Cercospora leaf spot (CLS), caused by the fungal pathogen Cercospora beticola, is one of the most destructive foliar diseases on sugar beet. It severely affects productivity and profitability of the sugar beet industry. CLS is managed by using resistant cultivars, rotating with non-host crops, and applying effective fungicides in a timely manner. In North Dakota and Minnesota, site-specific fungicides, such as quinone outside inhibitors (QoIs) and demethylation inhibitors (DMIs), had been widely and extensively applied to control C. beticola which has developed resistances to these fungicides. The mycelial growth, spore production, spore germination, and aggressiveness of QoI and/or DMI resistant isolates were compared to sensitive isolates in a laboratory and greenhouse study. Results indicated that the QoI and/or DMI resistant isolates had a relatively slower disease development on sugar beet leaves due to their fitness penalty in sporulation and mycelial growth but still caused high disease severities as sensitive isolates. Fungicides were evaluated to manage the QoI and/or DMI resistant C. beticola isolates in a sensitivity study and a greenhouse and field study. Copper-based multisite activity fungicides were evaluated for controlling fungicide resistant C. beticola. The mean EC50 values for nine copper-based chemicals ranged from 1 to 10 ug/ml using a spore germination assay. In a greenhouse study, Fertileader (a copper-based fertilizer) caused leaf injury and was not evaluated, but the other tested chemicals provided significantly better control of CLS compared to the control check with Badge X2, Champion, Cuprofix, COCS and Ridomil having significantly small AUDPC. Newer site specific fungicides with different modes of action that have never been used for CLS management in North Dakota and Minnesota were also tested. The mean EC50 values were 4.9, 33.1, 99.4, and 481.6 ug/ml using mycelial growth assay and 5.7, 4.1, 9.2, and 4.2 ug/ml using spore germination assay for cyprodinil, fluazinam, pydiflumetofen, and Chlorothalonil, respectively. In a two-year field study, all the fungicides resulted in significantly better disease control, significantly higher beet tonnage, and recovered sucrose compared to the nontreated check. However, none of tested fungicide treatments performed better than the industry?s standard fungicide, triphenyltin hydroxide.

Magistrantūros studijų baigiamojo darbo tyrimų tikslas buvo ištirti cukrinių runkelių ligotumą, nustatyti grybinių lapų ligų paplitimą ir žalingumą cukriniuose runkeliuose bei nustatyti apsaugos priemonių, mažinančių ligų plitimą efektyvumą. Lauko eksperimentas buvo atliktas 2012 m. Lietuvos agrarinių ir miškų mokslų centro (LAMMC) Rumokų bandymų stotyje. Dirvožemis sekliai glėjiškas paprastasis išplautžemis (Haplic-Epihypogleyic Luvisol – Idg8-p). Darbo objektas - cukrinių runkelių (Beta vulgaris saccharifera) grybinės lapų ligos. Darbo metodai: Cukrinių runkelių lapų ligotumo, fungicidų biologinio efektyvumo, ligų žalingumo matavimai nustatyti tiesioginio matavimo, skaičiavimo ar svėrimo būdu pagal priimtas lauko eksperimento vykdymo metodikas (Šurkus, Gaurilčikienė, 2002). Tyrimų duomenys statistiškai įvertinti vieno veiksnio arba dviejų veiksnių kiekybinių požymių dispersinės analizės metodais, taikant kompiuterinę programą ANOVA (Tarakanovas, Raudonius, 2003). Darbo rezultatai: Tyrimų metais cukriniuose runkeliuose labiausiai plito cukrinių runkelių rudmargė ir baltuliai, kurių pažeidimo intensyvumas atitinkamai siekė 11,91 ir 1,81 proc. Didžiausias biologinis fungicido efektyvumas nuo cukrinių runkelių rudmargės nustatytas laukeliuose, kuriuose vieną ir du kartus buvo naudojamas fungicidas Maredo (vienkartinio purškimo norma 1,0 l ha-1, dukartinio - 0,75 l ha-1). Jo biologinis efektyvumas atitinkamai siekė 65,79 – 92,06 proc. ir 86,39 – 94,19 proc. Didžiausias... [toliau žr. visą tekstą] / The main objective of Master thesis research was to investigate the intensity of sugar beet diseases, determine the fungal disease prevalence and harmfulness of sugar beets, and determine the effect of chemical plant control against sugar beet diseases.The research was made in the Rumokai Experimental Station of the Lithuanian Research Centre for Agriculture and Forestry in 2012. The soil type – Haplic-Epihypogleyic Luvisol – Idg8-p. Object of the research – sugar beet (Beta vulgaris saccharifera) fungal leaf diseases. Working methods: biological effectiveness of fungicides and disease harmfulness measurements were determined while using direct measurements, calculations or weighing according field experimental techniques (Šurkus, Gaurilčikienė, 2002). Research data have been statistically evaluated with a single factor or two factor analysis of variance of quantitative methods of evidence, using a computer program ANOVA (Tarakanovas, Raudonius, 2003). Research results: The most effective fungicide against Cercospora leaf spot disease in the once and twice treatment field of sugar beet plants was Maredo (once treatment rate 1,0 l ha-1, twice treatment rate 0,75 l ha-1). Its efficiency was highest and reached 65,79 – 92,06 % and 86,39 – 94,19 %. The most effective fungicideagainst Ramularia leaf spot disease in the once and twice treatment field of sugar beet plants was also Maredo. Its efficiency reached 75,41 – 93,52 % and 82,76 – 93,89 %. The highest significant root... [to full text]