Effect of temperature and precipitation on the occurrence of Trichoderma ear rot in Europe

Abstract Trichoderma species are widespread soil-living fungi known for their roles in both agriculture and natural ecosystems. While some species are effective biocontrol agents against plant pathogens, others, such as T. afroharzianum, have recently been identified as pathogenic, causing diseases such as Trichoderma ear rot in maize and infections in wheat. The occurrence of Trichoderma ear rot is strongly influenced by environmental factors, particularly temperature and precipitation. This study aims to assess the occurrence and distribution of Trichoderma ear rot in maize across Europe and to evaluate the effects of environmental factors, particularly temperature and precipitation, on its incidence. Over a seven-year period (2018–2024), 345 samples of maize cobs, stalks, and soil samples were collected from 72 locations in Europe. The obtained Trichoderma isolates (n = 130) were identified to the species level, and their pathogenicity to maize was tested under controlled conditions. Weather data, including temperature and precipitation, were recorded at each location and correlated with Trichoderma ear rot occurrence. Additionally, in vitro and in vivo climate chamber trials were conducted to determine the favorable temperature conditions for disease development. Our results indicate that T. afroharzianum was the most prevalent species isolated from maize cobs and agricultural soils, exhibiting strong pathogenicity in maize cobs. Correlation analysis between the occurrence of T. afroharzianum and environmental factors revealed that high temperatures (> 19.6°C mean temperature), particularly during the summer months, strongly favored the presence of infections with T. afroharzianum, while cooler and wetter regions (< 18.2°C mean temperature) showed little to no disease caused by pathogenic Trichoderma species. In vitro and in vivo climate chamber experiments confirmed these results observed in the field. The growth rate of T. afroharzianum isolates was significantly higher than that of other Trichoderma species, with an optimal temperature range of 28‒32°C.