branch size was not affected by intra-row spacing when trees were coppiced at 0.25 m; however, when coppiced at 0.5 m, trees spaced at 1 m had more and larger branches (P < 0.05) than trees spaced at 0.5 m. Intra-row spacing did not influence tree herbage biomass when trees were spaced at 0.5 m whereas trees coppiced at 0.25 m and spaced at 1 m produced less woody and herbaceous biomass than trees spaced at 0.5 m (P < 0.05). A strong relationship (P < 0.0001) was found between tree herbage biomass and the number of main branches greater than 0.01 m (r2 = 0.80). The results, based on growth characteristics and tree herbage biomass production, suggest that Robinia pseudoacacia L. would be an excellent candidate as a silvopastoral component in the southeastern USA.

The mate attraction signal of Heliothis subflexa (Hs) females consists of a multicomponent sex pheromone blend. In this study, we assessed the intraspecific importance of three groups of compounds found in Hs pheromone glands: three acetate esters (Z7-16:OAc, Z9-16:OAc, and Z11-16:OAc), two 14-carbon aldehydes (14:Ald and Z9-14:Ald), and one 16-carbon alcohol (Z11-16:OH). Because the relative importance of pheromone components may vary in different regions, we conducted experiments in Eastern US (North Carolina) and Western Mexico (Jalisco). Our experiments in Eastern US showed that when the acetates were omitted from a 7-component blend in rubber septa, fewer males were caught in cone traps. Subsequent experiments conducted both in Eastern US and Western Mexico indicated that the addition of Z9-16:OAc alone does not increase attraction of male Hs, while Z11-16:OAc does. The Hs male response to Z7-16:OAc differed between the two regions. In Eastern US, significantly more males were attracted to a minimal three-component blend to which Z7-16:OAc was added, but this was not the case in Western Mexico. The two 14-carbon aldehydes also showed differential attraction between the two regions. 14:Ald and Z9-14:Ald appeared not to play any role in the sexual communication of Hs in Eastern US, but reduced trap catches in Western Mexico. The alcohol Z11-16:OH was tested in two concurrent dose-response studies with Hs males in Western Mexico, one using a minimal blend and one using a complete blend. The minimal three-component blend provided a more discriminating tool for delineating dose-response effects of Z11-16:OH than the seven-component blend. In the minimal blend, the optimal dose of Z11-16:OH was 1%, while in the complete blend similar numbers of males were caught when the alcohol ranged from 1 to 25%.

Eight dual-flow continuous culture vessels (700 ml) were used to compare in vitro effects of toxic, endophyte-infected (E+), endophyte-free (E−), and non-toxic, endophyte-infected (EN) Jesup tall fescue (vegetative stage) on ruminal fermentation at 4 levels (0, 150, 300, and 450 g kg −1 DM) of concentrate supplementation (ground corn) for a total of 12 experimental diets in a randomized incomplete block design with 2 replicates. Each culture vessel was offered a total of 15 g DM d −1 . Forage was fed in four equal portions (fed at 03:00, 09:00, 15:00, and 21:00 h); and corn was fed in two equal portions (fed at 09:00 and 21:00 h). Headspace gas and liquid samples were analyzed for methane, ruminal culture pH, ammonia–N, and volatile fatty acid production. Ammonia–N output (g d −1 ) varied by grass; EN had lower values compared to those of E+ and E−. Increasing the level of grain linearly decreased ruminal culture pH, ammonia–N, acetate production, and the acetate-to-propionate ratio, whereas propionate and butyrate production increased with higher grain supplementation. Ruminal fermentation was minimally altered by the presence of the endophyte; however, for the highest level of grain fed (450 g kg −1 DM fed) the methane production pattern for all three grasses was altered. In addition to having the lowest ruminal ammonia–N accumulation, the non-toxic, endophyte-infected fescue resulted in the lowest methane production measured.

Heterosis is considered to be of little importance in soybean (Glycine max L. Merr.) because the crop is produced as "pure-line" cultivars or blends of inbred lines. The F 1 generations Holladay/ Hutcheson (Cross 1) and Brim/Boggs (Cross 2) were generated by hand pollinations. Inbred generations were generated by bulk selfing. The F 1 , F 2 , F 3 , F 4 , and F 5 generations were yield-tested in replicated bordered single row plots in multiple years and locations. The average yield of Cross 1 F 1 was 16% greater than that of the highest-yielding parent and the average yield of the Cross 2 F 1 was 5% greater than the highest-yielding parent. Cross 1 showed significant inbreeding depression when regressed on percentage inbreeding which is clear evidence of dominance for yield. Possible genetic bases for heterosis in soybean include gene complementation or interaction of duplicate favorable loci in repulsion, linked dominant alleles that are inherited as a unit, a greater number of dominant alleles in the F 1 than either parent separately, multiple dosage-dependant regulatory loci, and/or overdominance. The existence of heterosis should be evidence that superior gene combinations are possible. The magnitude of yield heterosis may be a useful criterion for selection among biparental crosses.

Lysimachia asperulifolia Poir., rough–leaf loosestrife, is a federally endangered species that is restricted to longleaf pine savanna – pocosin ecotones in North and South Carolina. Potential causes of the limited fruit and seed production typical of this species and possible effects of prescribed fire on these causes were examined. It was determined that insects rarely visit flowers and that the visitors, Augochlorella spp. and Lasioglossum spp., are not effective pollinators. However, results of artificial pollinations do not support the hypothesis that pollinator limitation alone restricts seed production. Levels of fertility and S allele diversity may vary across natural populations and, combined with ineffective pollination, enforce restricted fruit and seed production. Pollen fertility, amount of flowering, and number of fruits produced in natural populations did not increase following prescribed fire. Restricted seed germination further limits recruitment of genetic variation into populati...

Organic farming can enhance soil biodiversity, alleviate environmental concerns and improve food safety through eliminating the applications of synthetic chemicals. However, yield reduction due to nutrient limitation and pest incidence in the early stages of transition from conventional to organic systems is a major concern for organic farmers, and is thus a barrier to implementing the practice of organic farming. Therefore, identifying transition strategies that minimize yield loss is critical for facilitating the implementation of organic practices. Soil microorganisms play a dominant role in nutrient cycling and pest control in organic farming systems, and their responses to changes in soil management practices may critically impact crop growth and yield. Here we examined soil microbial biomass and N supply in response to several strategies for transitioning from conventional to organic farming systems in a long-term field experiment in Goldsboro, NC, USA. The transitional strategies included one fully organic strategy (ORG) and four reduced-input strategies (withdrawal of each or gradual reduction of major conventional inputs—synthetic fertilizers, pesticides (insecticides/fungicides), and herbicides), with a conventional practice (CNV) serving as a control. Microbial biomass and respiration rate were more sensitive to changes in soil management practices than total C and N. In the first 2 years, the ORG was most effective in enhancing soil microbial biomass C and N among the transition strategies, but was accompanied with high yield losses. By the third year, soil microbial biomass C and N in the reduced-input transition strategies were statistically significantly greater than those in the CNV (averaging 32 and 35% higher, respectively), although they were slightly lower than those in the ORG (averaging 13 and 17% lower, respectively). Soil microbial respiration rate and net N mineralization in all transitional systems were statistically significantly higher than those in the CNV (averagely 83 and 66% greater, respectively), with no differences among the various transition strategies. These findings suggest that the transitional strategies that partially or gradually reduce conventional inputs can serve as alternatives that could potentially minimize economic hardships as well as benefit microbial growth during the early stages of transition to organic farming systems.

We used a decadal data set, with weekly to biweekly sampling in April‐October and monthly sampling in November‐ March, to characterize climatic (hurricane-level storms, a sustained 3-yr drought) and anthropogenic influences on N and P concentrations and loadings to a large eutrophic, poorly flushed estuary, the Neuse Estuary of the Albemarle‐Pamlico Estuarine System. Mass volume transport data were obtained with cross-estuary transect flow measurements taken near the entrance to the estuary. Although trends were minimally influenced by hurricanes, analyses were significantly affected by the sustained drought near the end of the study. As examples, decreasing trends in total N (TN), total P (TP), and bottom-water dissolved oxygen concentrations, and in TN loadings were significant considering all data, but these trends were not significant when the sustained drought was excluded from analysis. In addition, the trend in TN loading was especially sensitive to the initial sampling period. NH concentrations dramatically increased (overall by ;500%) as a 1 4 persistent trend regardless of attempts to control for climatic events. An increasing trend in NH also was documented 1 4 in an adjacent, rapidly flushed Coastal Plain estuary, the Cape Fear. The NH data suggest a regional-scale effect of high 1 4 inputs from inadequately controlled, increasing nonpoint sources. The fragility of TN loading trends, the striking increase in NH concentrations, and the lack of management emphasis on controlling nonpoint sources such as ‘‘new’’ industri1 4 alized swine production collectively do not support recent reports of achievement of a 30% reduction in TN loading to the Neuse. Nonpoint sources remain a critical target for reduction to alleviate the negative effects of cultural eutrophication in this system, as in many estuaries throughout the world.

Knowledge of the influence of environmental factors on weed populations is important in developing sustainable turfgrass management practices. Studies were conducted to evaluate the relationship of green and false-green kyllinga population densities with elevation and edaphic factors in turfgrass systems. Studies were conducted on five different golf courses in North Carolina, three affected by green kyllinga, and two affected by false-green kyllinga. According to Spearman correlation coefficients, both green and false-green kyllinga were correlated with increasing soil volumetric water content, whereas correlation of other edaphic variables varied among sites and species. Stepwise logistic regression confirmed the correlation of volumetric water with green kyllinga presence, but model components varied among sites for false-green kyllinga. Increasing green kyllinga populations correlated with increasing soil sodium; however, sodium did not reach a level believed to be detrimental to turfgrass growth. No other variables correlated with green or false-green kyllinga across all sites. We hypothesized that the lack of significant correlations was due to the overall influence of relative elevation on edaphic variables. According to principal components analysis (PCA), relative elevation had a profound impact on the measured edaphic variables at all sites. However, results of PCA at one site differed sharply from other sites. Results from that site demonstrate the potentially strong effects of management practices to alter edaphic trends normally observed with topography.

The multicolored Asian lady beetle Harmonia axyridis (Pallas) is often a pest during autumn, when large numbers take flight and subsequently land on and enter buildings. Open field experiments were conducted during the autumn flight to examine the role of linear contrast in visually attracting beetles. White targets printed with 61 by 15-cm stripes that varied in orientation and degree of contrast were covered in insect adhesive, attached to a white background panel, and erected in sites known to be attractive to flying beetles. Flights occurred when temperatures rose above 21°C. Diurnally, peak flight occurred between 1400 and 1600 hours but shifted progressively earlier within that framework as the flight season advanced. Beetles significantly chose targets with high contrast, black stripes; the number of beetles landing on all other contrast levels did not differ significantly from controls. Vertically positioned stripes attracted more beetles than horizontal ones, but not significantly. The effects of high contrast were absolute rather than relative. The number of beetles landing on targets with 50% contrast stripes did not increase when these were the highest contrast targets available. Results suggest that visual intensity contrast is key to understanding the behavior of H. axyridis in autumn and call into question some commonly accepted ideas regarding choice of overwintering sites. First, during migratory flight, H. axyridis is not visually attracted to the color white per se, and second, it is unlikely that, during flight, pheromones are involved in beetle orientation.

To determine whether Heliothis virescens and H. subflexa, two closely related sympa- trically occurring species, differ in their antennal responses to conspeciÞc and heterospeciÞc pher- omone compounds, we recorded electroantennogram (EAG) responses of male and female antennae of both species to eight different compounds loaded on Þlter paper dispensers. If antennal responses were found to differ in the two species, EAG-recordings from F1 hybrids and backcrosses between these species could be used in developing an understanding of the genetic architecture of variation in olfactory signal perception. However, all compounds elicited EAG responses in all male antennae tested, and no quantitative differences in response were found between the two species, except for the response to 1 mg (Z)-11-hexadecenol (Z11Ð16:OH), which elicited larger EAG responses in H. subflexa than in H. virescens males. This difference is consistent with the idea that this pheromone component is less important in the biology of H. virescens. Female antennae of both species were less responsive to the major sex pheromone compound, (Z)-11-hexadecenal (Z11Ð16:Ald), than male antennae; 10 g Z11Ð16:Ald, which elicited strong EAG responses in males, produced female EAGs similar to control puffs of air. However, higher doses of Z11Ð16:Ald elicited signiÞcant EAG responses in female antennae of both species. Female antennae of both species also responded to most other pheromone compounds, except Z11Ð16:OH. These results support the hypothesis that autodetection of sex pheromones occurs in females of bothH.virescens andH.subflexa. Whether females behaviorally respond to any, or to combinations, of these compounds remains to be elucidated.

Imazamox ammonium salt at 53 g ae/ha applied postemergence in the fall to imidazolinone-resistant wheat controlled Italian ryegrass 98 to 100% 10 wk after treatment (WAT). Control 22 WAT was 88 to 98% at two locations and 55% at a third location. Imazamox was more effective applied in fall to three- to four-leaf Italian ryegrass than when applied in spring to one- to three-tiller Italian ryegrass. Split applications, with 27 g/ha applied in fall and spring, were no more effective than 53 g/ha applied in fall. Pendimethalin preemergence in combination with fall-applied imazamox increased control 22 WAT 10 to 33 percentage points at two of three locations. Imazethapyr ammonium salt plus imazapyr isopropylamine salt applied at 47 plus 16 g ae/ha and imazamox at 44 or 53 g/ha were similarly effective, whereas imazethapyr at 70 g/ha was ineffective. Control by imazapic ammonium salt at 70 g ae/ha was equal to or greater than control by imazamox at 44 or 53 g/ha. Imazamox, imazethapyr plus imazapyr, and imazapic controlled diclofop-resistant and -susceptible Italian ryegrass. Thifensulfuron plus tribenuron mixed with imazamox increased Italian ryegrass control in field and greenhouse experiments, whereas dicamba reduced control compared with imazamox applied alone. Control by imazamox plus 2,4-D was similar to or greater than control by imazamox alone.