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Be Careful Which Hybrids You Match in Refuge Acres

Also cast a wary eye when evaluating comparisons, live or on paper.

Rootworm Bt corn is one of the hottest items on the block, definitely more popular than the introduction of sliced bread, by all accounts. So when you attend farm shows or field days, be sure you understand what you're looking at, and what trade-offs might be for various ways of handling these hybrids.

Here is a checklist that could help you steer clear of pitfalls, and get a more honest feel for whether rootworm Bt corn fits on your farm. And if it doesn't, how will you handle the refuge acre situation. Federal guidelines issued when the technology was approved require 20% of the acres in the same field be planted to regular, non-Bt rootworm corn. It can be treated with a soil insecticide or a seed-applied treatment, such as Poncho 1250, but it must not carry the rootworm trait. The idea is so that enough beetles survive and mate with resistant beetles so tat all resistant beetles don't constantly mate only with resistant beetles. That could eventually develop resistant strains, that could wipe out the effectiveness of the technology.

Environmental alarmists some 10 yeas ago predicted that resistant insects would be found within two years of release of Bt hybrids. Corn borer was the first on the scene, over a decade ago. So far, those resistance claims haven't materialized. But entomologists say following label specifications about refuge acre will be one of the keys to maintaining viability of the technology.

Justin Warren, AgriGold research testing agronomist in south-central Illinois, led the discussion at a field day near Monticello, Ill., last week.

If you're evaluating plots at field days, ask to see the same hybrid with and without the Bt rootworm trait. Remember, however, that even though hybrids are supposed to be identical, introducing the trait typically carries along baggage that could change some traits slightly. The new procedure used to produce Monsanto's VT3 rootworm event corn reportedly is more precise at inserting the train.

If you only see a competitor's Bt rootworm corn in a test, and not the isoline to that hybrid that goes along with it, be careful about conclusions, Warren says. You could wind up comparing apples and oranges.

Inquire about how the plots were treated since planting. How long have they been without water?

When deciding what to plant in your refuge acres next spring, remember that one choice is the isoline of the rootworm Bt hybrid, or in other words, the hybrid without the trait. If you include so many rows of the refuge hybrid in your planter box and use a soil insecticide on those rows that gives you a built in way to run yield checks in the fall, Warren notes.

Another option is to select a hybrid of different genetics that's possibly more naturally-resistant to rootworms than some other hybrids. You're not going to get tolerance anywhere near what the Bt rootworm trait will provide, but you might get more tolerance than just picking a hybrid at random, or even using the non-Bt version of the hybrid you're planting on most acres.

If you opt to go with a genetically different hybrid in the refuge rows, make sure it has good seedling vigor and is about the same maturity as the other Bt hybrid nest to it. That way you can avoid potential problems with delays in emergence and maturity later in the season.

Note that while Poncho 1250 is an option on refuge corn instead of applying a soil insecticide, data continues to show that Poncho 1250 is not particularly effective against large infestations of rootworms.

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