Tar Spot Research Articles

Catch Diversity of Small Scale Lobster Fishery in Southern Coast of Sri Lanka

The lobster fishery is one of the well-established, highly valued commercial fisheries on the Southern coast of Sri Lanka. There are five spiny lobster species, Panulirus homarus, P. longipes, P. ornatus, P. versicolor and P. penicillatus are recorded in the Southern coast of Sri Lanka. However, the heavy fishing pressure and other anthropogenic interventions have caused a significant depletion of some of these species. Therefore, in order to identify the vulnerability of the lobster species, we studied the species, gender and sexual maturity compositions of the lobster catch with the data collected from nine different lobster landing sites along the southern coast of Sri Lanka during 2019 and 2020. Minitab and MS Excel software were used for the descriptive statistical analysis. According to the results, the dominant species in the sampled landings was P. homarus, with the average percentage of 73.16% in 2019 and 84.65% in 2020. However, least abundant P. ornatus species’ average percentages were 0.74% in 2019 and 0.27% in 2020. Moreover the results reveals the male:female 1:1 sex ratio of the lobster catches as 1:0.9 in 2019 and 1:0.89 in 2020. Most importantly, among all females, there were 43.01% in 2019 and 37.31% in 2020 percentages borne eggs while 48.53% in 2019 and 47.03% in 2020 percentage of females were identified with tar spots. Therefore, considerable caught of tar spotted and egg bearing female lobsters might be a major cause of lobster stock depletion in Southern coast of Sri Lanka. Thus present study would be a preliminary guide for the future studies on sustainable lobster fishery management approach.
 Keywords: Lobsters fishery, Southern coast, Panulirus homarus, Tar spots, Sri Lanka

Fungicide Fundamentals and Insurance Applications

Last year, in the Corn Belt, rising corn prices fueled producer willingness to make “insurance” fungicide applications to hedge against possible yield losses from foliar disease. Newer disease risks—especially tar spot—also spurred some producers toward a more aggressive spray program. Market realities mean that “insurance” fungicide applications are likely to continue in 2022. But crop costs and returns will change, and CCAs should help their producers keep in mind corn fungicide fundamentals—even when sky‐high prices may impact decision‐making more than disease management fundamentals. Earn 0.5 CEUs in Integrated Pest Management by reading the article and taking the quiz at https://web.sciencesocieties.org/Learning‐Center/Courses.

Phyllachora species infecting maize and other grass species in the Americas represents a complex of closely related species.

The genus Phyllachora contains numerous obligate fungal parasites that produce raised, melanized structures called stromata on their plant hosts referred to as tar spot. Members of this genus are known to infect many grass species but generally do not cause significant damage or defoliation, with the exception of P. maydis which has emerged as an important pathogen of maize throughout the Americas, but the origin of this pathogen remains unknown. To date, species designations for Phyllachora have been based on host associations and morphology, and most species are assumed to be host specific. We assessed the sequence diversity of 186 single stroma isolates collected from 16 hosts representing 15 countries. Samples included both herbarium and contemporary strains that covered a temporal range from 1905 to 2019. These 186 isolates were grouped into five distinct species with strong bootstrap support. We found three closely related, but genetically distinct groups of Phyllachora are capable of infecting maize in the United States, we refer to these as the P. maydis species complex. Based on herbarium specimens, we hypothesize that these three groups in the P. maydis species complex originated from Central America, Mexico, and the Caribbean. Although two of these groups were only found on maize, the third and largest group contained contemporary strains found on maize and other grass hosts, as well as herbarium specimens from maize and other grasses that include 10 species of Phyllachora. The herbarium specimens were previously identified based on morphology and host association. This work represents the first attempt at molecular characterization of Phyllachora species infecting grass hosts and indicates some Phyllachora species can infect a broad range of host species and there may be significant synonymy in the Phyllachora genus.

Plan for Tar Spot Disease in the Us and Cascading Supply Effects in '22

Plan for Tar Spot Disease in the Us and Cascading Supply Effects in '22

Fungal plant pathogens observed on perennial cereal crops in New York during 2017–2018

AbstractPerennial grain crops are emerging as a promising addition to sustainable agricultural systems because of their low-input requirements and delivery of ecosystem services. However, adoption of these crops is expected to bring novel management challenges, including those related to plant diseases. In New York, fungal pathogens of annual grains have a significant impact on crop yield and value and are generally controlled through a combination of host resistances, cultural practices and chemical fungicides. Without the availability of crop rotation and soil tillage practices, disease control in perennial grain systems may be problematic, and little is known about perennial grain crop susceptibility to local plant pathogen populations. During 2017 and 2018, ongoing field trials of two perennial grain crops recently introduced in New York, intermediate wheatgrass (IWG; Thinopyrum intermedium) and perennial cereal rye (PCR; Secale cereale), were assessed for the presence of putative fungal pathogens on actively growing plants, overwintered crop residue and harvested grain. A total of nine potential host–pathogen combinations were recorded based on symptomology, pathogen morphology and DNA sequences. Common annual crop pathogens were recovered most frequently, but, at one site, Phyllachora graminis, causal fungus of tar spot and a pathogen not previously reported on crops in New York, was found on IWG. Residue colonization by an important toxigenic pathogen (Fusarium graminearum) was high in both crops, though mycotoxin levels in associated grain were low, indicating either the hosts or environment were unsuitable for disease development. Seed-borne fungal communities differed across crops and locations, and black point, a condition caused by Alternaria and Bipolaris fungi and indicative of compromised grain quality, was prevalent in PCR under some conditions. Growing PCR with intercropped red clover (Trifolium pratense L.) resulted in less Stagonospora colonization of stem residue, and PCR grown with an oat (Avena sativa L.) nurse crop had a reduced incidence of black point. These alternative cultural practices may prove useful for managing disease in perennial grains. Our results suggest that the incorporation of perennial crops into the agricultural landscape will lead to familiar plant disease problems requiring new solutions as well as new problems that may require significant research investments.

Revisiting Rhytisma lonicericola: Morphological Characterization and Molecular Phylogenetic Analysis

Rhytisma lonicericola was identified as a tar spot fungus on Lonicera sp. in 1902, and has since been recorded on several species of Lonicera in China, Japan, and Korea. Most of the previous records of R. lonicericola have been based on a list of disease occurrences in the absence of any formal morphological identification or molecular analyses. Using six newly obtained specimens collected in the past 2 years, we confirmed the tar spot fungus found on L. japonica in Korea as R. lonicericola based on morphological examinations and molecular phylogenetic analyses. This fungus was distinguished from R. xylostei, another tar spot fungus on Lonicera, by ascospore size and geographical distributions. We present detailed mycological information and, for the first time, DNA sequence data useful for the identification of R. lonicericola.

Identification and fine mapping of a major QTL (qRtsc8-1) conferring resistance to maize tar spot complex and validation of production markers in breeding lines

Key messageA major QTL of qRtsc8-1 conferring TSC resistance was identified and fine mapped to a 721 kb region on chromosome 8 at 81 Mb, and production markers were validated in breeding lines.Tar spot complex (TSC) is a major foliar disease of maize in many Central and Latin American countries and leads to severe yield loss. To dissect the genetic architecture of TSC resistance, a genome-wide association study (GWAS) panel and a bi-parental doubled haploid population were used for GWAS and selective genotyping analysis, respectively. A total of 115 SNPs in bin 8.03 were detected by GWAS and three QTL in bins 6.05, 6.07, and 8.03 were detected by selective genotyping. The major QTL qRtsc8-1 located in bin 8.03 was detected by both analyses, and it explained 14.97% of the phenotypic variance. To fine map qRtsc8-1, the recombinant-derived progeny test was implemented. Recombinations in each generation were backcrossed, and the backcross progenies were genotyped with Kompetitive Allele Specific PCR (KASP) markers and phenotyped for TSC resistance individually. The significant tests for comparing the TSC resistance between the two classes of progenies with and without resistant alleles were used for fine mapping. In BC5 generation, qRtsc8-1 was fine mapped in an interval of ~ 721 kb flanked by markers of KASP81160138 and KASP81881276. In this interval, the candidate genes GRMZM2G063511 and GRMZM2G073884 were identified, which encode an integral membrane protein-like and a leucine-rich repeat receptor-like protein kinase, respectively. Both genes are involved in maize disease resistance responses. Two production markers KASP81160138 and KASP81160155 were verified in 471 breeding lines. This study provides valuable information for cloning the resistance gene, and it will also facilitate the routine implementation of marker-assisted selection in the breeding pipeline for improving TSC resistance.

Tar Spot: a New Fungus Amongus

AbstractTar spot fungus is a new reason to stay on your corn‐scouting toes, especially if you’re in the central Corn Belt. It was first found in northern Illinois and Indiana in 2015 before spreading to 12 other states and one Canadian province. Corn yield losses range from 20 to 60 bu/ac, and tar spot can also trigger complications such as lodging. The article will tell you what to look for as well as provide prevention and management tips. Information herein comes from members of The Crop Protection Network, a collaboration of 35 U.S. and Canadian plant pathologists. Special thanks to Michigan State University, Ontario Ministry of Agriculture, Purdue University, and the Universities of Kentucky, Iowa, Minnesota, and Wisconsin–Madison. Earn 1 CEU in Integrated Pest Management by reading the article and taking the quiz at https://bit.ly/3H4KX1x. View all CEUs online at https://web.sciencesocieties.org/Learning‐Center/Courses.

Identification of resistance for Phyllachora maydis of maize in exotic‐derived germplasm

AbstractTar spot of maize (Zea mays L.), caused by the obligate biotroph Phyllachora maydis Maubl., is an emerging disease in the United States and Canada, and the identification of sources of resistance for tar spot will enable the development of resistant hybrids. In 2019 and 2020, 25 accessions from the germplasm enhancement of maize (GEM) project containing exotic introgressions in elite backgrounds were evaluated in nine environments for tar spot severity. Environmental conditions had a major influence on disease development, as tar spot severity varied across locations with only four of the nine locations showing moderate to high levels of disease. In five environments, disease levels were low and disease severity data was not collected or used. Accessions were visually evaluated for tar spot during reproductive growth stages in three environments and during vegetative growth stages in one environment. There was a strong correlation between resistance to P. maydis across locations where accessions were evaluated in reproductive growth stages. Two accessions, GEMS‐0066 and GEMS‐0226, were the most resistant and could prove useful for tar spot resistance breeding. These accessions are publicly available and able to be directly used in breeding programs.

Diagnosis and recommendations for management of trees and shrubs in green squares in Warsaw based on research on fungal diseases

Key messageComprehensive management of urban greenery is a key approach to control fungal diseases of trees and shrubs to avoid the deterioration in their health status.Preliminary investigations on the health status related to fungal diseases of trees and shrubs growing in four green squares in Warsaw were conducted in 2017–2019. The examined plants were affected by diseases that are commonly identified in urban greenery, e.g., powdery mildew (causal agents: Sawadaea tulasnei, S. bicornis, Podosphaera leucotricha, Podosphaera sp., Erysiphe alphitoides, E. magnifica, E. berberidis, E. flexuosa and E. adunca), rusts (Gymnosporangium sabinae, Melampsora laricis-populina), apple scab (Venturia inaequalis), tar spot of maple (Rhytisma acerinum), and oyster mushroom (Pleurotus ostreatus). The causal agents of the diseases were identified based on their morphological (macro- and microscopic) features. Preventing and managing fungal plant diseases and reduction of their effects are the key tasks in conscious management of urban greenery. To address this issue, the study presents basic guidelines based on the application of various recommended actions and good practices, which constitute a comprehensive and sustainable strategy for integrated protection of trees and shrubs against these diseases. The implementation of the strategy for complex management of urban greenery is a crucial measure aimed at maintenance of a high health status of urban plants.

Fungicide Efficacy on Tar Spot and Yield of Corn in the Midwestern United States

Tar spot of corn caused by Phyllachora maydis has recently led to significant yield losses in the eastern corn belt of the Midwestern United States. Foliar fungicides containing quinone outside inhibitors (QoI), demethylation inhibitors (DMI), and succinate dehydrogenase inhibitors (SDHI) are commonly used to manage foliar diseases in corn. To mitigate the losses from tar spot, 13 foliar fungicides containing single or multiple modes of action (MOA/Fungicide Resistance Action Committee groups) were applied at their recommended rates in a single application at the standard VT/R1 (tassel/silk) growth stage timing to evaluate their efficacy against tar spot in a total of eight field trials in Illinois, Indiana, Michigan, and Wisconsin during 2019 and 2020. The single MOA fungicides included either a QoI or DMI. The dual MOA fungicides included a DMI with either a QoI or SDHI, and fungicides containing three MOAs included a QoI, DMI, and SDHI. Tar spot severity estimated as the percentage of leaf area covered by P. maydis stroma on the ear leaf of the nontreated control at dent growth stage ranged from 1.6 to 23.3% in the trials. Averaged across eight field trials all foliar fungicide treatments significantly reduced tar spot severity, but only Delaro 325SE (prothioconazole + trifloxystrobin), Revytek 3.33LC (mefentrifluconazole + pyraclostrobin + fluxapyroxad), and Veltyma 3.34S (mefentrifluconazole + pyraclostrobin) significantly increased yield over the nontreated control. When comparing groups of fungicide treatments by the number of MOAs, foliar fungicide products that had two or three MOAs decreased tar spot severity over not treating and products with one MOA. In addition, the fungicide group that contained all three MOAs significantly increased yield over not treating with a fungicide or using a single MOA group.

Fungicide Efficacy During a Severe Epidemic of Tar Spot on Corn in the United States and Canada in 2021

A 2021 epidemic of tar spot of corn caused by Phyllachora maydis led to significant yield losses in the midwestern United States and Ontario, Canada. Uniform fungicides trials consisting of nine foliar fungicides applied at the tassel (VT) or silk (R1) growth stage were evaluated for tar spot management in five field trials in the midwestern United States and Ontario, Canada, in 2021. All nine foliar fungicide treatments significantly reduced tar spot severity, but only Delaro Complete (prothioconazole + fluopyram + trifloxystrobin), Revytek (mefentrifluconazole + pyraclostrobin + fluxapyroxad), and Veltyma (mefentrifluconazole + pyraclostrobin) protected yield compared with the nontreated control.

Contour-Based Detection and Quantification of Tar Spot Stromata Using Red-Green-Blue (RGB) Imagery.

Quantifying symptoms of tar spot of corn has been conducted through visual-based estimations of the proportion of leaf area covered by the pathogenic structures generated by Phyllachora maydis (stromata). However, this traditional approach is costly in terms of time and labor, as well as prone to human subjectivity. An objective and accurate method, which is also time and labor-efficient, is of an urgent need for tar spot surveillance and high-throughput disease phenotyping. Here, we present the use of contour-based detection of fungal stromata to quantify disease intensity using Red-Green-Blue (RGB) images of tar spot-infected corn leaves. Image blocks (n = 1,130) generated by uniform partitioning the RGB images of leaves, were analyzed for their number of stromata by two independent, experienced human raters using ImageJ (visual estimates) and the experimental stromata contour detection algorithm (SCDA; digital measurements). Stromata count for each image block was then categorized into five classes and tested for the agreement of human raters and SCDA using Cohen's weighted kappa coefficient (κ). Adequate agreements of stromata counts were observed for each of the human raters to SCDA (κ = 0.83) and between the two human raters (κ = 0.95). Moreover, the SCDA was able to recognize “true stromata,” but to a lesser extent than human raters (average median recall = 90.5%, precision = 89.7%, and Dice = 88.3%). Furthermore, we tracked tar spot development throughout six time points using SCDA and we obtained high agreement between area under the disease progress curve (AUDPC) shared by visual disease severity and SCDA. Our results indicate the potential utility of SCDA in quantifying stromata using RGB images, complementing the traditional human, visual-based disease severity estimations, and serve as a foundation in building an accurate, high-throughput pipeline for the scoring of tar spot symptoms.

First Report of Tar Spot of Maize (Zea mays) Caused by Phyllachora maydis in Pennsylvania

First Report of Tar Spot of Maize (<i>Zea mays</i>) Caused by <i>Phyllachora maydis</i> in Pennsylvania

Genomic Prediction of Resistance to Tar Spot Complex of Maize in Multiple Populations Using Genotyping-by-Sequencing SNPs.

Tar spot complex (TSC) is one of the most important foliar diseases in tropical maize. TSC resistance could be furtherly improved by implementing marker-assisted selection (MAS) and genomic selection (GS) individually, or by implementing them stepwise. Implementation of GS requires a profound understanding of factors affecting genomic prediction accuracy. In the present study, an association-mapping panel and three doubled haploid populations, genotyped with genotyping-by-sequencing, were used to estimate the effectiveness of GS for improving TSC resistance. When the training and prediction sets were independent, moderate-to-high prediction accuracies were achieved across populations by using the training sets with broader genetic diversity, or in pairwise populations having closer genetic relationships. A collection of inbred lines with broader genetic diversity could be used as a permanent training set for TSC improvement, which can be updated by adding more phenotyped lines having closer genetic relationships with the prediction set. The prediction accuracies estimated with a few significantly associated SNPs were moderate-to-high, and continuously increased as more significantly associated SNPs were included. It confirmed that TSC resistance could be furtherly improved by implementing GS for selecting multiple stable genomic regions simultaneously, or by implementing MAS and GS stepwise. The factors of marker density, marker quality, and heterozygosity rate of samples had minor effects on the estimation of the genomic prediction accuracy. The training set size, the genetic relationship between training and prediction sets, phenotypic and genotypic diversity of the training sets, and incorporating known trait-marker associations played more important roles in improving prediction accuracy. The result of the present study provides insight into less complex trait improvement via GS in maize.

Tar Spot Disease Quantification Using Unmanned Aircraft Systems (UAS) Data

Tar spot is a foliar disease of corn characterized by fungal fruiting bodies that resemble tar spots. The disease emerged in the U.S. in 2015, and severe outbreaks in 2018 caused an economic impact on corn yields throughout the Midwest. Adequate epidemiological surveillance and disease quantification are necessary to develop immediate and long-term management strategies. This study presents a measurement framework that evaluates the disease severity of tar spot using unmanned aircraft systems (UAS)-based plant phenotyping and regression techniques. UAS-based plant phenotypic information, such as canopy cover, canopy volume, and vegetation indices, were used as explanatory variables. Visual estimations of disease severity were performed by expert plant pathologists per experiment plot basis and used as response variables. Three regression methods, namely ordinary least squares (OLS), support vector regression (SVR), and multilayer perceptron (MLP), were used to determine an optimal regression method for UAS-based tar spot measurement. The cross-validation results showed that the regression model based on MLP provides the highest accuracy of disease measurements. By training and testing the model with spatially separated datasets, the proposed regression model achieved a Lin’s concordance correlation coefficient (ρc) of 0.82 and a root mean square error (RMSE) of 6.42. This study demonstrated that we could use the proposed UAS-based method for the disease quantification of tar spot, which shows a gradual spectral response as the disease develops.

Fungal diseases of trees and shrubs growing in Siberian Square in Warsaw

A good condition of trees and shrubs growing in urban green areas is one of the key aspects of management. Plant monitoring, including recognition of symptoms of diseases caused by pathogenic fungi and prevention of their spread, is one of the ways of supporting the process of maintenance of green areas. The aim of the study was to conduct preliminary investigations of plants growing in Siberian Square in Warsaw infected by phytopathogenic fungi. The research carried out in 2017-2019 in Siberian Square in Warsaw revealed that the most common diseases observed on the trees and shrubs were caused by powdery mildew fungi infecting maples, poplars, apple trees, and barberry shrubs. Sawadaea tulasnei, Erysiphe adunca, Erysiphe berberidis , and Podosphaera leucotricha ( Erysiphales ) were identified as the causal agents of powdery mildew . Pathogens causing leaf spots and leaf lesions were identified as Venturia inaequalis on Malus x purpurea ’Ola’ and Rhytisma acerinum on Acer platanoides . Rust caused by Melampsora laricis-populina ( Pucciniales ) and basidiomata of Pleurotus ostreatus were detected on infected Populus nigra ‘Italica’ trees

Diagnostics of the genus Acer L. diseases using the pathographic method on the territory of Sokolovogorsk Park in Saratov

The article analyzes the diseases and pests of the trees of the genus Acer L. It was found out that the most resistant species on the territory of the studied object is Acer negundo L. It was found out also that 80-95% of black spot (Rhytisma acerinum) affect the leaves of Acer platanoides L., and powdery mildew (Uncinula aceris Sacc) damages them either. The brown spot (Phyllosticta fraxinicola) affects 50-68% of Acer campestre. The most effective chemical preparations have been determined, i.e. Skor (85-97%). Iron vitriol for the table (at a concentration of 8-10%, 400 g per 100 water) effectively helped to cope both with lichens - lichens disappeared during 4-6 days, and with powdery mildew, various rot disappeared up to 70-89%. Effective biological preparations have been identified to combat spottiness, such as Baktofit (positive result - 83%), Gamair (positive result - 80%), Fitosporin-M (positive result -78%).

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.

Genetic analysis of the tree leaf disease microfungus Rhytisma acerinum

In the work presented in silico DNA sequence and dendrogram analyses were carried out to reveal molecular diversity and genetic distances among Rhytisma entries and related species based on gene bank data mining. The study revealed that R. acerinum shows the closest genetic distance to R. polare. DNA nucleotide variation detected raised a need for consensus between the Linnean morphological and the new molecular systematics.