Ratios of certain organochlorine pollutants in fish tissues are significantly different between the eastern and western North Atlantic and have been used to identify recent (<1 year) transatlantic migrants of Atlantic bluefin tuna (Thunnus thynnus). In this study we observed limited variation of organochlorine pollutant ratios across collections of young-of-the-year (YOY) bluefin tuna from the western North Atlantic (WNA) and eastern North Atlantic (ENA) in different years and highly significant differences between WNA and ENA YOY samples each year and for all years combined. A significant increase in organochlorine ratios was noted between YOY and age-1 ENA bluefin tuna, consistent with the movement of YOY out of the Mediterranean Sea and into the ENA. Using baseline organochlorine ratios from WNA YOY to identify recent eastern migrants, 29% of age-2, 33% of age-3, and 24% of age-4 juvenile bluefin tuna in the WNA were identified as recent migrants from the east during 2011 and 2012. Applying baseline ratios from age-1 ENA bluefin tuna to identify recent migrants from the WNA, 14.3% of age-2, 9.5% of age-3, and 0% of age-4 juvenile bluefin tuna caught in the Bay of Biscay fishery were identified as recent western migrants during 2010 and 2011. These data reveal substantial connectivity of juvenile bluefin tuna across the North Atlantic and demonstrate that WNA juveniles are heavily subsidized by eastern fish.

Global travel and trade in combination with climate change are expanding the geographic distribution of plant pathogens. The bacterium Xylella fastidiosa is a prime example. Native to the Americas, it has spread to Europe, Asia, and the Middle East. To assess the risk that pathogen introductions pose to crops in newly invaded areas, it is key to survey their diversity, host range, and disease incidence in relation to climatic conditions where they are already present. We performed a survey of X. fastidiosa in grapevine in Virginia using a combination of quantitative PCR, multilocus sequencing, and metagenomics. We also analyzed samples from deciduous trees with leaf scorch symptoms. X. fastidiosa subspecies fastidiosa was identified in grapevines in all regions of the state, even in Northern Virginia, where the temperature was below −9°C for 10 days per year on average in the years preceding sampling. Unexpectedly, we also found for the first time grapevine samples infected with X. fastidiosa subspecies multiplex ( Xfm). The Xfm lineage found in grapevines had been previously isolated from blueberries in the Southeastern United States and was distinct from that found in deciduous trees in Virginia. The obtained results will be important for risk assessment of X. fastidiosa introductions in other parts of the world.

Trematode cercariae inhabit predictable environments and respond to trigger cues with genetically fixed releaser responses when foraging for the upstream host. The effect of light and gravity on the transmission of Echinostoma caproni cercariae to Biomphalaria glabrata was investigated experimentally. Transmission chambers were constructed of clear polyvinyl chloride pipe. Snails were constrained within the chamber to prevent movement, while permitting the cercariae to swim freely. A trial consisted of 2 infected B. glabrata shedding E. caproni cercariae placed at the center of the chamber, with 5 uninfected B. glabrata placed 10 cm on either side (or above and below) of the shedding snails as sentinels. There was no significant difference in the prevalence of infection sentinel snails in either experiment (light vs. dark or top vs. bottom); however, mean intensity was significantly higher in sentinel snails in the dark portion of the chamber (42.5 vs. 10.4; P = 0.001) and the top of the transmission chamber (66.1 vs. 38.0; P = 0.0003). There was a high correlation between the number of metacercariae collected from sentinel snails and the total number of infective units (metacercariae + unsuccessful cercariae): r = 0.992 (light vs. dark) and r = 0.957 (top vs. bottom), respectively, at cercariae densities estimated from 22 to 3,304/L. The results suggest that cercariae of E. caproni exhibit negative photo- and geotaxis in searching for a second intermediate host. Stereotypical releaser responses to environmental trigger cues (light and gravity) allow E. caproni cercariae to exploit flexible strategies for completing the life cycle consistent with the broad range second intermediate and definitive hosts used by E. caproni cercariae and adults, respectively.

The invasive tree of heaven, Ailanthus altissima (Miller) Swingle, was first confirmed dying from Verticillium wilt (caused by both Verticillium nonalfalfae Inderb. et al. formerly V. albo-atrum Re...

In November 2014, leaves of ornamental pear (Pyrus calleryana, cultivar unknown) with bright orange to reddish spots typical of infection by a rust fungus were submitted to the Virginia Tech Plant Disease Clinic from a landscape in Frederick County, VA, for diagnosis. Brown aecia with bulbous bases resembling acorns, characteristic of European pear rust (pear trellis rust) caused by Gymnosporangium sabinae, were present on the lower leaf surface (Kern, 1973). Two ornamental pear trees that had been in the landscape for many years were heavily infected and scattered leaf lesions were observed on other ornamental pear trees in the neighborhood. Samples of infected leaves were sent to the USDA ARS Systematic Mycology & Microbiology Lab to confirm the presence of G. sabinae and for deposit in the U. S. National Fungus Collections (specimen number BPI 893287). Morphological characters were consistent with G. sabinae. Aecia were hypophyllous, in necrotic spots, roestelioid, 2–5 mm high, balanoid, splitting along sides with apex intact; peridial cells (n=20) sub-hyaline, verrucose to spinulose, elongated, 58–119 um × 10–22 µm; aeciospores (n=30) light brown to yellowish-brown, minutely verrucose, globose to ovoid, 22–29 um × 26–35 µm, with walls 3–5 µm thick. DNA was extracted from aecia on one representative leaf sample and the ITS2 and 5′ end of the 28S rDNA regions were amplified and sequenced using the primers Rust2inv and LR6 (Aime, 2006) (KU593568). Sequences were 99 – 100% identical to G. sabinae sequences in GenBank, including sequences from G. sabinae in New York (JN969962–JN96996). G. sabinae can infect leaves, fruit and young twigs and causes serious disease on ornamental pear and European pear (Pyrus communis). The alternate hosts of G. sabinae are in Juniperus section Sabina, but although a Juniperus species was present in the neighborhood, no signs of rust disease or cankers were found on any of the junipers. European pear rust has been reported elsewhere in the United States (CA, CT, MI, NY) and in Canada (BC); however, it has not previously been reported in Virginia. A report from Alabama could not be confirmed. Although European pear is not widely grown commercially in Virginia, it is grown as a backyard fruit tree, and ornamental pear is common in the landscape. G. sabinae can overwinter on both its pear and juniper hosts, increasing its potential for spread. Eastern red cedar (J. virginiana) is susceptible and commonly present, and invasive volunteer seeding of ornamental pears occurs within the region; therefore, we expect the rust fungus to spread to commercial and backyard ornamental and European pears. Because this rust can cause severe defoliation, reduction in yield and dieback of pear, as well as mummification of fruit (Prokopova, 2011), awareness of the presence of this disease is critical to its management on both ornamental and fruit-producing pears. This is the first report of European pear rust on ornamental pear in Virginia.