Exploring Grower-sourced Data to Understand Spatiotemporal Trends in the Occurrence of a Vector, Pseudococcus maritimus (Hemiptera: Pseudococcidae) and Improve Grapevine Leafroll Disease Management.

Grapevine leafroll disease is a significant concern in the wine grape industry, as it spreads rapidly and contributes to economically significant reductions in yield and grape quality. Our objective was to utilize 5 yr of grower-sourced data from Napa (California, USA) to improve local and regional disease management efforts. Specifically, we applied a spatially integrated multivariate clustering technique to improve understanding of spatiotemporal trends in Pseudococcus maritimus (Ehrhorn) male populations-the primary vector in the region. We also implemented generalized linear mixed models to evaluate the effects of two key practices, insecticide sprays and roguing, on disease incidence. Results show P. maritimus has a biannual flight pattern in the study area, with the first flight peaking in early May and the second between early August and early September. Clusters of P. maritimus flight data fall largely within the vineyard footprints of individual growers, but also showed clear neighborhood effects. We found that when disease incidence within a block is <1%, consistent monitoring and removal of diseased vines is required to contain within-block spread. As within-block disease incidence grows to 1-20%, both insecticide applications and roguing are effective practices to reduce spread. At incidence levels >20%, roguing is a critical practice. Our results emphasize the importance of individual management efforts, but also the value of programs that engage the wider neighboring community and highlight the power of community data collection to guide decision-making.

Quantifying Planococcus ficus (Hemiptera: Pseudococcidae) Invasion in Northern California Vineyards to Inform Management Strategy.

The spread and impact of invasive species in exotic ranges can be mitigated by increased understanding of pest invasion dynamics. Here, we used geospatial analyses and habitat suitability modeling to characterize the invasion of an important vineyard pest, vine mealybug (Planococcus ficus Signoret, Hemiptera: Pseudococcidae), using nearly 15,000 trapping records from throughout Napa County, California, between 2012 and 2017. Spatial autocorrelation among P. ficus detections was strongest at distances of ~250 m and detectable at regional scales (up to 40 km), estimates of the rate and directionality of spread were highly idiosyncratic, and P. ficus detection hotspots were spatiotemporally dynamic. Generalized linear model, boosted regression tree, and random forest modeling methods performed well in predicting habitat suitability for P. ficus. The most important predictors of P. ficus occurrence were a positive effect of precipitation in the driest month, and negative effects of elevation and distance to nearest winery. Our results indicate that 250-m quarantine and treatment zones around P. ficus detections are likely sufficient to encompass most local establishment and spread, and that implementing localized regulatory procedures may limit inadvertent P. ficus spread via anthropogenic pathways. Finally, surveys of P. ficus presence at >300 vineyard sites validated that habitat suitability estimates were significantly and positively associated with P. ficus frequency of occurrence. Our findings indicate that habitat suitability predictions may offer a robust tool for identifying areas in the study region at risk to future P. ficus invasion and prioritizing locations for early detection and preventative management efforts.

Xylella fastidiosa: Insights into an Emerging Plant Pathogen.

The bacterium Xylella fastidiosa re-emerged as a plant pathogen of global importance in 2013 when it was first associated with an olive tree disease epidemic in Italy. The current threat to Europe and the Mediterranean basin, as well as other world regions, has increased as multiple X. fastidiosa genotypes have now been detected in Italy, France, and Spain. Although X. fastidiosa has been studied in the Americas for more than a century, there are no therapeutic solutions to suppress disease development in infected plants. Furthermore, because X. fastidiosa is an obligatory plant and insect vector colonizer, the epidemiology and dynamics of each pathosystem are distinct. They depend on the ecological interplay of plant, pathogen, and vector and on how interactions are affected by biotic and abiotic factors, including anthropogenic activities and policy decisions. Our goal with this review is to stimulate discussion and novel research by contextualizing available knowledge on X. fastidiosa and how it may be applicable to emerging diseases.

Increased Zinc Availability Enhances Initial Aggregation and Biofilm Formation of Streptococcus pneumoniae.

Bacteria growing within biofilms are protected from antibiotics and the immune system. Within these structures, horizontal transfer of genes encoding virulence factors, and promoting antibiotic resistance occurs, making biofilms an extremely important aspect of pneumococcal colonization and persistence. Identifying environmental cues that contribute to the formation of biofilms is critical to understanding pneumococcal colonization and infection. Iron has been shown to be essential for the formation of pneumococcal biofilms; however, the role of other physiologically important metals such as copper, zinc, and manganese has been largely neglected. In this study, we investigated the effect of metals on pneumococcal aggregation and early biofilm formation. Our results show that biofilms increase as zinc concentrations increase. The effect was found to be zinc-specific, as altering copper and manganese concentrations did not affect biofilm formation. Scanning electron microscopy analysis revealed structural differences between biofilms grown in varying concentrations of zinc. Analysis of biofilm formation in a mutant strain lacking the peroxide-generating enzyme pyruvate oxidase, SpxB, revealed that zinc does not protect against pneumococcal H2O2. Further, analysis of a mutant strain lacking the major autolysin, LytA, indicated the role of zinc as a negative regulator of LytA-dependent autolysis, which could affect biofilm formation. Additionally, analysis of cell-cell aggregation via plating and microscopy revealed that high concentrations of zinc contribute to intercellular interaction of pneumococci. The findings from this study demonstrate that metal availability contributes to the ability of pneumococci to form aggregates and subsequently, biofilms.

Relative Preference and Localized Food Affect Predator Space Use and Consumption of Incidental Prey.

Abundant, localized foods can concentrate predators and their foraging efforts, thus altering both the spatial distribution of predation risk and predator preferences for prey that are encountered incidentally. However, few investigations have quantified the spatial scale over which localized foods affect predator foraging behavior and consumption of incidental prey. In spring 2010, we experimentally tested how point-source foods altered how generalist predators (white-footed mice, Peromyscus leucopus) utilized space and depredated two incidental prey items: almonds (Prunus dulcis; highly profitable) and maple seeds (Acer saccharum; less profitable). We estimated mouse population densities with trapping webs, quantified mouse consumption rates of these incidental prey items, and measured local mouse activity with track plates. We predicted that 1) mouse activity would be elevated near full feeders, but depressed at intermediate distances from the feeder, 2) consumption of both incidental prey would be high near feeders providing less-preferred food and, 3) consumption of incidental prey would be contingent on predator preference for prey relative to feeders providing more-preferred food. Mouse densities increased significantly from pre- to post-experiment. Mean mouse activity was unexpectedly greatest in control treatments, particularly <15 m from the control (empty) feeder. Feeders with highly preferred food (sunflower seeds) created localized refuges for incidental prey at intermediate distances (15 to 25m) from the feeder. Feeders with less-preferred food (corn) generated localized high risk for highly preferred almonds <10 m of the feeder. Our findings highlight the contingent but predictable effects of locally abundant food on risk experienced by incidental prey, which can be positive or negative depending on both spatial proximity and relative preference.