Control Of Cercospora Leaf Spot Research Articles

Regev, a New Hybrid Fungicide for Control of Cercospora Leaf Spot on Sugar Beet

Cercospora leaf spot (CLS) is one of the most yield-limiting foliar disease of sugar beet in the United States. Standard practices to control this disease include selection of tolerant varieties, crop rotations, and reliance on fungicides. However, genetic resistance still requires some fungicides for acceptable control under high disease pressure, and there are only a limited number of fungicides registered for control of this disease. Regev® is a newly registered hybrid fungicide for sugar beet disease control that contains eight biological active ingredients from tea tree oil (TTO) and one active ingredient from the synthetic fungicide, difenoconazole. Tea tree oil provides a new and unique mode of activity against both fungal and bacterial plant pathogens, and it has a low resistance risk. Eight trials were conducted to evaluate Regev for efficacy against Cercospora leafspot, and sugar beet yield and quality benefits in Minnesota and Michigan. Five of the trials had slightly different treatments with the primary goal of allowing trialists to conduct trials with treatments that were appropriate for their locations. However, one of the trials at the Northwest Research and Outreach Center (NWROC) of the University of Minnesota in Crookston, Minnesota, was conducted three times over the years 2021, 2022, and 2023. Across the eight trials, spray programs that included Regev provided control of Cercospora leaf spot equal to standard fungicide programs.

Nighttime Applications of Germicidal UV Light to Suppress Cercospora Leaf Spot in Table Beet.

Cercospora leaf spot (CLS), caused by the hemibiotrophic fungus Cercospora beticola, is a destructive disease affecting table beet. Multiple applications of fungicides are needed to reduce epidemic progress to maintain foliar health and enable mechanized harvest. The sustainability of CLS control is threatened by the rapid development of fungicide resistance, the need to grow commercially acceptable yet CLS-susceptible cultivars, and the inability to manipulate agronomic conditions to mitigate disease risk. Nighttime applications of germicidal UV light (UV-C) have recently been used to suppress several plant diseases, notably those caused by ectoparasitic biotrophs such as powdery mildews. We evaluated the efficacy of nighttime applications of UV-C for suppression of CLS in table beet. In vitro lethality of UV-C to germinating conidia increased with increasing dose, with complete suppression at 1,000 J/m2. Greenhouse-grown table beet tolerated relatively high doses of UV-C without lethal effects despite some bronzing on the leaf blade. A UV-C dose >1,500 J/m2 resulted in phytotoxicity severities greater than 50%. UV-C exposure to ≤750 J/m2 resulted in negligible phytotoxicity. Older (6-week-old) greenhouse-grown plants were more susceptible to UV-C damage than younger (2- and 4-week-old) plants. Suppression of CLS by UV-C was greater when applied within 6 days of C. beticola inoculation than if delayed until 13 days after infection in greenhouse-grown plants. In field trials, there were significant linear relationships between UV-C dose and CLS control and phytotoxicity severity, and a significant negative linear relationship between phytotoxicity and CLS severity at the final assessment. Significant differences between UV-C doses on the severity of CLS and phytotoxicity indicated an efficacious dose near 800 J/m2. Collectively, these findings illustrate significant and substantial suppression by nighttime applications of UV-C for CLS control on table beet, with potential for incorporation in both conventional and organic table beet broadacre production systems.

Effects of pyraclostrobin rotations and tank-mixtures on Cercospora beticola sensitivity and Cercospora leaf spot control in sugarbeet

Sugarbeet production supplies approximately 50–60% of domestic sugar in the United States. One of the most economically important foliar diseases of sugarbeet is Cercospora leaf spot (CLS), caused by Cercospora beticola. Fungicide resistance is a major concern due to the frequent applications needed to control multiple infection cycles each season and the reliance on single-site fungicides. Reduced C. beticola sensitivity to multiple fungicide groups, including the quinone outside inhibitors (QoIs) has been observed. The QoI fungicide Headline (23.6% pyraclostrobin) was exceptionally effective in controlling CLS until high levels of reduced sensitivity stabilized in C. beticola populations. This study aimed to test application programs to minimize C. beticola pyraclostrobin resistance development and maximize CLS management. Rotation (high- and low-risk) and tank-mixture programs integrating pyraclostrobin (Headline™) with mancozeb (a multi-site fungicide) treatments were evaluated in 2019 and 2020 field studies. For all Headline programs, distributions of C. beticola pyraclostrobin sensitivities were not significantly different from each other but differed from the non-treated control (P < 0.05). In 2020, a significant increase in the percentage of isolates with half-maximal effective pyraclostrobin concentrations ≥5 μg/ml was noted in all Headline treatments (P < 0.05), even where a single application of Headline alone was used. Furthermore, no additional CLS control, yield, or sugar benefits from Headline were observed when compared to grower standard programs without Headline (P > 0.05). In conclusion, pyraclostrobin-based products used in chemical rotations or tank-mixtures were not more beneficial than lower-risk programs despite their historical CLS control efficacy.

The Use of a New Ionic Derivative of Salicylic Acid in Sugar Beet Cultivation

The need for sustainable development in the context of pesticide use has been recognized by the European Union. The “Farm to Fork Strategy” indicates a goal of 50% reduction in pesticide use by 2030. To address this challenge, we used the concept of ionic liquids to modify known resistance inducers, i.e., a group of substances whose action is indicated as an alternative to fungicides. A new, patented substance developed by us, which is a choline 3,5-dichlorosalicylate, has been tested in the context of its use in sugar beet cultivation with the aim of controlling Cercospora leaf spot (CLS). The results suggest that the use of this substance in combination with one fungicide treatment reduces disease infection and produces yields very similar to the use of a standard protection program assuming the use of two fungicides. Such results provide the basis for further development of 3,5-dichlorosalicylate in terms of its use in agriculture. Thanks to its use, it was possible to resign from one fungicide treatment, while maintaining protection against CLS and yields at the same level as for the full fungicide protection program. Such an approach is in line with European Union policies.

A picolinamide fungicide for controlling Cercospora-leaf spot (CLS) of sugar beet

A picolinamide fungicide for controlling Cercospora-leaf spot (CLS) of sugar beet

Evaluation of adjuvants added to fungicides for controlling Cercospora leaf spot on sugar beet

Cercospora Leaf Spot (CLS) is a destructive foliar disease of sugar beet caused by Cercospora baticola. Recent development of resistance to several classes of chemicals by C. beticola coupled with untimely applications and/or frequent rainfall after fungicide applications have resulted in reduced efficacy of fungicides in controlling CLS. Adjuvants are typically included in fungicide formulations as inert ingredients to improve retention, delivery, and efficacy against targeted pathogens. In the greenhouse trials, three recommended fungicides (Penncozeb®, Inspire® XT, and Badge® SC) were applied and evaluated alone or in mixtures with four adjuvant types (Complex®, Preference®, Cerium Elite®, and Transfix®) before and after inoculation with C. beticola. Disease severity was recorded 14 days post-inoculation. Greenhouse trials showed that application of fungicides before disease onset resulted in reduced disease severity. Inspire XT had lower disease severity than Penncozeb or Badge SC. Adjuvants alone were not effective at controlling CLS. Among all fungicide-adjuvant combinations, only Complex and Inspire resulted in lowest disease severity. In the field trials, fungicides were applied alone or with three adjuvants. Disease severity was evaluated at 14 days intervals and recoverable sucrose (i.e., sugar yield) was measured at harvest. Field trials showed significant variations between years in disease severity and sugar yield (P < 0.001). These variations may be caused by lack of rain events immediately after the fungicide application or during the following two days. The finding that addition of adjuvants did not improve the efficacies of fungicides at controlling CLS was because if there was no rain, then the adjuvants should not be any better than formulated fungicide. Thus, more experiments are necessary with similar and different adjuvant-fungicide combinations.

Cultivar and Fungicide Evaluations for Cercospora Leaf Spot Control in Organic and Conventional Table Beet Production

Cercospora leaf spot (CLS), caused by the fungal pathogen Cercospora beticola, is the most destructive foliar disease of table beet (Beta vulgaris ssp. vulgaris) in Wisconsin, USA, and globally. Under conducive conditions, symptomatic lesions on the leaf expand and coalesce forming large necrotic areas that can ultimately lead to complete defoliation. This damage reduces productivity and threatens the ability to mechanically harvest. CLS damage also detracts from the visual appeal of fresh market bunched beets to such an extent that growers risk buyer rejection if CLS severity is observed to be greater than 5%. Fungicide use for CLS control is threatened by the emergence of resistant C. beticola strains, and the application of host resistance is constrained by limited knowledge of cultivar reaction to CLS in table beet. This study aimed to address the knowledge gaps of fungicide efficacy and cultivar reaction by conducting replicated field trials in multiple table beet growing environments across Wisconsin. Broad variation for resistance to CLS was observed among the 10 included cultivars. The mean area under disease progress curve (AUDPC) across environments for the most susceptible cultivar was 267% greater than the most resistant cultivar. Spearman correlations between environments for mean cultivar AUDPC value ranged from 0.71 to 0.99, revealing consistent cultivar CLS reactions across environments. Although susceptible cultivars surpassed 5% severity in all environments, the resistant cultivars remained below this threshold in six of the 10 environments. By comparison with resistant sugar beet (Beta vulgaris ssp. vulgaris) cultivars, however, all tested table beets appeared susceptible to CLS, highlighting the potential for a CLS breeding effort in table beet. Neither of the evaluated Organic Materials Review Institute–listed treatments were effective at limiting CLS disease progress, whereas both tested conventional fungicides significantly reduced disease severity over the nontreated plots. These findings may provide helpful guidance to table beet growers affected by CLS in Wisconsin and beyond.

Performance efficiency of some biocontrol agents on controlling Cercospora leaf spot disease of sugar beet plants under organic agriculture system

This investigation was carried out on commercial organic field in the Fayoum Governorate of Egypt under conditions of natural infection, 2020/2021 and 2021/2022 to evaluate the effectiveness of four commercial biocides—Blight Stop (Trichoderma harzianum), Bio Zeid (T. album), Root Guard (Bacillus subtilis), and Bio ARC (B. megaterium)—as well as, four biocontrol agents (T. harzianum, T. album, B. subtilis, and B. megaterium) in controling Cercospora beticola Sacc, the main causal of Cercospra leaf spot (CLS) disease on sugar beet in an organic farming systems. All biocontrol agents and commercial biocides sprayed at the recommended dose in a two spray regime with 15 days between sprays, were significantly reduced Cercospora beticola, total amino acid and juice impurities (K, Na and α-a N %) in comparison to control treatment. All bioagents and biocides put to the test resulted in a significant rise in phenolic compound values, total chlorophyll, sucrose (%), purity (%), root, top and sugar yield quality of sugar beet during both seasons. Spraying Blight Stop was the most effective treatment followed by T. harzianum. B. megaterium was the least effective biocide treatment compared with the control treatment during the two growing seasons.

Potential Impacts of Eminent Fungicide, Certain Bacterial and Fungal Antagonists for Controlling Cercospora Leaf Spot Disease in Sugar Beet.

Potential Impacts of Eminent Fungicide, Certain Bacterial and Fungal Antagonists for Controlling Cercospora Leaf Spot Disease in Sugar Beet.

Seed Bio-priming Mediated Control of Cercospora Leaf Spot and Bacterial Wilt Disease Resistance in Chilli (Capsicum annuum L.) under New Alluvial Zone

The potential bio-control agents Trichoderma harzianum, and Pseudomonas fluorescens in alone or combinationwere used as seed bio-priming for reviewing their efficacy in the reduction of the devastating diseases, theCercospora leaf spot (Cercosporacapsici) and Bacterial wilt (Ralstonia solanacearum) of chilli (Capsicum annuumL.). Considering two important seasons, the Rabi season was comparatively vital as its disease severity wasmore. In chilli, the disease index was significantly reduced in combining the Trichoderma harzianum +Pseudomonas fluorescens treated seeds, followed by the T. harzianum treatment compared to the control (hydroprimed)against cercospora leaf spot of chilli. In case of Bacterial wilt, it was found that T3 followedbyPseudomonas fluorescens treated seeds. Chilli seeds were primed with Trichoderma harzianum + Pseudomonasfluorescens revealed maximum disease protection that was displaying favour in pre-kharif and early stage(35DAS) in comparison to rabi and 60DAS of chilli production. The ability of genotype indicated variationwhere the distinct variation was noticeable in V2 (G-4) mentioning its high tolerance at 35DAS. Theapplication of combined bio-priming may be suitable to control both Cercospora leaf spot and Bacterial wiltof chilli.

The first detection of multiple resistant (MBC and QoI) strains of Cercospora beticola Sacc. in Poland

Long-term and intensive use of fungicides may lead to fungal resistance to active ingredients, even with different modes of action. In Poland, Cercospora leaf spot (CLS), the most remarkable disease of sugar beet, is mainly controlled with benzimidazoles (MBC), triazoles (DMI), and strobilurins (QoI). A constant monitoring of the emergence and the development of resistant fungal strains is required by the limited number of active ingredients. On the basis of RFLP analysis application, the aim of the study was to determine and monitor simultaneous appearing of C. beticola strains with E198A and G143A mutations. Mutation E198A in the β-tubulin gene is the main reason for MBC-resistance. Whereas mutation G143A in the cytochrome b is responsible for QoI-resistance. Most of the 414 tested C. beticola isolates (90%) were able to grow (growth inhibition percentage<50%) on the medium amended with 1 μg/ml thiophanate-methyl, and 34% of the isolates on the medium amended with 1 μg/ml azoxystrobin. Based on the PCR-RFLP analysis both mutations were detected in 44% of the tested isolates. The current study is the pioneer detection of multiple resistances to MBC and QoI fungicides in C. beticola in Poland and the European Union. The presence of multiple resistant isolates in the population of pathogens is adverse and this phenomenon requires thorough monitoring and registration of new active ingredients, allowing effective control of CLS.

Trichoderma asperellum (NST-009): A potential native antagonistic fungus to control Cercospora leaf spot and promote the growth of 'Green Oak' lettuce (Lactuca sativa L.) cultivated in the commercial NFT hydroponic system

Leaf spot caused by Cercospora lactucae-sativae is one of the most damaging diseases of ‘Green Oak’ lettuce in Thailand. This study was conducted to estimate the effectiveness of Trichoderma asperellum NST-009, a native strain in Thailand, to manage the leaf spot disease and enhance the growth of ‘Green Oak’ lettuce in a nutrient film technique (NFT) hydroponic system. In vitro tests showed that T. asperellum NST-009 significantly inhibited the mycelial growth of C. lactucae-sativae by 72.50%, and its antifungal metabolite from the culture filtrate of T. asperellum NST-009 inhibited the mycelial growth of C. lactucae-sativae by 93.26%. In the hydroponics experiment, T. asperellum NST-009 reduced the disease severity index by 67.51% compared to the inoculated control and significantly stimulated the growth of the ‘Green Oak’ lettuce in terms of the plant height (8.62%), canopy width (16.67%), leaf number (18.39%), shoot fresh weight (25.71%), root fresh weight (39.26%), and total P in the leaves (31.45%) compared to the control. In addition, T. asperellum NST-009 was found to survive in both the lettuce leaves and roots at 100.00%.

A strategy for controlling Cercospora leaf spot, caused by Cercospora beticola, by combining induced host resistance and chemical pathogen control and its implications for sugar beet yield

Cercospora beticola populations resistant to methyl benzimidazole carbamate (MBC), quinone outside inhibitor (QoI), and demethylation inhibitor (DMI) fungicides have been reported in Egypt. This pathogen causes a difficult to control variant of Cercospora leaf spot (CLS) on sugar beet. We conducted field experiments over two years to investigate treatment efficacies on MBC- and QoI-resistant, but partially DMI-sensitive, C. beticola from a research farm in Sakha, Egypt. DMI fungicides showed moderate efficacy with half the maximal effective concentration (EC50). Efficacy was 67.2–69.1% and 63.4–63.6% for epoxiconazole (EPO) and propiconazole (PRO), respectively. When each fungicide was mixed with salicylic acid (SA) at EC50 (EPO + SA) and EC50 (PRO +SA), efficacy was 77.5–79.1% and 77.0–78.2%, respectively. The QoI fungicide, azoxystrobin, showed lower efficacy (46.4–49.5%) when applied alone, but enhanced efficacy when combined with SA at EC50/EC50 (77.0–78.2%). Carbendazim alone was only 47.5–45.1% effective, but when mixed with SA, had a 67.1% co-toxicity factor in vitro, indicating antagonism between components. An Artemisia cina aqueous extract (WEA) combined with SA (WEA/SA) showed 76.0–78.2% efficacy, compared with 69.0–71.0% and 49.0–52.7% for WEA and SA, respectively. Single treatments were classified into five sensitivity classes from sensitive (<1) to resistant (>100) based on their EC50 values. Significant increases in insensitivity were observed from 2015/16 to 2017/18. All treatments increased total yield, sucrose percentage, and recoverable white sugar compared with the untreated control. A combination of control strategies could allow for effective disease and fungicide resistance management.

Sensing the occurrence and dynamics of Cercospora leaf spot disease using UAV-supported image data and deep learning

The most damaging foliar disease in sugar beet is Cercospora leaf spot (CLS), caused by Cercospora beticola Sacc. The pathogen is expanding its territory due to climate conditions, generating the need for early and accurate detection to avoid yield losses. In Germany, monitoring and control strategies are based on visual field assessments, with the parameter disease incidence (DI). This parameter triggers warning systems when a threshold is achieved, and decision-making takes place for fungicide application. However, visual scoring is a time-consuming activity that requires well-trained personnel and is the principal bottleneck for CLS control. Digital technologies can support this process. Thus, the present work is based on two trial fields conducted and monitored in 2020 using an unmanned aerial vehicle (UAV) equipped with a multispectral camera. Image data were collected in time series during the vegetation period. Trials were sown with different sugar beet varieties; for field management, there was employed diverse fungicide strategies, and artificial inoculation took place in a spot manner. Parallel to the flight mission and additional assessment of DI, disease severity (DS) via KWS scale was collected by experts as so-called ground truth (GT). Combined with image-processing, it was possible to catalogize plants in field trials, identify them over time, and use them for training and testing models. A convolutional neural network (CNN) supported by cataloged data was trained to perform classification of the disease presence in time-series, and performance was evaluated. As the last image processing step, maps were generated showing site-specific distribution of the diseased plants in the field. Generated maps can serve as a basis for application maps in practical cultivation or the evaluation of variety performance in variety trials. The presented methodological approach provides high precision and sensitivity in CLS detection and offers the potential to automate processes of CLS monitoring for different application areas.

Verification of Fungicide and Its Application Frequency for Management of Frog Eye Leaf Spot (Cercospora capcisi) on Hot Pepper Under Rain Fed Condition at Bako

Cercospora leaf spot is caused by Cercospora capcisi is an important disease which reduces the productivity of hot pepper (Capsicum spp.). Field experiment was conducted to evaluate different fungicides and its application frequencies against Cercospora leaf spot in order to select an important fungicides and its application frequency at Bako Agricultural Research Center. The experiment was laid out in randomized complete block design with three replication. Two different fungicides (Mancozeb 80WP and Trust-Cymocop 439.5WP) and four application frequencies (two, three, four and five) times with untreated control were used. Data on disease severity, area under disease progress curve, marketable yield and unmarketable yield of hot pepper were recorded. The result revealed that, both fungicides sprayed control Cercospora leaf spot which is significantly different from untreated check in disease severity, area under disease progress curve (AUDPC) and marketable yield. However, application frequencies of fungicides were not significantly different on disease severity, AUDPC and marketable yield of the plant. Application of Trust Cymocop 439.5WP reduces 26.67% relative yield loss of hot pepper over control check. An economic analysis was done for fungicides and shows feasibility of fungicide application for management of Cercospora leaf spot. Fungicide which has the highest Marginal Rate of Return was used for recommendation. Two times application of Trust-Cymocop 439.5WP was recommended to reduce disease severity and yield loss of the plant. Keywords: Cercospora leaf spot, frequency, hot pepper, and trust-Cymocop 439.5WP DOI : 10.7176/JBAH/9-20-01 Publication date :October 31 st 2019

Streptomyces sp. has different effectify to control two different pathogens

Soil microbes can act as biological agents to control pathogens, for example Streptomyces sp. which has known to produce secondary metabolites in the form of antibiotics that can inhibit the growth of several pathogenic fungi. If Streptomyces sp. sprayed to peanut leaves, it reduced the severity of disease of Gajah, Garuda, Kancil and Hypoma 1 varieties, which indicated by a high disease suppression with efficacy value more than 50%. Streptomyces sp. also inhibited 0.42% Fusarium oxysporum growth (moler pathogen) in vitro. However, in vivo assay, it did not suppress the development of moler disease which indicated by the high value of severity and infection rate, also low efficacy of disease suppression. So, this was an example that Streptomyces sp. was effective for controlling Cercospora leaf spot disease in peanut, but not effective to control moler disease in shallots.

Perspectives of chemical controlling Cercospora leaf spot (Cercospora beticola Sacc.) based on laboratory tests

Chwościk buraka wywoływany przez Cercospora beticola Sacc. należy do chorób buraka cukrowego (Beta vulgaris L.) o istotnym znaczeniu ekonomicznym. Celem badań było wytypowanie substancji czynnych, możliwych do stosowania w ochronie buraka cukrowego, które mogłyby zastąpić substancje wycofywane lub nieskuteczne ze względu na wzrost odporności patogena. W badaniach wykorzystano 14 izolatów C. beticola oraz substancje czynne: spiroksamina, boskalid, fluopyram, biksafen, fluoksapyroksad, krezoksym metylu, prochloraz, cyprodynil, pentiopyrad, izopyrazam. Analizy polegały na ocenie hamowania wzrostu poszczególnych izolatów przez wybrane substancje w stężeniach 1, 5 i 25 μg/ml. Spośród badanych substancji czynnych w stężeniach 1, 5 i 25 μg/ml wzrost kolonii C. beticola najlepiej hamowały prochloraz i krezoksym metylu. Cyprodynil i spiroksamina najskuteczniej ograniczały wzrost izolatów jedynie w najwyższym testowanym stężeniu – 25 μg/ml. Pozostałe badane substancje czynne słabo ograniczały wzrost kolonii. Wyniki badań sugerują, że chemiczna ochrona buraka cukrowego będzie dużym wyzwaniem dla plantatorów. The Cercospora leaf spot caused by Cercospora beticola Sacc. is one of the most important economic diseases of sugar beet (Beta vulgaris L.). The aim of the study was to select active substance that can be used in the protection of sugar beet, which could replace the withdrawn or ineffective substance due to the increased resistance of the pathogen. In the study used 14 isolates of C. beticola and active substances: spiroxamine, boscalid, fluopyram, bixafen, fluoxapyroxad, krezoxim-methyl, prochloraz, cyprodinil, pentiopyrad, isopyrazam. The analysis consisted of assessing the growth inhibition of individual isolates by selected substances in concentrations of 1, 5, and 25 μg/ml. Among the tested active substances at concentrations of 1, 5, and 25 μg/ml, the growth of C. beticola isolates was most effectively inhibited by prochloraz and kresoxim-methyl. Cyprodinil and spiroxamine most effectively inhibited the growth of isolates only in the highest tested concentration – 25 μg/ml. The remaining active substances tested poorly limiting the growth of the colony. Results suggest that chemical protection of sugar beet will be a great challenge for growers.

Optimizing Cercospora Leaf Spot Control in Table Beet Using Action Thresholds and Disease Forecasting.

Cercospora leaf spot (CLS), caused by the fungus Cercospora beticola, is the dominant foliar disease affecting table-beet production in New York. CLS epidemics occur annually and, if uncontrolled, will rapidly lead to defoliation. In broad-acre production, season-long maintenance of healthy leaves is important to facilitate harvest by top-pulling. Fungicides are the dominant means of CLS control and applications are initiated at an action threshold of 1 CLS lesion/leaf. Regular fungicide application occurs thereafter without regard for scheduling based on weather-based risk. The current action threshold was evaluated with selected fungicides in two replicated field trials. Copper oxychloride + copper hydroxide and propiconazole significantly improved CLS control if initiated prior to infection. Pydiflumetofen + difenoconazole significantly reduced area under the disease progress stairs compared with other fungicides tested and was most efficacious when applications began at 1 CLS lesion/leaf. Six replicated field trials also evaluated the utility of scheduling fungicides on weather-based risk rather than a calendar approach. Two risk thresholds (moderate and high) integrating the accumulation of daily infection values based on temperature and relative humidity from a forecaster for CLS in sugar beet were evaluated. Applications of pydiflumetofen + difenoconazole were reduced from three to two by using the forecaster at either risk threshold compared with calendar applications without affecting CLS control. For propiconazole, the moderate risk threshold provided CLS control equivalent to calendar applications and saved one spray per season. Thus, there was substantial scope to reduce spray frequency by scheduling based on weather-based risk rather than calendar applications. The optimal risk thresholds for pydiflumetofen + difenoconazole and propiconazole were high and moderate, respectively. In these trials, periods of high risk occurred less frequently than moderate risk, increasing the reapplication intervals and, hence, represented a less conservative approach to disease management.

First report of QoI resistance in Cercospora beticola in sugar beet in Japan

QoI fungicides have been an important tool for controlling Cercospora leaf spot (CLS) of sugar beet in Japan. In 2013, CLS control failed at an experimental plot in Okhotsk subprefecture of Hokkaido after the application of trifloxystrobin. Among isolates of Cercospora beticola, the causal agent of CLS, collected from this field were the first QoI-resistant strains found in Japan based on bioassays, culture assays and detection of G143A mutation in the cytochrome b gene. Additionally, our surveys of commercial fields in 2014–2015 revealed the widespread QoI resistance of C. beticola in Hokkaido.

Verification of Fungicide and Its Application Frequency for Management of Frog eye Leaf Spot (Cercospora capcisi) on Hot Pepper Under Rain Fed Condition at Bako

Cercospora leaf spot is caused by Cercospora capcisi is an important disease which reduces the productivity of hot pepper (Capsicum spp.). Field experiment was conducted to evaluate different fungicides and its application frequencies against Cercospora leaf spot in order to select an important fungicides and its application frequency at Bako Agricultural Research Center. The experiment was laid out in randomized complete block design with three replication. Two different fungicides (Mancozeb 80WP and Trust-Cymocop 439.5WP) and four application frequencies (two, three, four and five) times with untreated control were used. Data on disease severity, area under disease progress curve, marketable yield and unmarketable yield of hot pepper were recorded. The result revealed that, both fungicides sprayed control Cercospora leaf spot which is significantly different from untreated check in disease severity, area under disease progress curve (AUDPC) and marketable yield. However, application frequencies of fungicides were not significantly different on disease severity, AUDPC and marketable yield of the plant. Application of Trust Cymocop 439.5WP reduces 26.67% relative yield loss of hot pepper over control check. An economic analysis was done for fungicides and shows feasibility of fungicide application for management of Cercospora leaf spot. Fungicide which has the highest Marginal Rate of Return was used for recommendation. Two times application of Trust-Cymocop 439.5WP was recommended to reduce disease severity and yield loss of the plant. Keywords: Cercospora leaf spot, frequency, hot pepper, and trust-Cymocop 439.5WP DOI : 10.7176/JBAH/9-20-01 Publication date :October 31 st 2019