Tar spot, a fungal foliar disease, affects most maize types commonly grown in Florida, such as sweet corn, field corn, and criollo corn. This disease is characterized by brown-to-black, raised structures called stromata, which are embedded in leaf tissue. As a polycyclic disease, tar spot lesions can increase in number as the disease progresses throughout the growing season, leading to reduction of photosynthetic area on the leaves. Tar spot has recently emerged as a significant threat in Florida and in the United States, with reports of up to 100% incidence in maize fields in south Florida. Tar spot occurrence and development in Florida is influenced by several factors, such as environmental conditions, maize types, crop maintenance, and corn growth stages. The purpose of this publication is to promote awareness among Florida growers regarding this newly identified disease and its management practices.

Fusarium wilt, caused by Fusarium oxysporum f. sp. apii (Foa), is a vascular disease affecting celery. This soilborne pathogen is classified into four distinct pathogenic races: 1, 2, 3, and 4. Notably, race 4 emerges as the most virulent, representing the latest evolutionary development of this pathogen, which was first reported in 2013 in California. In 2022, celery plants in South Florida exhibited typical Fusarium wilt symptoms, with the disease reaching a 100% incidence and causing yield losses ranging from 20 to 100%. Given the significance of celery as a vegetable crop and the severity of this outbreak, the primary objective of this study was to identify and characterize the causal agent of Fusarium wilt in South Florida. The second goal aimed to test the pathogenicity and virulence of the Fusarium isolates from Florida on celery and parsley plants. Using race-specific primers and dual-loci phylogenetic analyses, the isolates surveyed in this study were identified as Foa race 4. Pathogenicity assays in the greenhouse showed that the Foa race 4 isolate from celery induced disease not only on the two celery cultivars (Duda 30 and Duda 71) but also on two commonly cultivated parsley varieties (curly and Italian). Our study also revealed that the Foa race 4 significantly (P < 0.05) affected plant health attributes in all cultivars, including plant height, total plant weight, and root weight. Interestingly, the pathogen exhibited higher (P < 0.0001) virulence on parsley than celery based on vascular discoloration. These findings strongly indicate the urgency of comprehending and managing Fusarium wilt on celery and related crops. Furthermore, the ability of Foa race 4 to affect different plant species highlights a potential threat to agricultural production, emphasizing the need for proactive measures to mitigate the impact of this virulent pathogen.

Tar spot, caused by Phyllachora maydis, is an established maize disease in the Midwest of the United States but remains an emerging concern in Florida. While this pathogen can overwinter on plant residue, its survival in Florida’s subtropical environment is not well understood. This study evaluated how environmental factors affect the germination of P. maydis ascospores and stroma integrity. Symptomatic maize leaves were incubated under four conditions: Histosol soil (muck), Krome soil (rocky), 4 °C, and 23 °C. Extensive leaf decomposition occurred in both soil types, with most plant material degraded after eight weeks, while the stroma maintained its structure. Despite this, ascospore germination declined across all conditions. After eight weeks, ascospores incubated at 4 °C retained 25% viability, while those at 23 °C had the lowest germination (0.7%). Ascospores from leaves buried in soil exhibited low viability (1–6%), with no significant differences between soil types ($\mathit{p}=0.9944$). Weather analysis revealed that increased temperature reduced germination rates, while higher humidity enhanced them. These findings suggest that P. maydis displays limited survivability under Florida-like conditions, with germination rates declining over time. Therefore, cultural practices such as tillage, already employed by corn producers in Florida, may be effective in reducing sources of P. maydis inoculum.

Northern (Exserohilum turcicum) and southern (Bipolaris maydis) corn leaf blights threaten fresh-market sweet corn in Florida, yet region-specific data on efficacy and economics of fungicide programs are scarce. Four replicated field trials were conducted in Belle Glade, FL (spring 2023, spring 2024, fall 2024, spring 2025) comparing eight treatments with foliar programs that contrasted early pre-tassel (V3/V7 growth stages; mancozeb mixed with single-site fungicides) with systemic-only programs beginning at tasseling/silking (VT/R1). Yield was collected in 2023 and 2025. Under high disease pressure (disease severity > 80%), early fungicide programs reduced relative area under disease progress curve (rAUDPC) more than VT and R1 programs. Results were consistent across independent epidemics: in southern corn leaf blight epidemics, programs initiated at V3 and V7 limited mean rAUDPC to 19% versus 47% in non-treated; in northern corn leaf blight epidemic, V3/V7 programs averaged 6% versus 36% in non-treated. Yield responses paralleled disease control. The best programs protected yield by 2.44 t ha⁻¹ in 2023 (two pass V7 and R1) and by 1.93 t ha⁻¹ in 2025 (four pass grower standard). Treated plots showed greater kernel filling, which mediated most of yield response. Economic results were favorable, with typical program costs covered by ≤0.4 t ha⁻¹ of protected yield, and top programs demonstrated ROI of 92 to 762%. In subtropical sweet corn, starting protection by V7 and maintaining coverage through VT/R1 maximizes blight suppression, safeguards kernel fill, and improves profitability. Streamlined two-pass programs can match three- or four-pass schedules while reducing inputs and stewardship risks.

Southern corn leaf blight (SCLB) is caused by the fungal pathogen Bipolaris maydis (syn . Cochliobolus heterostrophus Drechsler) and is a common disease of fall crops of sweet corn. Phenotyping for SCLB resistance is performed through visual scoring, which is subjective and may limit genetic gain for this quantitative trait. As an alternative, we integrated computer vision (CV)‐based phenotyping, genome‐wide association studies (GWASs), and predictive breeding approaches to dissect the genetic basis of SCLB resistance. We utilized a sweet corn diversity panel with 693 genotypes, for which whole‐genome resequencing produced a high‐density single‐nucleotide polymorphism (SNP) dataset. Broad‐sense heritability for visual scoring ranged from 0.44 to 0.73, while CV‐based phenotyping produced estimates ranging from 0.56 to 0.73 in multi‐environment resistance trials conducted across 5 years and three locations. We performed GWAS using 16,755,210 SNPs and identified 41 associated SNPs. Genomic selection (GS) models on visual scoring phenotypes achieved moderate prediction accuracies under cross‐validation of untested genotypes across characterized environments (0.22–0.47) and high prediction accuracies when predicting tested genotypes in uncharacterized environments (0.49–0.68). Using CV‐based phenotypes for GS, we observed prediction accuracies of 0.45–0.47 under the untested genotypes in the characterized environments cross‐validation scheme and 0.59–0.62 under the tested genotypes in the uncharacterized environments scheme. GS demonstrated reliability for ranking the individuals across a gradient of environments. These findings identify candidate loci and predictive breeding strategies to accelerate the development of resistant sweet corn cultivars.

In 2024, bacterial strains KXB24, KXB25 and KXB45 were isolated from sweet corn ( Zea mays L.) plants exhibiting foliar chlorosis and streaking, typical symptoms of bacterial infection, in the Everglades Agricultural Area in Florida, USA. A polyphasic taxonomic study was conducted on these strains. Phylogenetic analysis of 16S rRNA gene sequences, whole-genome comparisons and biochemical characterization confirmed that the isolates belong to the Pantoea genus. The Biolog Gen III MicroPlate system identified substrate utilization profiles that were unique to these strains, distinguishing them from closely related Pantoea species. The strain KXB24 showed positive utilization of d -serine, γ-amino-butyric acid, citric acid and other compounds. On nutrient agar, KXB24, colonies are circular, smooth, convex and yellow and do not produce fluorescent pigment on King’s medium B. The DNA G+C content of KXB24 was determined to be 57.0 mol%. Based on phenotypic distinctions, phylogenomics evidence, average nucleotide identity values below 94.26% and digital DNA–DNA hybridization values below 57.9% when compared to type strains of recognized Pantoea species, we propose Pantoea graminicola sp. nov., with KXB24 ^T (=NCPPB 4802 ^T =LMG 33887 ^T ) as the type strain. This discovery enriches the current understanding of Pantoea species and calls for further research into the potential role of P. graminicola in sweet corn disease aetiology and its broader agricultural impacts.