Effectiveness of fungicides with different modes of action against net blotch disease of two-rowed spring barley

Abstract

Net blotch disease caused by Pyrenophora teres is one of the most damaging fungal diseases of barley crop. This study screened comparatively the effectiveness of eleven fungicide products applied to malting barley (Hordeum vulgare L. conv. distichum Alef.) cultivar ‘Daciana’ in conditions from Transylvania. After fungicide treatment, the net blotch disease index decreased an average of 70.37-78.04% relative to untreated control. Fungicide application ensured an average of 28.66% grain yield increase, 7.51% thousand grains weight increase and 4.36% grain starch content increase relative to untreated control. Top performance was obtained by using products that contained demethylation inhibitors targeting sterol biosynthesis in combination with other active substances with a different mode of action particularly targeting mitochondrial respiration. It is a difficult task to achieve top performance on all dimensions: strict disease suppression, high quantity and quality grain yields. Preventing the occurrence of pathogen resistance to fungicide and minimizing negative effect on crop as well as remanence in the plant, are the main challenges for fungicide use and should receive further attention.

Net blotch (Pyrenophora teres Drechsler): An increasingly significant threat to barley production

“…P. teres is a hemibiotrophic pathogen that maintains a saprophytic lifestyle between two vegetation seasons (Suciu et al 2021;Tini et al 2022). It is transmitted through infected plant residues and persists in infected stubble, plant debris and barley seeds (Figure 2).…”

“…The sexual stage involves the formation of pseudothecia with asci and ascospores, while in the asexual stage, the pathogen forms conidiophores with conidia. Both stages can serve as primary inoculum sources for new infections (Suciu et al 2021;Vasighzadeh et al 2022). To produce a larger amount of primary inoculum, the pathogen requires cooler and more humid environmental conditions (McLean et al 2009).…”

“…Plant Protection Science, 60, 2024 (1): 1-30 https://doi.org/10.17221/122/2023-PPS Nonetheless, based on the available evidence, under longer-lasting cooler and humid conditions, the process of infection typically begins with the germination of mature conidia and ascospores on the surface of green barley plant parts (Liu et al 2011;Martin et al 2021;Suciu et al 2021). A suitable wet period of 5−30 hours or even longer is necessary for successful infection, followed by appropriate temperatures.…”

“…The first phase is biotrophic and asymptomatic and is characterized by penetration into epidermal cells and spread within the mesophyll. The second phase occurs after a few days and manifests as the appearance of chlorosis and necrosis, marking the transition of the pathogen into a necrotrophic stage (Suciu et al 2021). The necrotro-phic stage is dominant, and the newly formed germ tubes are often highly branched (Jørgensen et al 1998).…”

“…The main classes of fungicides currently used worldwide for controlling net blotch are succinate dehydrogenase inhibitors (SDHI), demethylation inhibitors (DMI) and quinone outside inhibitors or strobilurins (QoI) (Sierotzki et al 2007;Sooväli & Koppel 2010;Mair et al 2016;Rehfus et al 2016;Stepanović et al 2016;McLean & Hollaway 2019;Suciu et al 2021;Tini et al 2022).…”