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2001 Full Season BT Corn Performance

By: Steve Norberg

This study is to help determine which is more profitable to grow Bt corn or Non-Bt corn. Much of the information a farmer needs to make this decision is not available. Such as what is the value of the Bt gene to farmers in NW Missouri?

The value of the Bt gene is going to depend on the European corn borer population in the field and how damaging it is to the crop. Unfortunately European corn borer pressure varies from location to location and year to year. Usually heavy corn producing areas in Iowa and Kansas get more damage to the European corn borer than NW Missouri.

This research helps to quantify how much damage we get in this area. This research is in its fourth year. The experiment uses isolines to determine the advantage of the Bt gene for farmers. Isolines are hybrids or cultivars, which are identical except for the gene, you are interested in (IE. Bt gene). The table below shows research where isoline where produced side by side to determine the value of the Bt gene.

Table 1. Summary of differences in yield by planting Bt vs. Non-Bt corn in NW Missouri.

Year Location # of pairs of
Isolines * /
# locations
Yield of Bt
Isoline
(bu/acre)
Yield of
non-Bt
Isoline
(bu/a)
Value of Bt
gene in
(bu/ a)

1997 Hundley-Whaley & Graves 2 pair / 2 loc. 142.1 139.5 2.6
1998 Hundley-Whaley & Graves 9 pair / 2 loc. 141.5 142.0 - 0.5
1999 Hundley-Whaley 5 pair / 1 loc. 93.5 94.3 -0.8
2000 Graves 9 pair/1 loc. 126.6 119.6 7.1
2000 Hundley-Whaley 9 pair/ 1 loc. 138.4 137.3 1.1
2001 Graves 9 pair 1 loc. 134.6 129.1 5.5
2001 Hundley-Whaley 9 pair / 1 loc. 125.5 98.7 26.8
Avg. Hundley-Whaley 5.84
Avg. Graves 3.48

*Only isolines with the same numbers were used in comparisons unless specified they were isolines. Differences in yield range from losing a 0.8 bu/a to saving 26.8 bu/acre. Any yield increase is going to have to pay for any increased seed cost and technology fee charged by seed companies.

If you figured the Bt seed cost's $24 extra per bag and that a bag covered three acres then you would have to make at least $8 per acre in increased yield to break even. At $1.70/bushel it would take 4.7 bu/acre to pay for the seed cost not figuring interest on seed purchase.

Buying Bt seed is like buying insurance against the European corn borer. Prior to 2001 at Hundley-Whaley Bt did not pay, however this year it paid of big. This without considering any marketing problems with countries that do not desire genetically modified organisms (GMO's).

Some things to consider are scouting and spraying in bad years, which may have been the most economical treatment although not in the experiment, also it is important to consider the difference between non-bt hybrids, which can be seen this year on the Hundley-Whaley farm (page 17). Natural resistance to corn borer decreases damage from corn borer from 40 to 14 bushels per acre which decreases the need for the bt gene. How long the corn crop will stand in the field is another important consideration when deciding to spray or use bt technology.