IN ANY given spring, you can usually go somewhere in the Midwest where cold, wet spring weather and crusty soil conditions forced farmers to replant more of their corn than usual.

This year Ohio was one area where weather was less than cooperative after planting. “Replant acres were higher than average in many areas of the Corn Belt,” says Jim Beuerlein, an agronomy professor with Ohio State University. “Here in Ohio, farmers normally need to replant less than 1% of corn acres. In 2005, conditions were variable, but growers replanted more than 10% of their corn acreage. Cold, wet conditions and soil crusting were the biggest issues.”

Early planting

Planting corn earlier in pursuit of higher yields has become an accepted gamble for an increasing number of farmers. But the conventional wisdom on soybeans has changed to favor earlier planting too. Until recently, agronomists told farmers that since the soybean plant produces seed according to day length, rather than total gathered heat units as with corn, the risk/reward ratio for beans still favored delayed planting. That's not the case anymore, according to Iowa State Extension soybean agronomist Palle Pedersen.

“Many farmers still consider May 15 as early when planting soybean in Iowa. That was the old recommendation,” Pedersen says. “Dramatic changes and better technology have moved the planting date earlier and earlier every year. There are two major reasons for the earlier planting. First of all, soybean responds favorably to early-planting dates if soil conditions are ideal for planting. Secondly, the potential risk of stand-reducing, late-spring frost is offset by the opportunity to capture maximum soybean yield potential when early-season growing conditions are favorable.”

Pedersen points out that early planting comes with significant pest and disease challenges as well, but contends that the potential for higher yields makes it worthwhile to plant early and manage for the potential problems. “Concerns about low soil temperatures include the increased probability of injury to the seedling from pathogens, insects, and also the risk of frost injury to newly emerged plants since the growing point is above ground,” he says. A prime example was the growing season of 2005, when cold soils slowed root development and made the stand more susceptible to root-rotting pathogens.

If there is a history of seedling diseases from Phytophthora, Pythium, Rhizoctonia or Fusarium, Pedersen recommends a seed treatment.

“Early planting can also coincide with high populations of bean leaf beetles,” Pedersen says. “Bean leaf beetles can easily be managed by foliar insecticide or an insecticide seed treatment, so that shouldn't hold you back from a higher yield potential. In Iowa, controlling early-season problems helps maximize the yield benefit from planting the last week of April through the first week of May.”

Pedersen says products such as Syngenta's CruiserMaxx Pak, a combination of Cruiser insecticide seed treatment and ApronMaxx fungicide seed treatment, fit well against the challenges of early-planted beans. Further, he notes that his initial research indicates that seed-applied insecticides provide some suppression of soybean aphids. “Seed-applied insecticide won't stop aphids completely, but it can suppress the fast-multiplying pests long enough to help you discover that they are in the field and get out with a timely spray treatment to avoid significant feeding damage,” he says.

In 2004, 23% of soybean growers used a seed-applied fungicide and less than 1% used a seed-applied insecticide. Syngenta, which sees continued growth potential in its seed treatment business, projects that 15 to 20% of seed treated in 2005 will have been its insecticide-fungicide combo, CruiserMaxx Pak.

Seed coatings

A small but growing number of farmers, including John Komer of Norwalk, OH, minimized the headaches that accompany replant decisions by using seed corn coated with Intellicoat Early Plant, a polymer coating that prevents germination of the seed until soil temperatures are right. Developed by Landec Ag, the coating protects corn in the soil and allows corn growers to plant up to four weeks earlier than usual while avoiding the risk of chilling injury. The coating can include fungicide and insecticide seed treatments as well.

“We had our 125 acres of corn planted by April 11,” Komer says. “Then we got 3 in. of rain with 8 in. of snow on top of it. It stayed cold, in the 50s, for 30 days. The uncoated seed just rotted, and we have to replant 85 to 90 acres. But the Intellicoat corn germinated later, and the population was good enough that we didn't have to replant any of it.”

Roger Stang, a Norwalk-based agronomist for the Sunrise Co-op, says many of his customers in the area had similar experiences.

“We had great planting weather for the first 10 days of April and then it turned back to winter,” he explains. “The uncoated seed that had sprouted just sat idle for three to four weeks and we had all sorts of seedling diseases. About 50% of the acres needed to be replanted, but the seed planted with the Intellicoat prevented germination when soil temperatures dropped below 50∞ and protected the seed until conditions were right again.”

Landec Ag also promotes the use of its Intellicoat for relay cropping of soybeans and wheat. It allows the farmer to plant soybeans between 15-in. rows of winter wheat in early May. The coating delays emergence for 20 to 30 days so that the soybeans are just starting to come up when the wheat is harvested.

Intellicoat Early Plant seed coating adds a cost of about $10 to $12/acre. Though the product works as advertised, grower adoption of the product has been steady, but not yet fast enough to capture the interest of larger seed companies such as Monsanto, Pioneer and Syngenta. (These large companies have been focused primarily on seed treatment products, including variations of Poncho and Cruiser.) For now, Intellicoat is still a niche product that smaller seed companies hope to use as a point of difference from the big companies. Intellicoat is currently marketed through nine seed partners: Beck's Hybrids, Atlanta, IN; Dyna-Gro Seed, a division of United Agri Products, Greeley, CO; Fielder's Choice Direct, Monticello, IN; Horizon Genetics, Mason City, IL; Hubner Seed Company, West Lebanon, IN; Legend Seed, De Smet, SD; Ottilie Seed, Marshalltown, IA; Seed Consultants, Washington Court House, OH; and Southern States, Richmond, VA.

Fungicide protection

Garst Seed Company introduced a polymer-based seed treatment called ProCoat for soybeans in 2004. Although it does not delay germination according to temperature the way Landec's Intellicoat does, ProCoat is less expensive and provides fungicide protection from disease stresses that result from early planting. The ProCoat polymer keeps more of the fungicide (ApronMaxx) in place next to the seed, which improves the efficacy of the fungicide and reduces handling concerns. ProCoat offers broad-spectrum protection against soilborne diseases caused by fungi such as Pythium, Phytophthora, Rhizoctonia and Fusarium. It also provides some protection from seedborne diseases caused by Sclerotinia and Phomopsis.

Garst reports that producers recorded a more than 3-bu./acre yield advantage from fields planted with ProCoat-treated seed. The company says more uniform emergence is a big part of those yield increases and that the flat per-unit fee of $2.50 for ProCoat more than pays for itself.

DDT'S LOST LEGACY?

If you've noticed more soil insect pressure in your fields the past few years, increased no-till, adaptable insect populations and earlier planting are probably the main contributing factors. But something else could be behind today's burgeoning soil insect pests.

Syngenta technical crop manager Cliff Watrin speculates that rebounding soil insect populations may be at least partly due to the waning effects of a long-banned pesticide. Dichlorodiphenyl trichloro-ethane (DDT) was widely used to control soil insects before the persistent organic pollutant was banned in the U.S. in 1972.

“I believe soil insects have been rebounding from DDT over the past 30 years,” Watrin says. “The soil insect pressure we are seeing now may seem heavier than we are used to, but if you take a long view, this is probably actually closer to what the ‘natural’ soil insect populations would have been before DDT.”

Today, many years after the initial ban of DDT, residual amounts of the compound can still be detected in soils where it was used and in adjacent watersheds. One study of the Mississippi river in 1998 found DDT (or one its signature chemical breakdown components) in 67% of streambed sediment samples and in 14% of surface water samples.

However, results of a Cornell University study conducted by researcher Jixin Tang and released in 1999 showed that DDT's bioavailability as a toxin becomes significantly reduced over time, with virtually complete reduction in toxicity after 30 years. That's good news for wildlife today. But it also means any legacy of soil insect suppression that DDT might have been causing in corn and soybean fields is now most certainly gone. Without today's new methods of control, including insecticides, seed treatments and corn rootworm-resistant genetically modified hybrids, soil insects and the mayhem they cause would have free rein.