Commercial Wheat Fields Research Articles

Temperature and relative humidity in a commercial bread wheat field, recorded by an automated meteorological station and a digital sensor in the Yaqui Valley, Sonora, Mexico

Meteorological parameters determine most agronomic events, with temperature being the climatological factor most closely related to the annual productivity of a crop. The objective of this work was to monitor the temperature and relative humidity at different growth stages of a commercial bread wheat field, during the crop season 2017-2018. The work was carried out with data obtained from December 12, 2017 (sowing date) to April 18, 2018, from a mobile OMEGA OM-EL-USB-2 sensor within the field, sown with the bread wheat cultivar Borlaug 100, located in Block 1020, in the Yaqui Valley, Sonora, Mexico, and from the Block 910-CIANO meteorological station, located 8 km away, which is the closest to the field. Calculations were made for the average temperature, relative humidity and cold units (CU). In addition, the data was filtered by day and night time, considering daytime data from 7:00 to 18:00 and nighttime data from 19:00 to 06:00. The CU recorded by the sensor was higher with 384 than the meteorological station, which accumulated a total of 321. The temperature during the day was on average 2.9 °C higher than that recorded by the meteorological station, and 1.6 °C lower at night. The relative humidity recorded by the sensor was 5 % higher than that recorded by the meteorological station.

Winter wheat response to plant density in yield contest fields

AbstractSeeding rate recommendations for wheat (Triticum aestivum L.) are often 150–450 seeds m−2. However, we hypothesize that wheat grown with high resource availability (i.e., fertility and moisture) can maximize yield under considerably lower rates. Our objectives were to explore winter wheat response to low populations under high resource availability using yield‐contest fields as a case study. A factorial experiment evaluated four wheat varieties (i.e., Joe, WB‐Grainfield, Langin, and LCS Revere) exposed to five seeding rates (50, 100, 150, 200, and 250 seeds m−2) during five seasons in commercial wheat fields managed by yield‐contest winning producers near Leoti, KS. Fields were silt‐loam soils with high available water‐holding capacity, long‐term history of manure application with non‐limiting fertility, and adopted a sorghum [Sorghum bicolor (L.) Moench]–fallow–wheat rotation. Plant density ranged from 26 to 341 plants m−2 and yield ranged from 3.2 to 6.8 Mg ha−1. Water use efficiency of 19.5 kg ha−1 mm−1 suggested no management limitations to yield. Quadratic models portrayed the grain yield–plant density relation well, with 95% of the maximum yield reached at 68 to 91 plants m−2 for crops sown at the optimum date (4 out of 5 years), and at 312 plants m−2 for a late‐sown crop. Greater fall temperature accumulation reduced the relative yield between the maximum and minimum seeding rates. There was no variety × plant density interaction and Langin was the most consistent yielding variety across environments. Optimum plant density for winter wheat in environments with high resource availability may be considerably lower than current recommendations.

Relationship between the leaf area index and wheat grain yield in commercial fields in the Yaqui valley, Sonora, Mexico

The leaf area index (LAI) is a key plant parameter for modeling the mass exchange and energy between the biosphere and the atmosphere, which allows the study of development, growth, and agronomic yield of crops. The critical period for diminishing the wheat leaf area occurs 30 days around flowering and may cause a reduction in the real number of spikes/m2, spikelets/spike, number of grains/m2, and grain weight. The objective was to determine the relationship between the LAI and grain yield during the phenological development, in different sowing dates in thirteen commercial wheat fields, sown with durum cultivar CIRNO C2008, in the Yaqui Valley, Sonora, Mexico, during the fall-winter 2021-2022 crop season. Field surveys were carried out to monitor crop development, and to take readings of the LAI using a linear ceptometer; also, four 1 m2 samples were harvested from each field in order to count the number of spikes and to calculate grain yield. The LAI was not constant in ten of the selected fields according to the development of wheat; however, there were three fields (B-703, B-725, and B-1512) where there was a positive correlation between the LAI and grain yield which reached more than 8.2 t ha-1. The highest expression of the LAI occurred during ½ grain formation. The average grain yield of the monitored fields was 7.22 t ha-1, being December 14, 2021, the sowing date with the highest yield (8.43 t ha-1), while the highest number of spikes/m2 occurred on the December 11 sowing date with 428. Measurement of the LAI indirectly, could be considered an appropriate method, but environmental conditions and agronomic management by producers must be taken into account in order to make yield estimates.

Research on Dynamic Monitoring of Grain Filling Process of Winter Wheat from Time-Series Planet Imageries

Remote sensing has been used as an important means of monitoring crop growth, especially for the monitoring of the formation of crop yield in the middle and late growth period. The information acquisition on the yield formation period of winter wheat is of great significance for winter wheat growth monitoring, yield estimation and scientific management. Hence, the main goal of this study was to verify the possibility of monitoring the grain-filling process of winter wheat and its in-field variability using an alternative non-destructive method based on orbital remote sensing. High-resolution satellite imageries (3 m) were obtained from the PlanetScope platform for three commercial winter wheat fields in Jiangsu Province, China during the reproductive stage of the winter wheat (185–215/193–223/194–224 days after sowing (DAS)). Based on the quantitative analysis of vegetation indices (VIs) obtained from high-resolution satellite imageries and three indicators of the winter wheat grain-filling process, linear, polynomial and logistic growth models were used to establish the relationship between VIs and the three indicators. The research showed a high Pearson correlation (p < 0.001) between winter wheat maturity and most VIs. In the overall model, the remote sensing inversion of the dry thousand-grain weight has the highest accuracy and its R2 reaches more than 0.8, which is followed by fresh thousand-grain weight and water content, the accuracies of which are also considerable. The results indicated a great potential to use high-resolution satellite imageries to monitor winter wheat maturity variability in fields and subfields. In addition, the proposed method contributes to monitoring the dynamic spatio-temporality of the grain-filling progression, allowing for more accurate management strategies in regard to winter wheat.

Influence of the temperature and relative humidity on the incidence of wheat leaf rust (Puccinia Triticina Eriks.) in southern Sonora, Mexico, during three crop seasons

The influence of climate upon a plant disease is a consequence of the causal agent and its interaction with the host plant. Plants present distinctive elements by the effect of climate, whether they are adverse or beneficial to their growth and development, as well as for their exposure or protection from those climatic factors. The objective of this work was to analyze the influence of temperature and relative humidity in relation to commercial wheat fields which presented leaf rust in different areas of the southern region of the state of Sonora, Mexico, during the crop seasons 2017-2018, 2018-2019, and 2019-2020. Weather data were recorded from 23 weather stations that belong to the automated weather station network of the state of Sonora which comprise the Yaqui and Mayo Valleys. A Voronoi diagram was constructed to delimit the region which corresponded to each weather station, and so to locate each of the commercial wheat fields with leaf rust incidence, in order to analyze the weeks in which disease incidence was high. A “t student test” of independent samples was performed in order to compare the weather variables (average, maximum and minimum temperature, as well as relative humidity) during the three crop seasons, from the weather stations where commercial wheat fields were detected with the presence of leaf rust, with respect to those where the disease was not present. Relative humidity was the main key factor for the presence of leaf rust, since it is the variable where the mean of groups with and without the presence of leaf rust, showed statistical significant difference in each crop season, unlike the average and the minimum temperature which showed difference only during the 2017-2018 crop season, and the maximum temperature during 2019-2020.

Increasing Winter Wheat Grain Yield by Replicating the Management Adopted in High-Yielding Commercial Fields

Large winter wheat yield gaps between farmer yields and yield potential in the southern Great Plains indicate the need to improve recommendations of best management strategies to profitably bridge this gap. Many studies have been completed on individual management factors pre-determined by the individual researcher, but we are not aware of studies comparing combination of practices that producers are currently using, which would be more relevant for real-world scenarios. Our objective was to determine the yield gains resulting from management intensification using combination of practices currently adopted in commercial wheat fields. Four management intensities (i.e., Low, Average, High, and Top) were derived from a survey of 656 commercial fields, and replicated in trials conducted in four and six locations in western and central Kansas. Management intensities were tested factorially on two adapted varieties. Grain yield in central Kansas ranged from 45.5 bu/a in the Low management intensity to 69.3 bu/a in the High and Top intensities, with the Average management increasing yields by 30% as compared to the Low intensity, and the High management increasing yields 18% from the Average. The variety WB4269 outyielded Zenda (63.2 and 58.7 bu/a) across central environments. In western Kansas, there was a significant variety by management interaction, where wheat yield increased from the Low and Average intensities to the High and Top intensities (72.8–78.9 to 90.7–96.0 bu/a). The WB-Grainfield and KS Dallas varieties produced similar yields in the western environments. Using similar management practices as the producers with high-yield results in central and western Kansas narrowed the yield gap, and further increases in management intensification were not warranted. Variety selection played an important role either by increasing attained yields or by interacting with management practices.

The gene Sr38 for bread wheat breeding in Western Siberia

Present-day wheat breeding for immunity exploits extensively closely related species from the family Triticeae as gene donors. The 2NS/2AS translocation has been introduced into the genome of the cultivated cereal Triticum aestivum from the wild relative T. ventricosum. It contains the Lr37, Yr17, and Sr38 genes, which support seedling resistance to the pathogens Puccinia triticina Eriks., P. striiformis West. f. sp. tritici, and P. graminis Pers. f. sp. tritici Eriks. & E. Henn, which cause brown, yellow, and stem rust of wheat, respectively. This translocation is present in the varieties Trident, Madsen, and Rendezvous grown worldwide and in the Russian varieties Morozko, Svarog, Graf, Marquis, and Homer bred in southern regions. However, the Sr38 gene has not yet been introduced into commercial varieties in West Siberia; thus, it remains of practical importance for breeding in areas where populations of P. graminis f. sp. tritici are represented by avirulent clones. The main goal of this work was to analyze the frequency of clones (a)virulent to the Sr38 gene in an extended West Siberian collection of stem rust agent isolates. In 2019–2020, 139 single pustule isolates of P. graminis f. sp. tritici were obtained on seedlings of the standard susceptible cultivar Khakasskaya in an environmentally controlled laboratory (Institute of Cytology and Genetics SB RAS) from samples of urediniospores collected on commercial and experimental bread wheat f ields in the Novosibirsk, Omsk, Altai, and Krasnoyarsk regions. By inoculating test wheat genotypes carrying Sr38 (VPM1 and Trident), variations in the purity of (a)virulent clones were detected in geographical samples of P. graminis f. sp. tritici. In general, clones avirulent to Sr38 constitute 60 % of the West Siberian fungus population, whereas not a single virulent isolate was detected in the Krasnoyarsk collection. The Russian breeding material was screened for sources of the stem rust resistance gene by using molecular markers specif ic to the 2NS/2AS translocation. A collection of hybrid lines and varieties of bread spring wheat adapted to West Siberia (Omsk SAU) was analyzed to identify accessions promising for the region. The presence of the gene was postulated by genotyping with specif ic primers (VENTRIUP-LN2) and phytopathological tests with avirulent clones of the fungus. Dominant Sr38 alleles were identif ied in Lutescens 12-18, Lutescens 81-17, Lutescens 66-16, Erythrospermum 79/07, 9-31, and 8-26. On the grounds of the composition of the West Siberian P. graminis f. sp. tritici population, the Sr38 gene can be considered a candidate for pyramiding genotypes promising for the Novosibirsk, Altai, and Krasnoyarsk regions

On-farm data-rich analysis explains yield and quantifies yield gaps of winter wheat in the U.S. central Great Plains

With an annual production of ∼60 Mt, the U.S. accounts for about 8% of the global wheat (Triticum aestivum L.) production. Still, quantification of the yield gaps (YG) and major management factors to reduce it are scarce. We used Kansas, the largest wheat producing state in the U.S. located in the central Great Plains, for an initial assessment of on-farm yield and YG. We collected field-level management (37 variables), weather (8 variables), soil (two variables) and yield data from 656 commercial wheat fields over three harvest years (2016–2018) to (i) quantify management adoption levels, Ya, and YG, and (ii) identify interactions among management practices and weather variables using a data-rich approach. We also used our data as a case-study to detect whether differences in crop management among regions justified data clustering by crop zones. Water-limited yield potential (Yw) was simulated for each field-year using actual soil and weather data and the SSM-Wheat model. Fields were grouped in three climate zones based on their long-term climatology and important differences in cropping systems between zones. Grain yield averaged 3.8 Mg ha−1 and ranged from 0.3–7.1 Mg ha−1 across all regions and years. The YG averaged 44 %, with seasons with high Yw resulting in greater YG. Management practices most often associated with grain yield were management of nitrogen (N), phosphorus (P), and sulphur (S) fertilizer, as well as foliar fungicide and its interaction with variety reaction to major diseases, although these depended on in-season weather. Our analyses highlighted many other genotype × management × environment interactions explaining winter wheat Ya, such as regional-specific cultivar maturity and the dependency of sowing date (and its relation to seeding rate) on cropping system.

Crop Cycle and Tillage Role in the Outbreak of Late Wilt Disease of Maize Caused by Magnaporthiopsis maydis.

The destructive maize late wilt disease (LWD) has heavy economic implications in highly infected areas such as Israel, Egypt, and Spain. The disease outbreaks occur near the harvest, leading to total yield loss in severe cases. Crop rotation has long been known as an effective means to reduce plant diseases. Indeed, agricultural soil conservation practices that can promote beneficial soil and root fungi have become increasingly important. Such methods may have a bioprotective effect against Magnaporthiopsis maydis, the LWD causal agent. In this two-year study, we tested the role of crop rotation of maize with either wheat or clover and the influence of minimum tillage in restricting LWD. In the first experiment, wheat and clover were grown in pots with LWD infected soil in a greenhouse over a full winter growth period. These cultivations were harvested in the spring, and each pot’s group was split into two subgroups that underwent different land processing practices. The pots were sown with LWD-sensitive maize cultivar and tested over a whole growth period against control soils without crop rotation or soil with commercial mycorrhizal preparation. The maize crop rotation with wheat without tillage achieved prominent higher growth indices than the control and the clover crop cycle. Statistically significant improvement was measured in the non-tillage wheat soil pots in sprout height 22 days after sowing, in the healthy plants at the season’s end (day 77), and in shoot and cob wet weight (compared to the control). This growth promotion was accompanied by a 5.8-fold decrease in pathogen DNA in the plant stems. The tillage in the wheat-maize growth sequence resulted in similar results with improved shoot wet-weight throughout the season. In contrast, when maize was grown after clover, the tillage reduced this parameter. The addition of commercial mycorrhizal preparation to the soil resulted in higher growth measures than the control but was less efficient than the wheat crop cycle. These results were supported by a subsequent similar experiment that relied on soil taken from commercial wheat or clover fields. Here too, the wheat-maize growth cycle (without permanent effect for the tillage) achieved the best results and improved the plants’ growth parameters and immunity against LWD and lowered pathogen levels. In conclusion, the results of this study suggest that wheat and perhaps other crops yet to be inspected, together with the adjusted tillage system, may provide plants with better defense against the LWD pathogen.

Short communication: A predictive model for the time course of seedling emergence of Phalaris brachystachys (short-spiked canary grass) in wheat fields

Aim of study: A predictive model of the seedling emergence pattern of Phalaris brachystachys Link (short-spiked canary grass) was developed, aimed to contribute to support a more efficient management of this troublesome, competitive weed in winter cereal crops around its native Mediterranean range and in different areas of the world where it is introduced.Area of study: Southern (Andalusia) and northern Spain (Navarra).Material and methods: A model describing the emergence pattern of P. brachystachys in cereal fields based on accumulation of hydrothermal time in soil was developed and validated. For model development, cumulative emergence data were obtained in an experimental field, while an independent validation of the model was conducted with data collected in two commercial wheat fields from climatically contrasting regions of Spain.Main results: The relationship between cumulative emergence and cumulative hydrothermal time (CHT) was well described by a Logistic model. According to model predictions, 50% and 95% seedling emergence takes place at 108 and 160 CHT above base water potential for seed germination, respectively. The model accurately predicted the seedling emergence time course of P. brachystachys in the two commercial wheat fields (R2 ≥ 0.92).Research highlights: This model is a new tool that may be useful to improve the timing of control measures to maximize efficiency in reducing P. brachystachys infestations in cereal crops.Phalaris brachystachys Link (short-spiked canary grass) is a competitive weed that affects winter cereal crops around its native Mediterranean basin and in different areas of the world where it is introduced. The development of a predictive model of the seedling emergence pattern may contribute to support a more efficient management of this species. In this work, a model describing the emergence time course of P. brachystachys in cereal fields based on accumulation of hydrothermal time in soil was developed and validated. For model development, cumulative emergence data were obtained in an experimental field, while an independent validation of the model was conducted with data collected in two commercial wheat fields from climatically contrasting regions of Spain. The relationship between cumulative emergence and cumulative hydrothermal time (ΘCHTT) was well described by a Logistic model. According to model predictions, 50% and 95% seedling emergence takes place at 108 and 160 ΘCHTT above base water potential for seed germination, respectively. The model accurately predicted the seedling emergence time course of P. brachystachys in the two commercial wheat fields (R2 ≥ 0.92).Research highlights: This model is a new tool that may be useful for fine-tuning the timing of control measures to maximize efficiency in reducing P. brachystachys infestations in cereal crops.

Diversity, rate, and distribution of wheat midge parasitism in the Peace River region of Alberta, Canada

AbstractWheat midge,Sitodiplosis mosellana(Géhin) (Diptera: Cecidomyiidae), is a major pest of wheat (Poaceae) that was first reported in the Peace River region of northwestern Alberta, Canada in 2011. Although parasitism is an important factor of mortality in wheat midge elsewhere, little is known about the prevalence, species, or distribution of wheat midge parasitoids in the Peace River region. To address this knowledge gap, we conducted a survey of wheat midge parasitoids in commercial wheat fields across the region in 2016 and 2017. For a given field, parasitism of wheat midge larvae ranged from 36 to 71%. All but one parasitoid (n= 2167) were identified asMacroglenes penetrans(Kirby) (Hymenoptera: Pteromalidae). The exception was a specimen in the genusInostemmatentatively identified asI. walkeriKieffer (Hymenoptera: Platygasteridae). These findings identify parasitism as an important factor that is suppressing populations of wheat midge in the Peace River region, provide the first report ofInostemma walkerifor North America, and provide the first report of this species as a parasitoid ofS. mosellana.

Movement patterns of the grey field slug (Deroceras reticulatum) in an arable field

We report the results of an experiment on radio-tracking of individual grey field slugs in an arable field and associated data modelling designed to investigate the effect of slug population density in their movement. Slugs were collected in a commercial winter wheat field in which a 5x6 trapping grid had been established with 2m distance between traps. The slugs were taken to the laboratory, radio-tagged using a recently developed procedure, and following a recovery period released into the same field. Seventeen tagged slugs were released singly (sparse release) on the same grid node on which they had been caught. Eleven tagged slugs were released as a group (dense release). Each of the slugs was radio-tracked for approximately 10 h during which their position was recorded ten times. The tracking data were analysed using the Correlated Random Walk framework. The analysis revealed that all components of slug movement (mean speed, turning angles and movement/resting times) were significantly different between the two treatments. On average, the slugs released as a group disperse more slowly than slugs released individually and their turning angle has a clear anticlockwise bias. The results clearly suggest that population density is a factor regulating slug movement.

Population Dynamics of Wheat Root Pathogens Under Different Tillage Systems in Northeast Oregon.

No-till or direct seeding can be described as seeding directly into the crop stubble from the previous season without use of tillage. A reduction in tillage can result in many benefits, including increased soil organic matter, increased water holding capacity, and reduced fuel costs. However, the effect of no-till and reduced tillage on crop root disease profiles is poorly understood. To study the effect of tillage on disease dynamics, soil samples were collected from commercial wheat fields representing a wide range of tillage strategies in fall 2016 and fall 2017. Because precipitation might affect soilborne diseases, wheat fields located across a diverse gradient of precipitation zones of the dryland Pacific Northwest were selected. Fusarium spp., Pythium spp., and Rhizoctonia spp. were quantified from soil samples using soil dilution plating and quantitative PCR (qPCR) assays. Results of dilution plating showed that the colony counts of Fusarium, Pythium, and Rhizoctonia at the genus level were negatively associated with tillage. However, the same patterns were not observed when specific causal agents of Fusarium, Pythium, and Rhizoctonia that are known to be pathogenic on wheat were quantified with qPCR. Furthermore, precipitation affected the population density of some fungal pathogens (F. culmorum, P. ultimum, and R. solani AG 8). Within the scope of inference of this study, results of this study indicate that the benefits of adopting reduced tillage likely outweigh potential risk for increased root disease.

Wheat soil-borne mosaic: Yield loss and distribution in the US Pacific Northwest

Soil-borne wheat mosaic virus (SBWMV), the causal agent of Wheat soil-borne mosaic (WSBM) was discovered for the first time in the dryland wheat production zone of the US Pacific Northwest (PNW) in 2008. Current WSBM distribution in the Walla Walla Valley that spans the Oregon/Washington border was documented during 2017 and 2018. Yield loss estimates of rainfed winter wheat were also determined for this growing region. WSBM is more widely distributed in the Walla Walla Valley than was previously estimated. Significant reductions of grain yield (40%), biomass (37%), and heads per area (34%) were documented in association with SBWMV infection in commercial winter wheat fields each year. Test weight was reduced by 2.3% (P = 0.08). No significant difference in the number of spikelets per head was observed in association with WSBM. This work is part of an ongoing effort to provide management solutions to WSBM.

Dense subsoils limit winter wheat rooting depth and soil water depletion

AbstractDense subsoils pose a challenge to dryland winter wheat (Triticum aestivum L.) production in the Palouse region of the semiarid northwestern United States. Subsoils, commonly fragipans and argillic horizons, may restrict root growth and limit crop access to critical stored soil water, but this phenomenon is not well characterized in the Palouse. During the 2017–2018 growing season, an on‐farm study of soil profiles in two commercial winter wheat fields in eastern Washington and northern Idaho was established to observe the effects of soil bulk density on winter wheat root system depth and subsoil water depletion. At harvest, grain yield, root density, soil bulk density, and postharvest soil water and nitrogen content were measured to 120 cm at 15‐cm segments in the profile. Root‐restrictive depth (RRD) was defined as the depth where root density was less than or equal to 0.25 intersections cm−2 cross‐sectional area. Soil bulk density negatively affected root density and consequently increased the probability of shallow RRD. Shallow RRD was common, with 38% of profiles having RRD less than or equal to 105 cm. Postharvest soil‐water content at the bottom of the measured profile (105–120 cm) was 41% higher in profiles with RRD of 90 cm than nonrestricted profiles. Yield declined with increase in postharvest soil water content at 105–120 cm depth. Findings indicate that dense subsoils can reduce stored soil water depletion by limiting root density and root system depth that, in turn, limits yield.

Remote Sensing Data to Detect Hessian Fly Infestation in Commercial Wheat Fields

Remote sensing data that are efficiently used in ecological research and management are seldom used to study insect pest infestations in agricultural ecosystems. Here, we used multispectral satellite and aircraft data to evaluate the relationship between normalized difference vegetation index (NDVI) and Hessian fly (Mayetiola destructor) infestation in commercial winter wheat (Triticum aestivum) fields in Kansas, USA. We used visible and near-infrared data from each aerial platform to develop a series of NDVI maps for multiple fields for most of the winter wheat growing season. Hessian fly infestation in each field was surveyed in a uniform grid of multiple sampling points. For both satellite and aircraft data, NDVI decreased with increasing pest infestation. Despite the coarse resolution, NDVI from satellite data performed substantially better in explaining pest infestation in the fields than NDVI from high-resolution aircraft data. These results indicate that remote sensing data can be used to assess the areas of poor growth and health of wheat plants due to Hessian fly infestation. Our study suggests that remotely sensed data, including those from satellites orbiting >700 km from the surface of Earth, can offer valuable information on the occurrence and severity of pest infestations in agricultural areas.

Landscape effects on Hessian fly, Mayetiola destructor (Diptera: Cecidomyiidae), distribution within six Kansas commercial wheat fields

Crop production of a significant portion of the Great Plains has greatly simplified the landscape, which can affect insect pest outbreaks. The Hessian fly is an important economic pest of wheat, a major crop grown in the region. However, outbreaks are often limited to localized events, which may be difficult to predict. Better understanding of where Hessian fly outbreaks are more likely to occur would help producers make informed management decisions. Therefore, the objective of our study was to describe the spatial distribution of Hessian fly infestation within commercial wheat fields, while examining how a simplified landscape may contribute to the distribution of Hessian fly infestations. Spatial distribution modeling was conducted in select fields (n = 6) infested with Hessian fly puparia. A geographic information system was used to create sampling grids for each field (n = 34–50 sample points/field), with one meter row of plants sampled at each sample point. The number of puparia and plants infested at each sample point were used to construct Hessian fly distribution maps for each field. Correlations between environmental factors and fly distribution were then examined. Results show that host plants (wheat and grasses) adjacent to the borders of study fields did not affect the distribution of puparia or plants infested within the field. Rather, the proportion of wheat within a 1 km radius of sampled fields affected the level of Hessian fly infestation, with a smaller proportion of wheat within the 1 km radius increasing the probability of Hessian fly infestation in sampled fields. The results of this study show previously unknown distribution of Hessian fly infestation within commercial wheat fields, resulting in new hypotheses about Hessian fly management in agroecosystems.

Explicit wheat production model adjusted for semi-arid environments

Current literature suggests that wheat production models are limited either to wide-scale or plot-based predictions ignoring pattern of habitat conditions and surficial hydrological processes. We present here a high-spatial resolution (50 m) non-calibrated GIS-based wheat production model for predictions of aboveground wheat biomass (AGB) and grain yield (GY). The model is an integration of three sub-models, each simulating elemental processes relevant for wheat growth dynamics in water-limited environments: (1) HYDRUS-1D, a finite element model that simulates one-dimensional movement of water in the soil profile; (2) a two-dimensional GIS-based surface runoff model; and (3) a one-dimensional process-driven mechanistic wheat growth model. By integrating the three sub-models, we aimed to achieve a more accurate spatially continuous water balance simulation with a better representation of root zone soil water content (SWC) impacts on plant development. High-resolution grid-based rainfall data from a meteorological radar system were used as input to HYDRUS-1D. Twenty-two commercial wheat fields in Israel were used to validate the model in two seasons (2010/11 and 2011/12). Results show that root zone SWC was accurately simulated by HYDRUS-1D in both seasons, particularly at the top 10-cm soil layer. Observed vs simulated AGB and GY were highly correlated with R2 = 0.93 and 0.72 (RMSE = 171 g m−2 and 70 g m−2) having low biases of -41 g m−2 (8%) and 52 g m−2 (10%), respectively. Model sensitivity test showed that HYDRUS-1D was mainly driven by spatial variability in the input soil characteristics while the integrated wheat production model was mostly affected by rainfall spatial variability indicating the importance of using accurate high-resolution rainfall data as model input. Using the integrated model, we predict decreases in AGB and GY of c. 10.5% and c. 12%, respectively, for 1 °C of warming and c. 7.7% and c. 7.3% for 5% reduction in rainfall amount in our study sites. The suggested model could be used by scientists to better understand the causes of spatial and temporal variability in wheat production and the consequences of future scenarios such as climate change.

Fusarium subtropicale, sp. nov., a novel nivalenol mycotoxin–producing species isolated from barley (Hordeum vulgare) in Brazil and sister to F. praegraminearum

ABSTRACTSurveys were conducted in commercial wheat and barley fields in the south central production regions of state of Paraná, Brazil, from 2011 to 2015. Spikes displaying visible Fusarium head blight symptoms were collected and the pathogen isolated from the tissues. The 754 Fusarium isolates recovered were identified by a high-throughput multilocus genotyping assay (MLGT) designed to identify trichothecene toxin–producing fusaria (i.e., formerly B-clade, but referred to here as F. sambucinum species complex lineage 1 [FSAMSC-1]) together with sequencing a portion of the translation elongation factor 1-α (TEF1) gene. One strain was discovered that appeared to be closely related to but phylogenetically distinct from F. praegraminearum based on the relatively low 97.7% TEF1 identity and positive genotype obtained with one of the two F. praegraminearum species–specific MLGT probes. Molecular phylogenetic analyses of a 10-gene data set resolved this novel FSAMSC-1 species and F. praegraminearum as sisters. Formally described herein as F. subtropicale, it is phenotypically distinct from the 22 other FSAMSC-1 species in that it produces mostly 1–3-septate macroconidia. Whole-genome sequence data were used to predict its potential to produce mycotoxins. Chemical analyses confirmed that F. subtropicale could produce the mycotoxins 4,15-diacetylnivalenol, butenolide, culmorin, and fusarin C in vitro, and the pathogenicity experiment revealed that F. subtropicale could infect but not spread in susceptible hard red spring wheat cultivar “Norm.”

First Report of Tawny Blotch Caused by Parastagonospora caricis on Phalaris arundinacea in New York

Leaf spots were observed on reed canarygrass (Phalaris arundinacea L.) growing in a commercial wheat field in Seneca County, NY, during summer 2016. Lesions were elliptical to cigar shaped, brown-red, and ringed by a light tan band with an irregular margin. Mature lesions contained single erumpent points of white tissue in their center. Damage was most severe in the lower canopy, where spots had coalesced to cover entire leaves. Symptomatic leaf tissue was surface sterilized in 1.65% sodium hypochlorite, rinsed with sterile distilled water, and placed on potato dextrose agar (PDA) amended with antibiotics. Cultures kept at 22°C under a 12-h photoperiod consistently yielded slow growing, cottony mycelium with a pale pink pigment and abundant pycnidia. Pycniospores produced by monosporic isolates grown on PDA amended with sterilized leaves of reed canarygrass were narrow, roughly cylindrical with equally blunt ends. They contained three to eight septa and measured 27.1 to 49.2 μm (mean, 37.7 μm) × 2.5 to 7.4 μm (mean, 5.4 μm) (n = 55). Morphology, symptomology, and host were characteristic of tawny blotch caused by Stagonospora foliicola (Bres.) Bubak (Sprague 1950). Two isolates were sequenced for species identification using the internal transcribed spacer region of rRNA, RNA polymerase subunit II gene, and β-tubulin gene. Sequences (GenBank KY604740, MF593838, and MF593839, respectively) had a 99 to 100% identity match to the type culture of Parastagonospora caricis deposited in GenBank and did not show homology to the type isolate of S. foliicola from Maryland. Although colony color of the New York isolates did not match that described for P. caricis, pycniospores produced on PDA without plant tissue amendments measured 61.2 × 6.3 µm, consistent with those recorded from the type culture of P. caricis (Quaedvlieg et al. 2013). A specimen was deposited at the Cornell herbarium (CUP-068300), and a representative culture was stored at CBS-KNAW (CBS 144011). Using one New York isolate, Koch’s postulates were completed in a greenhouse with 2-month-old, potted reed canarygrass. A conidial suspension of 1 × 10³ spores/ml in sterile water was washed from 2-week-old cultures grown on PDA amended with reed canarygrass leaves. Three pots were treated with the fungus, and three pots received a sterile water control treatment. Plants were spray inoculated with a fine mist until runoff and incubated under plastic bags for 24 h. After 2 weeks, inoculated plants showed symptoms typical of those seen in the field, and the pathogen was reisolated from multiple lesions. Control plants showed no signs of disease, and no fungi were isolated from their leaves. Tawny blotch is one of the most important diseases of reed canarygrass worldwide (Braverman et. al. 1986), and the damage can be significant under humid or moist conditions (Zeiders 1975). This disease may impact the quality and quantity of forage. P. caricis was first identified on Carex acutiformis in the Netherlands and has not been recorded from other hosts or locations. To the authors’ knowledge, this is the first report of P. caricis infecting reed canarygrass. It is possible that other North American reports of S. foliicola lacking DNA sequence data could be misidentifications of P. caricis, and both organisms should be considered in future studies of tawny blotch on associated grasses.