Project Overview

Reports

Commodities

• Agronomic: corn

Target Pests

• Target Pests: other

Practices

• Pest Management: genetic resistance, pesticide resistance management

The southwestern corn borer Diatraea grandiosella (SWCB) is an historically significant pest of corn throughout the southern U.S. Since 1996, SWCB has been effectively managed through the use of Bt corn. However, in 2014 and 2015, SWCB were found surviving in Arizona on corn expressing the Cry1F Bt protein, and in 2022, SWCB were reported to be infesting Arizona corn expressing Cry1Ab + Cry1F and Cry1Ab + Cry1F + Vip3Aa. In 2023, SWCB were collected from corn expressing Cry1Ab + Cry1F in New Mexico. The New Mexico collection in currently in the laboratory at Texas A&M University. Putatively Bt resistant SWCB appear to be spreading in the southwestern U.S., and it is conceivable that Bt resistant alleles in SWCB in Arizona and New Mexico could move eastwardly into major southern corn production areas. It is vital to southern U.S. corn production that Bt resistant SWCB be characterized for resistance to the currently available Bt proteins utilized in corn for corn borer management. This research will potentially identify Bt proteins that are still efficacious, will aid in developing Bt resistance management plans, and will provide the information necessary to develop Extension bulletins and outreach presentations regarding managing Bt resistant SWCB. The data derived from the current proposal will lay the foundation for studies on cross-resistance, resistance inheritance (dominant or recessive, polygenic or monogenic), and the testing of homozygous and heterozygous resistant SWCB on current pyramided corn hybrids. Additionally, these resistant SWCB could be used in identifying resistance mechanisms and genes, allowing for development of rapid DNA-based resistance monitoring.

We will perform diet-based bioassays using the SWCB collected in New Mexico from Bt corn to determine susceptibility to all above-ground Bt traits currently utilized in U.S. corn production. These include Cry1A, Cry1A.105, Cry1F, Cry2Ab2, and Vip3Aa. Once responses to the various Bt proteins are determined, we will know which, if any, Bt proteins remain effective towards Bt resistant SWCB collected in New Mexico. This information is critical for developing informed Bt resistance mitigation plans. We must know what Bt technologies may be planted in areas where resistance is detected.

Utilizing the information we learn from the current project concerning the extent of Bt resistance in SWCB, we will develop Extension bulletins targeting at risk corn production areas in Arizona, New Mexico, and Texas with methods to mitigate Bt resistant SWCB where they occur and how to avoid developing Bt resistance SWCB issues. We will also utilize the information we learn to develop outreach presentations that will be delivered to corn growers in Arizona, New Mexico, and Texas.

The impact of this research could be extremely important. It is vital that we address the Bt resistant SWCB problem before it spreads, and mitigation becomes much more difficult and costly. Corn growers currently facing issues with Bt resistant SWCB will learn how to manage them and mitigate resistance, which in turn will prevent the spread of resistance into major corn productions regions. The cost of not proactively addressing the issue could lead to reduced yields, increased use of insecticides, and increased corn production costs.

The objective of the current proposal is to ascertain the level of resistance in SWCB originating from Antelope Wells (NM) to all Bt proteins currently available in corn for lepidopteran pest management.

This project will serve as a seed project directed towards a critical, emerging issue. Data from this project will aid in establishing Bt resistant SWCB in the laboratory, from which studies on cross-resistance, resistance inheritance (dominant or recessive, polygenic or monogenic), and testing of heterozygous SWCB on current pyramided corn hybrids could be performed. Additionally, these resistant SWCB could be used in identifying resistance mechanisms and genes, allowing for development of rapid DNA-based resistance monitoring.

The foundation of this project is to document and quantify Bt resistance in SWCB. Although Bt resistance in SWCB has been detected in the past, no data has been published in a refereed journal. The only information available is scant and exists in a white paper (US EPA 2018). Other information is not available to the public.

Once responses to the various Bt proteins are determined, we will know which, if any, Bt proteins remain effective towards Bt resistant SWCB collected in New Mexico. This information is critical for developing informed Bt resistance mitigation plans. We must know what Bt technologies may be planted in areas where resistance is detected.

This research, and the establishment of the Bt resistant SWCB colony in the laboratory will lead to more in-depth research to determine the characterization, and properties of the resistance such as gene dominance, monogenicity, cross-resistance and redundant killing ability of pyramided Bt corn toward homozygous and heterozygous Bt resistant SWCB, Bt resistance genomics, and development of marker-based rapid resistance monitoring procedures.

The information derived from this project will aid in the development of EPA and Extension materials that will be used to educate corn growers on the steps they should take to mitigate Bt resistant SWCB populations.