QWhat is the application rate equivalence for a field of BT corn vs a field of Organic corn spraying BT as an insecticide?

What is the application rate equivalence for a field of BT corn vs a field of Organic corn spraying BT as an insecticide?

AExpert Answer

What a great question! It even caused me to put down my breakfast of coffee and mixed GMO and non-GMO grain cereal. Note in passing that, worldwide, coffee is being devastated by coffee rust disease: resistance has been discovered, but one way to protect our crops from disease in the future will be biotechnology. An example of this is GMO blight-resistant chestnut, where a gene from wheat destroys the plant-damaging toxic chemical produced by the fungus, so rendering the tree disease-resistant.


But I digress. This is difficult to calculate perfectly, but we can do some back-of-the-napkin estimations from available data:

  • In the commercial Bt for application (www.cdms.net/ldat/ld4KK005.pdf), the bacteria is 54 percent, and the application rate (from the label) is about 1 lb. per acre, with repeat applications every 3–14 days; this is then about one-half lb. per acre per application. Let’s say every seven days for a crop life of four months; then the amount would be 8 lb. of Bt bacteria per acre.

Now to a Bt crop, using corn (maize) as the example:

This is interesting! It means that the Bt in Bt-containing crops contains about the same level of Bt as is applied by organic farmers when they spray the bacteria. Now, of course, the bacteria is not 100 percent Bt protein, so I need to check with colleagues on that and amend this answer when I have that information.
However, note that EPA also reported that plant-produced Bt biodegraded over 42 days and had a half-life of 4.5 days in test soils. As Bacillus thuringiensis is a natural soil bacterium, there is an additional amount of Bt in soils from this natural source.

Posted on April 18, 2018
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