Different maize (Zea mays L.) inbreds influence the efficacy of Beaveria bassiana against major maize caterpillar pests, which is potentially affected by maize pathogen resistance

Authors: Dowd, Patrick; Johnson, Eric

Submitted to: Biocontrol Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/12/2022
Publication Date: 4/13/2022
Citation: Dowd, P.F., Johnson, E.T. 2022. Different maize (Zea mays L.) inbreds influence the efficacy of Beaveria bassiana against major maize caterpillar pests, which is potentially affected by maize pathogen resistance. Biocontrol Science and Technology. 32(7):847-862. https://doi.org/10.1080/09583157.2022.2055745.
DOI: https://doi.org/10.1080/09583157.2022.2055745

Interpretive Summary: Direct damage to corn ears by both insect feeding and rots caused by fungal molds cause billions of dollars in worldwide yield losses. Molds can also produce toxins that are harmful to people and livestock adding millions of dollars of indirect losses for corn related industries. Sustainable pest control practices like host-plant resistance to prevent mold and applying bioinsecticides for insect control are being promoted over reliance on chemical pesticides. We now recognize that integrating multiple sustainable control practices can be complicated and is poorly understood. Interactions can be beneficial or harmful. For example, a widely used fungal bioinsecticide can inhibit the growth of some fungal plant diseases. In this case, we treated corn leaves with this biopesticide and found the treatment was less effective in killing caterpillar pests when the leaves were from some (not all) plants with resistance to a corn mold. Thus, crop production agriculture must consider additional effects and interactions while developing and deploying integrated pest controls in order to provide the most effective and comprehensive strategies for sustainable pest management.

Technical Abstract: Plant resistance factors, such as secondary metabolites and proteins, are known to affect the viability of insect fungal pathogens. Different plant varieties can have different levels of plant pathogen resistance, which could potentially influence efficacy of insect pathogens. Leaves from twelve maize (Zea mays L.) inbreds with different reported resistance to Fusarium and/or Aspergillus pathogens were examined for their influence on the efficacy of two different commercial strains of Beauveria bassiana (Bals.-Criv.) Vuill. against corn earworms, Helicovepa zea (Boddie) and fall armyworms, Spodoptera frugiperda (J.E. Smith). For leaf assays with first instar caterpillars, mortality on day 2 ranged from an inbred dependent high of 92% to a low of 14% for corn earworms, and from a high of 84% to a low of 22% for fall armyworms. Leaves that caused the greatest inhibition of B. bassiana efficacy had the greatest amount of caterpillar damage compared to corresponding control leaves that were not treated with B. bassiana. Damage ratings due to Fusarium graminearum (Schwabe) infection were often correlated with the mortality levels of both species of B. bassiana treated caterpillars that fed on leaves, suggesting that maize resistance factors to F. graminearum were interfering with the efficacy of B. bassiana. The study suggests that the interaction between plant pathogen resistance factors and insect pathogens should be considered when developing both new plant varieties and biocontrol strains that may be used for insect pest management where possible.