Sensitivity of Cercospora beticola to fungicides in Slovakia

Abstract

The fungus Cercospora beticola Sacc. is the one of the most important pathogens on the sugar beet. The frequent application of fungicides with the same mode of action increase a risk of development of resistant strains of the pathogen. Occurrence of C. beticola resistant strains has been never researched in Slovakia. In this work, C. beticola isolates were collected from 10 localities of Slovakia and analysed for fungicide resistance in laboratory conditions. Nine fungicides with different mode of action were tested – trifloxystrobin + cyproconazole, kresoxim-methyl + epoxiconazole, azoxystrobin + cyproconazole, thiophanate-methyl + tetraconazole, thiophanate-methyl, prochloraz + propiconazole, picoxystrobin, tetraconazole, and difenoconazole. The results confirmed, that occurrence of fungicide resistance in C. beticola population was established in Slovakia. Different criteria of assessment of fungicide resistance (based on EC50 and on growth rate – inhibition percentage) showed slightly different results, but both criteria confirmed resistant C. beticola strains to thiophanate-methyl, picoxystrobin and difenoconazole. Fields with higher frequency of application of these fungicides significantly supported the development of resistant strains. Assessment of any C. beticola strains have not confirmed reduced sensitivity to active ingredients tetraconazole and prochloraz + propiconazole. The lowest level of risk of fungicide resistance was confirmed in the locality Oslany. It is very important to focus on anti-resistant strategy and reduce of using fungicides on localities, where the occurrence of resistant C. beticola strains was confirmed – Dolné Saliby (thiophanate-methyl and picoxystrobin) and Senec (picoxystrobin and difenoconazole).

The Efficacy of Fungicides Against Cercospora beticola in Field Conditions

“…8 (Plan Tonic + Plan Tonic). It corresponds with our previous findings (Hudec et al 2020) where picoxystrobin (included in the preparation Acanto) reached a low inhibition effect on the mycelial growth of C. beticola in laboratory conditions. Bolton et al (2012) compared the laboratory and field efficacy of tetraconazole.…”

“…DMI fungicides are broadly used in the fungicide treatment of sugar beet against CLS. While FRAC considers the DMi fungicides (e.g., tetraconazole) as a middle-risk group of resistance development, other authors found an increase in less susceptible strains of C. beticola in the field (Hudec et al 2020). Cercospora beticola isolates originated from treated plots are usually less sensitive to the fungicides than those that originated from untreated plots.…”

Evaluation of several fungicides on mycelial growth and conidial germination of Alternaria species causing leaf spots in sunflowers under in vitro conditions

“…Based on its constituent compounds, propiconazole belongs to the triazole fungicide, which inhibits fungal growth by inhibiting sterol biosynthesis, an essential component in fungal cell defense (Rouabhi 2010). Propiconazole can inhibit the growth of C. beticola (Hudec et al 2020) and A. helianthi (Usha et al 2019). Evaluated for mycelial growth and conidial germination can determine the sensitivity of pathogenic fungi to fungicides.…”

A new method for single spore isolation and fungicide resistance monitoring of Cercospora beticola, and the first report of QoI‐resistant isolates with G143A or F129L mutations of the CbCyt b gene in China

“…Another study also emphasized that field isolates of C. beticola with EC 50 value >1.0 μg/mL for pyraclostrobin needed to be monitored closely (Secor et al, 2010). Currently, QoI-resistant strains of C. beticola were found in the United States (Bolton et al, 2013), Canada (Trueman et al, 2013), Slovakia (Hudec et al, 2020), Japan (Kayamori et al, 2020) and Serbia (Balandžić et al, 2020). Previous reports also demonstrated that resistance to QoI was attributed to a point mutation in Cyt-b gene, including the amino acid substitution of alanine for glycine at codon 143 (G143A), the substitution of phenylalanine with leucine at codon 129 (F129L) or substitution of glycine with arginine at codon 143 (G143R) (Bolton et al, 2013;Ma et al, 2018;Dixon et al, 2020).…”