What’s Wisconsin’s #1 soybean weed problem?

        Chris Boerboom, UW Extension Weed Specialist, makes a case that it’s fast becoming glyphosate-resistant volunteer corn.  Of course volunteer corn isn’t difficult to control if producers are willing to spray a grass herbicide in addition to glyphosate on soybeans.  Researchers in Minnesota and Illinois suggest 75 to 90 “clumps” of volunteer corn per acre will knock soybean yields down by about 1 percent.  That equates to about 1 clump for every 500 square feet (a relatively low density). For a 50 bushel per acre soybean yield a 1 percent yield loss equates to 0.5 bushel.  Even this minimal yield loss will pay for a tank-mixed grass herbicide applied at relatively low rates.  Most postemergence grass herbicides (ACCase inhibitors) are very effective in controlling volunteer corn.  The notable exception is that Poast Plus can be less effective.  These herbicides can be tank mixed with glyphosate, but the adjuvant requirements may be greater than the typical ammonium sulfate (AMS) added with glyphosate and may depend if a glyphosate formulation is “loaded” (requires no additional surfactant) or “non-loaded” (surfactant is required). 

        The key to volunteer corn management is to know if the field had glyphosate-resistant corn the previous year. If so, scout to determine if volunteer corn is present. It will be much more cost effective to include a postemergence grass herbicide in the initial glyphosate application than to make a second application just to control the volunteer corn.  A second application may require a higher herbicide rate plus the additional application cost.  In total, this may cost $10/acre or more than if the postemergence grass herbicide was tank mixed with the first application.  Herbicide options to control volunteer corn include:  Arrow, Assure II, Fusilade DX, Fusion, and SelectMax. 

Food vs. Fuel vs. Fool

        Remember last summer when the Grocery Manufacturer’s Association blamed ethanol for raising corn prices and ultimately food prices in the marketplace?  Since that time several university and USDA studies basically came to the conclusion that such a premise was baloney (or bologna in food science vernacular).  Commodities only constitute about 19 percent of the retail food cost to begin with.  Currently corn prices have taken a dive, but food prices have remained high.  In fact, according to Doane’s Agricultural Report, food giant Kraft more than doubled last year’s net income, pocketing a cool $1.4 billion.   

Aphid-resistant Soybeans

        Universities and seed companies are identifying and/or developing strains of soybeans resistant to soybean aphid.  Look for them at a dealer near you in the coming years.   

Foliar Fungicides on Corn

        Applying foliar fungicides to corn has been a popular topic and practice the past three years.  Initially, there was very little research and experience with the practice.  Sale pitches hinged upon selected localized strip trials along with nice color photos of corn leaves with and without disease symptoms.  For the past several years there have been hundreds of university trials done across the Corn Belt, including Wisconsin.  The results have been surprisingly consistent from this standpoint:  yield responses have been highly variable and inconsistent.  This is not surprising when the genetic diversity of corn hybrids for disease resistance is mixed with a range of environmental conditions that may favor or inhibit disease proliferation.  One thing is for sure, foliar fungicide applications to corn as a routine practice across all acres is going to be a net loser.  With application and chemical costs totaling $25 to $30 per acre in 2009, producers are going to have to be pretty sure of a significant yield boost from the fungicide application.  Selecting hybrids with known disease resistance or tolerance is probably a better initial approach to limiting yield losses from disease pressure. 

Horsing Around with Corn Hybrids

        Sometimes a corn hybrid is referred to as a “workhorse” or a “racehorse.”  What exactly does that mean and is either or both necessarily good?  Effectively these terms refer to how a hybrid performs in a particular type of yield environment (low, average, or high).  For example, a workhorse hybrid outperforms most other hybrids in low yielding environments (e.g. drought years) but is well below the performance of most hybrids in good crop years.  Conversely, a racehorse stresses to a low finish in poor crop years but will lead the pack in high yield years.  Both hybrid horse types will yield about average in most crop years.

        Joe Lauer, UW Extension Corn Agronomist, evaluated over 2500 hybrids that had been tested in at least seven different environments to see if racehorse and workhorse hybrids actually exist and to what extent.  He found that 6 percent of the hybrids exhibited racehorse tendencies and 8 percent fell into the workhorse category.  The vast majority of hybrids, 86 percent, were stable and yielded about the same relative to other hybrids in both low and high yield environments. For a grower selecting hybrids, workhorse hybrids are not desirable and should be avoided.  True racehorses are risky because they can bust under stress.  Plant breeders strive for a modified racehorse, one that is at least average in poor crop years but progressively above average in normal to high-yielding years.  All of this equine talk speaks to the foundation principle for selecting corn hybrids------select those hybrids that perform consistently well across a range of environments.