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Corn (Zea mays L.) kernel infection by Aspergillus flavus and subsequent aflatoxin accumulation in grain can have a deleterious effect on both humans and animals that consume contaminated grain. Predicting the aflatoxin risk is challenging due to complex interactions of biotic and abiotic stress factors that govern and exacerbate the phenomenon. The goal of this study was to determine whether a drought index could be used to predict the risk for pre-harvest aflatoxin contamination in corn. Risk assessment was approached at: 1) field (plot) level with data obtained from an in-field controlled experiment (Mississippi study), and 2) state level, where corn fields were sampled at a county level (Georgia study). The data used for this study consisted of historical records on aflatoxin contamination collected over thirteen growing seasons from 2000 to 2011, 2013, and 2014 at Mississippi State, Mississippi (1), and from random corn fields in 53 counties across Georgia between 1977 and 2004 (2). A controlled experiment was conducted at Mississippi with two soil types (a Leeper silty clay loam and a Myatt loam), and three commercial hybrids characterized by different susceptibility levels to aflatoxin contamination. The Agricultural Reference Index for Drought (ARID), a generic drought index for calculating drought on daily basis was evaluated as an aflatoxin risk prediction tool. Mid-silk day was selected to split each growing season into two time periods, which were further divided into positive and negative weeks representing weeks after and before mid-silk, respectively. Weekly ARID factors were calculated for all periods to evaluate the in-season alterations in aflatoxin risk. In both studies, multiple logistic regression models were used to predict aflatoxin risk as a function of the weekly ARID values. In Mississippi, risk level changes were additionally tested according to soil type and corn hybrid aflatoxin susceptibility. The United States Food and Drug Administration restricts corn grain consumption by humans and young animals if the contamination level is above 20 μg/kg; thus, this threshold (20 μg/kg) was selected to develop a binary dependent variable for the logistic model from the raw aflatoxin data. The results revealed that ARID might be used as a predictive tool to assess aflatoxin risk, soil type and hybrid susceptibility to aflatoxin contamination were statistically significant independent factors, and there are critical week windows during the growing season when changes in drought conditions affect the likelihood for aflatoxin contamination. These findings can be used to minimize risk by adapting site-specific management strategies such as triggering irrigation during critical risk weeks, selecting the most appropriate hybrid for a given site/location based on soil type, and determining optimum harvest date.

Aflatoxin is a mycotoxin produced by the Aspergillus flavus fungi that can severely contaminate corn grain. The U.S. Food and Drug Administration (FDA) have set a limit of 20 ppb, total aflatoxin, for interstate commerce of food and feed as it can induce liver cancer in humans and animals. Contamination is exacerbated by high temperatures, drought conditions and light-textured soil which are all common in Georgia (GA). Lack of irrigation infrastructure can further amplify drought stress and aflatoxin contamination. Accurate aflatoxin assessment requires the collection of multiple corn samples, is expensive and conducted at harvest which does not allow for the use of in-season mitigation strategies to reduce the risk. Given the expense of measurement and the consequences of crop loss, an important goal for agricultural extension services is the prediction and identification of years and counties at higher risk of aflatoxin contamination. This would allow growers to deploy management tactics to reduce risk and to reduce unnecessary expense on aflatoxin testing. In this research, aflatoxin levels were analysed by Poisson kriging and used to validate a strategy for identifying high risk years and counties. It is based on mapping risk factors (Maximum June temperatures, June rainfall, % corn planted area and % soil drainage types) that are above key thresholds. The aflatoxin data used were county level, collected unevenly in space and time from 1977 to 2004 in 53 counties in southern GA. Averaging and typical geostatistical methods were unreliable for producing a temporal summary of the spatial patterns because aflatoxin data were highly skewed and approached a Poisson distribution, and averages for counties with fewer observations are less reliable. Poisson kriging down-weights the influence of these in variogram computation and the estimation process. Comparison tests confirmed significant differences in aflatoxin levels between counties and years that were identified as having different levels of risk using the risk factors approach. Sensitivity analysis for Poisson kriged aflatoxin risk showed that the more years of data are clearly better for this analysis, but fewer than 15 years of data were not advisable.

Aflatoxin is a fungal toxin contaminating corn and causing liver cancer in humans and animals. Contamination is driven by high temperatures and drought. Aflatoxin assessment is expensive so extension services need to identify high risk areas so irrigation, planting strategies and corn varieties can be adapted. This research presents a web-based decision support tool for risk illustrated with a case study from southern Georgia. The tool employs the approach, developed by Kerry et al. (2017b) where exceedance of key thresholds in temperatures, rainfall, soil type and corn production are used to determine risk. The tool also includes NDVI to indicate drought stress and could be further expanded to include new risk factors and adapted to other crops.

Herbicide resistant Palmer amaranth (Amaranthus palmeri) has rapidly become a dominant weed management issue in agronomic crops of the Southeast US. The small size of Palmer amaranth seeds, relative to other common weeds, provides an opportunity to use physical weed control through high-biomass, rolled cover crop mulches, in conjunction with herbicide tools. Experiments were conducted to characterize Palmer amaranth suppression and light permeability from a range of rye biomass levels. There was an inverse relationship between Palmer amaranth emergence and rye biomass that was described by a log-logistic regression model. In the absence of rye, there was approximately 80% Palmer amaranth emergence, while the highest rate of rye biomass prevented Palmer amaranth emergence. A log-logistic regression model also described the amount of photosynthetic active radiation transmitted through rye mulch in a green house experiment. The highest level of rye biomass reduced the amount of light to 13% of full sunlight, while 5370 kg ha−1 of rye caused a 50% reduction of light transmission; a similar level of rye biomass (P = 0.93) reduced Palmer amaranth emergence by 50%. Effective suppression of Palmer amaranth will depend upon the ability to produce high-biomass rye. Field experiments evaluated changes in planting date, seeding rate, and nitrogen application on rye biomass production. Maximum rye biomass in April occurred when rye was planted prior to middle-November. However, a 50% reduction in rye biomass resulted from middle-December planting of rye, providing growers with a short planting interval for high-biomass rye production. Additionally, rye seeding rate did not increase rye biomass accumulation indicating that delays in autumn sowing cannot be overcome with plant density. Finally, nitrogen fertilizer applied at planting consistently increased rye biomass production 23–33% relative to non-fertilized controls averaged over all planting dates. Additional research is needed to evaluate how repeated high-biomass cover crop systems affect weed management systems, other pest complexes, and soil moisture status in the sandy soils of the southeast Coastal Plain.

Sugar crops grown for biofuel production provide a source of simple sugars that can readily be made into advanced biofuels. In the mild climate of the southeastern USA, sugar beet can be grown as a winter crop, providing growers with an alternative crop that is complementary to existing summer crops. Experiments evaluated autumn planting dates from September to December on the yield of five varieties of sugar beet harvested in the spring. A linear relationship existed between sugar beet canopy width and thermal time. Plant canopy diameter increased

Worldwide avocado consumption is growing due to potential health benefits. Most research has been focused on ‘Hass’, which does not perform well in Florida. Fatty acids and volatile organic compounds (VOCs) were evaluated in 14 avocado genotypes grown in East-Central Florida conditions and compared to ‘Hass’. Two saturated and five unsaturated fatty acids were detected. Total oil content (TOC) was 11–25%, with 58.2–71.5% unsaturated fatty acids (UFA). ‘FL Hass’ contained 20% TOC, near the average for genotypes tested, but with a low UFA of 61.9%. ‘PA-6206’ (a ‘Hass’ x ‘Bacon’ seedling) and ‘35707’ (a ‘Catalina’ seedling) had higher TOC and UFA than other genotypes, while the mostly West Indian types such as ‘Simmonds’, ‘Day’, ‘Pflume’ and ‘Miguel’ had low TOC. Detected VOCs were acetaldehyde, hexanal, (E)-2-hexenal, limonene, α-cubebene, α-copaene, and β-caryophyllene. Most genotypes contained most of the VOCs. ‘Monroe’ lacked C6 aldehydes, and ‘Pflume’, ‘Bernecker-43’, ‘Lula’ and ‘35707’ lacked some or all sesquiterpenes.

The colonization of maize (Zea mays L.) and peanut (Arachis hypogaea L.) by the fungal pathogen Aspergillus flavus results in the contamination of kernels with carcinogenic mycotoxins known as aflatoxins leading to economic losses and potential health threats to humans. The regulation of aflatoxin biosynthesis in various Aspergillus spp. has been extensively studied, and has been shown to be related to oxidative stress responses. Given that environmental stresses such as drought and heat stress result in the accumulation of reactive oxygen species (ROS) within host plant tissues, host-derived ROS may play an important role in cross-kingdom communication between host plants and A. flavus. Recent technological advances in plant breeding have provided the tools necessary to study and apply knowledge derived from metabolomic, proteomic, and transcriptomic studies in the context of productive breeding populations. Here, we review the current understanding of the potential roles of environmental stress, ROS, and aflatoxin in the interaction between A. flavus and its host plants, and the current status in molecular breeding and marker discovery for resistance to A. flavus colonization and aflatoxin contamination in maize and peanut. We will also propose future directions and a working model for continuing research efforts linking environmental stress tolerance and aflatoxin contamination resistance in maize and peanut.

Winter cover crops were evaluated for their effect on Amaranthus palmeri establishment and growth in cotton production. Cover crops examined included rye and four winter legumes: narrow-leaf lupine, crimson clover, Austrian winter pea, and cahaba vetch. Each legume was evaluated alone and in a mixture with rye. Cover crop biomass in monoculture was greatest for rye and lupine (>6750 kg ha−1), while clover, pea, and vetch were less and ranged from 2810 to 4610 kg ha−1. Cover crop biomass was more than doubled when rye was mixed with clover or vetch relative to the legume monoculture. In early-June, A. palmeri densities were 46 seedlings m−2 in the non-disturbed areas between cotton rows in the fallow, while populations were 80% relative to the non-cover crop fallow treatment, while control from clover, vetch and lupine ranged from 64 to 70%. The relationship between A. palmeri control in between cotton rows and cover crop biomass was described by a log-logistic regression model with 4530 kg ha−1 providing median weed control (Bio50); predicted A. palmeri control was 25, 50, and 75% from 2950, 4900, and 8600 kg ha−1 cover crop biomass, respectively. However, A. palmeri plants in the cotton rows prevented yield production in the absence of herbicides. Where A. palmeri was controlled with herbicides, the highest yields occurred following rye, with lower yields following lupin/rye mixture and treatments including pea. Management of herbicide resistant weed species requires diverse management tactics; this may include high-biomass cover crops to reduce weed establishment between crop rows. However, greater research effort is needed to devise weed management options for the crop row that do not rely exclusively on the diminishing array of herbicide tools.

Two important mycotoxins, aflatoxin and fumonisin, are among the most potent naturally occurring carcinogens, contaminating maize ( Zea mays ) and affecting crop yield and quality. Resistance of maize to pre-harvest mycotoxin contamination, specifically aflatoxin produced by Aspergillus flavus and fumonisin produced by Fusarium verticillioides , is a goal in breeding programs that screen for these important traits with the aim of developing resistant commercial hybrids. We conducted two years of field evaluations on 87 inbred lines originating primarily in China and Mexico and not previously screened for resistance. The objectives of our study were to identify resistant germplasm for breeding purposes and to examine possible relationships between resistances to the two mycotoxins. Aflatoxin and fumonisin were present in samples harvested from all lines in both years. Concentrations of total aflatoxin ranged from 52.00 ± 20.00 to 1524.00 ± 396.00 μg kg − 1 , while those of fumonisin ranged from 0.60 ± 0.06 to 124.00 ± 19.50 mg kg − 1 . The inbred lines TUN15, TUN61, TUN37, CY2, and TUN49 showed the lowest aflatoxin accumulation and CN1, GT601, TUN09, TUN61, and MP717 the lowest fumonisin accumulation. TUN61 showed the lowest accumulation of both mycotoxins. This study confirmed previous observations that high levels of aflatoxin can coexist with fumonisin, with 55 maize lines showing a positive correlation coefficient between the concentrations of aflatoxin and fumonisin and 32 lines showing a negative correlation coefficient. These selected lines, particularly TUN61, may provide sources of resistance to mycotoxin contamination in breeding programs. However, the mechanism of resistance in this germplasm remains to be identified. Future research should also address factors that influence the fungus–plant interaction, such as herbivory and environmental stress.