Pest population dynamics are related to a continental overwintering gradient.

Overwintering success is an important determinant of arthropod populations that must be considered as climate change continues to influence the spatiotemporal population dynamics of agricultural pests. Using a long-term monitoring database and biologically relevant overwintering zones, we modeled the annual and seasonal population dynamics of a common pest, Helicoverpa zea (Boddie), based on three overwintering suitability zones throughout North America using four decades of soil temperatures: the southern range (able to persist through winter), transitional zone (uncertain overwintering survivorship), and northern limits (unable to survive winter). Our model indicates H. zea population dynamics are hierarchically structured with continental-level effects that are partitioned into three geographic zones. Seasonal populations were initially detected in the southern range, where they experienced multiple large population peaks. All three zones experienced a final peak between late July (southern range) and mid-August to mid-September (transitional zone and northern limits). The southern range expanded by 3% since 1981 and is projected to increase by twofold by 2099 but the areas of other zones are expected to decrease in the future. These changes suggest larger populations may persist at higher latitudes in the future due to reduced low-temperature lethal events during winter. Because H. zea is a highly migratory pest, predicting when populations accumulate in one region can inform synchronous or lagged population development in other regions. We show the value of combining long-term datasets, remotely sensed data, and laboratory findings to inform forecasting of insect pests.

Analysis of Cotton Leafroll Dwarf Virus P0 Gene Sequences from South Carolina Reveals Low Variability Among Isolates.

Cotton leafroll dwarf virus (CLRDV) is emerging across the major cotton-producing states of the southern United States. Because it was detected in nearly all cotton-producing states within a few years of its initial detection in the United States, the spread of the virus has apparently occurred rapidly. In this study spanning three growing seasons in South Carolina, we collected CLRDV isolates from symptomatic and asymptomatic cotton plants in 10 counties. The genomic region encoding P0, the viral suppressor of RNA silencing, was sequenced and compared among CLRDV isolates. Low variability among CLRDV P0 sequences from South Carolina isolates with similarities to other United States isolates was revealed by amino acid sequence alignment and phylogenetic analysis. Low variability among South Carolina isolates was also confirmed by sequencing a subset of eight near-complete genomes of CLRDV isolates. Although sequence variability was low among South Carolina isolates, this data should be taken in the context of all United States isolates, for which diversity may be higher than initially expected. Sequences gathered in this study add to the body of knowledge on CLRDV diversity in the United States.

Spatiotemporal Distribution of Two Euschistus spp. Stink Bugs (Hemiptera: Pentatomidae) in Southeastern Farmscapes.

Stink bugs (Hemiptera: Pentatomidae) are ubiquitous, cryptic, phytophagous pests that are found in many crops. In agroecosystems, individuals disperse from adjacent noncrop hosts and tend to aggregate or cluster within fields. In this study, we characterized the distribution of Euschistus servus (Say) and Euschistus tristigmus (Say) (Hemiptera: Pentatomidae) over 2 yr at three southeastern United States farmscapes. Stink bugs were captured in pheromone-baited traps, and Spatial Analysis by Distance Indices (SADIE) used to identify the location of significant aggregations by habitat type and season. Euschistus servus adults were more likely to be captured in pecan orchards, cotton, other crops, or unmanaged habitats than in woodland habitats. Significant aggregations of E. servus were detected in a variety of habitats including pecan, corn, cotton, peanut, and tobacco, as well as fallow and hay fields, pastures, and hedgerows. Fewer adult E. tristigmus were captured than E. servus adults, and E. tristigmus adults were typically trapped and aggregated in woodland habitats. The resulting data provide an important understanding regarding the seasonal movement and relative abundance levels of stink bug populations, which are critical to the development of integrated pest management strategies.

Vertical and temporal distribution of Helicoverpa zea (Lepidoptera: Noctuidae) larvae in determinate and indeterminate soybean.

Most oviposition by Helicoverpa zea (Boddie) occurs near the top of the canopy in soybean, Glycine max (L.) Merr, and larval abundance is influenced by the growth habit of plants. However, the vertical distribution of larvae within the canopy is not as well known. We evaluated the vertical distribution of H. zea larvae in determinate and indeterminate varieties, hypothesizing that larval distribution in the canopy would vary between these two growth habits and over time. We tested this hypothesis in a naturally infested replicated field experiment and two experimentally manipulated cage experiments. In the field experiment, flowering time was synchronized between the varieties by manipulating planting date, while infestation timing was manipulated in the cage experiments. Larvae were recovered using destructive sampling of individual soybean plants, and their vertical distribution by instar was recorded from three sampling points over time in each experiment. While larval population growth and development varied between the determinate and indeterminate varieties within and among experiments, we found little evidence that larvae have preference for different vertical locations in the canopy. This study lends support to the hypothesis that larval movement and location within soybean canopies do not result entirely from oviposition location and nutritional requirements.

Location of Helicoverpa zea (Lepidoptera: Noctuidae) larvae on different plant parts of determinate and indeterminate soybean.

Helicoverpa zea (Boddie) is a damaging pest of many crops including soybean, Glycine max (L.), especially in the southern United States. Previous studies have concluded that oviposition and development of H. zea larvae mirror the phenology of soybean, with oviposition occurring during full bloom, younger larvae developing on blooms and leaves, intermediate aged larvae developing on varying tissue types, and older larvae developing on flowers and pods. In a field trial, we investigated the presence of natural infestations of H. zea larvae by instar in determinate and indeterminate soybean varieties. In complementary experiments, we artificially infested H. zea and allowed them to oviposit on plants within replicated cages (one with a determinate variety and two with an indeterminate variety). Plants were sampled weekly during the time larvae were present. In the natural infestation experiment, most larvae were found on blooms during R3 and were early to middle instars; by R4, most larvae were found on leaves and were middle to late instars. In contrast, in the cage study, most larvae were found on leaves regardless of soybean growth stage or larval stage. Determinate and indeterminate growth habit did not impact larval preference for different soybean tissue types. Our studies suggest H. zea larvae prefer specific tissue types, but also provide evidence that experimental design can influence the results. Finally, our finding of larval preference for leaves contrasts with findings from previous studies.

Introduction: Reimagining Epidemics.

Over the past year, historians of medicine have found our discipline invested with a new sense of relevance. In trying to make sense of epidemics past and present, many of us have been substantially influenced by Charles Rosenberg's 1989 Daedalus essay, "What Is an Epidemic? AIDS in Historical Perspective." Writing in the middle of another unfolding global pandemic, Rosenberg suggested that all epidemics possessed similar forms of social choreography, and that applying a narrative framework could help to understand their sequence, structure, and social impact. This issue of the Bulletin offers contributions from thirteen scholars working in various geographic, chronological, and thematic areas that engage with Rosenberg's fundamental historical question about what defines an epidemic, although the question takes on different forms, and different forms of urgency, in each of their works.

Transforming a U.S. scholarly concentrations program internationally: lessons learned.

BACKGROUND: Scholarly Concentrations programs in U.S. medical schools aim to instill passion for critical thinking and promote careers in academic medicine. The rise of these programs has seen variable goals, structure, and outcomes. Transformation of these programs internationally is in its infancy. METHODS: We describe implementation of the Johns Hopkins School of Medicine Scholarly Concentrations program, offering Basic Science, Clinical Science, Medical Ethics/Healing Arts, History of Medicine, and Public Health/Community Service, at Bezmiâlem Vakif University in Istanbul, Turkey. Over six modules in the preclinical years, students develop a faculty-mentored experience which encourages the acquisition of attitudes and skills for self-directed, lifelong learning and scholarship. This culminates in abstract and project presentation. We report program characteristics (context and logistics) and outcomes (student engagement and experiences). RESULTS: The Scholarly Concentrations program at Bezmiâlem began in 2014, with nearly two completed cohorts of students. In comparison to Johns Hopkins, students at Bezmiâlem begin at an earlier age (thus do not have as much prior research experience) and are subsequently evaluated for residency in terms of test scores rather than scholarship and publications, but have a similar level of intellectual curiosity and desire to take ownership of their project. Eighty-two percent of Bezmiâlem students stated the project they pursued was either their own idea or was an idea they formed after meeting with their mentor. Students at Bezmialem were more likely to choose Clinical Science projects (p = 0.009). Only 5% of Bezmiâlem students in end-of-course survey felt dissatisfied with the level of ownership they experienced with their project, a frequency similar to that seen by Johns Hopkins students (2%). CONCLUSIONS: Scholarly Concentrations programs play an important role in U.S. medical schools, and these programs can be successfully implemented internationally. The Scholarly Concentrations program at Johns Hopkins has been transformed to a program at Bezmiâlem in Istanbul, the first program outside North America or the European Union. When designing these programs, one must consider the context, logistics, student engagement, and outcomes. While long-term outcomes are needed, this can serve as a model for implementation elsewhere.

Spatial Distributions of Thrips (Thysanoptera: Thripidae) in Cotton.

A 4-yr study was conducted to determine the degree of aggregation of thrips and injury in cotton, Gossypium hirsutum L., and their spatial association with a multispectral vegetation index (normalized difference vegetation index [NDVI]) and soil apparent electrical conductivity (ECa). Using the Spatial Analysis by Distance IndicEs analyses (SADIE), adult thrips were significantly (P < 0.05) aggregated in 4 out of 24 analyses for adult thrips (17%), 4 out of 24 analyses for immature thrips (17%), and 2 out of 15 analyses for injury (13%). The SADIE association tool showed that NDVI values were associated with adult thrips in 2 out of 20 paired datasets (10%), with immature thrips in 3 out of 20 paired datasets (15%), and with thrips injury in 1 out of 14 paired datasets (7.1%). Soil ECa values were generally more associated with thrips variables than NDVI, with shallow ECa positively associated with adult thrips in 6 out of 21 paired datasets (28.6%), with immature thrips in 8 out of 21 paired datasets (40.0%), and with thrips injury in 8 out of 14 paired datasets (57.1%). The greater frequency of positive associations between thrips variables and soil ECa suggests a greater potential for site-specific management, particularly in the Coastal Plain of the southeastern United States, where soil types are highly variable.