The U.S. Department of Agriculture–Agricultural Research Service (USDA-ARS) has been a leader in weed science research covering topics ranging from the development and use of integrated weed management (IWM) tactics to basic mechanistic studies, including biotic resistance of desirable plant communities and herbicide resistance. ARS weed scientists have worked in agricultural and natural ecosystems, including agronomic and horticultural crops, pastures, forests, wild lands, aquatic habitats, wetlands, and riparian areas. Through strong partnerships with academia, state agencies, private industry, and numerous federal programs, ARS weed scientists have made contributions to discoveries in the newest fields of robotics and genetics, as well as the traditional and fundamental subjects of weed–crop competition and physiology and integration of weed control tactics and practices. Weed science at ARS is often overshadowed by other research topics; thus, few are aware of the long history of ARS weed science and its important contributions. This review is the result of a symposium held at the Weed Science Society of America’s 62nd Annual Meeting in 2022 that included 10 separate presentations in a virtual Weed Science Webinar Series. The overarching themes of management tactics (IWM, biological control, and automation), basic mechanisms (competition, invasive plant genetics, and herbicide resistance), and ecosystem impacts (invasive plant spread, climate change, conservation, and restoration) represent core ARS weed science research that is dynamic and efficacious and has been a significant component of the agency’s national and international efforts. This review highlights current studies and future directions that exemplify the science and collaborative relationships both within and outside ARS. Given the constraints of weeds and invasive plants on all aspects of food, feed, and fiber systems, there is an acknowledged need to face new challenges, including agriculture and natural resources sustainability, economic resilience and reliability, and societal health and well-being.

The past 50 yr of advances in weed recognition technologies have poised site-specific weed control (SSWC) on the cusp of requisite performance for large-scale production systems. The technology offers improved management of diverse weed morphology over highly variable background environments. SSWC enables the use of nonselective weed control options, such as lasers and electrical weeding, as feasible in-crop selective alternatives to herbicides by targeting individual weeds. This review looks at the progress made over this half-century of research and its implications for future weed recognition and control efforts; summarizing advances in computer vision techniques and the most recent deep convolutional neural network (CNN) approaches to weed recognition. The first use of CNNs for plant identification in 2015 began an era of rapid improvement in algorithm performance on larger and more diverse datasets. These performance gains and subsequent research have shown that the variability of large-scale cropping systems is best managed by deep learning for in-crop weed recognition. The benefits of deep learning and improved accessibility to open-source software and hardware tools has been evident in the adoption of these tools by weed researchers and the increased popularity of CNN-based weed recognition research. The field of machine learning holds substantial promise for weed control, especially the implementation of truly integrated weed management strategies. Whereas previous approaches sought to reduce environmental variability or manage it with advanced algorithms, research in deep learning architectures suggests that large-scale, multi-modal approaches are the future for weed recognition.

Fomesafen is a protoporphyrinogen oxidase–inhibitor herbicide with an alternative mode of action that provides PRE weed control in strawberry [Fragaria×ananassa (Weston) Duchesne ex Rozier (pro sp.) [chiloensis×virginiana]] produced in a plasticulture setting in Florida. Plasticulture mulch could decrease fomesafen dissipation and increase crop injury in rotational crops. Field experiments were conducted in Balm, FL, to investigate fomesafen persistence and movement in soil in Florida strawberry systems for the 2014/2015 and 2015/2016 production cycles. Treatments included fomesafen preplant at 0, 0.42, and 0.84 kg ai ha−1. Soil samples were taken under the plastic from plots treated with fomesafen at 0.42 kg ha−1 throughout the production cycle. Fomesafen did not injure strawberry or decrease yield. Fomesafen concentration data for the 0.0- to 0.1-m soil depth were described using a three-parameter logistic function. The fomesafen 50% dissipation times were 37 and 47 d for the 2014/2015 and 2015/2016 production cycles, respectively. At the end of the study, fomesafen was last detected in the 0.0- to 0.1-m depth soil at 167 and 194 d after treatment in the 2014/2015 and 2015/2016 production cycles, respectively. Fomesafen concentration was less than 25 ppb on any sampling date for 0.1- to 0.2-m and 0.2- to 0.3-m depths. Fomesafen concentration decreased significantly after strawberry was transplanted and likely leached during overhead and drip irrigation used during the crop establishment.

Fomesafen is a protoporphyrinogen oxidase (PROTOX) inhibitor that has the potential to be used as an alternative mechanism of action for PRE nutsedge and broadleaf weed control in Florida production of small fruit and vegetables. Fumigation in the raised-bed plasticulture system may increase herbicide persistence. Fomesafen persistence could dissuade Florida growers from using the herbicide for fear of injury to subsequent susceptible crops. Field experiments were conducted in Balm, FL, in 2015 and 2016 to investigate the effect of fumigation on fomesafen dissipation, eggplant tolerance, and purple nutsedge control. Treatments included fomesafen at 0.42 kg ai ha−1, S-metolachlor at 1.06 kg ai ha−1, and a nontreated control in either a fumigated bed injected with a combination of 39% 1,3-dichloropropene and 59.6% chloropicrin at 336 kg ha−1 or no fumigant. Fomesafen concentration in the soil decreased by 83% and 96% from application to harvest in 2015 and 2016, respectively. Fumigation did not affect fomesafen dissipation in either year. At 2 wk after transplant (WATr), fomesafen caused 14% eggplant injury. Injury decreased to less than 5% at 6 WATr. Fomesafen and S-metolachlor treatments did not reduce eggplant height or yields compared with the nontreated control. Fumigation and fomesafen did not decrease purple nutsedge density; however, S-metolachlor applications resulted in a 48% reduction. Further research is needed to assess efficacy on broadleaf and grass weeds.

Mulches used in plasticulture systems could decrease dissipation of fomesafen, a protoporphyrinogen oxidase inhibitor, and dissuade producers from using the herbicide for fear of crop injury in subsequent growing seasons. Field experiments were conducted in Balm, FL, in 2015 and 2016 to investigate the effect of different plastic mulches on fomesafen dissipation, squash tolerance, and efficacy on purple nutsedge. Squash was injured less than 5% from fomesafen applications. The use of plastic mulches reduced purple nutsedge density at transplant by 60% compared with the no-mulch treatment. At transplant, treatments with low-density polyethylene mulch (LDPE), virtually impermeable film (VIF), and totally impermeable film (TIF) mulch had greater than 2-fold the fomesafen concentrations than treatments with clear or no mulch. At harvest in 2015, LDPE, VIF, and TIF treatments had greater fomesafen concentrations than clear and no-mulch treatments; however, concentrations in 2016 were similar for all treatments. Fomesafen can persist at high concentrations throughout the growing season in Florida plasticulture possibly limiting producer options for crop rotation and the use of cover crops.

Purple and yellow nutsedge are problematic weeds in Florida small fruit and vegetable production. EPTC and fomesafen are PRE herbicides that suppress both nutsedge species, but field application in Florida has shown control to be erratic. Greenhouse experiments were conducted in Gainesville, FL, from May to August 2014 and in Wimauma, FL, from March to May 2015 to investigate susceptibility of purple and yellow nutsedge to EPTC and fomesafen applications. Treatments included EPTC at 2.91 kg ai ha−1 and fomesafen at 0.42 kg ai ha−1 at 0, 3, 6, 9, 12, and 15 d after planting (DAP) tubers, plus a nontreated control. EPTC and fomesafen applications averaged across timings decreased purple and yellow nutsedge emergence, shoot height, leaf number, and shoot mass compared to the nontreated control. Herbicide applications 0 DAP reduced purple nutsedge emergence greater than 65% compared to the nontreated control and caused at least 74% injury 4 wk after planting. Herbicide applications 0 DAP decreased yellow nutsedge emergence and shoot mass compared to the nontreated control by at least 86 and 93%, respectively. Applications of EPTC and fomesafen have the ability to suppress short-term purple and yellow nutsedge growth. Applications made at or prior to tuber sprouting maximize herbicide efficacy.

Neuropathological findings from 39 acquired immune deficiency syndrome (AIDS) autopsies of primarily neurologically symptomatic patients and 7 brain biopsies from AIDS patients performed at St. Paul’s Hospital, Vancouver, British Columbia are reported. Autopsy findings included human immunodeficiency virus-1 (HlV)-type multinucleated giant cell (MNGC)-associated encephalitis seen in 17 patients, toxoplasmosis in 7 patients, and cytomegalovirus encephalitis and/or microglial nodule-associated nuclear inclusions in brain parenchyma in 9 patients. Central nervous system lymphoma was identified in 11 autopsy patients and in 4 of 7 brain biopsies. Infectious processes including HIV encephalitis were seen in 10 of 11 autopsied patients with lymphoproliferative lesions in the brain parenchyma, while 40% of patients without lymphoma had HIV-type MNGC or opportunistic infections. CNS lymphoma was not significantly increased in incidence in patients with a clinical history of zidovudine treatment, but increased duration of survival after the diagnosis of AIDS was associated with increased incidence of lymphoma in both untreated and zidovudine-treated patients. Patients displaying HIV MNGC within microglial nodules had a shorter mean duration of survival after diagnosis of AIDS than those patients with HIV encephalitis with dispersed MNGC, white matter vacuolation, and gliosis.

Although the incidence of invasive group A streptococcal disease in northern Australia is very high, little is known of the regional epidemiology and molecular characteristics. We conducted a case series of Northern Territory residents reported between 2011 and 2013 with Streptococcus pyogenes isolates from a normally sterile site. Of the 128 reported episodes, the incidence was disproportionately high in the Indigenous population at 69·7/100 000 compared to 8·8/100 000 in the non-Indigenous population. Novel to the Northern Territory is the extremely high incidence in haemodialysis patients of 2205·9/100 000 population; and for whom targeted infection control measures could prevent transmission. The incidences in the tropical north and semi-arid Central Australian regions were similar. Case fatality was 8% (10/128) and streptococcal toxic shock syndrome occurred in 14 (11%) episodes. Molecular typing of 82 isolates identified 28 emm types, of which 63 (77%) were represented by four emm clusters. Typing confirmed transmission between infant twins. While the diverse range of emm types presents a challenge for effective coverage by vaccine formulations, the limited number of emm clusters raises optimism should cluster-specific cross-protection prove efficacious. Further studies are required to determine effectiveness of chemoprophylaxis for contacts and to inform public health response.

The characteristically aggregated frequency distribution of macroparasites in their hosts is a key feature of host–parasite population biology. We begin with a brief review of the theoretical literature concerning parasite aggregation. Though this work has illustrated much about both the sources and impact of parasite aggregation, there is still no definitive analysis of both these aspects. We then go on to illustrate the use of one approach to this problem – the construction of Moment Closure Equations (MCEs), which can be used to represent both the mean and second moments (variances and covariances) of the distribution of different parasite stages and phenomenological measures of host immunity. We apply these models to one of the best documented interactions involving free-living animal hosts – the interaction between trichostrongylid nematodes and ruminants. The analysis compares patterns of variability in experimental infections of Teladorsagia circumcincta in sheep with the equivalent wildlife situation – the epidemiology of T. circumcincta in a feral population of Soay sheep on St Kilda, Outer Hebrides. We focus on the relationship between mean parasite load and aggregation (inversely measured by the negative binomial parameter, k) for cohorts of hosts. The analysis and empirical data indicate that k tracks the increase and subsequent decline in the mean burden with host age. We discuss this result in terms of the degree of heterogeneity in the impact of host immunity or parasite-induced mortality required to shorten the tail of the parasite distribution (and therefore increase k) in older animals. The model is also used to analyse the relationship between estimated worm and egg counts (since only the latter are often available for wildlife hosts). Finally, we use these results to review directions for future work on the nature and impact of parasite aggregation.

The paper describes the results of over 300 factorial experiments carried out in each factory area in the years 1934–49 for the Sugar Beet Research and Education Committee of the Ministry of Agriculture as a result of co-operation between Rothamsted workers and the agriculturists and fieldmen attached to the beet factories. All the experiments tested the effects of levels of nitrogen, phosphate and potash, and rather more than half tested the effect of salt also.

Except on fen soils, nitrogen gave substantial responses in all factory areas, especially in the presence of high levels of potash or salt. Large variations in response from season to season were closely associated with the rainfall of the preceding winter months, responses being greater after wet winters than dry ones.

In spite of some selection of sites in favour of greater responses, the average net returns from phosphate were relatively small.

The effect of potash was closely linked with the amount of nitrogen applied; in the presence of nitrogen, dressings well above the level of 1·2 cwt. K2O per acre tested in the experiments are likely to give a useful net return. Soils derived from the Chalky Boulder Clay seem to be exceptional in showing no response. Apart from this, there were only small variations in responses to nitrogen and potash between factory areas. The application of 5 cwt. salt gave substantial responses in almost all parts of the country, whether or not potash was also applied; on the other hand, responses to potash were usually small when salt was also applied.

Whilst there was a general relationship between soil analysis for phosphate and potash (citric acid method) and crop response, adjustments to the optimal dressings according to soil analysis were not of sufficient reliability to be of much practical value.

Peat soils change gradually as a result of drainage and cultivation, losing depth through shrinkage, oxidation and blowing, changing in character through increases in mineral matter and ‘drumminess’, and changing in productivity and manurial requirements. The sequence of changes has been studied in the field and a number of stages distinguished which may be recognized quite simply from the texture of the ploughed layer. Texture is a field assessment of the type and condition of the peat and the proportion and nature of the mineral matter associated with it. The Fenland soils have been classified as follows: (1) peat soils, (2) peaty mineral soils, (3) organic mineral soils and (4) mineral soils. Further subdivision into textural classes depends on recognizing the mineral combinations or fractions as in texturing mineral soils

Analysis of samples of the ploughed layer in the laboratory has shown that organic matter or loss on ignition figures, expressed as a percentage of the oven-dried soil, can be used for recognizing the kind of soil; use is made of this in considering those earlier experiments for which organic matter figures could be calculated.