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Phyllachora maydis is a fungal pathogen causing tar spot of corn ( Zea mays L.), a new and emerging, yield-limiting disease in the United States. Since being first reported in Illinois and Indiana in 2015, P. maydis can now be found across much of the corn growing regions of the United States. Knowledge of the epidemiology of P. maydis is limited but could be useful in developing tar spot prediction tools. The research presented here aims to elucidate the environmental conditions necessary for the development of tar spot in the field and the creation of predictive models to anticipate future tar spot epidemics. Extended periods (30-day windowpanes) of moderate mean ambient temperature (18–23 °C) were most significant for explaining the development of tar spot. Shorter periods (14- to 21-day windowpanes) of moisture (relative humidity, dew point, number of hours with predicted leaf wetness) were negatively correlated with tar spot development. These weather variables were used to develop multiple logistic regression models, an ensembled model, and two machine learning models for the prediction of tar spot development. This work has improved the understanding of P. maydis epidemiology and provided the foundation for the development of a predictive tool for anticipating future tar spot epidemics.

High-throughput sequencing (HTS) has expanded our perspective on the distribution and diversity of plant viruses. Furthermore, improvements in HTS and decreasing sample costs have enabled the discovery of novel plant viruses in field-collected samples. This study examined the putative virome of cotton samples collected from fields across the southern United States. Leaf samples were collected, and total RNA was extracted. Library preparation was performed from pooled samples within locations before sequencing on an Illumina platform. Sequenced libraries were mapped to the cotton reference genome, and the resulting sequences were de novo assembled. A metatranscriptomics analysis revealed complete genome contigs of cotton leafroll dwarf virus in all tested samples. Additionally, 29 putative families of RNA and DNA plant viruses co-infecting cotton were found. Seven families of RNA viruses were more prevalent across all locations. These families included Botourmiaviridae , Hypoviridae , Mitoviridae , Narnaviridae , Partitiviridae , Solemoviridae , and Totiviridae . The information obtained in this investigation will help develop a broader perspective on cotton virus diversity and whether co-infections of viruses can influence (negatively or positively) plant physiology, product quality, and yield.

Redbanded stink bug, Piezodorus guildinii (Westwood), is a significant soybean pest across the mid-south region of the United States. The objectives of these studies were to characterize: (1) redbanded stink bug oviposition in relationship to soybean maturity group (MG), plant structure, crop phenology, and vertical distribution within the plant canopy; and (2) redbanded stink bug adult sex ratios in relationship to soybean phenology. A total of 5645 redbanded stink bug eggs in 421 egg masses (clusters) were field collected from naturally-occurring populations in MG IV and V soybean over a three year period (2009 to 2011). The mean number of eggs within a cluster was 16.6 ± 0.3. Plant structures by MG interactions were highly significant with more egg masses oviposited on leaves in MG IV (79.4%) and more on pods in MG V (72.7%). The ratio of females to males was similar in all soybean growth stages except R5, where the sex ratio increased to 1.4:1, coinciding with peak oviposition. Only 29.9% of egg clusters in MG IV and 18.3% of egg clusters in MG V were oviposited in the upper 35 cm of the soybean canopy. Based on these results, sampling strategies and insecticide application placement for stink bugs may require modification.

ABSTRACT Cercospora cf. sigesbeckiae is an ascomycete fungal pathogen that infects various plants, including important agricultural commodities, such as soybean. Here, we report the first draft genome sequence and assembly of this pathogen.