Integrated Clay-Azoxystrobin and Trichoderma-Based Treatments for Managing Magnaporthiopsis maydis Maize Late Wilt Disease

Magnaporthiopsis maydis, the causal agent of maize late wilt disease (LWD), is a destructive soil-borne pathogen for which effective and sustainable control remains challenging. We evaluated an integrated management strategy combining clay-based azoxystrobin formulations with Trichoderma-based seed coating in two maize hybrids differing in susceptibility to LWD: the highly susceptible sweet maize hybrid Prelude and the moderately susceptible fodder hybrid Colossus. Bentonite- and sepiolite-based azoxystrobin formulations were applied alone or with two Trichoderma mixtures under net-house conditions. Based on an in vitro assay, T. asperellum, T. longibrachiatum, and T. virens, which inhibited pathogen growth by 37 to 53%, were selected and combined. At the latent mid-season stage, treatment effects on plant growth were limited, but qPCR showed that pathogen DNA levels in infected, untreated Prelude plants were up to 24-fold higher than in Colossus. In Prelude, several treatments reduced pathogen DNA to 2–9% of the infected control. By the end of the season, treatment efficacy became more pronounced. In Colossus, bentonite-azoxystrobin alone or combined with Trichoderma-based seed coating performed best, increasing shoot weight by 62 to 67%, cob weight by 85 to 90%, and health indices by 52 to 67% relative to the infected control. In Prelude, Trichoderma-based seed coating combined with sepiolite-azoxystrobin produced the strongest response, increasing shoot and cob weight by 116 and 145%, respectively. Across both cultivars, clay-based formulations, alone or combined with biological treatment, reduced pathogen DNA to near zero. These findings support this integrated approach for LWD management under net-house conditions, pending field validation.