Source: Christina DiFonzo, Michigan State University Extension, Department of Entomology
Some major changes were made to the Handy Bt Trait Table updated for 2018. To improve readability, trait packages are now alphabetized instead of grouped by seed company. Also, letter abbreviations for insect names and herbicides were replaced with simple Xs.
Last year an “ineffectiveness” column was added, listing insect x Bt combinations with field-failures, confirmed resistance or cross-resistance in lab assays of the field. For 2018, this column has the same format, but is relabeled “Resistance to a Bt protein in the trait package has developed in.” This column is intended to track cases of resistance development to Bts, plus alert producers and consultants to potential management problems. Depending on the insect, resistance may be widespread, as in western bean cutworm, or regional, as in corn rootworm. Since the Trait Table is a national publication, check with local Extension educators and seed dealers to determine the status of Bt resistance in your local area.
Note that based on overwhelming evidence from lab assays and the field, companies removed western bean cutworm control from Cry1F Bt hybrids. Only hybrids with the Vip3A Bt protein provide reliable control of this insect. For all other hybrid packages, western bean cutworm infestations should be managed using a combination of scouting and spraying at threshold.
The updated table does not include the new Enlist (2-4D tolerance) trait. Hopefully it can be incorporated into the table next season.
The publication has a column titled 'Resistance to a Bt protein in the trait package has developed in:' to highlight insect x Bt combinations with documented field-failures, confirmed resistance or cross-resistance. These statements are based on published lab assays and/or field research. This column is intended to alert growers and consultants to potential management problems, influence seed selection, and encourage field scouting.
It is important to note that the Trait Table is a national publication and resistance may be widespread (as in western bean cutworm) or regional (as in corn rootworm). Check with your local seed company or extension personnel for the types of Bt resistance present in your area.