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Corn+Soybean Digest

Think Different: Input Addiction Aids Resistance


Are you a farmer who buys into the retailer/company/lender logic of adding more inputs to the spray tank, just in case insects or disease might be out there? Or are you fortunate to have a trusted source who scouts and openly discusses practices that can lead to weed, insect and disease resistance?

University of Illinois Entomologist Mike Gray calls such sales thinking "Insurance Pest Management," which is a bad substitute for the proper IPM, Integrated Pest Management.

We've written ad nauseam about the need for soil-applied residual herbicides in soybeans to begin to slow the glyphosate-resistance weed outbreak in the Midwest. Unfortunately only 65% of farmers stated they are more likely to use herbicides with residual activity in 2012, according to a recent survey at Commodity Classic.

Another scary statistic from that same survey indicated that 65% of farmers plan to make "preventive" fungicide applications. Hopefully retailers recommend multiple mode-of-action products to reduce potential resistance to corn and soybean diseases, as several companies are pushing multiple applications per season.

To learn how one Illinois grower thinks different about fungicide effectiveness, read "Walk Your Fields" on page 6. And check out "Bring Out the Best in Continuous Corn" on page 12 for further fungicide value knowledge.

One more resistance concern involves western corn rootworm and Bt corn. Monsanto is investigating rootworm performance complaints in 437 fields in 11 Corn Belt states, or 0.2% of total acres planted to Bt hybrids carrying its Cry3Bb1 trait. This is the first Bt rootworm trait where university researchers found field-evolved resistance in continuous cornfields with repeated use of Cry3Bb1 hybrids.

Given a growing geography of problems, Gray and a group of 21 other university and USDA-ARS entomologists sent a letter to the EPA in March. It detailed their concerns with future durability of the SmartStax pyramid (stack) of Cry3Bb1 + Cry34/35Ab1 traits when used as a solution in known rootworm problem areas, given the fact that the refuge was reduced from 20% to 5%. Since half of this current stack may have resistance issues, that puts more potential resistance pressure on Cry34/35Ab1 due to smaller refuge. And this is a concern because more companies are developing similar pyramid hybrids with Cry34/35Ab1.

Until further research sorts out these concerns, farmers should rotate different Bt rootworm traits in fields with a history of western corn rootworm problems, or rotate to soybeans.

I sincerely thank you for reading and for being willing to Think Different.

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