Number Of Fungicide Applications Research Articles

Management of chickpea Ascochyta blight using fungicides and cultivar resistance improves grain yield, quality, and grower profitability.

International production of chickpea is under constant threat from the fungal disease Ascochyta blight (Ascochyta rabiei). In Australia, there is limited cultivar resistance, and disease management is reliant on foliar applied fungicides. Several recently registered fungicides in Australia that combine active ingredients with different modes of actions, have been shown to have curative properties. In this study, in the presence of Ascochyta blight, disease severity, grain yield and quality were measured and the subsequent gross margin for growers calculated in seven field experiments conducted in Victoria (Australia) across three seasons. These experiments investigated the effects of: two cultivars with differing disease resistance (PBA Striker and Genesis 090), and several fungicide strategies for the control of Ascochyta blight. Fungicides that combine different modes of actions (Tebuconazole + Azoxystrobin, Bixafen + Prothioconazole and Fludioxonil + Pydiflumetofen) were applied before a rainfall event (preventative) or after the first signs of disease (post-infection). Older, single active fungicides compared included Captan, Chlorothalonil, and Propiconazole, all applied preventatively. Maximum disease severities ranged from 87% at Horsham and 94% at Curyo across three seasons with Nhill recording 87% during 2020. Demonstrating the benefit of cultivar resistance for Ascochyta blight management, grain yield losses were substantially lower in the partially resistant cultivar Genesis 090 (64%) compared to the susceptible cultivar PBA Striker (96%), at Curyo in 2020. The preventative fungicide strategies reduced grain yield losses from 96 and 64% to 51 and 15% for PBA Striker and Genesis 090, respectively, demonstrating the benefit of fungicides in Ascochyta blight management. Across seasons and environments, a comparison between fungicides applied preventatively or post-infection highlighted both were both profitable ($23-$1,095/ha), except when dry conditions limited grain yield to less than 0.6 t/ha. The post infection timing had greater yield losses in sites/seasons with higher rainfall, but with dual active ingredient fungicides and partially resistant cultivars this timing could allow a reduction in the number of fungicide applications, thus improving profitability. These experiments highlighted the importance of controlling Ascochyta blight through cultivar resistance and fungicides to improve grain yields, grain quality, and grower profitability.

Efficacy of Fungicides Used to Manage Downy Mildew in Cucumber Assessed with Multiple Meta-Analysis Techniques.

A nationwide, quantitative synthesis of fungicide efficacy data on management of cucurbit downy mildew (CDM) caused by Pseudoperonospora cubensis is needed to broadly evaluate fungicide performance. Three-level meta-analysis, three-level meta-regression, and network meta-analyses were conducted on data from 46 cucumber (Cucumis sativus) CDM fungicide efficacy studies conducted in the eastern United States retrieved from Plant Disease Management Reports published between 2009 and 2018. Three response variables were examined in each analysis: disease severity, marketable yield, and total yield, from which percent disease control and percent yield return compared with nontreated controls was calculated. Moderator variables used in the three-level meta-analysis or three-level meta-regression included year, disease pressure, number of fungicide applications, and slicing or pickling cucumbers. In the network meta-analysis, fungicides were grouped by common combinations of Fungicide Resistance Action Committee Codes and modes of action. Overall, fungicides significantly (P < 0.001) reduced disease severity and increased marketable and total yields, resulting in a mean 54.0% disease control and 61.9% marketable and 73.3% total yield return. Subgroup differences were observed for several fungicide applications, control plot disease severity, and cucumber type for marketable yield. Based on the meta-regression analysis for disease severity by year, fungicide efficacy has been decreasing from 2009 to 2018, potentially indicating broad development of fungicide resistance over time. Treatments containing quinone inside inhibitors, pyridinylmethyl-benzamides, and protectants and treatments containing oxysterol binding protein inhibitors and protectants most effectively reduced disease severity. The most effective fungicide combinations for disease control did not always result in the highest yield return.

Winter Wheat Variety Response to Timing and Number of Fungicide Applications During the 2020–2021 Growing Season in Kansas

The objective of this project was to evaluate the yield response of different winter wheat varieties to different fungicide management treatments during the 2020–2021 growing season in Kansas. Fourteen varieties were evaluated under four fungicide treatments (no fungicide, application either at jointing, heading, or at both stages) in four locations across Kansas in a split-plot design. Disease incidence was assessed approximately 20 d after each fungicide application. Septoria blotch and tan spot were the most prevalent early-season diseases at the studied fields, while stripe rust, leaf rust, and tan spot prevailed later in the season. While varieties responded differently to fungicide management and there was a range in yield response across locations, there was an overall yield increase of 4.2 bushels per acre resulting from the jointing fungicide application; 10.3 bu/a from the heading fungicide; and 9.9 bu/a from the combination of both applications. Although there were some similarities, the ranking of the highest yielding varieties was not uniform across locations. While different reactions occurred regarding the response of the varieties to fungicide management, overall susceptible varieties had a greater response to fungicide management compared to varieties with intermediate or high levels of genetic resistance. Our preliminary data suggest that the application of fungicide to winter wheat in Kansas might be advantageous, but the degree of this benefit will depend upon the environment, variety, and level of disease incidence.

Stemphylium Leaf Blight: A Re-Emerging Threat to Onion Production in Eastern North America.

Stemphylium leaf blight (SLB), caused by Stemphylium vesicarium, is a foliar disease of onion worldwide, and has recently become an important disease in the northeastern United States and Ontario, Canada. The symptoms begin as small, tan to brown lesions on the leaves that can progress to defoliate plants. Crop loss occurs through reduced photosynthetic area, resulting in smaller, lower-quality bulbs. Leaf necrosis caused by SLB also can compromise bulb storage, as green leaves are required for the uptake of sprout inhibitors applied prior to harvest. The pathogen can overwinter on infested onion residue and infected volunteer plants. Asymptomatic weedy hosts near onion fields may also be a source of inoculum. Production of ascospores of the teleomorph (Pleospora allii) peaks in early spring in northeastern North America, often before the crop is planted, and declines rapidly as daily mean air temperatures rise. Conidia are usually present throughout the growing season. Application of fungicides is a standard practice for management of the complex of fungi that can cause foliar diseases of onion in this region. Recent assessments have shown that populations of S. vesicarium in New York and Ontario are resistant to at least three single-site mode-of-action fungicides. Three disease prediction systems have been developed and evaluated that may enable growers to reduce the frequency and/or number of fungicide applications, but the loss of efficacious fungicides due to resistance development within S. vesicarium populations threatens sustainability. The lack of commercially acceptable onion cultivars with sufficient resistance to reduce the number of fungicides for SLB also limits the ability to manage SLB effectively. Integrated disease management strategies for SLB are essential to maintain profitable, sustainable onion production across eastern North America.

Winter Wheat Variety Response to Timing and Number of Fungicide Applications During the 2019–2020 Growing Season in Kansas

The objective of this project was to evaluate the yield response of different winter wheat varieties to different fungicide management treatments during the 2019–2020 growing season in Kansas. Fourteen varieties were evaluated under four fungicide treatments (no fungicide, application either at jointing, heading, or at both stages) in five locations across Kansas in a split-plot design. Disease incidence was assessed approximately 20-d after each fungicide application. Septoria blotch and tan spot were the most prevalent early-season diseases at the studied fields, while stripe rust, leaf rust, and tan spot prevailed late in the season. Late-season diseases had a greater effect on grain yield when compared to early-season diseases. While varieties responded differently to fungicide management, there was an overall yield increase of 1.8 bushels per acre resulting from the jointing fungicide application; 3.3 bu/a from the heading fungicide; and 4.3 bu/a from the combination of both applications. Overall, susceptible varieties had a greater response to fungicide management compared to varieties with intermediate or high levels of genetic resistance. Late-season drought and heat stress affected three out of five locations (Belleville, Conway Springs, and Hutchinson planted late), resulting in less effect of fungicide management than in the other two locations (Ashland Bottoms and Hutchinson planted in the optimal timing). Although there were some similarities, the ranking of the highest yielding varieties was not uniform across locations. Our preliminary data suggest that the application of fungicide to winter wheat in Kansas might be advantageous, but the degree of this benefit will depend upon the environment and on the variety.

Estimating optimum plot size with radiometer for experiments on soybeans treated with fungicide

ABSTRACT Spectral remote sensing and proximal sensors are important tools for managing the plant-pathogen relationship. The lack of experimental planning and the probability of error in agricultural studies may result in work repetition and, consequently, in financial expenses and costs with human resources. To reduce such problems, determining the optimum size of the experimental plot for treatments is one of the adopted methods. The objective of this study was to estimate the optimum plot size for reflectance in soybeans that were treated with different fungicide levels according to the methods of modified maximum curvature and maximum distance. Reflectance readings were carried out for the soybean crop with a radiometer GreenSeeker®, considering basic units of 0.45 m² in an area of ten rows, 10 m long, for each treatment. Treatments were applied to create a gradient of Asian soybean rust, varying the number of fungicide applications. Data were collected in two phenological stages (R5.5 and R6), obtaining 300 simulations of experimental area for each stage. Based on the results, the use of 5.40 m² plots with a group of three rows, 4 m long, is recommended.

A Threshold-Based Decision-Support System for Fungicide Applications Provides Cost-Effective Control of Citrus Postbloom Fruit Drop.

Postbloom fruit drop (PFD) of citrus, caused by Colletotrichum acutatum sensu lato and C. gloeosporioides sensu lato, is an important disease in the humid tropics of the American continent. PFD mainly affects flowers, on which typical symptoms are characterized by orange-brown lesions with presence of acervuli. The disease has a sporadic occurrence, but preventative fungicide sprays are applied every season. The objective of this study was to evaluate the effectiveness of a fungicide spray strategy for PFD based on a predictive model of C. acutatum conidium germination linked to weather conditions. Fungicide sprays were performed when the model predicted pre-established thresholds of 10, 15, 20, and 25% of germinated spores (T10, T15, T20, and T25, respectively). Five experiments were conducted in two different seasons in the state of São Paulo, Brazil. PFD control efficacy of the threshold-based treatments was compared with a nontreated control and to a calendar-based spray system. Additionally, an economic analysis was performed to assess the gross income revenues of the fungicide spraying strategies. Disease control in plots treated at T10, T15, and T20 was as effective as the calendar-based strategy. The number of fungicide applications was reduced by 33 to 71% when sprays were applied at T15 and T20, and gross income increased or was comparable to that of the other treatments. Therefore, using a conidium germination model with a threshold of 15 or 20% is recommended as a spraying strategy for PFD management in Brazil.

Combining quince (Cydonia oblonga) rootstock with soil-applied calcium chloride solution as a strategy to control brown spot (Stemphylium vesicarium) incidence in Abbé Fétel pear fruits

Brown spot (Stemphylium vesicarium) is a fungal disease widespread in European pear industry. The high number of fungicide applications required to control the disease can promote strains with fungicide resistance. The aim of the present study was to assess the effectiveness of soil- applied water solution of calcium chloride in combination with rootstock to control the incidence of brown spot in Abbe Fetel pear. Soil salinity, stem water and osmotic potential, along with fruit fraction of calcium and defence-mechanism related-enzymes such as peroxidase, polyphenol oxidase, phenyl-alanine ammonia-lyase, and β-1,3-glucanase were investigate in tree grafted on Fox 11 (Pyrus communis L.) and Sydo®, a quince (Cydonia oblonga) rootstock. Both grafting combinations were fertigated or not with calcium chloride. Sydo® showed a positive effect in reducing brown spot severity on Abbe Fetel. Compared to Fox 11, fruits from trees grafted on Sydo® showed higher calcium concentrations, fraction of calcium pectate, fruit firmness, polyphenol oxidase, phenyl- alanine ammonia-lyase and β-1,3-glucanase levels. Fruit calcium concentration was positively correlated with disease fruit tolerance. However, soil calcium applications were ineffective in promoting fruit calcium partitioning. Calcium chloride applications decreased leaf osmotic and stem water potential in trees grafted onto Sydo®, but this wasn’t found in those grafted on Fox 11. In conclusion, Sydo® rootstock promoted Ca acquisition, osmotic adjustment at leaf and fruit level, fruit synthesis of defence-related enzymes that all together reduced brown spot severity in Abbe Fetel pear.

Chemical Control of Asian Soybean Rust and Its Effect in the Yield and Quality of Soybean Seeds

The objective of this study was to evaluate the effect of a foliar fungicide commonly used to control Asian soybean rust (Phakopsora pachyrhizi) in the physiological and sanitary quality of soybean seeds. The experiment was carried out during the 2012/13 field season, with six treatments and four replications arranged in a randomized complete block design. The following treatments were evaluated: T1 (no fungicide application); one application at R1 stage; two applications at R1 and R3 stages; three applications at R1, R3, and R5 stages; four applications at R1, R3, R5, and R6 stages and five applications at R1, R3, R5, R6 and R7 stages. Seeds yield, seed weight, viability and vigor assessments were used to measure the impact of foliar fungicide applications on soybean yield and seed quality. The results indicated that four fungicide applications provide higher grain yield, increased seed weight, and germination percentages within commercial standards. In contrast, the number of fungicide applications did not correlate with the sanitary quality of the seeds.

Effectiveness of Fungicide on Soybean Rust in the Southeastern United States: A Meta-Analysis

Soybean rust (SBR), caused by the fungus Phakopsora pachyrhizi Sydow, has been of concern to soybean (Glycine max Merrill) growers in the southern United States since its introduction in 2004. As this fungus develops, pustules become numerous on the underside of leaves, which then turn yellow and drop prematurely, resulting in fewer pods, and poorly developed seeds. Our objective was to evaluate the efficacy of fungicide use in controlling SBR by conducting a meta-analysis of 61 published and unpublished trials across the southern United States from 2004 to 2014. We analyzed fungicide efficacy based on factors such as specific classes of fungicide, active ingredients, number of fungicide applications, target growth stage upon initial application, level of disease pressure, and year of the study. Fungicides significantly increased yield and 100-seed weight and decreased the severity of SBR. The means of SBR severity, yield, and 100-seed weight in fungicide-treated plants were 9% (95% confidence interval: 2%, 21%), 128% (121%, 135%), and 121% (116%, 128%), respectively, of those calculated in the control plants. By using meta-analysis to analyze fungicide efficacy across multiple field trials, we were able to determine that one application of a strobilurin fungicide when plants were either beginning pod development (R3) or developing seeds (R5) was the most cost-effective approach to controlling SBR and increasing 100-seed weight.

Meta-Analysis of a Web-Based Disease Forecast System for Control of Anthracnose and Botrytis Fruit Rots of Strawberry in Southeastern United States.

Strawberry production in Florida and South Carolina is affected by two major diseases, anthracnose fruit rot (AFR) and Botrytis fruit rot (BFR), caused by Colletotrichum acutatum and Botrytis cinerea, respectively. The effective management of both diseases traditionally relied on weekly fungicide applications. However, to improve timing and reduce the number of fungicide sprays, many growers follow the Strawberry Advisory System (StAS), a decision support system for forecasting fungicide applications based on environmental conditions and previously developed models. The objective of this study was to perform a meta-analysis to determine the effectiveness of the StAS for AFR and BFR management compared with a calendar-based spray program. Thirty-nine trials were conducted from 2009 to 2014 in Florida and South Carolina commercial strawberry fields. Meta-analysis was conducted to quantify the treatment effects on four effect sizes, all based on the difference in response variables for StAS and the calendar-based treatments in each trial. The mean difference in BFR incidence, AFR incidence, yield, and number of marketable fruit between the two treatments was not significantly different from 0 (P < 0.05). However, the number of fungicide applications per season was reduced by a median of seven when using the StAS, a 50% reduction in sprays compared with the calendar-based approach. Effect sizes were not influenced by location or the favorability of the environment for disease development. These findings indicate that use of StAS in commercial fields is effective in controlling fruit rot diseases with no reduction in yield while substantially reducing fungicide applications.

Multivariate forecasting model to optimize management of grape downy mildew control

Aim of this study was to develop a forecasting model for Plasmopara viticola to achieve rational disease management and to reduce the use of copper treatments in organic farming. Starting from meteo-climatic, agronomic and phytopathological data a partial least squares discriminant analysis was developed. Three different strategies were compared: treatments according to the established organic agricultural practice (standard); treatments according to the predictive model and untreated control where no fungicides against downy mildew were applied. The modelling approach was divided into three phases: 1) model calibration; 2) field testing and 3) a posteriori model performance evaluation. The prediction was separately considered and modelled for: i) disease onset and ii) disease progress. The results for phase 1 show a percentage of correct classification equal to 91.8 % for the disease onset with 3 days elapsed between the prediction of first potential attack and disease onset and to 91.23 % for disease progress. In field testing phase the percentage of correct classification was equal to about 81 % for both the analysed years (2009 and 2010). In the phase 3 the percentages were quietly higher for the 2009. The number of fungicide applications on the partial least squares discriminant analysis model was almost half compared with standard schedule both in 2009 and 2010. Finally this approach showed the possibility to reduce fungicidal treatments and to avoid applying copper not essential for disease control representing a first step in the model validation.

Effect of formulation and repeated applications on the enantioselectivity of metalaxyl dissipation and leaching in soil.

Soil incubation and column leaching experiments were conducted to address the question of whether the type of formulation (unsupported versus clay supported) and repeated applications of the chiral fungicide (RS)-metalaxyl affected the enantioselectivity of its dissipation and leaching in a slightly alkaline, loamy sand agricultural soil. Regardless of the type of formulation and the number of fungicide applications, the R-enantiomer of metalaxyl was degraded faster than the S-enantiomer, but the individual degradation rates of R- and S-metalaxyl were highly affected by the different application regimes assayed (t1/2 = 2-104 days). Repeated applications accelerated the degradation of the biologically active R-metalaxyl enantiomer, whereas they led to slower degradation of the non-active S-metalaxyl enantiomer. The type of formulation had less influence on the dissipation rates of the enantiomers. For all formulations tested, soil column leachates became increasingly enriched in S-enantiomer as the number of fungicide applications was increased, and application of metalaxyl to soil columns as clay-based formulations reduced the leaching of both enantiomers. Pesticide application conditions can greatly influence the enantioselective dissipation of chiral pesticides in soil, and hence are expected to exert a great impact on both the biological efficacy and the environmental chiral signatures of pesticides applied as mixtures of enantiomers or racemates to agricultural soils.

Barley spot blotch intensity, damage, and control response to foliar fungicide application in southern Brazil

Barley spot blotch (SB) is a frequent foliar disease of the brewing barley crop in southern Brazil. At present, there are few reports regarding the efficacy of fungicide spray programs in relation to the severity of SB damage to barley crop yield. The goals of this study were as follows: 1) to determine the crop growth stage at which severity of SB was most strongly related to grain yield (GY), thousand kernel weight (TKW), and granulometry (G) damage in brewing barley and 2) to evaluate the efficacy of fungicides in controlling SB and the effect of fungicide application timing on disease intensity and yield. The experiments were performed using the BRS Cauê barley cultivar at Muitos Capões municipality, Rio Grande do Sul State, southern Brazil, during the 2009 and 2010 growing seasons. The experiments involved a randomized complete block design with five treatments and four replicates. The treatments varied by the number of fungicide applications. The control received no fungicide application. SB severity assessments were performed at the following growth stages: main stem and one tiller developed, main stem and four tillers developed, swelling 2nd node detectable, flag leaf ligule just visible, full boot, and 50% of spikes visible. SB severity data were integrated as a function of time to determine the area under the disease progress curve (AUDPC). SB resulted in damage of up to 49.2% and 34.6% in GY, 19.9% and 19.7% in TKW, and 26.0% and 11.2% in G in the 2009 and 2010 growing seasons, respectively. A frequency of three and four foliar fungicide applications controlled 70.1% and 78.3% of SB in the 2009 growing season and 85.8% and 88.6% in the 2010 growing season, respectively. GY and SB severity showed a significant negative relationship in both the 2009 and 2010 growing seasons and at all growth stages evaluated. The greatest GY damage related to SB severity occurred at the final growth stages at full boot and 50% of spikes visible. There was a significant negative relationship between AUDPC and GY, with damage coefficients of 17.19 and 22.94 in the 2009 and 2010 growing seasons, respectively. There was a positive net return on barley GY, TKW, and G when four fungicide applications were used for SB control.

Fruit Quality, Phytochemical Content, and Disease Severity of Muscadine Grapes Affected by Fungicide Applications

Muscadine grapes are high in phytochemicals beneficial to humans, such as resveratrol and ellagic acid. Four studies were conducted to explore the relationship between phytochemical content, berry quality, and disease control fol- lowing full season or early season applications of fungicides. In each study foliar and fruit diseases were lower in the full season treatment compared to the control, and some treatments with fewer applications reduced fruit diseases to the same level as the full season treatment. In Study 1 the full season (9 applications) and azoxystrobin treatments (3 applications) resulted in significantly lower berry disease scores than the control treatment. There were no significant differences in vine vigor, foliar diseases, or bitter rot scores among treatments where fungicide applications were stopped at various pre- harvest intervals ranging from 56 to 0 days (Study 3), or in disease scores between the full season (8 applications) and early season treatments (4 applications) of six fungicide treatments (Study 4). Sugar levels were highest in berries from the full season, azoxystrobin, and control fungicide treatments, and berries from the least efficacious treatments for dis- ease control had almost ten times as much resveratrol as those from the most efficacious treatments (Study 1). Ellagic acid and resveratrol levels were lower in berries from fungicide treated vines than from untreated vines (Study 3). The number of fungicide applications can be reduced to as few as four without an increase in berry disease scores; however, when dis- eases of muscadine grapes are controlled, levels of beneficial phytochemicals may decrease.

Fungicide use in processing tomatoes in New Zealand

Fungicide use in processing (field) tomatoes from 1995 to 2009 on the East Coast of the North Island of New Zealand has been documented using data extracted from growers' annual spray diary records. During this period, 26 different fungicides—some of which are also used as bactericides—were used by growers to control a range of plant diseases. The number of fungicide applications to each crop ranged from 10 to 28, with fewer applications in very dry seasons. Inorganic copper (mainly copper hydroxide), applied to control both bacterial and fungal diseases, was the most commonly used material, followed by chemicals in the dithiocarbamate, chloro-nitrile and pyridinamine groups. These four multi-site ‘protective’ fungicide groups accounted for 90% of all disease-control products used during the 15-year period. Site-specific fungicides (e.g. benzimidazoles, phenylamides, dicarboximides, dimethomorph and strobilurins) were used much less frequently. The exclusive use of fungicides at risk from fungicide resistance development (most commonly the site-specific fungicides) was generally avoided and therefore overall risk of the development of fungicide resistance in processing tomatoes in Hawke's Bay is believed to be low. This study demonstrated that the number of fungicide applications per crop has increased about two-fold since 1995 while, during the same period, insecticide applications decreased.

Analysis of management and site factors to improve the sustainability of smallholder coffee production in Tarrazú, Costa Rica

Many coffee agroecosystems in Latin America have been transformed with the goal of maximizing yields. In these intensively managed farming systems, inorganic fertilizers are commonly used, with important agronomic, economical and ecological consequences. This study reviews the relationship between fertilizer application, coffee yield and quality indicators and soil chemical properties in coffee farms of the Los Santos region in Costa Rica.The mean nitrogen (N) input rate in farms employing inorganic fertilizer was 212±16.7kgha−1y−1. Yield reported by farmers had a positive marginally significant relationship with nutrient application rates. Cup quality attribute responded positively to calcium oxide (CaO) applications. Variables related to production and quality indicators were number of fungicide applications, soil exchangeable calcium (Ca) and acidity, elevation of the terrain, and number of stems per plant. Soil exchangeable Ca was positively correlated with the ratio of crop yield per unit of applied N fertilizer. In those farms with higher N input rates, soil pH was significantly lower. We suggest that the N saturation hypothesis developed for temperate forests under N atmospheric deposition is applicable to this perennial agroecosystem. This hypothesis predicts changes in the soil chemistry and nutrient retention capacity, and a reduction of Net Primary Productivity (NPP).

Produção e características físico-químicas dos cachos da videira 'BRS Clara' sob cobertura plástica e sombrite em safra fora de época

Devido às condições climáticas favoráveis à ocorrência de doenças fúngicas em uvas de mesa, tem-se buscado a adoção de tecnologias que propiciem a redução nos custos de produção, sendo uma alternativa o cultivo de uvas sob cobertura plástica. O objetivo deste trabalho foi avaliar a produção e as características físico-químicas dos cachos da videira 'BRS Clara' enxertada sobre o porta-enxerto IAC-766 'Campinas', em cultivo protegido durante a safra fora de época, visando à redução da aplicação de fungicidas para o controle do míldio. Os experimentos foram realizados em pomares comerciais localizados em Uraí e Marialva-PR. As videiras foram conduzidas no sistema latada, em espaçamento de 4,0 x 4,0 m, em Uraí, e de 2,0 x 5,0 m, em Marialva. O delineamento experimental foi o inteiramente casualizado, com dois sistemas de cultivo protegido (sob cobertura plástica e sob sombrite) e sete repetições. No experimento conduzido em Uraí, não foram verificadas diferenças entre os sistemas de cultivo protegido quanto às características produtivas e químicas das bagas, como o teor de sólidos solúveis totais, índice de maturação e pH. Verificou-se a ocorrência do míldio somente nas folhas, sendo a incidência e a severidade menor nas videiras sob cobertura plástica (0,5 e 0,02%, respectivamente). Em Marialva, também não houve influência das coberturas nas características produtivas das videiras. Entretanto, o teor de sólidos solúveis totais das bagas sob cobertura plástica foi superior em relação àquelas sob sombrite (19,6 e 17,2ºBrix, respectivamente). Não foi detectada a ocorrência de míldio em nenhum dos sistemas de cultivo protegido nessa localidade. Conclui-se que o uso da cobertura plástica permite a redução do número de aplicações de fungicidas para o controle do míldio, sem alterar as características produtivas da uva 'BRS Clara'.

Evaluation of a revision of the BSPcast decision support system for control of brown spot of pear

Summary. Control of brown spot of pear requires fungicide treatments of pear trees during the growing season. Scheduling fungicide sprays with the Brown spot of pear forecasting system (BSPcast) provides significant fungicide savings but does not increase the efficacy of disease control. Modifications in BSPcast were introduced in order to increase system performance. The changes consisted of: (1) the use of a daily infection risk (Rm≥0.2) instead of the 3-day cumulative risk (CR≥0.4) to guide the fungicide scheduling, and (2) the inclusion of the effect of relative humidity during interrupted wetness periods. Trials were performed during 2 years in an experimental pear orchard in Spain. The modifications introduced did not result in increased disease control efficacy, compared with the original BSPcast system. In one year, no reduction in the number of fungicide applications was obtained using the modified BSPcast system in comparison to the original system, but in the second year the number of treatments was reduced from 15 to 13. The original BSPcast model overestimated the daily infection risk in 6.5% of days with wetness periods with low relative humidity during the wetness interruption, and in these cases the modified version was more adequate.

Evaluation of fungicide efficacy and application frequency for the control of ascochyta blight in chickpea

Field experiments were conducted during 2002–2004 at Saskatoon, Swift Current and Kyle, Saskatchewan to assess the effect of application frequency, timing and rotation of different fungicides on the suppression of ascochyta blight, and on yield and seed quality of chickpea cultivars ‘Myles’, ‘Sanford’ and ‘CDC Yuma’. Fungicides tested included chlorothalonil, azoxystrobin, pyraclostrobin, mancozeb and boscalid. Ascochyta blight severity ranged from 21 to 99% in untreated control plots and was significantly reduced through fungicide applications to levels below 25% in the most efficacious treatments. Increasing the number of fungicide applications was beneficial under high disease pressure, but was not always correlated with better ascochyta blight control. A pre-flower application had a positive effect by suppressing ascochyta blight severity, increasing seed yield or one-thousand seed weight in almost all experiments. Higher numbers of applications were not always correlated with higher seed yield and better seed quality. This may be due in part to poor yields in 2004 at Saskatoon and Kyle where above-average rainfall resulted in excessive vegetative growth. Different fungicide rotations had less of an impact on ascochyta blight management than the timing and the number of applications, but under moderate to high disease pressure, including strobilurin fungicides was beneficial. Five applications of mancozeb at two-week intervals were significantly less efficacious compared with rotations with other products.