Integrating a chemical fungicide and Bacillus subtilis BIOUFLA2 ensures leaf protection and reduces ear rot (Fusarium verticillioides) and fumonisin content in maize

Abstract

Fungicides in maize production under tropical conditions reduce losses from foliar diseases, but only a few reduce ear rot incidence or mycotoxin contamination in kernels. Biocontrol agents (BCAs) may reduce postharvest losses but their efficacy has not been demonstrated in field conditions. Here, we evaluated the use of bacterial isolates in tandem with fungicides on Fusarium verticillioides incidence and fumonisin content. After an early screening, Bacillus subtilis and Streptomyces araujoniae isolates were used in field trials. Maize plants were sprayed twice: at the end of the vegetative stage (V9) and at the beginning of the reproductive stage (R1). Sprays were made by applying water, B. subtilis strain BIOUFLA2, S. araujoniae strain ASBV‐1T, or fungicide (cyproconazole + azoxystrobin) in different combinations, totalling nine treatments. Ten days later, all maize ears were inoculated with F. verticillioides. Plants were assessed for foliar diseases, grain yield, F. verticillioides incidence and fumonisin content in kernels. The treatment with two fungicide sprays reduced most of the foliar diseases but not F. verticillioides incidence in kernels. Twice‐sprayed B. subtilis and S. araujoniae reduced F. verticillioides, but did not protect leaves against other pathogens. All treatments encompassing a fungicide followed by one of the BCAs reduced F. verticillioides incidence compared to control. Twice‐sprayed fungicide increased fumonisin by 50% compared to water control, while fungicide followed by B. subtilis decreased the fumonisin content by 40%. Replacing the second chemical spray with S. araujoniae did not reduce the fumonisin content but provided a higher yield than a twice‐sprayed fungicide. Exclusive use of chemical fungicides may not ensure higher grain quality and yield, but the integration with B. subtilis BIOUFLA2 can accomplish both.

Environmentally Friendly Wheat Farming: Biological and Economic Efficiency of Three Treatments to Control Fungal Diseases in Winter Wheat (Triticum aestivum L.) under Field Conditions

“…were potential biological agents for the control of Fusarium head blight (FHB). Guimaraes et al (2020) [44] evaluated the use of bioagents (B. subtilis + Streptomyces araujoniae), in combination with fungicides (cyproconazole + azoxystrobin), on the incidence of Fusarium verticillioides in maize crop. These authors found that spraying bioagents separately from fungicides was less efficient in controlling diseases than combination spraying.…”

Integrating a Bacillus‐based product with fungicides by foliar application to protect soybean: a sustainable approach to avoid exclusive use of chemicals

“…applied on leaves can colonize the plant and reach the pods or seed issues 8,41,42 . Then, BBP foliar treatments may protect the grains by reducing pathogenic fungi or even mycotoxin content 23 …”

“…One hypothesis of this work is that BBP alternated or combined with compatible chemical fungicides would better control multiple soybean diseases than conventional fungicide programs. Furthermore, beneficial bacteria can colonize the plant issues and establish positive feedbacks with the plant for a long time, protecting the commercial parts even after harvest 22,23 . The application of BBP by foliar sprays may assure the protective activities of bacterial agents against plant diseases during pre‐ and post‐harvest stages 24,25 .…”

“…Furthermore, beneficial bacteria can colonize the plant issues and establish positive feedbacks with the plant for a long time, protecting the commercial parts even after harvest. 22,23 The application of BBP by foliar sprays may assure the protective activities of bacterial agents against plant diseases during preand post-harvest stages. 24,25 Then, the other hypothesis of the study is that BBP protects the soybean against multiple diseases even after harvesting the seeds.…”

“…The correct moment to apply BBP by foliar application, in combination with usual fungicide management, may improve plant protection in its whole cycle. 23 As a result, this work aimed to verify the activity of BBP against foliar, pods and post-harvest pathogens of soybean by alternating or combining it with chemical fungicides usually applied to control Asian rust (Phakopsora pachyrhizi) and leaf spots. Furthermore, we investigated the influence of chemical fungicides on bacterial growth at different times of application.…”