Timing Of Fungicide Applications Research Articles

A framework for evaluating the value of agricultural pest management decision support systems

AbstractDisease management decision support systems (DSS) are typically prediction algorithms that help farmers assess the risk of an epidemic, to guide whether, and to what extent, fungicide treatment is needed. However, there is frequently little information presented to quantify the value of using the DSS, i.e. the likely increased profit or reduced impact to the environment, and the risks of failing to control the pest. Validation of DSS is often limited to a small number of sites and seasons, as extensive field testing is prohibitively expensive. It would therefore be beneficial to have a method to estimate the value of a DSS using existing data sets gathered for other purposes.We present a theoretical framework for evaluating the value of DSS, and then describe how this can be applied in practice using four case studies of contrasting DSS under different data constraints. The four case studies include DSS that guide (i) the total dose of pesticide applied; (ii) the number of sprays required; (iii) the timing of the first fungicide application in a spray programme; and (iv) infection risk alerts. We demonstrate how our theoretical framework can be used to evaluate DSS, using existing field and literature data to infer the benefits and risks associated with their use. The limitations of using existing data are explored.

Utilizing Disease Prediction Models to Time Fungicide Applications for Controlling Ripe Rot, Caused by Colletotrichum spp., in Maryland Vineyards.

Two previously published ripe rot prediction models, DF2-NN and GH2-DT, were evaluated for fungicide application timing efficacy in Maryland vineyards. Both models utilize leaf wetness duration (LWD), temperature, and grape cluster phenological stages as model parameters. These three parameters were tracked throughout the 2021 to 2023 seasons in three vineyards. The fungicide efficacy trials started at the veraison phenological stage and included a nontreated control, a 12-day interval treatment, and two model-triggered treatments when risk predicted by the models crossed a threshold. The severity of ripe rot on the clusters in each treatment was assessed when the fruit were mature. Ripe rot severity in the nontreated controls was higher during seasons with more LWD and more precipitation. Days in which the models were triggered by the environmental conditions primarily coincided with precipitation events and lengthy LWDs. The model-triggered treatments never had significantly higher ripe rot severity than the 12-day interval treatment but had significantly lower severities than the nontreated control in most trials which had high ripe rot pressure. Furthermore, the model-triggered treatments resulted in fewer fungicide applications than the 12-day interval treatment on average. The DF2-NN model appeared to be more accurate and useful for ripe rot prediction and treatment than the GH2-DT model because it triggered fewer fungicide applications while reducing ripe rot. This model may be useful for improving or maintaining ripe rot control with fewer fungicide inputs, which may be beneficial for the environment and the reduction of fungicide resistance selection.

Effect of the Timing of Fungicide Application on Yield and Quality Parameters of Wheat Infected with Fusarium Crown Rot Disease

Crown rot caused by Fusarium culmorum (FCR) is a common and important pathogen affecting the cereal industry through grain yield and quality losses. In this study, the effects of epoxiconazole plus prochloraz application and several other applications on disease severity and grain quality parameters including thousand-grain weight (TGW), grain yield (GY), protein (GP), Zeleny sedimentation (ZS), wet gluten (WG) and Grain index (GI), were assessed. The efficacy of epoxiconazole plus prochloraz, were determined in the T1 (ZGS25), T2 (ZGS34), and T3 (ZGS45) growth stages of winter wheat with seven alternative spray programs. These programs were based on (i) the application (SF) of seed fungicide to infected seeds (ii) control without fungicide (non-SF) and (iii) three different growth stages of wheat. The interaction between seed fungicide applied and fungicide application time was significant (P≤0.01) for DS, ZS, and WG. The effectiveness regarding the disease severity, TGW, and GY of epoxiconazole plus prochloraz in relation to FCR wheat showed significant (P≤0.01) changes depending on the application time. The disease severity resulted in lower T1-T2 (9.66%) and T1-T2-T3 (9.91%) stages than the other stages. The highest yields were obtained when the fungicide was applied twice at the T1-T2 stages. DS/TGW and DS/GY were negatively correlated and TGW/GY was positively correlated in SF.

Ramularia leaf spot management alternatives in barley optimizing the use of fungicides for its control: Doctoral thesis abstract

Ramularia collo-cygni (Rcc) is the causal agent of Ramularia leaf spot (RLS). The main management tool is the use of foliar fungicides, the impact of which on cereal safety is unknown. Therefore, the aim of this thesis was to optimise the management of ramulariosis in barley and to minimise fungicide residues in grain. The specific objectives were: (i) to validate a method for the detection and quantification of Rcc in seeds and seedlings by real-time PCR (qPCR), (ii) to determine the importance of seeds as a source of in-crop Rcc inoculum in production systems in Uruguay, (iii) to develop a methodology to determine the fungicides proposed for the control of rhamulariosis in barley grain, and (iv) to identify foliar fungicide application strategies to minimise rhamulariosis and ensure fungicide safety in the grain produced. The qPCR technique was validated for the detection and quantification of Rcc in barley seeds and seedlings. This qPCR technique will allow the optimal timing of foliar fungicide applications to be determined by detecting Rcc in seedlings. The amount of Rcc DNA in commercial lots varied within and between growing seasons, highlighting the importance of this tool for quantifying fungal load prior to sowing. A method was developed to quantify fungicide residues in barley grain. This method was extended to quantify fungicides in wheat grain and mycotoxins produced by the Fusarium species. This analytical methodology could be useful for monitoring compliance with maximum residue limits (MRLs) in winter cereal production. Foliar fungicide strategies for the control of RLS were evaluated in five trials over three consecutive years. The efficacy of fungicides in controlling the disease and ensuring grain safety was tested with fungicide residue levels below MRLs. The results contribute to the management of RLS with tools to reduce fungicide use and ensure barley grain safety.

Postinfection Application of Fenhexamid at Lower Doses in Conjunction with Captan Slowed Fungicide Resistance Selection in Botrytis cinerea on Detached Grape Berries.

Fungicide resistance is a limiting factor in sustainable crop production. General resistance management strategies such as rotation and mixtures of fungicides with different modes of action have been proven to be effective in many studies, but guidance on fungicide dose or application timing for resistance management remains unclear or debatable. In this study, Botrytis cinerea and the high-risk fungicide fenhexamid were used to determine the effects of fungicide dose, mixing partner, and application timing on resistance selection across varied frequencies of resistance via detached fruit assays. The results were largely consistent with the recent modeling studies that favored the use of the lowest effective fungicide dose for improved resistance management. In addition, even 10% resistant B. cinerea in the population led to about a 40% reduction of fenhexamid efficacy. Overall, our findings show that application of doses less than the fungicide label dose, mixture with the low-risk fungicide captan, and application postinfection seem to be the most effective management strategies in our controlled experimental settings. This somewhat contradicts the previous assumption that preventative sprays help resistance management.

Investigations into Economic Returns Resulting from Foliar Fungicides and Application Timing on Management of Tar Spot in Indiana Hybrid Corn.

Tar spot, caused by Phyllachora maydis, is the most significant yield-limiting disease of corn (Zea mays L.) in Indiana. Currently, fungicides are an effective management tool for this disease, and partial returns from their use under different disease severity conditions has not previously been studied. Between 2019 and 2021, two separate field experiments were conducted in each year in Indiana to assess the efficacy of nine foliar fungicide products and nine fungicide application timings based on corn growth stages on tar spot symptoms and stromata, canopy greenness, yield, and influence on partial returns. All fungicides evaluated significantly suppressed tar spot development in the canopy and increased canopy greenness over the nontreated control. Additionally, applications of mefentrifluconazole + pyraclostrobin, metconazole + pyraclostrobin, cyproconazole + picoxystrobin at tassel, and propiconazole + benzovindiflupyr + azoxystrobin between the tassel and dough growth stages were the most effective at significantly reducing disease severity, increasing canopy greenness, protecting yield, and offered the greatest partial return. Fungicide products varied in their ability to protect yield under low and high disease severity conditions relative to the nontreated control. Consistently, positive yield increases were observed when disease severity was high, which translated to greater profitability relative to low severity conditions. On average, the yield increases across foliar fungicide products and timed application treatments were 544.6 and 1,020.7 kg/ha greater, and partial returns using a grain value of $0.17/kg were $92.6/ha and $173.5/ha greater, respectively, when high severity conditions occurred. This research demonstrates that foliar fungicides and appropriately timed fungicide applications can profitably be used to manage tar spot in Indiana under high disease severity conditions.

Effect of Fungicide and Timing of Application on Management of Phoma Black Stem of Cultivated Sunflowers in the United States.

Phoma black stem (PBS), caused by Phoma macdonaldii Boerema (teleomorph Leptosphaeria lindquistii Frezzi), is the most common stem disease of sunflower (Helianthus annuus L.) in the northern Great Plains region of the United States. However, the impact of PBS on sunflower yield in the United States is unclear, and a near complete absence of information on the impact of fungicides on disease management exists. The objectives of this study were to determine the impact of PBS on sunflower yield, the efficacy of available fungicides, the optimal fungicide application timing, and the economic viability of fungicides as a management tool. Fungicide timing efficacy was evaluated by applying single and/or sequential applications of pyraclostrobin fungicide at three sunflower growth stages in 10 field trials between 2017 and 2019. Efficacy of 10 fungicides from the Fungicide Resistance Action Committee (FRAC) groups 3, 7, and 11 were evaluated in four field trials between 2018 and 2019. The impact of treatments on PBS were evaluated by determination of incidence, severity, maximum lesion height, disease severity index (DSI), and harvested yield. Nine of the 10 fungicides evaluated and all fungicide timings that included an early bud application resulted in disease reductions when compared with the nontreated controls. The DSI was negatively correlated to sunflower yield in high-yield environments (P = 0.0004; R2 = 0.3425) but not in low- or moderate-yield environments. Although FRAC 7 fungicides were generally most efficacious, the sufficient efficacy and lower cost of FRAC 11 fungicides make them more economically viable in high-yielding environments at current market conditions.

Influence of fungicide selection and application timing on take‐all root rot management under field and greenhouse conditions

AbstractTake‐all root rot (TARR) is a detrimental disease of ultradwarf bermudagrass (Cynodon dactylon × Cynodon transvaalensis; UDB) putting greens frequently diagnosed where warm‐season grasses are grown. Since this disease is largely aggregated and variable under field conditions, field research is difficult and often yields inconsistent results. Multiple pathogens have only recently been associated with this disease, so practical management solutions such as fungicide efficacy and fungicide application timing have not been thoroughly investigated. Therefore, the objectives of this research were to determine the influence of fungicide selection and fungicide application timing on take‐all root rot management under field and greenhouse conditions. In general, fungicides from the quinone outside inhibitor and/or demethylation inhibitor chemical classes provided the greatest reduction in take‐all root rot severity. Fungicide applications that were made when soil temperatures were between 77–86°F provided the greatest disease suppression. The in vivo greenhouse method developed in this research proved to be an efficient and consistent method to evaluate management practices such as fungicide efficacy on take‐all root rot. This research improves our understanding of fungicide efficacy and fungicide application timing for take‐all root rot management on ultradwarf bermudagrass.

Evaluation of foliar fungicides for frogeye leaf spot control and yield protection in soybean in Arkansas

The efficacy of fifteen foliar fungicides to control frogeye leaf spot (caused by Cercospora sojina K. Hara) and protect soybean grain yield was investigated over three years (2014–2016) in two field experiments. Experiments were divided into two fungicide groups: premix fungicides, which included combinations of quinone outside inhibitors (QoI), demethylation inhibitors (DMI), succinate dehydrogenase inhibitors (SDHI), or methyl benzimidazole carbamates (MBC), and solo fungicides, all DMI fungicides. Fungicides were applied once at the full pod (R4) in 2014 and 2015 and at the beginning seed (R5) growth stage in 2016. A very susceptible frogeye leaf spot cultivar, Armor 48R40, was used. Frogeye leaf spot severity at fungicide application timing average 1.0, 0.5, and 8.0% in 2014, 2015, and 2016, respectively. Final disease severity averaged 21.7, 14.5, and 15.1% in 2014, 2015, and 2016, respectively on the non-treated control. Azoxystrobin provided no disease control, suggesting the presence of QoI-resistant C. sojina. Three fungicides: azoxystrobin + difenoconazole, flutriafol, and thiophanate-methyl + tebuconazole applied at R4 provided effective disease control compared to the non-treated control. Fungicides applied at R5 provided no disease control. No fungicide provided significant grain yield protection in either experiment. Overall, the average yield protection trend by fungicides applied at R4 and R5 was 6.8 and 3.0%, respectively compared to the non-treated control. These data suggest that although foliar fungicides can provide effective frogeye leaf spot control, yield protection may be limited when applied at the R4 growth stage, particularly when disease severity exceeds 0.5% on a very susceptible soybean cultivar.

Efficacy of Fungicides and Optimization of Application Timing for the Management of Sclerotinia Rot of Mustard Caused by Sclerotinia sclerotiorum

Sclerotinia rot of rapeseed-mustard caused by Sclerotinia sclerotiorum (Lib.) de Bary has gained significant importance in Rajasthan, Punjab, Haryana and other major rapeseed-mustard growing areas of India in recent years. Fungicides are extensively used for the control of this disease since no commercial cultivars have been found resistant to S. sclerotiorum and other management practices have not been found very effective. Therefore, the present investigations were carried out to evaluate the efficacy of fungicides and to optimize application timing for the effective management of Sclerotinia rot of mustard. Among 08 fungicides tested in vitro, Carbendazim 50% WP and Propiconazole 25% EC were found most efficient at completely inhibiting the mycelial growth of S. sclerotiorum at all the concentrations tested. In an in vitro sclerotial (carpogenic) germination test, Carbendazim 50% WP completely inhibited sclerotial germination at 100, 250 and 500 ppm. Under artificial inoculation conditions in the field, Propiconazole 25% EC @0.1% was found most effective in reducing Sclerotinia rot incidence (87.04%) followed by Carbendazim 50% WP (83.33%) and Tebuconazole 25.9% EC (75.93%). Similarly, under natural epiphytotic conditions in field, Propiconazole 25% EC @0.1% was found best in disease incidence reduction (85.34%) with increased yield (40.00%) followed by Carbendazim 50% WP (81.25% & 38.09%) and Tebuconazole 25.9% EC (79.72% & 35.24%) in disease reduction and increased yield respectively. Differential time and frequency of application of Propiconazole @0.1% were tested and found that 02 applications i.e. 1st spray at 4.2 flowering stage i.e. 30% bloom stage (70 DAS) and 2nd spray at 4.3 flowering stage i.e. 50% bloom stage (85 DAS) was equally effective in disease incidence reduction (82.70%) with 03 applications i.e. 1st spray at 4.1 flowering stage i.e. 10-20% bloom stage (55 DAS), 2nd at 4.2 flowering stage (70 DAS) and 3rd at 4.3 flowering stage (85 DAS). Therefore, the optimization of fungicide application timing and the number of sprays with adequate concentrations is advisable to increase the cost-effectiveness of crop production while controlling the disease.

Integrated approach for the management of common bean rust (Uromyces appendiculatus) under field conditions

A field experiment was conducted to test the efficacy of different management practices and fungicide application timings for common bean rust management in Chitwan, Nepal. It was conducted in a randomized complete block design (RCBD) with two factors: management practices (Azoxystrobin, Trichoderma viride, maize intercropping + Trichoderma viride, Neem + Garlic extracts, and inoculated and untreated controls) and fungicide application timings (8 days after inoculation and 3 days after inoculation), each with three replications. The minimum disease severity was found with azoxystrobin, which was at par with neem + garlic extract and maize intercropping + Trichoderma at 50 days after inoculation (DAI). The maximum number of rust pustules per cm2 was observed in the control plots (7.56), followed by Trichoderma (4.79) at 50 DAI. The maximum necrotic colonies (%) were observed with the control (36.88%), followed by Trichoderma (25.15%), while the effects of other treatments were at par at 40 DAI. Maize intercropping with Trichoderma resulted in a maximum plant height (201.56 cm), which was at par with azoxystrobin (197.81 cm). The plants treated with azoxystrobin showed maximum green pod yield at one picking (2411.35 g) which was at par with maize intercropping + Trichoderma and neem + garlic extracts. Rust was controlled more effectively when the fungicides were sprayed at 4 DAI than 8 DAI. The maximum disease control was observed with Azoxystrobin; however, as other treatments also had comparable effects, an integrated approach could be adopted for the sustainable management of common bean rust.

Timing of oomycete-specific fungicide application impacts the efficacy against fruit rot disease in arecanut.

Fungicidal application has been the common and prime option to combat fruit rot disease (FRD) of arecanut (Areca catechu L.) under field conditions. However, the existence of virulent pathotypes, rapid spreading ability, and improper time of fungicide application has become a serious challenge. In the present investigation, we assessed the efficacy of oomycete-specific fungicides under two approaches: (i) three fixed timings of fungicidal applications, i.e., pre-, mid-, and post-monsoon periods (EXPT1), and (ii) predefined different fruit stages, i.e., button, marble, and premature stages (EXPT2). Fungicidal efficacy in managing FRD was determined from evaluations of FRD severity, FRD incidence, and cumulative fallen nut rate (CFNR) by employing generalized linear mixed models (GLMMs). In EXPT1, all the tested fungicides reduced FRD disease levels by >65% when applied at pre- or mid-monsoon compared with untreated control, with statistical differences among fungicides and timings of application relative to infection. In EXPT2, the efficacy of fungicides was comparatively reduced when applied at predefined fruit/nut stages, with statistically non-significant differences among tested fungicides and fruit stages. A comprehensive analysis of both experiments recommends that the fungicidal application can be performed before the onset of monsoon for effective management of arecanut FRD. In conclusion, the timing of fungicidal application based on the monsoon period provides better control of FRD of arecanut than an application based on the developmental stages of fruit under field conditions.

English

Narrow brown leaf spot disease of rice caused by fungus Cercospora oryzae Miyake emerged as potential threat to rice crop in previous few years worldwide and can cause more than 40% yield loss. The disease symptoms were noted on various commercially important rice varieties in the rice growing districts of Punjab province of Pakistan. Hence, the studies were planned to assess the effects of Propiconazole fungicide application timings and different rice varieties on the severity of narrow brown leaf spot (NBLS) disease of rice to develop an accurate management strategy for the disease. The Propiconazole fungicide was tested at three various growth phases (early booting, late booting, and soft dough) of four rice varieties against the percent severity of the NBLS disease The experiments were designed under strip-plot (crisscross) design with four replications at research area of Plant Pathology Department, University of Agriculture Faisalabad. Analysis of variance has demonstrated that the main and interactive effects of fungicide applications and rice varieties were found significant. The main effects of years were found non-significant but their interactions with fungicide application timings and rice varieties were significant. Fungicide applications at soft dough and late booting phases of rice variety B-515 were found least effective to reduce the disease severity, respectively. Fungicide application at early booting of rice variety PK-1121 was found most effective by reducing the maximum percent diseases severity (47.25%) compared to control. It is concluded that, to minimize hazardous effects of chemicals on the environment by practicing multiple sprays at inappropriate growth phases of rice crop, fungicides must be applied during the early and late booting phases of rice varieties on mildly resistance, susceptible and highly susceptible rice varieties to reduce NBLS disease severity and to enhance the rice production and quality

Application of Hydrothermal Time Models to Predict Sclerotial Germination of Athelia rolfsii.

Athelia rolfsii, causal agent of "southern blight" disease, is a soilborne fungal pathogen with a wide host range of more than 500 species. This study's objectives were to (i) quantify the effects of two environmental factors, temperature and soil moisture, on germination of A. rolfsii inoculum (sclerotia), which is a critical event for the onset of disease epidemics and (ii) predict the timing of sclerotial germination by applying population-based threshold-type hydrothermal time (HTT) models. We conducted in vitro germination experiments with three isolates of A. rolfsii isolated from peanuts, which were tested at five temperatures (T), ranging from 17 to 40°C, four matric potentials (Ψm) between -0.12 and -1.57 MPa, and two soil types (fine sand and loamy fine sand), using a factorial design. When Ψm was maintained between -0.12 and -0.53 MPa, T from 22 to 34°C was found to be conducive to sclerotial germination (>50%). The HTT models were fitted for a range of T (22 to 34°C) and Ψm (-0.12 to -1.57 MPa) that accounted for 84% or more of variation in the timing of sclerotial germination. The estimated base T ranged between 0 and 4.5°C and the estimated base Ψm between -2.96 and -1.52 MPa. The results suggest that the HTT modeling approach is a suitable means of predicting the timing of A. rolfsii sclerotial germination. This HTT methodology can potentially be tested to fine-tune fungicide application timing and in-season A. rolfsii management strategies. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.

Optimal timing of fungicide application to manage Fusarium head blight in winter barley.

Fusarium head blight is among the chief threats to profitable barley production, and fungicide applications are one of two main strategies for reducing FHB damage to barley crops. However, there is very little published information on optimal timing of such applications. A four-year field study was conducted with winter barley in Raleigh, North Carolina, to compare three timings for fungicide application: 50% spike emergence (Zadoks growth stage or GS 55), 100% spike emergence (GS 59), and six days after GS 59. Three winter barley cultivars with varying levels of FHB resistance were grown for four successive years (2018-2021) in a split-plot experiment and inoculated each spring with Fusarium-infected corn spawn. Three fungicides were compared: propiconazole + pydiflumetofen (Miravis Ace), prothioconazole + tebuconazole (Prosaro), and metconazole (Caramba). Correlations among visual symptoms and assays of harvested grain were modest, and were weakened by fungicide applications. Across years and cultivars, deoxynivalenol (DON) and percent Fusarium-infected kernels were most reduced relative to the nontreated control by fungicide applications at the latest timing (GS 59 + 6 d). The early (GS 55) timing resulted in DON not significantly different from the nontreated control. Based on these results, it is recommended that to minimize damage from FHB, fungicide should be applied to winter barley several days after GS 59 (100% spike emergence), and not before GS 59.

Refining Management of Apple Powdery Mildew in New York State with Weather-Based Fungicide Application Timing Programs.

In the absence of durable host resistance among commercial cultivars, chemical management continues to be an essential component of disease control in apple production. Apple powdery mildew, caused by the ascomycete Podosphaera leucotricha, is largely managed with regular fungicide applications from the host phenological stages of tight cluster to terminal bud growth set, with applications typically being made in a prophylactic manner irrespective of existing disease pressure. Here we evaluated two management programs that aligned fungicide applications to specific weather thresholds conducive to powdery mildew development using a rotation of single-site fungicides and sulfur. In three separate orchards among four cultivars, we compared powdery mildew disease progression over the growing season for each of the weather factor-based programs and a typical calendar-based application program. In each year of the trial, we found that management programs with weather-based fungicide applications provided levels of disease control similar to the calendar program but required 50 to 83.3% fewer mildew-specific fungicide applications throughout the growing season. Our results provide a framework with which to evaluate future weather-based management programs for apple powdery mildew management. This knowledge could be implemented in the creation of a powdery mildew disease management decision support system to better inform and aid fungicide application programs for continued sustainable apple production in the northeast United States.

Evaluation of a Model for Predicting Onset of Septoria nodorum blotch in Winter Wheat.

Prediction models that aid growers in making decisions on fungicide application are important components in the integrated management programs for several foliar diseases of wheat. The risk of Septoria nodorum blotch (caused by Parastagonospora nodorum) onset in winter wheat is influenced by location, amount of wheat residue in the field and cumulative daily infection values 2 weeks prior to day of year (DOY) 102. A model previously developed based on these predictor variables was evaluated to assess its ability to predict disease onset under field conditions. An experiment was conducted at three locations in North Carolina in 2018, 2019 and 2020, where plots were either treated with >20% wheat residue or received no residue treatment. Plots were monitored for disease symptoms, and disease onset was defined to have occurred when mean disease incidence in a plot was 50%. Of the 298 disease cases recorded, disease onset occurred early (i.e., prior to DOY 102) in 257 cases, while onset was late (i.e., on or after DOY 102) in 41 cases. Model accuracy based on correct classification ranged from 0.67 to 0.95, with a mean of 0.87 across study period. Similarly, sensitivity rates of the model ranged from 0.88 to 1.0 with a mean of 0.98 across all years. However, the model had a low specificity, with a mean rate of 0.15 across the study period. Overall, there was no significant difference in the frequency of observed and predicted cases in the study (χ2 = 0.50, P = 0.7788, df = 2). Time to disease onset was significantly correlated with grain yield and explained 26% of variation in yield (P < 0.0001). Results indicated that the disease onset model performs well in predicting early disease onset but requires further evaluation and improvement particularly in the Piedmont, where it over-predicted early onset in two successive years.

Evaluation of models based on a generic infection model for controlling early blight in potatoes

TOMCAST and two models (risk hours and critical days) based on a generic infection model (GI model) were evaluated for the timing of fungicide application to control early blight (Alternaria solani) in field experiments. A five-year experiment was conducted at AU Flakkebjerg with the starch potato cultivars Kardal (2016 & 2017), Avarna (2019 & 2020), and Allstar (2021). Barley kernels infested with Alternaria solani were used to inoculate the potatoes. The disease was assessed weekly, starting from the onset of the first symptoms. The impact of disease development was quantified using the area under the disease progress curve (AUDPC), the relative area under the disease progress curve (rAUDPC) as well as starch yield. An economic analysis was done to determine the profitability of the models. Fungicide application significantly suppressed early blight development in comparison to untreated plots. The fungicide-treated plants gave higher yields (10–35%) than the untreated plants. Nevertheless, the models reduced fungicide use by an average of 37–49%, without any yield or economic penalty. Most fungicides were saved with the TOMCAST model, but disease control and yield were generally lower than in plots treated according to the GI-based models. Overall, our study emphasizes the economic importance of early blight and the necessity of applying fungicides to control it. We also show the possibility of significantly reducing fungicide use by using decision support systems. For the first time, we demonstrate the feasibility of using GI models to time fungicide application to control early blight.

Optimal timing of fungicide applications on maize, soybean, and beans based on calendar and agrometeorological data

ABSTRACT The objective of this study was to determine the best method to establish optimal timing of fungicide applications on corn (Zea mays), soybean (Glycine max), and bean plants (Phaseolus vulgaris), by comparing results based on the calendar versus agrometeorological data. The experimental design was arranged in randomised blocks with three treatments and eight repetitions. Treatments consisted of control (without application of fungicides), application of fungicides based on the calendar (after establishing the need for chemical control, sprays occurring at intervals of 15 days), or by indication of the AgroDetecta™ programme (based on agrometeorological data). The variables evaluated were: disease incidence and severity, area under the disease progress curve (AUDPC), income components, and economic return. Among the integrated disease management tools investigated, it was concluded that chemical control improves crop health and yield for corn, soybean, and bean plants, especially when timing of treatment application is based on the calendar. The programme AgroDetecta™ showed promise as a decision-making tool for the best timing to spray, but requires adjustments for commercial use.

Timing of fungicide application against Cercospora leaf spot disease based on aerial spore dispersal of Cercospora beticola in sugar beet

Cercospora leaf spot is an important foliar disease in sugar beet caused by Cercospora beticola. Tolerant cultivars are available, but application of fungicides is still mandatory for disease control. The timing of the fungicide application is crucial as it determines the outcome of disease epidemiology. A disease incidence (DI) of 5% is widely used as a threshold for fungicide application. Recently a method was developed that allows the quantification of aerial spore dispersal of C. beticola for measuring spore flight intensity. It was aimed in this study to prove if fungicide application based on spore flight might improve disease control compared to DI. In a field trial with artificial inoculation, a single fungicide application at the onset of spore flight slowed down disease development as indicated by reduced disease severity and aerial spore dispersal. However, it did not provide sufficient control in terms of sugar yield. Only a second fungicide application based on spore flight detection achieved an efficacy similar to two fungicide applications based on DI. In contrast, a single fungicide application based either on spore flight or DI was sufficient in two on-farm trials under natural infection with moderate disease pressure. This highlights the necessity of an early timed first fungicide application followed by a second application under high disease pressure induced by artificial inoculation. Although fungicide application based on spore flight achieved sufficient control success in on-farm trials, it seems not to improve disease control compared to the usage of DI as threshold.