Search

Diverse field characteristics, weather patterns, and management practices can result in variable microclimates. The objective of this study was to relate in-field microclimate conditions with peanut diseases and yield and determine the effect of irrigation and fungicides within these environments. Irrigation did not have a major impact on disease and yield. Stem rot (Athelia rolfsii) and early (Passalora arachidicola) and late (Nothopassalora personata) leaf spot were most affected by changes in environmental patterns across seasons. Average nontreated stem rot was 12.9% in 2017, which dropped considerably in 2018 (0.2%) but emerged again in 2019 (3.2%). Stem rot incidence varied across the field, and the response to fungicides depended on management zone. Leaf spot defoliation in nontreated plots was severe in 2019, reaching an average of 73% at 126 days after planting, but only reached 15% in 2017 and 35% in 2019 at the same stage. A low-input fungicide schedule was able to reduce foliar disease in all zones and seasons but the microclimatic conditions in the low-lying area favored leaf spot in 2017 and 2018, although not in the dryer 2019 season. Seasonal differences in disease and plant growth affected the level of protection against average yield loss using a standard low-input program, which was not as great in 2017 (527 kg/ha) as in 2018 (2,235 kg/ha) or 2019 (1,763 kg/ha). Disease prediction models built on dynamic environmental factors in the context of multiple pathogens and natural field conditions could be developed to improve within-season management decisions for more efficient fungicide inputs.

Carinata (Brassica carinata) is an oilseed crop which, because of its non‐edible oil composition and favorable fatty acid profile, is proposed as a “green” sustainable aviation fuel. It can be grown as a winter crop in the southeastern USA or as a summer annual crop in northern latitudes. No crop models exist for carinata because it is a relatively new crop. The CROPGRO model is a mechanistic crop simulation of daily crop growth and development as a function of daily weather, soil properties, crop management, and species parameters. We adapted the CROPGRO model to simulate carinata based on growth analysis data collected over two seasons at three sites: Quincy, FL, Jay, FL, and Shorter, AL. The adaptation process required literature knowledge as well as optimization against field observations. The parameterization of model sensitivities to climatic factors is presented. The adapted model gave good simulations of carinata growth dynamics compared to observed growth during different seasons and locations and in response to N fertilization. While additional testing is appropriate, the model is sufficiently ready to be used for various applications. An example application is presented for the effect of sowing date on carinata yield and maturity over long‐term weather in the Southeastern USA.

Brassica carinata, a nonfood oilseed crop, is used to produce renewable fuels because of its high oil content and favorable fatty acid profile. Production in the southeastern United States is relatively new, and information on agronomic management practices to optimize growth and yield is limited. Since optimal seeding rate may depend on the land preparation method for this small‐seeded crop, a study was conducted to evaluate the effect of tillage system (conventional, no‐till, broadcast‐disc, and ripper‐roller) and seeding rate (1.12, 5.60, 10.09, and 14.57 kg seed ha−1) on the performance of B. carinata. A randomized complete block design with a strip‐plot restriction on randomization and four replications was implemented in Headland, AL, Jay, FL, and Quincy, FL, over five site‐years during the 2017–2018 and 2018–2019 growing seasons. Data were collected on soil residue cover; plant population; soil penetrometer resistance and moisture; biomass (including carbon and nitrogen); stalk diameter; yield and yield components; seed oil, protein, and glucosinolates concentration; and oil composition. Soil penetrometer resistance was significantly affected by tillage system, with the ripper‐roller consistently having the lowest penetration resistance values across all site‐years. Ripper‐roller tillage had the highest oil content and lowest protein and glucosinolate contents. Yield response to tillage system was variable. Among seeding rate treatments, yield was lowest at 1.12 kg seed ha−1 and similar among 5.60, 10.09, and 14.57 kg seed ha−1 at all site‐years. There was no tillage by seeding rate interaction for yield. Results indicate that among seeding rate treatments used, 5.6 kg seed ha−1 rate was optimal at all site‐years regardless of land preparation method and is thus the recommended seeding rate for commercial carinata production in the Southeastern United States.

The environmental consequences of using nonrenewable fossil fuels have motivated a global quest for sustainable alternatives from renewable sources. Carinata has been developed as a low carbon intensity, non‐food oilseed biomolecular platform to produce advanced drop‐in renewable fuels, meal, and co‐products. The crop is widely adaptable to grow in the humid subtropical and humid continental climatic regions of Asia, Africa, North America, South America, Europe, and Australia as a spring or winter crop. Carinata is heat tolerant, resistant to diseases and seed shattering with lower water‐use requirements than other oilseed brassicas. Adopting carinata in double‐cropping systems would require continuing research to integrate crop biology with agronomy, to understand growth and development and its interaction with agricultural inputs and management. Site‐specific best management agronomic practices and crop improvement research to develop frost‐tolerant, early‐maturing, nutrient use‐efficient, and high yielding varieties with desirable oil content and fatty acid profile will enhance the crop's adaptability and economic viability. The exploitation of intra‐ and interspecific and intra‐ and intergeneric diversity will further enhance carinata productivity and resistance to biotic and abiotic stresses. This review attempts to present a comprehensive description of carinata's biology, beginning with its origin and current state of distribution, availability of genetic and genomic resources, and a discussion of its morphology, phenology, and reproduction. A detailed analysis of the agronomy of the crop, including planting and germination and management practices, is presented in the context of crop growth and development. This will facilitate global adoption, sustainable production, and commercialization of carinata as a dedicated biofuel oilseed crop in diverse cropping systems and growing regions of the world, including the Southeast United States.

Plant-parasitic and free-living nematodes – bacterivores, fungivores, omnivores, predators – comprise the nematode community. Nematicide application and crop rotation are important tools to manage plant-parasitic nematodes, but effects on free-living nematodes and nematode ecological indices need further study. The nematicide fluopyram was recently introduced in cotton (Gossypium hirsutum) production and its effects on the nematode community need assessment. This research was conducted in 2017 and 2018 at a long-term field site in Quincy, FL where perennial grass/sod-based (bahiagrass, Paspalum notatum) and conventional cotton rotations were established in 2000. The objective of this research was to evaluate the effects of fluopyram nematicide, crop rotation phase, and irrigation on free-living nematodes and nematode ecological indices based on three soil sampling dates each season. We did not observe consistent effects of crop rotation phase on free-living nematodes or nematode ecological indices. Only omnivores were consistently negatively impacted by fluopyram. Nematode ecological indices reflected this negative effect by exhibiting a degraded/ stressed environmental condition relative to untreated plots. Free-living nematodes were not negatively impacted by nematicide when sod-based rotation was used.

Peanuts (Arachis hypogaea L.) have been one of the most profitable crops in the southeastern coastal plains but with increasing cost of production, growers continually seek to lower inputs and enhance overall profitability of their farms. Peanut cultivars with high yield potential and disease resistance along with drought tolerance are therefore obvious choices for sustainable production. Runner-type peanut cultivars were evaluated for pod yield and grade for three yr. Five peanut cultivars were evaluated in 2014 and 2015 and six cultivars in 2016 at the North Florida Research and Education Center, University of Florida, Quincy, FL. Cultivar performance was observed at different planting dates, four in 2014 and three in 2015 and 2016, to evaluate impacts of early, mid, and late planting with and without irrigation. Georgia cultivar GA-12Y consistently yielded greater than the other varieties in all yr of the study. Average pod yield for GA-12Y was 5980 kg/ha for three yr compared to 5140 kg/ha, 4730 kg/ha, 4890 kg/ha for GA-06G, FloRun 107, and TUFRunner 511, respectively. Florida cultivar TUFRunner 297 yielded greater (5300 kg/ha) than the rest of Florida cultivars irrespective of the planting date and had higher proportion of total sound mature kernels (TSMK) compared to GA-12Y in two of the three yr. Planting date had no impact on peanut pod yield in 2014 and 2015. However, peanut yield for all the cultivars was higher at later planting dates in 2016. The advantage of irrigation was not always consistent in all the yr, likely due to high rainfall during the study yr, removing that advantage.

Brown rust (caused by Puccinia melanocephala) and orange rust (caused by P. kuehnii) are two major diseases of sugarcane in Florida. To better understand the epidemiology of these two rusts, disease severity and weather variables were monitored for two seasons in cultivars CL90-4725 (susceptible to brown rust and resistant to orange rust) and CL85-1040 (susceptible to orange rust and resistant to brown rust). Brown rust was most severe during mid-May to mid-July, whereas orange rust severity peaked during two periods: mid-May to early August and then November to December. Overall, disease severity was higher for orange rust than for brown rust. Maximum disease severity was correlated with the number of hours at night with an average temperature of 20 to 22.2°C for brown rust one season and orange rust both seasons. Slightly higher correlation was obtained when relative humidity above 90% was included in the number of hours at night with an average temperature of 20 to 22.2°C for brown rust but not orange rust, suggesting that leaf wetness is not a limiting factor for either disease in Florida. Epidemics of brown rust began at lower night temperatures (16.7 to 22.2°C) in one season, but epidemics of orange rust lasted longer under higher temperatures. The correlation of rust severity on recently emerged leaves with conducive temperatures recorded in 10-, 20-, or 30-day windows starting 7 days before disease assessment suggested that earlier inoculum production is needed to create severe epidemics that result in yield loss.

International audience; Logistic regression models were developed from 5 years (2014 to 2018) of disease severity and weather data in an attempt to predict brown rust of sugarcane at the Everglades Research and Education Center in Belle Glade, Florida. Disease severity (percentage area of the top visible dewlap leaf covered by rust) was visually assessed in the field every 2 weeks for two varieties susceptible to brown rust. A total of 250 variables were derived from weather data for 10- to 40-day periods before each brown rust assessment day. A subset of these variables were then evaluated as potential predictors of severity of brown rust based on their individual correlation or their biological meaningfulness. Analyses of correlation and stepwise logistic regression allowed us to identify afternoon humid thermal ratio (AHTR), temperature-based duration variables, and their interaction terms as the most significant variables associated with brown rust epidemics of sugarcane in Florida. The nine best predictive models were identified based on model accuracy, sensitivity, specificity, and estimates of the prediction error. The prediction accuracy of these models ranged from 73 to 85%. Single-variable model BR2 (based on AHTR) classified 89% of the epidemic and 81% of the nonepidemic status of the disease. More than 83% of the epidemics and 81% of the nonepidemic status of sugarcane brown rust was correctly classified via multiple-variable models. These models can be used as components of a rust disease warning system to assist in the management of brown rust epidemics of sugarcane in south Florida.

Brassica carinata (carinata) has emerged as a potential biofuel source due to its high erucic acid content, making it desirable for various industrial applications. Nitrogen (N) and sulfur (S) are required as primary sources of nutrition for growth and development in different oilseed crops and their utilization is interdependent. The purpose of the study was to analyze the interactive effect of N and S nutrition on the growth and other physiological activities of carinata and B. napus (napus). Four treatments, i.e., optimum NS (+N+S, 100% N and 100% S), N limited (−N+S, 0% N, 100% S), S limited (+N−S, 100% N, 0% S), and NS limited (−N−S, 0% N and 0% S) of N and S in full-strength Hoagland solution were imposed in the current study. Effect of different NS treatments was observed on vegetative traits such as number of primary and secondary branches, total leaf area, total biomass production and allocation, and physiological traits such as production of photosynthetic pigments, net photosynthesis, electron transport, and other aspects for both carinata and napus. The traits of stem elongation, number of nodes, node addition rate, internode length, number of primary and secondary branches were 60%, 36%, 50%, 35%, 56%, and 83% lower, respectively, in napus in comparison to carinata. Different NS treatments also positively influenced the production of photosynthetic pigments such as chlorophyll (Chl) a and b and carotenoids in carinata and napus. The concentration of Chla was 11% higher in napus in comparison to carinata. The rate of net photosynthesis, electron transport, and fluorescence was 12%, 8%, and 5% higher based on overall value, respectively, in napus compared to carinata. On the other hand, the overall value for stomatal conductance decreased by 5% in napus when compared to carinata. Different growth-related traits such as vegetative (plant height, node number, internode length, leaf area, number of primary and secondary branches), reproductive (pod number, pod length, seeds per pod), and photosynthetic capacity in oilseed brassicas are correlated with the final seed and oil yield and chemical composition which are of economic importance for the adoption of the crop. Thus, the analysis of these traits will help to determine the effect of NS interaction on crop productivity of carinata and napus.

Preharvest estimation of cotton yield can help growers to determine their return on investment, assess weather-related damages, and adjust crop management. This publication outlines the steps to calculate a reliable estimate of cotton yield. Written by Michael J. Mulvaney, Emma Brooks, Pratap Devkota, Ethan Carter, De Broughton, Mark Mauldin, Joseph Iboyi, Mahesh Bashyal, David Wright, and Ian Small, and published by the UF/IFAS Agronomy Department, March 2021.

Organic farming is one of the fastest-growing segments of the agricultural industry in the United States and in Florida. Conservation tillage is often employed to reduce soil erosion, improve physical and biological properties of soil, and increase water use efficiency. This 5-page article aims to provide recommendations to row crop farmers who wish to implement conservation tillage practices during their transition to a certified organic system. Written by D. L. Wright, J. Moyer, D. Treadwell, I. M. Small, and S. George, and published by the UF/IFAS Agronomy Department, revised November 2020.

Late and early leaf spot are caused by Nothopassalora personata and Passalora arachidicola, respectively, and are damaging diseases of peanut (Arachis hypogaea L.) capable of defoliation and yield loss. Management of these diseases is most effective through the integration of tactics that reduce starting inoculum and prevent infection. The insecticide phorate was first registered in 1959 and has been used in peanut production for decades in-furrow at planting to suppress thrips. Phorate further provides significant suppression of Tomato spotted wilt virus infection beyond suppression of its thrips vector alone by activating defense-related responses in the peanut plant. From six experiments conducted from 2017 to 2019 in Blackville, SC, Reddick, FL, and Quincy, FL, significantly less leaf spot defoliation was exhibited on peanuts treated with phorate in-furrow at planting (26%) compared with nontreated checks (48%). In-season fungicides were excluded from five of the experiments, whereas the 2018 Quincy, FL, experiment included eight applications on a 15-day interval. Across individual experiments, significant suppression of defoliation caused by late leaf spot was observed from 64 to 147 days after planting. Although more variable within location-years, pod yield following phorate treatment was overall significantly greater than for nontreated peanut (2,330 compared with 2,030 kg/ha; P = 0.0794). The consistent defoliation suppression potential was estimated to confer an average potential net economic yield savings of $90 to $120 per hectare under analogous leaf spot defoliation. To our knowledge, these are the first data in the 61 years since its registration demonstrating significant suppression of leaf spot on peanut following application of phorate in-furrow at planting. Results support phorate use in peanut as an effective and economical tactic to incorporate to manage late and early leaf spot infections and development of fungicide resistance.

Most crops can be successfully grown using conservation planting technology. There has been resistance in using conservation tillage planting methods for peanut as many specialists from past years promoted deep plowing to bury plant residue that might carry various disease organisms. This document will help guide growers who want to use conservation tillage in making that change.https://edis.ifas.ufl.edu/ag187

Plant-parasitic nematodes (Rotylenchulus reniformis (reniform, RN), Helicotylenchus dihystera (spiral), and Mesocriconema ornatum (ring)) and yield were investigated in cotton phases of conventional (peanut-cotton-cotton) and sod-based (bahiagrass-bahiagrass-peanut-cotton) rotations with or without irrigation and fluopyram nematicide at a long-term research site, established in 2000, in Quincy, Florida, USA. Objectives were to determine impacts of nematicide application on cotton yield and evaluate effects of nematicide on plant-parasitic nematodes in these rotations in 2017 and 2018. Reniform nematode population densities were greater in conventional cotton than sod-based cotton. Ring and spiral nematode population densities were greater in sod-based cotton than conventional cotton. Plots receiving nematicide had increased RN population densities in preplant 2018 soil samples and spiral nematode population densities in preplant 2017, harvest 2017, preplant 2018, and harvest 2018 soil samples compared to untreated plots. Cotton seed yield in conventional rotation was increased by 18% following nematicide application in 2017 but decreased by 10% in sod-based rotation in 2018, relative to the untreated control. Sod-based rotation had greater cotton yield than conventional rotation in 2017 and 2018. Nematicide application did not improve cotton yield in sod-based rotation and was inconsistent in conventional rotation. Plant-parasitic nematodes (Rotylenchulus reniformis (reniform, RN), Helicotylenchus dihystera (spiral), and Mesocriconema ornatum (ring)) and yield were investigated in cotton phases of conventional (peanut–cotton–cotton) and sod-based (bahiagrass–bahiagrass–peanut–cotton) rotations with or without irrigation and fluopyram nematicide at a long-term research site, established in 2000, in Quincy, Florida, USA. Objectives were to determine impacts of nematicide application on cotton yield and evaluate effects of nematicide on plant-parasitic nematodes in these rotations in 2017 and 2018. Reniform nematode population densities were greater in conventional cotton than sod-based cotton. Ring and spiral nematode population densities were greater in sod-based cotton than conventional cotton. Plots receiving nematicide had increased RN population densities in preplant 2018 soil samples and spiral nematode population densities in preplant 2017, harvest 2017, preplant 2018, and harvest 2018 soil samples compared to untreated plots. Cotton seed yield in conventional rotation was increased by 18% following nematicide application in 2017 but decreased by 10% in sod-based rotation in 2018, relative to the untreated control. Sod-based rotation had greater cotton yield than conventional rotation in 2017 and 2018. Nematicide application did not improve cotton yield in sod-based rotation and was inconsistent in conventional rotation.

Integrated pest management (IPM) is a broad-based approach for pest control that has been used since the 1950s. This approach uses a variety of management tactics to keep pest levels below an economic threshold level. However, choosing the appropriate tactics in a timely manner can be difficult in many agricultural production systems. Technology is continually revolutionizing agricultural decision making by transforming large quantities of data into useful and timely information. The focus of this article will be on what makes a successful IPM strategy, and how novel technologies can possibly be incorporated. Pests impacting peanut production are continually adapting and evolving, thus the tools used to manage them must also have this capability. The future of pest management lies with finding ways to incorporate novel information into established IPM programs and adapting them for future changes in pest populations.

Integrating two years of bahiagrass (Paspalum notatum Flugge) into the peanut (Arachis hypogea L.) and cotton (Gossypium hirsutum L.) cropping system improves soil quality and crop production as compared to a conventional peanut-cotton-cotton rotation (CR). However, it is unclear if this system, known as a sod-based rotation (SBR), affects soil biological communities (e.g., soil microorganisms and nematodes) and their trophic interactions. Furthermore, how soil trophic groups respond to agricultural management (e.g., irrigation) is understudied. In April 2017, we collected pre-planting soil samples (0–30 cm) from cotton plots located in Quincy (Florida, United States) that had been under CR (cotton grown in two consecutive years) and SBR (cotton grown only once) for 17 years. We used amplicon sequencing to investigate soil microbial communities and an inverted microscope technique to quantify nematodes. Compared to CR, SBR significantly increased nematode alpha diversity (one-way ANOVA; P

Precision agriculture has emerged as a revolutionary technology, which transforms farming related data into useful information for agricultural decision-making. This paper compares precision farming technology with calendar-based approach in scheduling fungicide applications to manage potato (Solanum tuberosum L.) late blight disease. Three fungicide scheduling strategies were evaluated: calendar-based strategy, BlightPro decision support system based strategy (DSS-based strategy), and unsprayed control. Using results from 14 yr of computer simulation experiments for 59 locations in the United States, we constructed distributions of net return to all costs excluding fungicide cost and application cost per 0.41 ha (net return per 0.41 ha) for the calendar-based and DSS-based strategies at each location. These distributions were then compared using three risk management methods: stochastic dominance, stochastic dominance with respect to a function, and stochastic efficiency with respect to a function. The DSS-based strategy was identified as the most effective approach to manage late blight in terms of disease suppression, net return per 0.41 ha, and risk-adjusted net return. Results indicate that the DSS-based strategy is the preferred method to schedule fungicide applications. Under high disease pressure circumstances, the economic benefits to potato growers of adopting the precision agriculture technology ranged from US$30 to $573 per 0.41 ha. For risk neutral individuals, who are concerned about the difference between average net return per 0.41 ha, the benefits ranged from $30 to $305 per 0.41 ha. Except for growers raising the moderately resistant potato cultivars, more risk averse individuals tended to benefit more from adopting the precision agriculture technology, with benefits ranging from $38 to $573 per 0.41 ha.

Effective altruism is an ethical framework for identifying the greatest potential benefits from investments. Here, we apply effective altruism concepts to maximize research benefits through identification of priority stakeholders, pathosystems, and research questions and technologies. Priority stakeholders for research benefits may include smallholder farmers who have not yet attained the minimal standards set out by the United Nations Sustainable Development Goals; these farmers would often have the most to gain from better crop disease management, if their management problems are tractable. In wildlands, prioritization has been based on the risk of extirpating keystone species, protecting ecosystem services, and preserving wild resources of importance to vulnerable people. Pathosystems may be prioritized based on yield and quality loss, and also factors such as whether other researchers would be unlikely to replace the research efforts if efforts were withdrawn, such as in the case of orphan crops and orphan pathosystems. Research products that help build sustainable and resilient systems can be particularly beneficial. The “value of information” from research can be evaluated in epidemic networks and landscapes, to identify priority locations for both benefits to individuals and to constrain regional epidemics. As decision-making becomes more consolidated and more networked in digital agricultural systems, the range of ethical considerations expands. Low-likelihood but high-damage scenarios such as generalist doomsday pathogens may be research priorities because of the extreme potential cost. Regional microbiomes constitute a commons, and avoiding the “tragedy of the microbiome commons” may depend on shifting research products from “common pool goods” to “public goods” or other categories. We provide suggestions for how individual researchers and funders may make altruism-driven research more effective. [Formula: see text] Copyright © 2020 The Author(s). This is an open access article distributed under the CC BY 4.0 International license .

Epidemics of sugarcane orange rust (caused by Puccinia kuehnii) in Florida are largely influenced by prevailing weather conditions. In this study, we attempted to model the relationship between weather conditions and rust epidemics as a first step toward development of a decision aid for disease management. For this purpose, rust severity data were collected from 2014 through 2016 at the Everglades Research and Education Center, Belle Glade, Florida, by recording percentage of rust-affected area of the top visible dewlap leaf every 2 weeks from three orange rust susceptible cultivars. Hourly weather data for 10- to 40-day periods prior to each orange rust assessment were evaluated as potential predictors of rust severity under field conditions. Correlation and stepwise regression analyses resulted in the identification of nighttime (8 PM to 8 AM) accumulation of hours with average temperature 20 to 22°C as a key predictor explaining orange rust severity. The five best regression models for a 30-day period prior to disease assessment explained 65.3 to 76.2% of variation of orange rust severity. Prediction accuracy of these models was tested using a case control approach with disease observations collected in 2017 and 2018. Based on receiver operator characteristic curve analysis of these two seasons of test data, a single-variable model with the nighttime temperature predictor mentioned above gave the highest prediction accuracy of disease severity. These models have potential for use in quantitative risk assessment of sugarcane rust epidemics.

In-furrow nematicide application is a primary method for managing Rotylenchulus reniformis (Linford and Oliveira, 1940) in cotton (Gossypium hirsutum L.). Fluopyram is a relatively new non-fumigant nematicide and field data is needed to determine its efficacy at managing R. reniformis (reniform nematode, RN) in cotton production. To investigate, two experiments, consisting of multiple small plot field trials per experiment, were conducted in Quincy, FL. The first experiment evaluated optimal fluopyram application rate by comparing 0, 105, 131, 158, 184, and 236 g a.i./ha. The second experiment compared aldicarb, a common non-fumigant nematicide in cotton, with two fluopyram formulations, one at 184 g a.i./ha and another at 199 g a.i./ha. In the first experiment, fluopyram reduced RN abundances in 2 of 3 trials, and 236 g fluopyram/ha provided the most consistent management of RN soil populations, while 158 and 184 g fluopyram/ha were effective in one trial each. At 131 g a.i./ha or above, any fluopyram rate tested improved cotton yield compared with untreated in one trial, but did not affect yield in any other trial. In the second experiment, aldicarb reduced RN egg abundances in roots compared with untreated or fluopyram treatments. None of the nematicides affected yield in the second experiment. In summary, fluopyram was inconsistent for managing RN on cotton.

Brassica carinata A. Braun, grown as a winter crop on underutilized agricultural land in the southeast United States (SE US), may provide a new rotation alternative and augment income for producers. Widespread adoption of Brassica carinata as a winter crop in the SE US requires varieties with cold tolerance, acceptable and stable seed yield, oil content, protein content so that the crop will be complementary with the normal cultivation of summer crops such as cotton (Gossypium hirsutum L.), corn (Zea mays L.), soybean (Glycine max L. Merr), sorghum (Sorghum bicolor L. Moench) and peanut (Arachis hypogaea L.). The objective of this study was to evaluate the performance of 11 Brassica carinata genotypes for agronomically important traits including seed yield, oil and protein content, oil quality, days to bolting, flowering and maturity at three locations during two growing seasons (2015–2017) as a winter crop in the SE US. Interactions between genotype and environment played a crucial role in overall agronomic performance. This study provides key information on the effect of environmental conditions, such as precipitation and temperature on the agronomic performance of carinata along with generation of information related to region-specific requirements for the crop in the SE US. Days to maturity ranged from 154 to 165 days. The average yield of the 11 genotypes tested ranged from 2814 kg/ha to 3401 kg/ha, which were improved from earlier studies, demonstrating gain due to regional selection and breeding efforts. Total oil content ranged from 42.0 % to 52.4 %, while the erucic acid (C22:1) content ranged from 40.7 % to 42.9 % on a whole seed basis. Based on these results, specific genotypes with consistently high seed yield, oil, erucic acid and protein content with shorter life cycle irrespective of location or year were identified. Brassica carinata has potential as a viable bioenergy winter crop to be integrated into the cropping systems in the SE US and other regions of the world.

The tomato late blight pandemic of 2009 made late blight into a household term in much of the eastern United States. Many home gardeners and many organic producers lost most if not all of their tomato crop, and their experiences were reported in the mainstream press. Some CSAs (Community Supported Agriculture) could not provide tomatoes to their members. In response, many questions emerged: How did it happen? What was unusual about this event compared to previous late blight epidemics? What is the current situation in 2012 and what can be done? It's easiest to answer these questions, and to understand the recent epidemics of late blight, if one knows a bit of the history of the disease and the biology of the causal agent, Phytophthora infestans.

Precision agriculture technology can transform farming related data into useful information, which may lead to more efficient usage of agricultural resources and increase sustainability. This paper compares precision agriculture technology with traditional practices in scheduling fungicide application so as to manage late blight disease in tomato production. The following three fungicide scheduling strategies were evaluated: a calendar-based strategy, the BlightPro Decision Support System based strategy (DSS-based strategy), and a strategy that does not involve fungicide application. The data from field trials and computer simulation experiments were used to construct distributions of the net return per acre for the calendar-based and the DSS-based strategies. These distributions were then compared using three standard approaches to ranking risky alternatives, namely: stochastic dominance, stochastic dominance with respect to a function, and stochastic efficiency with respect to a function. Assuming no yield differences between the calendar-based and the DSS-based strategies, the calendar-based strategy was preferred for highly late blight susceptible cultivars, and the DSS-based strategy was preferred for moderately susceptible and moderately resistant cultivars. Assuming no yield differences, the value of the BlightPro Decision Support System ranged from &minus, $28 to $48 per acre. With the yield improvement for the DSS-based strategy included, the DSS-based strategy was preferred for the cultivars in all of the disease-resistance categories with the value ranging from $496 to $1714 per acre.

The objective of this study was to evaluate the utility of the BlightPro decision support system (DSS) for late blight management using computer simulation and field tests. Three fungicide schedules were evaluated: (i) calendar-based (weekly) applications, (ii) applications according to the DSS, or (iii) no fungicide. Simulation experiments utilized 14 years of weather data from 59 locations in potato-producing states. In situations with unfavorable weather for late blight, the DSS recommended fewer fungicide applications with no loss of disease suppression; and, in situations of very favorable weather for late blight, the DSS recommended more fungicide applications but with improved disease suppression. Field evaluation was conducted in 2010, 2011, 2012, and 2013. All experiments involved at least two cultivars with different levels of resistance. DSS-guided and weekly scheduled fungicide treatments were successful at protecting against late blight in all field experiments. As expected, DSS-guided schedules were influenced by prevailing weather (observed and forecast) and host resistance and resulted in schedules that maintained or improved disease suppression and average fungicide use efficiency relative to calendar-based applications. The DSS provides an interactive system that helps users maximize the efficiency of their crop protection strategy by enabling well-informed decisions.

The systemic fungicide mefenoxam has been important in the control of late blight disease caused by Phytophthora infestans. This phenylamide fungicide has a negative effect on the synthesis of ribosomal RNA; however, the genetic basis for inherited field resistance is still not completely clear. We recently observed that a sensitive isolate became tolerant after a single passage on mefenoxam-containing medium. Further analyses revealed that all sensitive isolates tested (in three diverse genotypes) acquired this resistance equally quickly. In contrast, isolates that were “resistant” to mefenoxam in the initial assessment (stably resistant) did not increase in resistance upon further exposure. However, there appeared to be a cost associated with acquired resistance in the initially sensitive isolates, in that isolates with acquired resistance grew more slowly on mefenoxam-free medium than did the same isolates that had never been exposed to mefenoxam. The acquired resistance of the sensitive isolates declined slightly with subsequent culturing on medium free of mefenoxam. To investigate the mechanism of acquired resistance, we employed strand-specific RNA sequencing. Many differentially expressed genes were genotype specific, but one set of genes was differentially expressed in all genotypes. Among these were several genes (a phospholipase “Pi-PLD-like-3,” two ATP-binding cassette superfamily [ABC] transporters, and a mannitol dehydrogenase) that were up-regulated and whose function might contribute to a resistance phenotype.

During the summers of 2012 and 2013, 39 tomato (Solanum lycopersicum) lines or varieties were evaluated for resistance to late blight in three separate field trials. In each trial, late blight was caused by field isolates of Phytophthora infestans clonal lineage US-23. Varieties with the late blight resistance genes Ph-1, Ph-2, Ph-3, and Ph-2 + Ph-3 were included, along with several heirloom varieties with grower-reported resistance and varieties with no known resistance. All six varieties with Ph-2 + Ph-3, along with NC25P, which is homozygous for Ph-3 only, showed a high level of resistance. Plum Regal F1, which is heterozygous for Ph-3 only, showed moderate resistance. Legend, the only variety with Ph-2 alone, also showed moderate resistance. Three heirloom varieties, Matt's Wild Cherry, Lemon Drop, and Mr. Stripey, showed a high level of resistance comparable with that of varieties with Ph-2 + Ph-3. New Yorker, possessing Ph-1 only, showed no resistance. Indeterminate varieties had significantly less disease than determinate varieties in two of the three trials. Overall, this study suggests that tomato varieties with both Ph-2 and Ph-3 can be used to effectively manage late blight caused by P. infestans clonal lineage US-23. Varieties possessing only Ph-2, or heterozygous for Ph-3, were better protected than those without any late blight resistance but might still require supplemental fungicide applications, while the variety that was homozygous for Ph-3 was highly resistant. Several heirloom varieties were also highly resistant, and the unknown mechanism of their resistance warrants further research. Finally, the plasticity observed in United States P. infestans populations over the past several decades necessitates continued monitoring for genetic changes within P. infestans that could lead to the breakdown of resistance reported here.

Phytophthora infestans, the causal agent of late blight disease, has been reported in the United States and Canada since the mid-nineteenth century. Due to the lack of or very limited sexual reproduction, the populations of P. infestans in the United States are primarily reproducing asexually and, thus, show a simple genetic structure. The emergence of new clonal lineages of P. infestans (US-22, US-23, and US-24) responsible for the late blight epidemics in the northeastern region of the United States in the summers of 2009 and 2010 stimulated an investigation into phenotypic traits associated with these genotypes. Mating type, differences in sensitivity to mefenoxam, differences in pathogenicity on potato and tomato, and differences in rate of germination were studied for clonal lineages US-8, US-22, US-23, and US-24. Both A1 and A2 mating types were detected. Lineages US-22, US-23, and US-24 were generally sensitive to mefenoxam while US-8 was resistant. US-8 and US-24 were primarily pathogenic on potato while US-22 and US-23 were pathogenic on both potato and tomato. Indirect germination was favored at lower temperatures (5 and 10°C) whereas direct germination, though uncommon, was favored at higher temperatures (20 and 25°C). Sporangia of US-24 released zoospores more rapidly than did sporangia of US-22 and US-23. The association of characteristic phenotypic traits with genotype enables the prediction of phenotypic traits from rapid genotypic analyses for improved disease management.

Fusarium ear rot of maize, caused by Fusarium verticillioides, reduces grain yield and quality and contaminates it with mycotoxins (fumonisin). As maize cultivars with complete resistance to Fusarium ear rot and fumonisin contamination have not been identified, and since the disease is difficult to control by conventional means, novel strategies for disease control and fumonisin reduction are required. One such strategy could involve the use of chemical elicitors that induce resistance in plants against a broad spectrum of pathogens, insects and abiotic stresses. In this study the ability of resistance elicitors to reduce infection by F. verticillioides and prevent fumonisin contamination in maize was investigated, and their impact on yield assessed. Five elicitors were selected based on their ability to activate different pathways in plant defence systems. The elicitors included β-amino butyric acid (BABA), benzothiadiazole (BTH), harpin protein, 2,6-dichloroisonicotinic acid (INA), and methyl jasmonate (MeJA). A fungicide containing difenoconazole (triazole) and azoxystrobin (strobilurin) as active ingredients and that has known fungicidal activity in other plant-pathogen interactions, but not specifically Fusarium ear rot, was also included. The plant resistance elicitors and fungicide were evaluated in multi-site field trials. Following artificial inoculation with F. verticillioides isolate MRC 826, a high fumonisin producer, visual rating of Fusarium ear rot severity was performed and fumonisin B1, B2 and B3 content of the grain quantified with high performance liquid chromatography. None of the five elicitors or the fungicide consistently reduced Fusarium ear rot and/or fumonisin contamination significantly. Treatment of maize with BTH resulted in a significant reduction in ear filling and yield in field trials. Treatment effects on fumonisin content were influenced by maize genotype and trial location, since significant interactions were observed between treatment, maize genotype and trial location. While the evaluated elicitors might be useful for prevention of maize foliar diseases, they were not effective at reducing Fusarium ear rot or fumonisin contamination. However, optimisation of elicitor application method, dose, frequency and timing could possibly yield improved results.

Fusarium ear rot of maize, caused by Fusarium verticillioides, is an important disease affecting maize production worldwide. Apart from reducing yield and grain quality, F. verticillioides produces fumonisins which have been associated with mycotoxicoses of animals and humans. Currently, no maize breeding lines are known with resistance to F. verticillioides in South Africa. The objective of this study, therefore, was to evaluate 24 genetically diverse maize inbred lines as potential sources of resistance to Fusarium ear rot and fumonisin accumulation in field trials at Potchefstroom and Vaalharts in South Africa. After artificial silk channel inoculation with F. verticillioides, Fusarium ear rot development was determined at harvest and fumonisins B1, B2, and B3 quantified. A significant inbred line by location effect was observed for Fusarium ear rot severity (P ≤ 0.001), although certain lines proved to be consistently resistant across both locations. The individual inbred lines also differed considerably in fumonisin accumulation between Potchefstroom and Vaalharts, with differentiation between susceptible and potentially resistant inbred lines only being possible at Vaalharts. A greenhouse inoculation trial was then also performed on a subset of potentially resistant and highly susceptible lines. The inbred lines CML 390, CML 444, CML 182, VO 617Y-2, and RO 549 W consistently showed a low Fusarium ear rot (–1. These lines could potentially act as sources of resistance for use within a maize breeding program.

The distribution and co-occurrence of four Fusarium species and their mycotoxins were investigated in maize samples from two susceptible cultivars collected at 14 localities in South Africa during 2008 and 2009. Real-time PCR was used to quantify the respective Fusarium species in maize grain, and mycotoxins were quantified by multi-toxin analysis using HPLC-MS. In 2008, F. graminearum was the predominant species associated with maize ear rot in the eastern Free State, Mpumalanga and KwaZulu-Natal provinces, while F. verticillioides was predominant in the Northwest, the western Free State and the Northern Cape provinces. In 2009, maize ear rot infection was higher and F. graminearum became the predominant species found in the Northwest province. Fusarium subglutinans was associated with maize ear rot in both years at most of the localities, while F. proliferatum was not detected from any of the localities. Type B trichothecenes, especially deoxynivalenol, and zearalenone were well correlated with the amount of F. graminearum, fumonisins with F. verticillioides, and moniliformin and beauvericin with F. subglutinans. This information is of great importance to aid understanding of the distribution and epidemiology of Fusarium species in South Africa, and for predicting mycotoxin contamination risks and implementing preventative disease management strategies.