Corn-growing Region Research Articles

Non-Aflatoxigenic Aspergillus flavus: A Promising Biological Control Agent against Aflatoxin Contamination of Corn.

Aflatoxins (AFs) are a family of mycotoxins produced by molds in agricultural products. To deal with this problem, one of the control methods is the biological solution using a non-pathogenic strain Aspergillus flavus NRRL 21882 (Afla-Guard). This study was conducted to evaluate the potential of A. flavus NRRL 21882 to control the AF contamination of corn in the field and during storage in 2018 and 2019. The experimental design consists of treatment at different vegetative stages of infested corn in the field trial. After the field has been harvested, half the corn kernels from both treated and control plots were treated with biopesticide; the other half of the kernels from each group were not treated and used as the control of the storage. Consequently, storage applications consisted of kernels: (1) not treated at all; (2) treated prior to storage; (3) field-treated; and (4) treated both in the field and prior to storage. After field trials, the AF content was very low in the treated plots, ranging from 0.50 to 1.04 μg/kg and from 0.50 to 0.73 μg/kg in 2018 and 2019, respectively, while the AF content in the control was 98.3 and 73.9 μg/kg in 2018 and 2019, respectively. After storage, corn kernels from field plots that were treated with the biopesticide (treated/control) showed low levels of AFs, even after they have been stored under conditions conducive to AF contamination. The biopesticide effect ranged from 98 to 99% and from 69 to 99% in the field and during storage, respectively. This paper has provided the first indications on AF biocontrol based on a competitive exclusion in the corn-growing region of Turkey. The data showed that spraying during the storage period did not provide any further prevention of AF contamination, and only treatment in the field had a significant effect on AFs that occurred in storage.

Recovery Plan for Tar Spot of Corn, Caused by Phyllachora maydis

Tar spot is a foliar disease of corn threatening production across the Americas. The disease was first documented in Mexico in 1904 and is now present in 15 additional countries throughout Central America, South America, and the Caribbean. Researchers and growers in Central America, South America, and the Caribbean consider tar spot to be a disease complex caused by multiple fungal pathogens. When environmental conditions are conducive for infection, these regions have experienced yield losses that can reach up to 100%. In 2015, tar spot was detected in the United States for the first time in Illinois and Indiana. Since that time tar spot has spread across the U.S. corn-growing region, and the disease has been found in Florida, Illinois, Indiana, Iowa, Michigan, Minnesota, Missouri, Ohio, Pennsylvania, and Wisconsin. In 2020, tar spot was also found in southwest Ontario, Canada. Losses in the United States due to tar spot totaled an estimated 241 million bushels from 2018 to 2020. With the potential to continue to spread across the U.S. corn-growing states, much greater losses could result when environmental conditions are conducive.

Bioeconomic model for optimal control of the invasive weed Zea mays subspp. (teosinte) in Spain

Teosinte is an invasive weed which emerged recently in Northeastern Spain, an important corn-growing region in Western Europe. It is causing substantial agronomic and economic damages and is threatening the availability of corn in the region. Farmers and regulatory agencies can choose from a number of strategies to control for teosinte infestations including adoption of specific cultural practices such as manual control constructing false seedbeds, as well as adopting corn rotations with other annual and perennial crops. In spite of the potential negative impacts of this weed, little is known about what the optimal control strategies are, both from the private (e.g. the farm) and social (e.g. regulatory agencies) perspectives. In response, we develop a dynamic optimization model to identify the sequence of control strategies that minimize private and social costs under low- and high-infestation level scenarios, for a fifteen-year planning horizon. We calibrate the model using biological data from experimental trials and economic parameters collected from farmers in the region. Our results suggest the economic losses of teosinte infestation can reach up to 9229 and 9398 €/ha for low- and high-infestation scenarios if nothing is done to control it. In addition, results show that optimal private and social strategies are different. For example, under high-infestation levels, private losses are minimized at 26.5% by not controlling in years 1–2, use false seedbeds in year 3, planting alfalfa in years 4–8, and planting corn thereafter in the total area. In contrast, social costs are minimized at 27.9% by adopting rotations starting year, return to corn mono-cropping in half the area after year four. Results show false seedbed and manual controls, currently recommended by the regulatory agency in low-infestation cases, are not socially optimal.

Prácticas socioculturales, turismo e identidad entre los hijos de migrantes yucatecos en Cancún

El centro turístico de Cancún en el sur de México atrae a muchas familias migrantes mayas originarias de la región maicera de la península yucateca, donde las tradiciones ceremoniales y rituales se conservan. En el nuevo escenario, la transmisión de prácticas y valores indígenas a las nuevas generaciones está en tensión constante con el contexto turístico de la ciudad. Desde la perspectiva de los hijos de las familias migrantes, nos enfocamos en el rol de la cultura maya para dar significado a las prácticas y construcciones sociales que ofrecen un sentido de congruencia a las vidas.

Spatial Distribution Patterns of Weed Communities in Corn Fields of Central Spain

The overall objective of this study was to identify common patterns in the spatial distribution of the major weed species present in the corn-growing region of central Spain, exploring the scale dependence of these patterns and the possible associations or dissociations between individual species. Weed density was assessed in 16 commercial fields using digital images acquired in a 9-m by 9-m sampling grid. A set of six species was found in all the fields: black nightshade, common cocklebur, fierce thornapple, johnsongrass, purple nutsedge, and velvetleaf. Spatial analysis by distance indices and inverse distance weighting interpolation methods were performed to create weed distribution maps. The results showed aggregated spatial distribution patterns for all individual species regardless their life cycle, annual or perennial. Some associations and dissociations among species were found in the analysis of interactions. Nevertheless, the spatial patterns of co-occurrence of weed species were field-specific and therefore cannot be considered general patterns of weed co-occurrence. In order to explore the scale dependence of these results, an additional study was conducted in an experimental field located in the same area using a 1.0-m by 0.75-m sampling grid. Although this resolution allowed for a better definition of the positions of the weed patches and weed-free gaps, the results obtained revealed similar patterns to those observed with a coarser sampling resolution.

Response of corn markets to climate volatility under alternative energy futures

Recent price spikes(1,2) have raised concern that climate change could increase food insecurity by reducing grain yields in the coming decades(3,4). However, commodity price volatility is also influenced by other factors(5,6), which may either exacerbate or buffer the effects of climate change. Here we show that US corn price volatility exhibits higher sensitivity to near-term climate change than to energy policy influences or agriculture-energy market integration, and that the presence of a biofuels mandate enhances the sensitivity to climate change by more than 50%. The climate change impact is driven primarily by intensification of severe hot conditions in the primary corn-growing region of the US, which causes US corn price volatility to increase sharply in response to global warming projected over the next three decades. Closer integration of agriculture and energy markets moderates the effects of climate change, unless the biofuels mandate becomes binding, in which case corn price volatility is instead exacerbated. However, in spite of the substantial impact on US corn price volatility, we find relatively small impact on food prices. Our findings highlight the critical importance of interactions between energy policies, energy-agriculture linkages, and climate change.

Variabilidad de Puccinia sorghi en la zona maicera núcleo Argentina

Common rust caused by Puccinia sorghi is one of the endemic diseases of corn in Argentina. It appears every year with different levels of severity depending on the genotype of the host, the biotypes of the pathogen, and the environmental conditions. Estimates of grain weight losses ranged from about 3 to 8% for 10% of the total leaf area affected. P. sorghi is a heteroic fungus that completes its cycle on an alternative host, Oxalis spp. Its complete cycle is feasible in mild winter regions around the world. The objective of this study was to describe the factors involved in the virulence of the pathogen in the interaction Zea mays-Puccinia sorghi. Using Rp isolines, 10 pathotypes of P. sorghi were identified from 16 isolates obtained from different locations in the provinces of Santa Fe (Oliveros, Venado Tuerto and Zavalla) and Buenos Aires (Pergamino). Polymorphisms in the DNA of the different isolates of P. sorghi from this core corn-growing region of Argentina were detected by RAPD methodology. These experiments showed the genetic heterogeneity of the pathogen in this area. A high consensus rate was determined (81.4 %) between the results obtained from the virulence biotypes and the results obtained by RAPD.

Plasma sex steroid concentrations and gonadal aromatase activities in African clawed frogs (Xenopus laevis) from South Africa.

Adult African clawed frogs (Xenopus laevis) were collected from a corn-growing region (CGR) and a non-corn-growing region (NCGR) with different exposure profiles for atrazine and related triazines. Physical, chemical, and biological parameters from the catchment areas were also measured. Frogs were surveyed for possible effects of exposure to triazine herbicides on plasma testosterone (T) and estradiol (E2) titers, gonadal aromatase activity, and gonad growth (GSI). Concentrations of both T and E2 varied among locations and were correlated to some accessory factors, such as pH, several ions, and metals. Greatest median plasma T concentrations (males: 19 ng/ml; females: 16 ng/ml) occurred in frogs inhabiting NCGR as compared to those from the CGR (males: 4 ng/ml; females: 1 ng/ml). Median E2 concentrations were also greater in frogs collected from the NCGR (males: 3 ng/ml; females: 28 ng/ml) than those in frogs from the CGR (males: 2 ng/ml; females: 5 ng/ml). Because some exposure to agricultural chemicals at both regions occurred, as did simultaneous exposures to multiple chemicals, a regression analysis was employed. Negative correlations were observed between plasma T concentrations and concentrations of atrazine, deisopropylatrazine, deethylatrazine, and tertbuthylazine in females and between T and diaminochlorotriazine in males. Estradiol in females exhibited a significant negative correlation with atrazine and deethylatrazine. No correlations were observed between gonadal aromatase activity or GSI and any of the agricultural chemicals measured. Median aromatase activities in ovaries varied among sampling sites ranging from 7 to >3000 times greater than those in males when measurable. Testicular aromatase activity was below the detection limit of the assay in male frogs at most of the sites. Although exposure to agricultural inputs did not affect aromatase activities, effects of atrazine or coapplied pesticides on sex steroid homeostasis cannot be excluded at this point.

Degradation of the Cry1Ab protein within transgenic Bacillus thuringiensis corn tissue in the field.

Large quantities of Bacillus thuringiensis (Bt) corn plant residue are left in the field after harvest, which may have implications for the soil ecosystem. Potential impacts on soil organisms will also depend on the persistence of the Bt toxin in plant residues. Therefore, it is important to know how long the toxin persists in plant residues. In two field studies in the temperate corn-growing region of Switzerland we investigated degradation of the Cry1Ab toxin in transgenic Bt corn leaves during autumn, winter and spring using an enzyme-linked immunosorbent assay (ELISA). In the first field trial, representing a tillage system, no degradation of the Cry1Ab toxin was observed during the first month. During the second month, Cry1Ab toxin concentrations decreased to approximately 20% of their initial values. During winter, there was no further degradation. When temperatures again increased in spring, the toxin continued to degrade slowly, but could still be detected in June. In the second field trial, representing a no-tillage system, Cry1Ab toxin concentrations decreased without initial delay as for soil-incorporated Bt plants, to 38% of the initial concentration during the first 40 days. They then continued to decrease until the end of the trial after 200 days in June, when 0.3% of the initial amount of Cry1Ab toxin was detected. Our results suggest that extended pre- and post-commercial monitoring are necessary to assess the long-term impact of Bt toxin in transgenic plant residues on soil organisms.

Evaluation of the natural refuge function for Helicoverpa arnigera (Lepidoptera: Noctuidae) within Bacillus thuringiensis transgenic cotton growing areas in north China.

The density of Helicoverpa armigera (Hübner) populations on Bacillus thuringiensis Berliner (Bt) transgenic cotton, corn, peanut, and soybean; differences in its development on Bt cotton and common (nontransgenic) cotton; and the potential for mating among populations from Bt cotton fields and other crop fields were investigated in the suburbs of Xinxiang City (Henan Province) and Langfang City (Hebei Province) in the southern and northern parts of north China, respectively. Although development of H. armigera on Bt cotton was much slower than on common cotton, there was a still high probability of mating between populations from Bt cotton and other sources due to the scattered emergence pattern of H. armigera adults, and overlap of the second and third generations. In a cotton and corn growing region, early and late planted corn provided suitable refugia for the third and fourth generations of H. armigera, but not for the second generation. In a cotton and soybean/ peanut mix system, noncotton crops provided a natural refugia from the second- to fourth-generation H. armigera, but function of the refuge would closely depend on the proportion of Bt cotton. Consequently, it may be necessary to compensate the original mixed cropping patterns in different areas for delaying resistance development of H. armigera to Bt cotton.

Developing a Soil Nitrogen Test for Improved Recommendations for Corn

Accurate, reliable N recommendations are important if farmers are to attain optimum economic benefits while minimizing the potential for negative impacts of N on the environment. This study was conducted to determine the feasibility and reliability of including a soil N test to adjust N recommendations for corn (Zea mays L.) and to evaluate which soil test parameters should comprise the test. Nitrogen rate response experiments were conducted at 54 sites throughout the corn-growing region of Minnesota from 1989 through 1992. Analysis of the data indicated that nitrate-N concentration in the surface 2 ft taken in the spring before planting provided a sound, useable relationship for a soil N test that was evaluated in terms of R 2 , frequency of errors, and practical feasibility [...]

Fall Armyworm Distribution and Population Dynamics in the Texas-Mexico Gulf Coast Area

Fall armyworm, Spodoptera frugiperda J. E. Smith, population trends were studied along the Mexican Gulf Coast, the Isthmus of Tehuantepec, and the Yucatan Peninsula using Hartstack pheromone traps. Trap capture generally peaked in November and December, while the lowest capture period occurred during mid year. A temporal progression in trap capture was noted during the early part of the year from Veracruz, Mexico, to the Lower Rio Grande Valley of Texas. A similar temporal progression in occurrence of larval populations from southern areas of the State of Tamaulipas to the Rio Grande Valley was also observed. Studies in an irrigated corn-growing region encompassing the Lower Rio Grande Valley in both southern Texas and northern Tamaulipas, Mexico (with ca. 200,000 ha of corn) showed the major fall armyworm emergence from the area occurred in June, resulting in an adult population of from 6.11X10^8 to 1.72X10^9 moths.