Leaf Blotch Disease Research Articles

The complete mitogenome of Alternaria tenuissima (Kunze) Wiltshire 1933 (Pleosporaceae), a fungus causing apple leaf blotch disease

Alternaria tenuissima (Kunze) Wiltshire 1933 is a plant pathogenic fungus mainly causing leaf blotch disease. Here, we de novo assembled mitochondrial genome of A. tenuissima isolate AT-1224. The total mitogenome size is 57,475 bp with 29.00% G + C content. The genome contained 12 coding genes and 15 hypothetical proteins, 34 transfer RNA (tRNA) genes and 2 ribosomal RNA (rRNA). There are 227 SSR repeats, range from 2 to 4 base pairs, most five repeats were AT (144), AAT (54), AG (33), AC (13) and AAG (5). The results also found 13 tandem repeats (>100 bp), the largest repeat were forward 2 times located from 13,405 to 20,024 bp and 25,549 to 32,168 bp. Phylogenetic analysis based on 17 species complete mitogenomes indicated that A. tenuissima mitogenome was closest to 2 species, A. solani and A. alternata, sister clade to 6 species, representing Curvularia clavate, Exserohilum rostratum, Exserohilum turcicum, Bipolaris cookie, Bipolaris oryzae and Bipolaris sorokiniana. Further analysis among common fungus in local apple orchards using mitochondrial protein-coding genes revealed A. tenuissima were closing to 2 Alternaria fungi and a fungus representing Phoma sp. These results provide a basic reference for identification and evolution studies of A. tenuissima on apple trees.

Complete genome sequence of a novel mitovirus isolated from the phytopathogenic fungus Alternaria alternata causing apple leaf blotch.

In this study, a novel mitovirus, tentatively designated as "Alternaria alternata mitovirus 2" (AaMV2), was isolated from the fungus Alternaria alternata f. sp. mali causing apple leaf blotch disease. The complete genome of AaMV2 is 3,157 nucleotides in length, with an A+U content of 68.10%. The genome has a single large open reading frame (ORF) encoding an RNA-dependent RNA polymerase (RdRp) protein with a molecular mass of 98.10 kDa. BLAST analysis revealed that AaMV2 has the highest sequence identity to Leptosphaeria biglobosa mitovirus 6, with 79.76% and 82.86% identity at the amino acid and nucleotide level, respectively. Phylogenetic analysis suggested that AaMV2 is a new member of the genus Duamitovirus within the family Mitoviridae. This is the first report of the complete genome sequence analysis of a mitovirus in A. alternata.

Effect of Chitosan on Increasing Beneficial Soil Microflora and Disease Suppression in Turmeric Plants in Humid Tropics of Kerala, India

The present study assessed the population of nitrogen fixers and phosphate solubilizers in the rhizosphere, and suppression of leaf blotch disease caused by Taphrina maculans (Order: Taphrinales, Family: Taphrinaceae) in turmeric plants in response to chitosan application. Leaf blotch disease caused by Taphrina maculans has recorded upto 37.60 % to 52.90 % yield loss in turmeric. Hence, control measures have to be adopted. Chitosan is a biopolymer derived from chitin, which could evoke defense responses in plants. The treatments for this study included, foliar spray of chitosan 2 g L-1 at monthly intervals (F1), foliar spray of chitosan 4 g L-1 at bimonthly intervals (F2), soil drenching of chitosan 2 g L-1 at monthly interval (S1) and soil drenching of chitosan 4 g L-1 at bimonthly interval (S2). The untreated plants served as the control. The population of beneficial soil microbes were assessed and soil application of chitosan was observed to have better effect over foliar application with respect to the population of nitrogen fixing bacteria. More population of nitrogen fixing bacteria was recorded in the soil where chitosan 4 g L-1 was applied as soil drenching at bimonthly interval (S2). The population of phosphate solubilizers were significantly higher over the control in all the chitosan treatments irrespective of the mode of application. However, the higher population of phosphate solubilizers were observed, when chitosan 2 g L-1 was given as foliar spray at monthly intervals (F1). The chitosan treated plants were also observed to have significantly lower incidence of leaf blotch disease compared to control plants. The use of chitosan as a plant biostimulant protects the plant from soil borne pathogens and increases the population of beneficial soil microflora, which have a role in improving the nutrient uptake by plants thereby enhancing the plant growth and yield.

PGPR-Soil Microbial Communities' Interactions and Their Influence on Wheat Growth Promotion and Resistance Induction against Mycosphaerella graminicola.

The efficiency of plant-growth-promoting rhizobacteria (PGPR) may not be consistently maintained under field conditions due to the influence of soil microbial communities. The present study aims to investigate their impact on three PGPR-based biofertilizers in wheat. We used the PGPR Paenibacillus sp. strain B2 (PB2), PB2 in co-inoculation with Arthrobacter agilis 4042 (Mix 2), or with Arthrobacter sp. SSM-004 and Microbacterium sp. SSM-001 (Mix 3). Inoculation of PB2, Mix 2, and Mix 3 into non-sterile field soil had a positive effect on root and aboveground dry biomass, depending on the wheat cultivar. The efficiency of the PGPR was further confirmed by the protection they provided against Mycosphaerella graminicola, the causal agent of Septoria leaf blotch disease. PB2 exhibited protection of ≥37.8%, while Mix 2 showed ≥47.9% protection in the four cultivars tested. These results suggest that the interactions between PGPR and native soil microbial communities are crucial for promoting wheat growth and protection. Additionally, high-throughput sequencing of microbial communities conducted 7 days after PGPR inoculations revealed no negative effects of PB2, Mix 2, and Mix 3 on the soil microbial community structure. Interestingly, the presence of Arthrobacter spp. appeared to mitigate the potential negative effect of PB2 on bacterial community and foster root colonization by other beneficial bacterial strains.

Alternaria arborescens and A. italica Causing Leaf Blotch on Celtis julianae in China.

Celtis julianae Schneid. is widely planted as a versatile tree species with ecological and economic significance. In September 2022, a leaf blotch disease of C. julianae was observed in Nanjing, Jiangsu, China, with an infection incidence of 63%. The disease led to severe early defoliation, significantly affecting the ornamental and ecological value of the host tree. The accurate identification of pathogens is imperative to conducting further research and advancing disease control. Koch's postulates confirmed that the fungal isolates (B1-B9) were pathogenic to C. julianae. The morphology of the characteristics of the pathogen matched those of Alternaria spp. The internal transcribed spacer region (ITS), large subunit (LSU) and small subunit (SSU) regions of rRNA, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), Alternaria major allergen gene (Alt a 1), RNA polymerase second largest subunit (RPB2), and portions of translation elongation factor 1-alpha (TEF1-α) genes were sequenced. Based on multi-locus phylogenetic analyses and morphology, the pathogenic fungi were identified as Alternaria arborescens and A. italica. The findings provided useful information for disease management and enhanced the understanding of Alternaria species diversity in China. This is the first report of A. arborescens and A. italica causing leaf blotch of C. julianae in China and worldwide.

Genome-Wide Association Analysis for Resistance to Coniothyrium glycines Causing Red Leaf Blotch Disease in Soybean.

Soybean is a high oil and protein-rich legume with several production constraints. Globally, several fungi, viruses, nematodes, and bacteria cause significant yield losses in soybean. Coniothyrium glycines (CG), the causal pathogen for red leaf blotch disease, is the least researched and causes severe damage to soybean. The identification of resistant soybean genotypes and mapping of genomic regions associated with resistance to CG is critical for developing improved cultivars for sustainable soybean production. This study used single nucleotide polymorphism (SNP) markers generated from a Diversity Arrays Technology (DArT) platform to conduct a genome-wide association (GWAS) analysis of resistance to CG using 279 soybean genotypes grown in three environments. A total of 6395 SNPs was used to perform the GWAS applying a multilocus model Fixed and random model Circulating Probability Unification (FarmCPU) with correction of the population structure and a statistical test p-value threshold of 5%. A total of 19 significant marker-trait associations for resistance to CG were identified on chromosomes 1, 5, 6, 9, 10, 12, 13, 15, 16, 17, 19, and 20. Approximately 113 putative genes associated with significant markers for resistance to red leaf blotch disease were identified across soybean genome. Positional candidate genes associated with significant SNP loci-encoding proteins involved in plant defense responses and that could be associated with soybean defenses against CG infection were identified. The results of this study provide valuable insight for further dissection of the genetic architecture of resistance to CG in soybean. They also highlight SNP variants and genes useful for genomics-informed selection decisions in the breeding process for improving resistance traits in soybean.

A Robust Approach for Identification and Classification of Turmeric Plant Leaf Diseases Using LDA-ANFIS Algorithm

Abstract: Agriculture is the backbone of a country and it plays a very important role in the economy. In the field of agriculture, it is very important to identify the disease of crops and its nature. Turmeric plant is a significant plant used in turmeric production, and turmeric powder is used as medicine for certain diseases and as an antiseptic. There are several pests and diseases with significant effects on turmeric yields and leaf spot disease (Curcuma longa) among the most significant ones. Leaf spot disease leads to large damages to the leaves. The disease initially emerges as small circular spots, then evolves instantly and spreads over the entire leaf surface. The disease ultimately ends up with complete die out of the leaves. The data base of different leaf images was created and processed using SFCM segmentation, and leaf images textural analysis was carried out using GLCM. The LDA-ANFIS classifier is used for classification method and it helps to improve the detection rate and reduce the entropy loss. It is highly efficient and accurate to detect the disease image with different number of categories (Leaf Spot, Leaf Blotch Disease and Bacterial Wilt Disease etc.). Experimental analysis is done to calculate the performance metric like as Accuracy, Precision, F measure, Recall, Sensitivity and Specificity. Then, the comparative analysis of the existing parameters is compared to the proposed algorithm parameters. The proposed system LDA-ANFIS algorithm performance value of accuracy is 98%.

Airborne inoculum dynamics of Polystigma amygdalinum and progression of almond red leaf blotch disease in Catalonia, NE Spain

AbstractThe dynamics of airborne ascospores and disease progress of red leaf blotch (RLB) of almond, caused by Polystigma amygdalinum, and their correlations with weather variables were studied from 2019 to 2021 in two almond orchards located in Lleida, NE Spain. Airborne ascospores were detected and quantified by real‐time qPCR using species‐specific primers for P. amygdalinum. Ascospores were detected mainly from April to June, with a high variability between the yearly cumulative concentrations. Positive significant correlations were found between the weekly proportion of airborne ascospores and the number of wet and mild days—either combined or separated— accumulated rainfall, number of rainy days, accumulated low temperatures on wet days, and mean and maximum relative humidity. In contrast, several thermal variables (maximum temperature, VPD, and number of warm days) were negatively correlated with ascospore catches. Positive significant correlations were found between the cumulative proportion of ascospores and RLB incidence and severity. Weekly variations in RLB incidence and severity showed significant positive correlations with the number of warm days while negative with the number of mild days. Severity was also positively correlated with several thermal variables (mean, maximum, and minimum temperature, and VPD), and negatively correlated with the number of cold days and wet and mild days. Stronger correlations were generally found with ascospore catches or disease progress when using concurrent weekly weather data. Gompertz, monomolecular, and logistic growth models were evaluated to describe RLB disease progress.

Inhibiting septoria leaf blotch disease severity of wheat plants by using foliar spray with two antagonists and growth regulators under natural field conditions

Septoria leaf blotch (SLB) disease caused by Mycosphaerella graminicola affect wheat plants causing serious losses in produced yield. Evaluation the potentiality of certain antagonists and growth regulators to suppress the SLB disease severity was performed under natural field conditions for two successive growing seasons whereas three wheat cultivars were sprayed with Pseudomonas fluorescens and Trichoderma harzianum as well as the growth regulators Gibberellic Acetic Acid, Indole Acetic Acid. All applied treatments showed their activity for decreasing the disease severity. The lowest disease severity and highest grains yield was recorded at fungicide Amistar treatment followed by growth regulators GAA, IAA and then the antagonists, P. fluorescens and T. harzianum in descending order. Based on the present finding, it could be concluding that the use of plant growth regulators as well as antagonists as foliar spray on wheat plants revealed reduction in SLB disease severity and increase in produced yield in return

Protective Effects of Systiva® Seed Treatment Fungicide for the Control of Winter Wheat Foliar Diseases Caused at Early Stages Due to Climate Change

Foliar fungal diseases are a serious threat to winter wheat production and climate change appears to favor pathogens associated with leaf blotch and tan spot symptoms in the Mediterranean area. The present work aimed to highlight these risks and propose appropriate disease management strategies by evaluating the seed treatment with the Systiva® (BASF) fungicide as a means to protect the crop against foliar fungal infections during the early growing stages. Towards that aim, plant tissue symptoms affected by the pathogens Pyrenophora tritici-repentis and Septoria spp. were systematically recorded in a study field in the region of Larissa, central Greece for three years (2016–2018), and the findings were associated with the monthly weather anomalies. Consequently, for the growing period of 2021–2022, a field experiment was established in the same disease prone field, comparing different doses of the seed treatment with Systiva® fungicide against leaf blotch and tan spot diseases. The evaluation was made by visual disease assessments, remote sensing with an unmanned aerial vehicle (UAV) and metagenomics analysis. Parallel measurements on straw residues were also made to characterize the plant residues perithecia (pseudothecia). Visual leaf disease assessments and UAV remote sensing data showed that Systiva® treatments at doses of 125 cc and 150 cc per 100 kg of wheat seed can reduce the percentage of infected wheat plants caused by foliar fungal pathogens at wheat growth stages GS23-25 and GS30-31. Moreover, the metagenomics analyses performed on the microbial communities revealed that Systiva® can decrease the degree of infection by P. tritici-repentis and Z. tritici but do not provide sufficient protection against P. nodorum. Foliar diseases were influenced by the soil surface area covered with straw residue with a high proportion of natural inoculum (pseudothecia/ascospores).

Pathotype diversity of Zymoseptoria tritici (Desm. Quaedvlieg & Crous) isolates collected from Central Anatolia, Turkey

AbstractSeptoria Leaf Blotch caused by Zymoseptoria tritici is a major disease of wheat affecting many wheat‐growing regions in the world. This study is the first to describe characteristics of the pathotype structure of Z. tritici isolates in Central Anatolia, Turkey, and to determine effective resistance genes for use in breeding strategies of Septoria Leaf Blotch Disease. Sixty isolates of Z. tritici were obtained from four intensive wheat production provinces during 2015 and 2017. The pathotypes were determined using a differential set that included 12 wheat genotypes. Twenty‐eight pathotypes were identified, and Pathotype 1 prevailed in all areas investigated. The K‐5 isolate from Konya province had the highest virulence on the differential genotypes and was characterized as Pathotype 28. Thirty‐nine of the isolates were virulent on the resistance gene Stb‐10, and all isolates were avirulent for the resistance gene Stb‐6. It appears that resistance genes Stb‐6 and Stb‐12 could be used in breeding new varieties against Septoria Leaf Blotch Disease.

Evaluation of Fungicides and Application Strategies for the Management of the Red Leaf Blotch Disease of Almond

Red leaf blotch (RLB) of almond, caused by Polystigma amygdalinum, is an important foliar disease of this nut tree in the Mediterranean basin and especially in Spain. In recent years, the control of this disease has become a key factor in the management of Spanish almond orchards. The management of RLB is not easy due to intrinsic factors of the disease (e.g., long infection and latency periods) and the low number of registered fungicides in this country. From 2015 to 2019, different field trials were conducted in the Lleida region, NE Spain, to evaluate the efficacy of several fungicide products and of application strategies to control this disease. Systemic fungicides, which included fluopyram, trifloxystrobin, and mixtures of fluopyram + trifloxystrobin and pyraclostrobin + boscalid, performed better than contact and penetrant products and showed up to 90% control against RLB. However, the efficacy of the tested fungicides varied depending on the year. In terms of application strategies, when fungicide applications were conducted following specific meteorological conditions (after 15 days from >15 mm rainfalls with ≈10–15 °C as the minimum average temperature), their efficacy was comparable to that of calendar-based treatments (every 14, 21, or 31 days from petal fall) but with fewer applications (depending on the year, 2–4 applications as compared with 5–9 for calendar treatments).

Two-Stage Convolutional Neural Networks for Diagnosing the Severity of Alternaria Leaf Blotch Disease of the Apple Tree

In many parts of the world, apple trees suffer from severe foliar damage each year due to infection of Alternaria blotch (Alternaria alternata f. sp. Mali), resulting in serious economic losses to growers. Traditional methods for disease detection and severity classification mostly rely on manual labor, which is slow, labor-intensive and highly subjective. There is an urgent need to develop an effective protocol to rapidly and accurately evaluate disease severity. In this study, DeeplabV3+, PSPNet and UNet were used to assess the severity of apple Alternaria leaf blotch. For identifications of leaves and disease areas, the dataset with a total of 5382 samples was randomly split into 74% (4004 samples) for model training, 9% (494 samples) for validation, 8% (444 samples) for testing and 8% (440 samples) for overall testing. Apple leaves were first segmented from complex backgrounds using the deep-learning algorithms with different backbones. Then, the recognition of disease areas was performed on the segmented leaves. The results showed that the PSPNet model with MobileNetV2 backbone exhibited the highest performance in leaf segmentation, with precision, recall and MIoU values of 99.15%, 99.26% and 98.42%, respectively. The UNet model with VGG backbone performed the best in disease-area prediction, with a precision of 95.84%, a recall of 95.54% and a MIoU value of 92.05%. The ratio of disease area to leaf area was calculated to assess the disease severity. The results showed that the average accuracy for severity classification was 96.41%. Moreover, both the correlation coefficient and the consistency correlation coefficient were 0.992, indicating a high agreement between the reference values and the value that the research predicted. This study proves the feasibility of rapid estimation of the severity of apple Alternaria leaf blotch, which will provide technical support for precise application of pesticides.

Comparison of models for leaf blotch disease management in wheat based on historical yield and weather data in the Nordic-Baltic region

Validation of models for plant disease management is a crucial part in the development of decision support systems in plant protection. Bespoke field trials are usually conducted to determine the performance of a model under practical conditions. However, field trials are very resource-demanding, and the use of already existing field trial data could significantly reduce costs for model validation. In this study, we took this novel approach to verify the performance of models for determining the need of fungicide applications against leaf blotch diseases in wheat by utilising historical weather data and yield data available from fungicide efficacy field trials. Two models based on humidity factors were used in the study. To estimate how specific humidity settings in the two models affect the number of recommended fungicide treatments per season, historical weather data from a 5-year period from weather stations in Denmark, Sweden, Norway, Finland, and Lithuania was used. The model output shows major differences between seasons and regions, typically recommending between one and three treatments per season. To determine the prediction potential of the models, data on yield gains from either one or two fungicide applications in fungicide efficacy trials conducted in wheat over a 5-year period in the five countries was utilised. The yield responses from fungicide treatments in the efficacy trials varied considerably between years and countries, as did the proportion of predictions of profitable treatments. In general, there was a tendency for the models to overestimate the need to apply fungicides (low specificity), but they rarely failed to recommend an application that was needed (high sensitivity). Despite the importance of having specific trials across regions in order to adjust models to local cropping and weather conditions, our study shows that historical weather data and existing field trial data have the potential to be used in model validation.

Assessment of Genetic Variability in Onion against Purple Leaf Blotch Disease under Field Conditions and its Management

Assessment of Genetic Variability in Onion against Purple Leaf Blotch Disease under Field Conditions and its Management

Identification and pathogenicity of Alternaria species associated with leaf blotch disease and premature defoliation in French apple orchards.

Leaf blotch caused by Alternaria spp. is a common disease in apple-producing regions. The disease is usually associated with one phylogenetic species and one species complex, Alternaria alternata and the Alternaria arborescens species complex (A. arborescens SC), respectively. Both taxa may include the Alternaria apple pathotype, a quarantine or regulated pathogen in several countries. The apple pathotype is characterized by the production of a host-selective toxin (HST) which is involved in pathogenicity towards the apple. A cluster of genes located on conditionally dispensable chromosomes (CDCs) is involved in the production of this HST (namely AMT in the case of the apple pathotype). Since 2016, leaf blotch and premature tree defoliation attributed to Alternaria spp. have been observed in apple-producing regions of central and south-eastern France. Our study aimed to identify the Alternaria species involved in apple tree defoliation and assess the presence of the apple pathotype in French orchards. From 2016 to 2018, 166 isolates were collected and identified by multi-locus sequence typing (MLST). This analysis revealed that all these French isolates belonged to either the A. arborescens SC or A. alternata. Specific PCR detection targeting three genes located on the CDC did not indicate the presence of the apple pathotype in France. Pathogenicity was assessed under laboratory conditions on detached leaves of Golden Delicious and Gala apple cultivars for a representative subset of 28 Alternaria isolates. All the tested isolates were pathogenic on detached leaves of cultivars Golden Delicious and Gala, but no differences were observed between the pathogenicity levels of A. arborescens SC and A. alternata. However, the results of our pathogenicity test suggest that cultivar Golden Delicious is more susceptible than Gala to Alternaria leaf blotch. Implications in the detection of the Alternaria apple pathotype and the taxonomic assignment of Alternaria isolates involved in Alternaria leaf blotch are discussed.

Induction of resistance in onion against purple leaf blotch disease through chemicals

Induction of resistance in onion against purple leaf blotch disease through chemicals

Evaluation of the reactions of some varieties of wheat against septoria leaf blotch disease (zymoseptoria tritici (Desm. Quaedvlieg & Crous)

Amaç: Bu araştırmada, Ege Bölgesi buğday ekim alanlarında yaygın olarak görülen, verim ve kaliteyi etkileyen Septorya yaprak lekesi hastalığına karşı bölgemiz koşullarında yaygın olarak yetiştirilen buğday çeşitlerinin reaksiyonları belirlenmiştir. Materyal ve Yöntem: Çalışmanın materyalini; enfekteli yapraklardan izole edilen ve tanısı gerçekleştirilmiş virülent Zymoseptoria tritici izolatı, bölgede yaygın olarak yetiştiriciliği yapılan (10 ekmeklik ve 5 makarnalık buğday çeşitleri) ve bu hastalığa hassas olan Touching-20 ve Tekirdağ buğday çeşitlerine ait tohumlar oluşturmaktadır. Çeşit reaksiyonu denemeleri, iklim odası ve sera koşullarında gerçekleştirilmiş, hastalık skalasına göre değerlendirmeler yapılarak çeşitlerin hastalığa karşı reaksiyon durumları belirlenmiştir. Araştırma Bulguları: İklim odası ve sera koşullarında gerçekleştirilen denemelerde, sadece Alatay çeşidi Orta Dayanıklı (MR) olarak belirlenmiş diğer çeşitler ise hassas ve çok hassas olarak tespit edilmiştir. Gönen 98, Ceyhan 99, Kaşifbey 95, Adana 99, Cumhuriyet 75 ve Ziyabey 98 çeşitlerinin ise ileride yapılacak ıslah çalışmaları için ümitvar olduğu düşünülmektedir. Sonuç: Çalışma ile Septorya yaprak lekesi hastalığına karşı bölgede yaygın olarak tercih edilen çeşitlerin durumu ilk kez belirlenmiştir. Ege Bölgesi'nde Septorya yaprak lekesi hastalığının epidemi yapması durumunda, yaygın olarak kullanılan buğday çeşitlerinin genelinin hassas bulunmasından dolayı, ürün ve verim kayıplarının yaşanabileceği endişesi duyulmaktadır. Ancak; orta dayanıklı olarak belirlenen Alatay çeşidinin, hastalığın her yıl görüldüğü alanlarda ekiminin önerilerek, epidemi riskinin bu şekilde daha aza indirgeneceği düşünülmektedir.

Seasonal Changes and the Interaction between the Horse Chestnut Leaf Miner Cameraria ohridella and Horse Chestnut Leaf Blotch Disease Caused by Guignardia aesculi

The horse chestnut leaf miner Cameraria ohridella (Lepidoptera: Gracillariidae) is an invasive pest of horse chestnut Aesculus hippocastanum (Sapindales: Sapindaceae) and has spread through Europe since 1985. Horse chestnut leaf blotch is a fungal disease caused by Guignardia aesculi (Botryosphaeriales: Botryosphaeriaceae) that also seriously damages horse chestnut trees in Europe. The interaction between the leaf miner and the fungus has not yet been sufficiently described. Therefore, the aim of the present study was to assess leaf damage inflicted to horse chestnut by both C. ohridella and G. aesculi during the vegetation season and to model their interaction. The damage to leaf area was measured monthly from May to September 2013 in České Budějovice, the Czech Republic using digital image analysis of sampled leaves. A simple phenomenological model describing the expected dynamics of the two species was developed. The study revealed that the damage caused by both the pests and the fungus varied significantly among sampling sites within the city. The overall leaf damage exceeded 50% in no-raking sites in August. The mathematical model indicates that infestation by C. ohridella is more affected by G. aesculi than vice versa. Guignardia aesculi is thus the superior competitor of the two species. Our findings highlight the delicate interplay between insect pests and fungal pathogens and the spatiotemporal dynamics influencing them, calling for more research in this understudied area.

Effects of Crop Rotation on Spring Wheat Yield and Pest Occurrence in Different Tillage Systems: A Multi-Year Experiment in Finnish Growing Conditions

Crop rotation and soil tillage are among key factors impacting cropping system productivity, pest management and soil health. To assess their role in northern cropping systems, we quantified the effects of crop rotation on spring wheat yield in different tillage systems based on a long-term (2005–2017) field experiment in southwestern Finland. In addition, effects of crop rotation on weeds, plant pathogens, and pest insects were assessed. Three types of crop rotation were compared: monoculture (spring wheat), 2-year rotation (spring wheat—turnip rape—spring wheat—barley) and 4-year rotation (spring wheat—turnip rape—barley—pea) under no-tillage and plowing. A diversified crop rotation improved spring wheat yield by up to 30% in no-tillage and by 13% under plowing compared with monoculture. Overall, the yield quantity and quality differences between crop rotations were higher in no-tillage plots than in plowed plots. The occurrence of weed species in spring wheat before herbicide control was highest in the four-year crop rotation and lowest in the wheat monoculture. For plant diseases, wheat leaf blotch disease severity, mainly caused by Pyrenophora tritici-repentis, was lowest in the most diverse crop rotation. On average, wheat leaf blotch disease severity was 20% less when wheat was grown every fourth year compared with wheat monoculture. The effect of crop rotation on stem and root diseases became apparent after 6 years of rotation and the disease index was lowest in the most diverse crop rotation. Neither rotation nor tillage affected the control need of wheat midge (Sitodiplosis mosellana). Based on our results, diverse crop rotations including cereals, oilseed crops, and legumes increase yield and reduce plant disease severity of spring wheat in Finland, with the magnitude being larger in no-tillage systems.