Erysiphe betae is an important leaf disease of sugar beet in Northern Europe The disease reduces sugar yield by several hkg if not controlled QoI fungicides in mixtures with azoles have provided reasonable control of powdery mildew and ID: 1045163
Download Presentation The PPT/PDF document "Introduction Sug ar beet powdery mildew ..." is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
1. IntroductionSugar beet powdery mildew caused by Erysiphe betae is an important leaf disease of sugar beet in Northern Europe. The disease reduces sugar yield by several hkg if not controlled. QoI fungicides in mixtures with azoles have provided reasonable control of powdery mildew and are usually applied two to three times per season at ¼ to ½ of the registered label rate in Denmark. The detection of the first QoI-resistant powdery mildew in 2018 in Denmark and Sweden gives rise to concerns (Heick et al. 2019). Furthermore, several azole compounds are currently under re-evaluation by the European Commission for re-registration and may be banned in the near future, which will constrain the implementation of sound anti-resistance strategies for fungal diseases. This project was initiated to (1) test different fungicide programs, including alternatives to the current standard recommendation, for their control of E. betae, and (2) screen for QoI resistance in the Danish and Swedish E. betae populations.Disease control and management of QoI resistance of sugar beet powdery mildew (Erysiphe betae) in ScandinaviaThies Marten Heick1, Annemarie Fejer Justesen1, Anne Lisbet Hansen2 and Lise Nistrup Jørgensen11Aarhus University, Department of Agroecology, Forsøgsvej 1, DK-4200 Slagelse2NBR Nordic Beet Research, Sofiehøj, Højbygaardvej 14, DK-4960 Holeby; Contact: thiesm.heick@agro.au.dkFigure 1. Disease assessments (%) of powdery mildew (top) and rust (bottom) at four different time points. Left location ‘Guldborg’, right ‘Flakkebjerg)References. Bolton and Neher (2014) Plant Disease 98, 1004-1004 Heick, TM et al. (2019) Plant Health Progress, 20 (3) Results Powdery mildew and rust (Uromyces betae) where the dominating diseases in both field trials. Powdery mildew developed more rapidly at the site of ‘Guldborg’. All two-sprays programs (treatments 2-8) controlled powdery mildew effectively. Programs containing sulfur (treatment 11 and 12; Kumulus S) provided control in line with the other chemical solutions against powdery mildew. The effect of Serenade ASO (Bacillus amyloliquefaciens) was low and varied across sites. Root yield and sugar content were similar for all treatments, except three times Serenade ASO, which yielded significantly lower. As in the previous year, QoI-resistant isolates were found in the Danish-Swedish E. betae population in 2019. Four of the 14 E. betae populations developed on leaves sprayed with pyraclostrobin. All four samples were tested positive for G143A. Two samples were from Sweden and two from Denmark, respectively.Discussion and ConclusionThe current recommendation for the control of fungal leaf diseases in sugar beet (two times 0.5 l/ha Opera) still provides high control of powdery mildew and rust. In the light of the potential ban of several products and the rise of fungicide resistance issues, investigations for alternative solutions have become very important. The results of the first year of this trial series indicate that control options exist. There is a real risk for the establishment. Sulfur showed good control against powdery mildew and could be used as a resistance breaker, should QoI resistance in E. betae spread further of QoI-resistance in Northern Europe, if measures against resistance build-up are not incorporated into fungicide spray programs.Table 1. Fungicide spray strategies targeting sugar beet powdery mildew. TreatmentT0T1T21Ubehandlet20.5 l/ha Opera0.5 l /ha Opera30.5 l/ha Revysol + 0.18 l/ha Comet Pro0.5 l/ha Revysol + 0.18 l/ha Comet Pro40.62 l/ha Comet Pro0.62 l/ha Comet Pro50.5 l/ha Amistar Gold0.5 l/ha Amistar Gold60.5 l/ha Propulse0.5 l/ha Amistar Gold70.5 l/ha Revysol + 0.18 l/ha Comet Pro0.25 l/ha Amistar Gold81 l/ha Revysol + 0.375 l/ha Comet Pro0.5 l/ha Amistar Gold94 l/ha Serenade ASO4 l/ha Serenade ASO4 l/ha Serenade ASO104 l/ha Serenade ASO0.62 l/ha Comet Pro4 l/ha Serenade ASO115 kg/ha Kumulus S5 kg/ha Kumulus S5 kg/ha Kumulus S125 kg/ha Kumulus S0.62 l/ha Comet Pro5 kg/ha Kumulus SMaterials and methodsField trials Two field trials in the powdery mildew-susceptible cultivar ‘Lombok’ were carried out in 2019 in Denmark. Fungicide treatments were applied at T0 before visual symptoms (July 22), T1 at onset (July 29), and T2 (August 19) according to Table 1. The effect of the different treatments was assessed weekly. The trials were assessed for diseases throughout the season and carried through to harvest. Screening for QoI resistance in powdery mildewFourteen leaf samples with powdery mildew were collected from farmers’ fields in Denmark and Sweden in mid-August and used for inoculation of disease-free plants (cv. ‘Lombok’ at growth stage 19). The infected plants were treated one day after inoculation with 0.5 l/ha Opera (epoxiconazole + pyraclostrobin) or 0.5 l/ha Comet Pro (pyraclostrobin). Field populations that developed infections despite fungicide treatment were sequenced for the presence of cytb point mutation G143A, which is associated with QoI resistance (Bolton and Neher 2014).This research was financed by the Danish Sugar Growers’ Association