Persistence of Antibiotic Resistance Genes Varies with Particle Size and Substrate Conditions in Recirculating Streams.

Antibiotic resistance (AR) determinants are enriched in animal manures, a significant portion of which is land-applied as a soil amendment or as fertilizer, leading to potential AR runoff and microbial pollution in adjacent surface waters. To effectively inform AR monitoring and mitigation efforts, a thorough understanding and description of the persistence and transport of manure-derived AR in flowing waters are needed. We used experimental recirculating mesocosms to assess water-column removal rates of antibiotic resistance genes (ARGs) originating from a cow manure slurry collected from a dairy farm. We quantified the effect of three benthic (i.e., bottom) substrate variations and particle sizes of manure slurry on water column removal rates. Overall, we observed variation in ARG behavior across substrate treatments and particle sizes. For ARGs associated with small particles, removal rates were higher in mesocosms with a substrate. tetW was typically removed at the highest rates across particle size and treatment, followed by ermB and blaTEM. Our data suggests that both substrate character and particle size exert control on the fate and transport of ARGs in surface waters, laying the foundation for future research in this area to establish a predictive framework for AR persistence and fate in flowing waters.

Fooling the Harlequin Bug (Hemiptera: Pentatomidae) Using Synthetic Volatiles to Alter Host Plant Choice.

Harlequin bug, Murgantia histrionica (Hahn) (Hemiptera: Pentatomidae), is a widespread pest that feeds on a variety of brassicaceous crops and other plants. To understand olfactory cues that mediate host-finding, and their possible utility in pest management, we deployed aggregation pheromone (mixed murgantiols = 10,11-epoxy-1-bisabolen-3-ols) and/or isothiocyanate (ITC) host plant volatiles with potted host plants and nonhost soybean, in field choice bioassays. Adults of both sexes were strongly attracted (10-31×) to collard host plants baited with pheromone lures, compared with unbaited collards, as were nymphs. Collard plants baited with lures containing allyl and/or benzyl-ITC showed a 1.3× and 1.9× increase in attractiveness, respectively, neither differing by life-stage nor sex; multiple lures showed additive attraction. Nonhost soybean, baited with pheromone lure, was 4.6-7.5× more attractive to adults than unbaited collard; conversely, baited collard was 124× more attractive than unbaited soybean. The stark difference in observed effect of pheromone lure between unpoisoned plants, and those poisoned with imidacloprid, indicated that attraction was underestimated by circa-daily counts of unpoisoned plants, presumably because if not poisoned, bugs rapidly abandoned the baited nonhost soybean plant. Results indicate that harlequin bugs can be misled to encounter and feed on nonhosts by their aggregation pheromone, but additional means may be needed to retain them. Attraction to hosts is increased both by the aggregation pheromone, and at least two host plant volatiles, allyl and benzyl-ITC. These results contribute to our knowledge of host finding in harlequin bug, and to possible trapping and trap cropping schemes for pest management.