Soil microbes from conservation agriculture systems reduce growth of Bt-resistant western corn rootworm larvae

Authors: PADDOCK, KYLE - University Of Missouri; Veum, Kristen; FINKE, DEBORAH - University Of Missouri; ERICSSON, AARON - University Of Missouri; Hibbard, Bruce

Submitted to: Journal of Pest Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/19/2023
Publication Date: 1/10/2024
Citation: Paddock, K.J., Veum, K.S., Finke, D.L., Ericsson, A.C., Hibbard, B.E. 2024. Soil microbes from conservation agriculture systems reduce growth of Bt-resistant western corn rootworm larvae. Journal of Pest Science. https://doi.org/10.1007/s10340-023-01725-2
DOI: https://doi.org/10.1007/s10340-023-01725-2

Interpretive Summary: Western corn rootworm (WCR) is a damaging pest of corn accounting for over $2 billion annually in management costs and yield losses. Practices aimed at improving soil health can influence soil microbiomes, but the role of soil microbiomes in pest management is not well known. This study found that the soil microbiome from a long-term, conservation management system (an extended corn-soybean-wheat rotation with cover crops under no-till) influenced WCR-corn interactions compared with the microbiome from a conventional management system (corn-soybean rotation under mulch tillage and no cover crops). The most common control tactic for WCR, transgenic (Bt) corn, was equally effective at controlling susceptible insects in the presence of both soil microbiomes. However, Bt-resistant insects demonstrated lower weight when grown in the presence of the conservation soil microbiome. These results show a potential pest management benefit of conservation management practices through changes in the soil microbiome. As interest in soil health and adoption of conservation practices continues to grow, this research will benefit producers and crop advisers by providing a better understanding of the impact of management decisions on the sustainability and profitability of corn production systems.

Technical Abstract: Sustainable agricultural management practices aimed at improving soil health can alter the soil microbiome, which can improve plant health and alter plant defenses against insects. The western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte, is a major belowground pest of corn throughout the U.S. Corn Belt. Pest management relies heavily on the planting of transgenic crops expressing Bacillus thuringiensis (Bt) toxins. In this study, we ask how corn-WCR interactions via the soil microbiome are affected by a conservation management system (extended corn-soybean-wheat rotation with cover crops under no-till) compared with a conventional management system (corn-soybean rotation under mulch tillage and no cover crops) when combined with WCR main control tactic, transgenic Bt corn. To do this, we applied soil microbes from the conservation and conventional management systems to two corn lines, one producing Bt and one non-Bt. We then reared Bt-resistant and Bt-susceptible WCR for 5 days on inoculated seedlings to examine both plant and insect changes in fitness. We found that Bt was effective against susceptible larvae in both soil treatments. Bt-resistant larvae were smaller when reared in the presence of soil microbes from the conservation management system. Comparing the microbial communities using 16S rRNA sequencing revealed that management practices influenced the microbiomes associated with the soil and the plant rhizosphere, but not the WCR microbiome. Yet, control of Bt-resistant WCR may be improved when using Bt corn in a conservation system without sacrificing Bt effectiveness in non-resistant insects. Our findings suggest there may be value for growers in utilizing conservation management practices, such as no-till and cover crops, in their agricultural systems through bottom-up changes to plant-insect interactions via the soil microbiome.