Long-term dynamics of causative agents of stem base diseases in winter wheat and reaction of Czech Oculimacula spp. and Microdochium spp. populations to prochloraz

Abstract

Cereal stem base diseases occur in the Czech Republic every year. In Europe today, there is a trend towards more comprehensive strategies for growing and protecting crops with the aim of reducing risks to the environment and to health associated with pesticide residues. Precise knowledge as to the dynamics of causative agents of stem base disease may constitute an important part of the decision support system for cereal-growing strategies. Over 17 years (1999–2015), 482,219 plants were collected within the Czech Republic and visually inspected for stem base disease symptoms. An in vitro culture test was then conducted to determine the causative agents. During 2012–2015, the response of Oculimacula spp. and Microdochium spp. populations to prochloraz was tested. The most plants infected with Oculimacula spp. (>6 %) were detected in 2004, 2008, 2014 and 2015. The lowest infection rates were recorded in 2005, 2006, 2011 and 2012, when the level did not exceed 2 %. Microdochium spp. occurred most frequently in 2003, 2006 and 2013 (29–37 % incidence). Its lowest occurrence was recorded in 2014, when only 13 % of plants were infected. All isolates of Microdochium spp. were sensitive to prochloraz. Some isolates of Oculimacula spp. showed low to medium resistance (12 and 5, respectively, from 86 total isolates through the entire testing period). In all years, ED50 for the Oculimacula spp. population was ≤0.1 μg ml−1. ED50 for Microdochium spp. ranged between 0.01 and 0.06 μg ml−1.