Background: When control mechanisms such as water temperature and biocide level are insufficient, Legionella, the causative bacteria of Legionnaires’ disease, can proliferate in water distribution systems in buildings. Guidance and oversight bodies are increasingly prioritizing water safety programs in healthcare facilities to limit Legionella growth. However, ensuring optimal implementation in large buildings is challenging. Much is unknown, and sometimes assumed, about whether building and campus characteristics influence Legionella growth. We used an extensive real-world environmental Legionella data set in the Veterans Health Administration (VHA) healthcare system to examine infrastructure characteristics and Legionella positivity. Methods: VHA medical facilities across the country perform quarterly potable water sampling of healthcare buildings for Legionella detection as part of a comprehensive water safety program. Results are reported to a standardized national database. We did an exploratory univariate analysis of facility-reported Legionella data from routine potable water samples taken in 2015 to 2018, in conjunction with infrastructure characteristics available in a separate national data set. This review examined the following characteristics: building height (number of floors), building age (reported construction year), and campus acreage. Results: The final data set included 201,936 water samples from 819 buildings. Buildings with 1–5 floors (n = 634) had a Legionella positivity rate of 5.3%, 6–10 floors (n = 104) had a rate of 6.4%, 11–15 floors (n = 36) had a rate of 8.1%, and 16–22 floors (n = 9) had a rate of 8.8%. All rates were significantly different from each other except 11–15 floors and 16–22 floors (P < .05, χ2). The oldest buildings (1800s) had significantly less (P < .05, χ2) Legionella positivity than those built between 1900 and 1939 and between 1940 and 1979, but they were no different than the newest buildings (Fig. 1). In newer buildings (1980–2019), all decades had buildings with Legionella positivity (Fig. 1 inset). Campus acreage varied from ~3 acres to almost 500 acres. Although significant differences were found in Legionella positivity for different campus sizes, there was no clear trend and campus acreage may not be a suitable proxy for the extent or complexity of water systems feeding buildings. Conclusions: The analysis of this large, real-world data set supports an assumption that taller buildings are more likely to be associated with Legionella detection, perhaps a result of more extensive piping. In contrast, the assumption that newer buildings are less associated with Legionella was not fully supported. These results demonstrate the variability in Legionella positivity in buildings, and they also provide evidence that can inform implementation of water safety programs.

Funding: None

Disclosures: Chetan Jinadatha, principal Investigator/Co-I: Research: NIH/NINR, AHRQ, NSF principal investigator: Research: Xenex Healthcare Services. Funds provided to institution. Inventor: Methods for organizing the disinfection of one or more items contaminated with biological agents. Owner: Department of Veterans Affairs. Licensed to Xenex Disinfection System, San Antonio, TX.

Biofumigation is practiced to control soilborne pests and weeds in agronomic fields. The objectives of this research were to assess the dose response of weed seeds to Indian mustard biofumigation and associate responses to seed dormancy state, initial dormancy, and seed parameters. A petri dish biofumigation methodology was developed to expose seeds of common lambsquarters, bird vetch, wild carrot, common ragweed, green foxtail, velvetleaf, hairy galinsoga, and red clover to allelochemicals produced after rehydrating 0 (control), 1.94, 2.90, 5.81, 11.61, and 17.41 mg cm−2 of dried mustard powder. Weed species expressed specific dose responses, estimated ED50, LD50, and maximal mortality. Hairy galinsoga and wild carrot were consistently the most affected by biofumigation, with maximal mortality reaching 97% and 95%, ED50 values for germination were 1.91 and 2.68 mg cm−2 , and LD50 values were 3.31 and 3.69 mg cm−2 of dried mustard tissue, respectively. Initial dormancy was assessed by germination and tetrazolium tests. Seed parameters such as testa thickness, relative weight of the testa, and seed size were measured directly by manual dissection, weighing seed structures, and stereomicroscopic imaging software measurements. Linear regression analyses revealed initial dormancy to be positively related to ED50 and LD50 values with a significant interaction with seed surface and seed width, respectively. Exposure to 5.81 mg cm−2 of dried mustard powder increased common ragweed seed mortality for after-ripened seeds by 293% and by 58% for primary dormant seeds compared with untreated seeds. Mortality of common lambsquarters secondary and primary dormant seeds increased by 730% and 106%, respectively, and for wild carrot by 1,193 and 156%, respectively. Results underline the potential to incorporate biofumigation into weed management programs for repression of susceptible weed species.

Major differences in above- ground biomass and tuber production of yellow nutsedge (Cyperus esculentus L. # CYPES) were not observed when corn (Zea mays L. “CO-OP S265”) was seeded on different dates (1st, 2nd, 3rd and 4th week of May; and 1st week of June). The final seedbed was prepared just prior to each seeding date and this cultivation stimulated dormant tubers to sprout. As a result, a large population of yellow nutsedge emerged with the corn at all seeding dates. Because fertilizer was banded near the corn row, yellow nutsedge biomass, tuber dry weight and number of tubers were higher within corn rows than between rows. Tuber size was affected by seeding date and shifted toward smaller tubers within corn rows and larger tubers between the rows as the corn was sown late. The optimum seeding date of corn was in the 3rd week of May when the highest corn yield was obtained and yellow nutsedge growth was generally reduced.

Efficacy of an indigenous fungus, Exserohilum monoceras, for the control of 3 Echinochloa species was evaluated and compared under both regulated greenhouse and screenhouse (field plots netted with 2 layers of metal mesh screening to exclude vertebrate pests) conditions. Under greenhouse conditions, an inoculum dose of 2.5 × 107 conidia m−2 killed all seedlings of both barnyardgrass and E. glabrescens, whereas an inoculum dose of 5.0 × 107 conidia m−2 was required to obtain 100% mortality of junglerice seedlings. The 1.5-leaf stage of all 3 Echinochloa species was the most susceptible. Increasing inoculum density increased weed control efficacy on younger or older Echinochloa seedlings. The highest level of control was observed for E. glabrescens, less for barnyardgrass, and least for junglerice. Under screenhouse conditions, Exserohilum monoceras caused more than 90% mortality of Echinochloa species when the inoculum was formulated as an oil emulsion or when applied as a dry powder.

A weed survey of 115 Nova Scotia lowbush blueberry fields was conducted during the summers of 1984 and 1985 to determine the most common and prevalent weeds associated with blueberry production. A total of 119 weed species were observed within the surveyed blueberry fields. The most common weed species were bunchberry, colonial bentgrass, poverty oatgrass, sheep sorrel, and false lily-of-the-valley. Weeds with low relative abundance in this study, but which may become more widespread, include three-toothed cinquefoil, Kentucky bluegrass, hair fescue, canker-root, and Canadian St. Johnswort.

Growth and regeneration of field horsetail (Equisetum arvense L. ♯ EQUAR) were investigated under field and greenhouse conditions. Field horsetail produced shoots during the entire summer but its growth was detrimentally affected by the presence of corn (Zea mays L.). Field horsetail regrew as well whether it had been hoed once or 16 times during the growing season; and during the subsequent summer, there were no significant differences between horsetail growth in plots kept weed-free the previous growing season and in plots where field horsetail grew freely. In the greenhouse, rhizome segments 1 cm long placed 15 cm deep easily regenerated plants. Simulations were done using the growth and regenerative ability of field horsetail to estimate its potential spread in agricultural fields. The results of these simulations indicate that this weed can infest a hectare within 6 yr of its introduction into a new area.

Data obtained from two experiments were used to identify and describe factors affecting crop loss due to weeds in forage stands. Timothy (Phleum pratense L. ‘Champ′) was established in presence or absence of barley (Hordeum vulgare L. ‘Bruce′), red clover (Trifolium pratense L. ‘Florex′), broadleaf weeds, and grass weeds. Botanical composition, soil water, soil nutrients, light interception, and plant cover were determined 4 and 6 weeks after seeding, and crop yield was determined at periodic forage harvest dates. Principal components analyses permitted the extraction of 12 factors and regression analyses demonstrated that these factors can be used to describe crop yield. Each factor can be estimated either by obtaining the rotated factor scores or by selecting a representative variable that can be substituted for the rotated factor scores in the regression models. The approach described in this paper should be tested with other crops and other weed complexes. It is suggested to use weed density in combination with weed and crop cover data to predict crop loss.

Field research was conducted from 1990 through 1992 to evaluate the effect of the fungal pathogen, Colletotrichum coccodes, on velvetleaf intra- and interspecific (with soybean) competition across a range of monoculture and 1:1 mixture densities. In pure stand, application of this velvetleaf foliar pathogen had little impact on seed yield of the weed. In these plots, velvetleaf intraspecific competition stimulated vertical growth and favored the rapid replacement of diseased leaf tissue that had prematurely senesced. In mixtures, however, C. coccodes inoculation differentially influenced the yield of both species. In two of three years, C. coccodes inoculation reduced velvetleaf seed yields by, an average, 60% compared with yields for control (uninoculated) plants. Velvetleaf suffered greater yield losses from soybean interspecific competition in the presence of C. coccodes, especially at the lower planting densities. The decline in velvetleaf yield was primarily attributed to the stunting effect of the pathogen, which allowed soybean plants to grow above the weed. Consequently, soybean yield losses within inoculated mixture plots were generally lower than for control plots, although significant increases (23%) in soybean yield were recorded only in 1992. The inoculation treatment had relatively little impact on the number of seeds produced per fruit or seed unit weight in both species regardless of whether plants were grown in monocultures or in mixtures. The finding that C. coccodes has only a limited effect on velvetleaf performance in pure stand, while having a significantly greater effect in a competitive environment with a soybean crop, has important ramifications as to the value and accuracy of initial efficacy testing that rates potential biocontrol agents based solely on their effect within pure stands of the target weed.

The plant pathogenic fungus Colletotrichum coccodes (Cc) and the plant growth regulator thidiazuron (TDZ) were evaluated in Maryland and Quebec for velvetleaf control in ‘Williams' and ‘Maple Arrow’ soybean. TDZ was applied at 0, 0.1, 0.2, 0.3, and 0.4 kg ai/ha alone or was combined with Cc at 109 spores/m2 when velvetleaf was at the 1- to 2-leaf (Trial 1) or 4- to 6-leaf (Trial 2) growth stages. Velvetleaf control increased with TDZ rate, and TDZ combined with Cc further increased control. TDZ reduced velvetleaf biomass and height, and Cc increased velvetleaf mortality. In Quebec, Cc also reduced the biomass of velvetleaf treated in Trial 1 and interacted positively with TDZ at this growth stage. Cc nearly halved the rates of TDZ required for 90 and 75% mortality of velvetleaf treated at the 1- to 2-leaf and 4- to 6-leaf stages to 0.09 and 0.12 kg/ha, respectively, in Quebec. Cc similarly lowered the rate of TDZ required for 75% stand reduction of velvetleaf in Trial 1 to 0.17 kg/ha in Maryland. Cool wet weather in Quebec contrasted with warm, dry weather in Maryland. Soybean biomass and yield were increased significantly by treatment with TDZ plus Cc in Trial 1 at both locations.

Phomopsis convolvulus Ormeno, a fungus, reduced growth and regeneration of field bindweed under greenhouse environments. Field bindweed seedlings at the cotyledon stage were severely injured and killed (95% mortality) with 108 conidia/m2. Three- to five-leaf seedlings (2 weeks old) were controlled when inoculated with 109 conidia/m2 (70% mortality; 98 and 89% reduction in dry weight of aboveground biomass and roots, respectively). This inoculum density reduced aboveground and root biomass, and adversely affected regeneration of 4-week-old seedlings and established plants, but few plants were killed. In controlled-environment studies, two inoculations were superior (P = 0.02) to one inoculation in reducing foliage aboveground of well-established seedlings (4 weeks old). However, new shoots produced between the first and second inoculation treatments were less diseased than expected.

Increasing the corn (Zea mays L. “CO-OP S265”) population from 33 300 to 133 300 plants per hectare in the field significantly reduced yellow nutsedge (Cyperus esculentus L. # CYPES) above-ground biomass, tuber number, tuber weight and yellow nutsedge height at the end of growing season, and significantly increased corn yield. Photosynthetically active radiation below corn canopies decreased with increasing corn population and corresponded to reductions in yellow nutsedge above-ground biomass, tuber weight and tuber number. These results demonstrate that available light is a major factor in yellow nutsedge competition with corn. The size of yellow nutsedge was also reduced at high corn densities. These results support the use of crop manipulation in an integrated yellow nutsedge management system in corn.

Four Centaurea species, diffuse knapweed (C. diffusa Lam. # CENDI, spotted knapweed (C. maculosa Lam. # CENMA), yellow starthistle (C. solstitatilis L. # CENSO), and the closely related Russian knapweed [Acroptilon repens (L.) DC. syn. Centaurea repens L. # CENRE] are serious introduced weeds which infest extensive areas of pasture and rangeland in Canada and the United States (1, 10, 14, 17, 18, 26, 30). Russian knapweed and yellow starthistle are also troublesome in cultivated land (1, 14, 26). These four species are members of the Cardueae tribe of the Asteraceae family and have been accidentally introduced from Eurasia as contaminants in crop seed.

The potential of Colletotrichum dematium f.sp. epilobii (ATCC 20981) to control fireweed (Epilobium angustifolium) was investigated. Under controlled environment conditions, plant age, inoculum density, length of the dew period, and temperature during the dew period affected the efficacy of C. dematium f.sp. epilobii. Seedlings sprayed with 1 × 109 conidia/m2 sustained the most damage. Susceptibility decreased with increasing plant age, and 10-wk-old plants were slightly affected by the fungus. Satisfactory levels of control were achieved when the dew period was >20 h and temperature during the dew period was 30 C. Control of fireweed increased when the C. dematium f.sp. epilobii conidia were suspended in a 25% v/v canola oil/water emulsion. Using this formulation, control of 4-wk-old seedlings was obtained with a 10-fold reduction in inoculum concentration (1 × 108 conidia/m2), the required dew period was reduced to 12 h, and the effect of the temperature during the dew period was minimized. In the field, C. dematium f.sp. epilobii alone or when amended with an oil emulsion failed to control fireweed growth. When the oil formulation of C. dematium f.sp. epilobii was tank mixed with a low rate of glyphosate, high levels of control were consistently achieved. Growth reduction achieved with this formulation was more than additive, suggesting a synergistic interaction. The effectiveness of the formulated conidial suspension of C. dematium f.sp. epilobii decreased with plant maturity, and 15-wk-old plants were not controlled. C. dematium f.sp. epilobii alone has limited potential as a candidate bioherbicide, but when formulated in an oil/water emulsion and combined with low rates of glyphosate, suppression of fireweed can be attained in the field.

A 3-yr field study was conducted to determine the effect of a biological control agent, Sclerotinia minor Jagger, and a common herbicide, Killex, on the population dynamics of dandelion and other broadleaf species and on the dandelion seed bank. Treatments were applied as one spring, one early autumn, or a spring plus an early autumn treatment per year. The response of the dandelion population to a spring herbicide treatment was similar to two applications per year (spring and early autumn). Significantly less dandelion control occurred after the first early autumn application of the herbicide. Two weeks after application, spring or early autumn treatments with S. minor were equally effective in suppressing dandelions. In the second year of the two applications per year of S. minor treatment, weed control was equivalent to the herbicide. By the third year of the one spring application of S. minor, weed control was equivalent to the herbicide. Generally over the study period, the early autumn application of S. minor was less effective than the spring or the spring and early autumn applications. The S. minor treatments significantly reduced the dandelion seed bank, and this effect was not significantly different from the Killex herbicide treatment. The rate, frequency, and seasonal timing of application had no effect on the dandelion seed-bank size, but terminating the application would gradually replenish the seed bank. Populations of white clover, broadleaf plantain, birdsfoot trefoil, and common ragweed were similarly suppressed by either the S. minor or the herbicide treatments. Yellow woodsorrel significantly increased after 1 yr of herbicide treatment compared with the S. minor and untreated control treatments, indicating a possible weed species shift. Turf quality was improved because of the herbicide and S. minor treatments, but grass injury and smooth crabgrass invasion were recorded in 17% of herbicide-treated plots.

The historic maternal environment; the identity of competing, neighboring plants; and biotic stresses, such as fungal disease and herbivory, interact to influence the competitive ability, reproductive output, and plasticity of weed populations. A weed capable of altering its phenotype in response to environmental factors is better able to compete for resources in agroecosystems, thereby reducing crop yields and contributing more seeds to the seed bank. Velvetleaf is a highly competitive annual weed in many North American cropping systems, exhibiting a high degree of phenotypic plasticity in response to biotic and abiotic factors. We examined the effects of seed size (small and large), competitive environment (with and without soybean), and stress level (none = no treatment, moderate = pathogen inoculation, high = pathogen plus herbicide) on velvetleaf allometry and reproductive output during three field seasons. Only under the high-stress treatment was velvetleaf biomass, height, and reproductive output compromised (> 15% each), and these traits were further reduced with soybean competition. Soybean competition alone reduced velvetleaf biomass (> 50%), height (25%), and seed output (50%), but effects of competition varied with stress level. Velvetleaf plants that originated from large seeds (≥ 10 mg) generally outperformed plants originating from small seeds (< 10 mg) except under the high-stress treatment. These findings suggest that velvetleaf life-history traits and reproductive output in the current generation are a function of both present and historic factors. Management strategies for this species should involve tactics that not only reduce its competitive ability (e.g., biomass, height) but also decrease its seed production via synergistic stressors such as increased crop competitiveness, reduced-rate herbicide applications, and pathogen infection.

The degree of resistance to linuron of a common ragweed biotype was investigated. Suspected linuron-resistant plants collected from a carrot field near Sherrington, Québec, were subjected to increasing rates of linuron under glasshouse conditions. Resistance to linuron of the common ragweed biotype was suspected because 33% of plants survived to reproduction after they were sprayed at a rate of 4.5 kg ai/ha, two times the dose rate recommended for linuron in carrots, and also because 3% of plants survived to reproduction after they were sprayed at a rate of 22.5 kg ai/ ha, 10 times the recommended dose. Susceptible plants collected from a field with no prior history of linuron use were all killed when sprayed at the lowest dose rate recommended, 1.125 kg ai/ha. The herbicide-resistance ratio was 29.0 for linuron, and for cross-resistance to atrazine, the ratio was 1.3, indicating that these plants exhibit greater resistance to linuron than to atrazine.

Progress in bioherbicide development has been hindered by the strict moisture and temperature requirements of the living active ingredient. Application of a jute fabric to areas treated with a Sclerotinia minor granular bioherbicide improved broadleaf weed control and broadened the effective application period to include the warm summer season. When turfgrass plots treated with the bioherbicide were covered with burlap fabric for 3 d, broadleaf weed (dandelion, white clover, broadleaf plantain, buckhorn plantain, ground ivy, and prostrate knotweed) control was greatly enhanced. The cover was made of natural jute fibers that retained water but had sufficient transparency to allow 33% light penetration for continued growth of the grass. Virulence of the bioherbicide was maintained under elevated temperatures that would otherwise reduce efficacy. The bioherbicide was ineffective in the summer unless covered, but dandelion density, broadleaf weed ground cover, and dandelion survival were all reduced by the bioherbicide when plots were covered, even if applications were made in July. The efficacy of the bioherbicide was also enhanced under favorable conditions, and covering permitted reduced application rates without loss of efficacy. When applied at a rate of 20 g/m2 and covered, S. minor granules exerted significantly greater biocontrol of dandelion than 40 g/m2 without covering. Covering for up to 5 d did not cause any adverse effects on the turfgrass. This approach may overcome one obstacle to the commercialization of the Sclerotinia minor bioherbicide, permitting its deployment under challenging environmental conditions.

The Wide Angle Search for Planet (WASP) project is one of the leading projects in the discovery of transiting exoplanets. We present 1) the current status of the WASP-North survey, 2) our recent exoplanet discoveries, and 3) we exemplify how these results fit into our understanding of transiting exoplanet properties and how they can help to understand exoplanet diversity.