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

Trichoderma species are widespread soil-living fungi known for their roles in both agriculture and natural ecosystems. While some species are used as effective biocontrol agents against plant pathogens, others, such as T. afroharzianum , have recently been identified as pathogenic, causing diseases like Trichoderma ear rot in maize and infections in wheat. The occurrence of Trichoderma species 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 effect of environmental factors, especially temperature and precipitation, on their occurrence. Over a seven-year period (2018–2024), 345 samples of maize cobs, stalks, and soil samples were received 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 gathered from each location and correlated with the occurrence of Trichoderma ear rot. Additionally, in vitro and in vivo climate chamber trials were conducted to confirm the favorable temperature conditions for disease development. Our results indicate that T. afroharzianum was the most prevalent species isolated from maize cobs and agricultural soil, 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 T. afroharzianum , while cooler and wetter regions (< 18.2 mean temperature) showed little to no occurrence of 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 compared to other Trichoderma species, with an optimal temperature range between 28 and 32°C.