Baseline Sensitivity and Control Efficacy of Various Group of Fungicides against Sclerotinia sclerotiorum in Oilseed Rape Cultivation

Nazanin Zamani-Noor

doi:10.3390/agronomy11091758

Abstract

Sclerotinia stem rot (SSR), caused by Sclerotinia sclerotiorum, is a devastating disease of oilseed rape that may cause significant yield losses if not controlled by cultural management strategies and fungicide applications. Studies were conducted to evaluate the efficacy of different group of fungicides as well as a biopesticide, including azoxystrobin, boscalid, fludioxonil, prothioconazole, tebuconazole, azoxystrobin/tebuconazole, boscalid/pyraclostrobin, prothioconazole/fluopyram and Bacillus amyloliquefaciens, on baseline sensitivity of S. sclerotiorum isolates under in-vitro conditions as well as control of SSR in the field. Artificial inoculation and mist irrigation prompt to reproducible SSR infection in oilseed rape cultivation. All compounds significantly reduced 36.7% to 86.9% SSR severity and increased 55.2% to 98.7% yield, 1.5% to 7.0% thousand grain-weight, 1.5% to 5.9% oil and 0.1% to 1.3% protein content. Fludioxonil, boscalid/pyraclostrobin and fluopyram/prothioconazole achieved strongest fungicidal activity against SSR. The biopesticide provided 36% of disease control. Under in vitro conditions, B. amyloliquefaciens not only strongly inhibited mycelial growth but also the formation of sclerotia in all concentrations. Boscalid and fludioxonil exhibited the highest level of fungicidal activity against S. sclerotiorum, with mean EC50 values of 1.23 and 1.60 μg a.s. mL−1. The highest variability of EC50 values between isolates was observed towards prothioconazole and azoxystrobin.

Highlights

Sclerotinia stem rot (SSR), caused by Sclerotinia sclerotiorum (Lib.) de Bary, is a disease of major importance worldwide
It was observed that oilseed rape plants potentially return more sclerotia by number or weight to the soil in comparison with the other crops tested in their study and potentially pose a bigger disease risk for following susceptible plants [3]
The specific objectives of the present study are to: (i) Evaluate the efficacy of a range of fungicides in different classes as well as a biopesticide against Sclerotinia stem rot in oilseed rape cultivation under field conditions; (ii) determine the effect of foliar applications of fungicides on yield and yield parameters of oilseed rape; (iii) in vitro screening sensitivity of S. sclerotiorum isolates to different concentrations of several fungicides with various mode of actions; and (iv) assess effects of different groups of fungicides on sclerotial formation

Summary

Introduction

Sclerotinia stem rot (SSR), caused by Sclerotinia sclerotiorum (Lib.) de Bary, is a disease of major importance worldwide. The pathogen has a remarkably broad host rang, which can infect more than 400 plant species, including economy important arable crops such as oilseed rape, mustards, soybean, and sunflower [1]. Central to the success of S. sclerotiorum as a plant pathogen is the production of several sclerotia on infested plants. Previous study demonstrated that the number of sclerotia inside the soil is an essential factor in disease outbreak and the sclerotial size and weight influenced the germination rate of sclerotia and production of ascospores [3]. It was observed that oilseed rape plants potentially return more sclerotia by number or weight to the soil in comparison with the other crops tested in their study and potentially pose a bigger disease risk for following susceptible plants [3]

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Conclusion