Application of fungicides for management of major root and lower stem rot diseases of wheat

Ivo Yanashkov, Svetla Maneva, Tzenko Vatchev

Abstract: Root and lower stem disease complex is among the most economically important diseases affecting small grain cereal crops causing seedling blight before or after emergence of the seedlings, root and lower stem rot in older plants. The causal agents of these pathological events include various soil and seedborne pathogenic fungi and fungal-like oomycetes. Fungicide seed treatment is a routine practice for the control of these pathogens in cereal crops. The fungicide products currently registered belong to several chemical groups, namely dithiocarbamates, imidazoles, oxathicarboxamides, pyrazole-4-carboxamides, triazoles, etc. The present study evaluated the effect of new and existing on the market fungicide formulations on mycelial growth of three major pathogens – Fusarium culmorum, Drechslera sorokiniana and Pythium ultimum, causing root and lower stem rot of wheat. Out of the fungicides tested in vitro, BAS 591 01 F (prochloraz 60 g/L + triticonazole 20 g/L), BAS 9242 4 F (thiram 200 g/L + carboxin 200 g/L), Vitavax 2000 (thiram 200 g/L + carboxin 200 g/L) and Rankona I-mix showed 100% inhibition of the mycelial growth and proved to be fungicidal on the three pathogenic fungi at 37.5, 75, 10 and 25 ml per liter of agar, respectively. BAS 700 05 F (fluoxapyroxide 333 g/L) and BAS 595 01 F (prochloraz 60 g/L + triticonazole 20 g/L) exhibited fungicidal properties against D. sorokiniana and completely inhibited the mycelial growth of F. culmorum and P. ultimum at 18.75 and 37.5 ml per liter of agar. The products that showed fungicidal action against the three pathogenic species were evaluated for their effectiveness in controlling damping-off of wheat (cultivar Madara) seedlings incited by each pathogenic species. Growth chamber pot experiments were conducted with treated and untreated seeds artificially inoculated with individual pathogen. Vitavax 2000 applied at the recommended dose of 200 ml per 100 kg of seeds proved to be the most effective in controlling damping-off in wheat seedlings caused by F. culmorum – 75.8% reduction of disease intensity, followed by Rankona I-mix at rate of 100 ml per 100 kg and BAS 9242 4 F at 300 ml per 100 kg with 69.4% and 63.3% levels of control, respectively. BAS 9242 4 F provided full control (96.1%) of the damping-off in wheat plants caused by D. sorokiniana. Significant but lesser disease reduction was achieved after treating the artificially infested seeds
with Rankona I-mix and Vitavax 2000 – 77.3% and 67.8%, respectively. All the three fungicides showed high levels of efficiency – between 92.2% и 81.9%, against damping-off caused by P. ultimum.

Keywords: fungicides; seed treatment; seedborne diseases; soilborne pathogens; wheat

Date published: 2017-09-13