Empirical-deterministic prediction of disease and losses caused by Cercospora leaf spots in sugar beets

Neben einer Negativ-Prognose des Epidemiebeginns, epidemieorientierten Bekämpfungsschwellen (BK) und einer wirtschaftlichen Schadensschwelle (WS) beinhaltet das Quaternäre IPS (Integriertes Pflanzenschutz)-Konzept zur Kontrolle des Cercospora-Befalls eine Verlustprognose. Die Verlustprognose erhält ihren praktischen Sinn dadurch, dass die epidemischen Stadien von BK und WS ein Intervall von 5–10 Wochen beinhalten. Die Befallsstärke (BS) zum Zeitpunkt von BK beträgt 0,01%, hingegen toleriert die Zuckerrübe 5% BS ohne wirtschaftlichen Schaden. Die Verlustprognose trifft daher Vorhersagen, ob der künftige Befallsverlauf die WS zum Erntezeitpunkt überschreiten wird und insofern, ob Bekämpfungsmaßnahmen benötigt werden. Das Modell ist als empirisch zu charakterisieren, nachdem die Herleitung der Verlustprognose auf 105 Feldstudien (Deutschland und Österreich) einer Epidemie von Cercospora beticola und ihren ertraglichen Konsequenzen beruht. Des Weiteren ist das Modell deterministisch, weil die Krankheitssituation zum gegenwärtigen Zeitpunkt die Prognose der zukünftigen Befallsentwicklung determiniert. In jeglicher Feldstudie implizierte der Epidemieverlauf eine Phase geringer Progression der BS, gefolgt von einem steilen Anstieg mit Tendenz zu einem Maximum des Befalls. Die Prognose des Befallsverlaufes in Submodul (i) basiert daher auf der sigmoiden Funktion „BS = BSmax/(1+exp(-(CW-a)/b))“. Demnach hängt die Kalkulation von BS von der Kalenderwoche (CW) und den Variablen BSmax, a und b ab. Letztere werden geschätzt mittels mathematischer Funktionen in Abhängigkeit vom Epidemiebeginn (CWBH5%), definiert als jene Kalenderwoche, zu der eine Befallshäufigkeit (BH) der Blätter von ≥5% eintritt. Die Verluste sind hierbei abhängig von der Fläche unter der Befallskurve (AUDPC). Für die Kalkulation der AUDPC-Werte finden die BS-Werte Verwendung, wie mit Submodul (i) geschätzt. Die Prognose von Verlusten an Rüben- und Bereinigtem Zuckerertrag geschieht auf Basis von Befalls-Verlust-Relationen (Submodul ii, iii). Die wirtschaftliche Schadensschwelle ist definiert als AUDPC=1, entsprechend einem Verlust an Bereinigtem Zuckerertrag von ≉1,5%. Folglich sind Fungizidapplikationen entbehrlich, sofern der Befall bis zur Ernte <AUDPC=1 verbleibt. Alle Berechnungen zur Modellentwicklung haben die Sorten-Anfälligkeiten „hoch“ und „gering“ berücksichtigt. Darüber hinaus benötigt die Verlustprognose Angaben über den zu erwartenden Ertrag und den voraussichtlichen Erntetermin. Diagnose und Erhebung des Befalls sind Voraussetzungen für die Anwendung des Modells, da die Einschätzung der zukünftigen Entwicklung auf einer Konkretisierung der gegenwärtigen Krankheitssituation gründet.Besides negative-prognosis of epidemic onset, epidemic spraying thresholds (ET) and economic damage threshold (DT), loss prediction is a part of the Quaternary IPM (Integrated Pest Management)-concept to control Cercospora leaf spots (CLS). The practical need of loss prediction originates from the fact, that disease levels of ET and DT implicate an interval of 5–10 weeks. Disease severity (DS) of ET for an initial treatment is 0.01, whereas the beet plant may tolerate 5% DS without economic losses. Therefore, in order to assess the necessity of control measures, the model is focused on to predict whether DS will exceed DT at harvest time. The model is empiric, because loss prediction was derived from epidemic and yield data of 105 field trials conducted in Germany and Austria (1993-2000). The model is also deterministic, because the disease incidence at present date and cultivar susceptibility determine the prediction of future disease progress. In every field study, course of DS involved a period of slight followed by a more or less steep increase tending to a maximum of DS. The incidence prediction in submodel (i), therefore, was based on the sigmoidal function “DS = DSmax/(1+exp(-(CW-a)/b))”, where the calculation of DS is depending on the actual calendar week (CW) and the variables DSmax, a and b. These variables are estimated through curve fittings depending on the epidemic onset (CWDIL5%), respectively the calendar week when disease incidence per leaf (DIL) increases to ≥5%. Losses are dependent on the area under disease progress curve (AUDPC). Creation of AUDPC-values is based on the DS-values as calculated by submodel (i). The prediction of losses is performed through disease-loss-relationships (submodel ii, iii). The economic damage threshold is defined as AUDPC=1, equal to a loss of ≉1.5% sugar. Therefore fungicide sprays may be avoided, if the AUDPC remains beneath 1 till scheduled harvest time. All calculations for model development involved two grades of cultivar susceptibility, either highly or low susceptible. Moreover, prediction of yield loss needs indications of expected yield and scheduled harvest time. Proper diagnosis and disease scoring is a precondition for error free functioning of the model, since future progress is estimated by an assessment of the actual incidence situation

Choice of fungicide seed treatment solution composition affecting dust emission from cereal crop seeds

Die Entstehung von Beizstaub stellt eine potentielle Verlustquelle fungizider Beizmittel dar und kann darüber hinaus eine unbewusste Quelle für die Freisetzung von Chemikalien gegenüber Nichtziel-Organismen und Anwendern bilden. In der vorliegenden Studie wurde eine Bewertung der Staubemission durch die Verwendung von verschiedenen Beizlösungszusammensetzungen (mit und ohne Additiv) anhand verschiedener Aufwandmengen und unterschiedlichem Saatgut durchgeführt. Nach der Verwendung eines standardisierten Behandlungsprotokolls wurde die Probenlagerung für eine definierte Zeit durchgeführt, woraufhin anschließend eine Staubmessung mittels Heubach-Dustmeter erfolgte. Je nach Verwendung von Additiven wurden verschiedene Staubemissionen nachgewiesen. Eine Gesamtreduktion des Staubniveaus wurde durch die Anwendung von Additiven im Vergleich zur alleinigen Verwendung von Saatgutbehandlungsmitteln gezeigt.Seed dust emission in small grain cereals is a possible loss path for fungicidal seed dressing and furthermore a source of unrecognized release of chemicals towards non target organisms and users. In the present study, an evaluation of dust emission was conducted due to the use of different slurry solution composition (with and without adjuvant), using different application rates and crop seeds. After using a standardized treatment protocol, sample storage was conducted for an appropriate defined time until dust measurement by Heubach-dustmeter was carried out. Different levels of dust were detected according to the use of adhesive adjuvants. An overall reduction of dust level was achieved by the application of adjuvants compared to the single use of seed dressings

Impact of adhesive adjuvants addition into seed treatments on the flowability of cereal crop seeds

Das Fließverhalten von Schüttgütern wird durch das Material der Oberfläche beeinflusst. Die Applikation von Saatgutbehandlungsmitteln führt zu einer Änderung der Grenzreibung zwischen einzelnen Getreidekörnern als Folge von Kontakt. In der vorliegenden Studie wurde ein Vergleich zwischen verschiedenen Beizlösungen, mit und ohne Additiv in Bezug auf die Fließfähigkeit durchgeführt. Es konnten, abhängig von den eingesetzten Zusatzpräparaten unterschiedliche Effekte detektiert werden. Die Verwendung von pflanzenölbasierten Adjuvantien Kantor® und Inteco® in Kombination mit den Saatgutbehandlungsmitteln EfA® und Rubin®TT reduzierte die Energiefreisetzung, verglichen mit der jeweiligen Varianten ohne Additiv, anhand der Verwendung von Weizen-, Gerste-, Roggen-, Hafer und Triticalesaatgut. Im Gegensatz dazu erhöhte die Zugabe des Polysiloxan-basierten Additivs MaximalFlow® die Energiefreisetzung in 70% aller Vergleiche, relativ zur Variante ohne Zusatz.Flow behavior of bulk material is influenced by surface material. The application of different seed treatment slurries indicate a change of boundary friction between the grains as a result of contact. A comparison between adjuvant added and single treated cereal seed was conducted in the present study to evaluate the impact on flowability. Related to the chemical components of the used adjuvants different impacts were detected. The use of plant oil based adjuvants Kantor® and Inteco® reduced the value of released energy compared to single use of seed treatments EfA® and Rubin®TT in crop seeds wheat, barley, rye, oat and triticale at 80% of treatments. Contrary to this, the addition of a polysiloxane based adjuvant MaximalFlow® increased the value of released energy representing flowability in 70% of treatments compared to single use of preparatio

Temporal Changes in Sensitivity of Zymoseptoria tritici Field Populations to Different Fungicidal Modes of Action

Septoria tritici blotch (STB; Zymoseptoria tritici), one of the most important foliar diseases in wheat, is mainly controlled by the intensive use of fungicides during crop growth. Unfortunately, Z. tritici field populations have developed various extents of resistance to different groups of fungicides. Due to the complete resistance to quinone outside inhibitors (QoIs), fungicidal control of STB relies mainly on demethylation inhibitors (DMIs) and succinate dehydrogenase inhibitors (SDHIs) as well as multi-site inhibitors. In this study, temporal changes in the sensitivity of Z. tritici to selected DMIs (tebuconazole, propiconazole, prothioconazole, prochloraz), SDHIs (boscalid, bixafen), and multi-site inhibitors (chlorothalonil, folpet) were determined in microtiter assays using Z. tritici field populations isolated in 1999, 2009, 2014, and 2020 in a high-disease-pressure and high-fungicide-input area in Northern Germany. For the four tested DMI fungicides, a significant shift towards decreasing sensitivity of Z. tritici field populations was observed between 1999 and 2009, whereby concentrations inhibiting fungal growth by 50% (EC50) increased differentially between the four DMIs. Since 2009, EC50 values of tebuconazole, propiconazole, and prochloraz remain stable, whereas for prothioconazole a slightly increased sensitivity shift was found. A shift in sensitivity of Z. tritici was also determined for both tested SDHI fungicides. In contrast to DMIs, EC50 values of boscalid and bixafen increased continuously between 1999 and 2020, but the increasing EC50 values were much smaller compared to those of the four tested DMIs. No changes in sensitivity of Z. tritici were observed for the multi-site inhibitors chlorothalonil and folpet over the last 21 years. The sensitivity adaptation of Z. tritici to both groups of single-site inhibitors (DMIs, SDHIs) mainly used for STB control represents a major challenge for future wheat cultivation

Composition and Predominance of Fusarium Species Causing Fusarium Head Blight in Winter Wheat Grain Depending on Cultivar Susceptibility and Meteorological Factors

Fusarium head blight (FHB) is one of the most important diseases of wheat, causing yield losses and mycotoxin contamination of harvested grain. A complex of different toxigenic Fusarium species is responsible for FHB and the composition and predominance of species within the FHB complex are determined by meteorological and agronomic factors. In this study, grain of three different susceptible winter wheat cultivars from seven locations in northern Germany were analysed within a five-year survey from 2013 to 2017 by quantifying DNA amounts of different species within the Fusarium community as well as deoxynivalenol (DON) and zearalenone (ZEA) concentrations. Several Fusarium species co-occur in wheat grain samples in all years and cultivars. F. graminearum was the most prevalent species, followed by F. culmorum, F. avenaceum and F. poae, while F. tricinctum and F. langsethiae played only a subordinate role in the FHB complex in terms of DNA amounts. In all cultivars, a comparable year-specific quantitative occurrence of the six detected species and mycotoxin concentrations were found, but with decreased DNA amounts and mycotoxin concentrations in the more tolerant cultivars, especially in years with higher disease pressure. In all years, similar percentages of DNA amounts of the six species to the total Fusarium DNA amount of all detected species were found between the three cultivars for each species, with F. graminearum being the most dominant species. Differences in DNA amounts and DON and ZEA concentrations between growing seasons depended mainly on moisture factors during flowering of wheat, while high precipitation and relative humidity were the crucial meteorological factors for infection of wheat grain by Fusarium. Highly positive correlations were found between the meteorological variables precipitation and relative humidity and DNA amounts of F. graminearum, DON and ZEA concentrations during flowering, whereas the corresponding correlations were much weaker several days before (heading) and after flowering (early and late milk stage)

Will Triazoles Still Be of Importance in Disease Control of Zymoseptoria tritici in the Future?

Septoria tritici blotch (STB), caused by Zymoseptoria tritici, is one of the most important foliar wheat diseases worldwide. Current control strategies of STB rely mainly on fungicides, whereby triazoles (demethylation inhibitors; DMIs) have been the backbone in the control of Z. tritici in the last decades. However, in recent years a gradual loss of sensitivity of Z. tritici to several active ingredients of the triazole group has been reported in several European wheat-growing areas. Nevertheless, a new triazole fungicide, namely, mefentrifluconazole, has recently become available in disease management of STB, which belongs to a completely new triazole subclass, the so-called isopropanol triazoles. In this study, the trend in sensitivity development of Z. tritici towards older triazoles (tebuconazole, prothioconazole, and propiconazole) and the new isopropanol triazole mefentrifluconazole was determined in microtiter assays using Z. tritici field populations isolated in 1999, 2009, 2014, and 2020 in a high-disease-pressure and high-fungicide-input area in northern Germany in order to investigate whether the loss of sensitivity of Z. tritici to older triazoles also applies to mefentrifluconazole. For the three triazole fungicides tebuconazole, prothioconazole and propiconazole, a significant shift towards decreasing sensitivity of Z. tritici field populations was observed from 1999 to 2020, whereas the efficacy of mefentrifluconazole in reducing the in vitro fungal growth by 50% (EC50) remained unchanged over the investigated period, demonstrating a stable sensitivity of Z. tritici towards mefentrifluconazole. Although older triazoles are suffering from a loss of sensitivity of Z. tritici field populations due to the selection and spread of less triazole sensitive strains within the Z. tritici population, the efficacy of the new triazole mefentrifluconazole with its unique isopropanol unit was not affected by these changes within the Z. tritici population. Thus, the introduction of such new molecular units could also represent an important contribution for older groups of active ingredients, which previously suffered from a loss of sensitivity

Quaternary Integrated Pest Management concept for powdery mildew in sugar beet. III. Economic damage threshold and loss prediction

Die ökonomische Schadensschwelle sowie die Verlustprognose sind Teil des Quaternären IPS (Integriertes Pflanzenschutz-System) –Konzeptes zur Bekämpfung des Echten Mehltaus in Zuckerrüben. Nach Auswertung von 73 Feldversuchen (1993-2004), durchgeführt unter den klimatischen Bedingungen Mitteleuropas, vermag der Echte Mehltau Verluste an bereinigtem Zuckerertrag von 10-15% auszulösen, der Zuckergehalt kann maximal um 0,5-0,7% (absolut) gemindert sein. Hohe Verluste sind wahrscheinlich unter der Bedingung eines frühen Epidemiebeginns im Juli sowie hoher Anfälligkeit der Zuckerrübensorte. Derartige Bedingungen führen ebenso zu einer Steigerung des αAmino-Stickstoff-Gehaltes, wodurch die Ausbeute an Zucker um 1-2% verringert wird. Die übrigen Nicht-Zuckerstoffe werden durch den Mehltau-Befall nicht signifikant beeinflusst. Unter Zusammenfassung aller Ertrags- und Qualitätsfaktoren wird mit Hilfe von Befalls-Verlust-Relationen unter Zugrundelegung des AUDPC (Area Under Disease Progress Curve) -Wertes eine wirtschaftliche Schadensschwelle von 2 definiert, gleichzusetzen mit einem Zuckerverlust von 1,8%. Im Hinblick auf eine Prognose von Verlusten ist die Überschreitung der wirtschaftlichen Schadensschwelle wahrscheinlich, sofern Erstbefall vor Mitte August auftritt. Im Falle von hoch anfälligen Sorten ist die Risikoperiode bis Ende August auszudehnen. Die Risikoperioden entsprechen den Behandlungszeiträumen für Fungizidapplikationen gegen den Echten Mehltau der Zuckerrübe.The economic damage threshold and loss prediction are part of the Quaternary IPM (Integrated Pest Management) -concept developed for the control of powdery mildew in sugar beets. The evaluation of 73 field trials, conducted under the climatic conditions in central Europe (1993-2004), established that powdery mildew may cause 10-15% sugar yield losses and 0.5-0.7 % (absolute) reductions of sugar content at the maximum. The losses occur preferably under conditions of early disease initiation in July and high susceptibility of cultivar. Such situations also may increase the content of αAminoNitrogen and, therefore, the recovery of sugar may be reduced by 1-2%. The other non sucrose components are not affected through powdery mildew. Derived from disease loss relationships and after summarising all yield and quality factors, the value of AUDPC (Area Under Disease Progress Curve) 2, equal to a sugar yield loss of 1.8 %, is defined as the economic damage threshold. In view of loss prediction, the exceeding of the economic damage threshold is likely if first symptoms appear before mid-August, the risk period is extended to the end of August in case of high susceptibility of cultivar. The risk periods are equal to action zones for fungicide treatments

Spatio-Temporal Prediction of the Epidemic Spread of Dangerous Pathogens Using Machine Learning Methods

Real-time identification of the occurrence of dangerous pathogens is of crucial importance for the rapid execution of countermeasures. For this purpose, spatial and temporal predictions of the spread of such pathogens are indispensable. The R package papros developed by the authors offers an environment in which both spatial and temporal predictions can be made, based on local data using various deterministic, geostatistical regionalisation, and machine learning methods. The approach is presented using the example of a crops infection by fungal pathogens, which can substantially reduce the yield if not treated in good time. The situation is made more difficult by the fact that it is particularly difficult to predict the behaviour of wind-dispersed pathogens, such as powdery mildew (Blumeria graminis f. sp. tritici). To forecast pathogen development and spatial dispersal, a modelling process scheme was developed using the aforementioned R package, which combines regionalisation and machine learning techniques. It enables the prediction of the probability of yield- relevant infestation events for an entire federal state in northern Germany at a daily time scale. To run the models, weather and climate information are required, as is knowledge of the pathogen biology. Once fitted to the pathogen, only weather and climate information are necessary to predict such events, with an overall accuracy of 68% in the case of powdery mildew at a regional scale. Thereby, 91% of the observed powdery mildew events are predicted

Confirmation of an ALS-resistant Lolium perenne population in Northern Germany

Auf einem Ackerschlag im Östlichen Hügelland Schleswig-Holsteins wurde in der Vergangenheit eine Fruchtfolge aus Wintergerste, Winterraps und Winterweizen in einer wiederkehrenden dreijährigen Frucht­folge angebaut. Im Herbst und Frühjahr 2014/15 wurden in eigenen Untersuchungen erstmals deutliche Bekämpfungsprobleme von Deutschem Weidelgras (Lolium perenne) auf dieser Ackerfläche dokumentiert. Aufgrund dieser Beobachtungen und dem Einsatz gleicher Wirkstoffe in den vergangenen Jahren wurde die Verdachtspopulation auf eine etwaige Resistenz getestet. Nach einer Pflanzenprobenahme im Frühjahr 2015 und sich anschließenden Wirkungsversuchen unter Gewächshausbedingungen mit verschiedenen Dosierungen von Wirkstoffen aus der Gruppe der ACCase- und ALS-Inhibitoren sowie einer molekularen Resistenzanalyse steht fest, dass in Schleswig-Holstein eine bis jetzt noch nicht näher betrachtete ALS-resistente Spezies bestätigt werden konnte. Es zeigte sich bei der Verdachtspopulation neben einer ausgeprägten Resistenz gegenüber ALS-Inhibitoren eine vermutlich zusätzliche metabolische Resistenz in Form von ersten Wirkungsverlusten gegenüber Aryloxyphenoxy-propionaten und Clethodim. DOI: 10.5073/JfK.2016.05.01, https://doi.org/10.5073/JfK.2016.05.01In the east of Schleswig-Holstein, in the recent years on a farmland were grown winter barley, winter oilseed rape and winter wheat in a three-year crop rotation. In autumn and spring 2014/15, severe problems to control perennial ryegrass (Lolium perenne) were recognized for the first time in field-trials. Based on these observations and the use of the same herbicides in recent years, the suspect population was tested for a possible herbicide resistance. After a plant sampling in the spring of 2015 and subsequent greenhouse bioassays with different doses of ACCase and ALS inhibitors, followed by a molecular resistance testing, a hitherto unknown ALS-resistant weed species was confirmed in Schleswig-Holstein. In addition to a marked resistance to ALS inhibitors, a poten­tial metabolic resistance in the form of first effect losses against aryloxyphenoxy-propionates and cle­thodim was observed in the suspect population. DOI: 10.5073/JfK.2016.05.01, https://doi.org/10.5073/JfK.2016.05.0