Although use of soil insecticides has dropped off recently, experts say corn growers should ponder this investment more carefully.

If you skipped using a soil insecticide on corn last year, you're part of the reason that the number of acres treated for rootworm and secondary soil pests dropped by about 25% between 1997 and 1999. Probably because of low corn prices, more rotation acres or fluctuating insect pressure, you were willing to risk soil insect damage to save input dollars. Perhaps it was the right decision.

This year? You may want to reconsider. New wrinkles in soil insect evolution are leading some experts to think that, depending upon where you farm, it's time to ponder options besides a roll of the dice. At the least, they say, plan to measure rootworm beetle populations this summer to help determine if an insecticide purchase might pay off for 2001.

New challenge Part of the concern is caused by the "rotation-resistant" western corn rootworm phenotype first discovered in 1995 in east-central Illinois and northwestern Indiana. Typically, rootworms that hatched in soybean fields died, and thus rotation was the natural cultural control.

That's all changing. "With the development of the new western corn rootworm phenotype that lays eggs in soybeans, a lot of growers are resorting to soil insecticides to protect corn planted after soybeans. And the problem seems to be spreading to new areas," says Dr. Kevin Steffey, University of Illinois entomologist. "At first the most rapid spread was eastward, but we observed new infestations in northern and western counties last year."

A joint forecasting study by Steffey and other university specialists projects that this year the rotation-resistant rootworm may appear in 28 counties of Illinois, the northern half of Indiana and parts of western Ohio and southern Michigan. Entomologists believe it might also have been found in a first-year northeastern Iowa cornfield last summer.

Eleven-bushel increase In 1999 trials, crop consultant Lance Murrell, Ida Grove, IN, saw evidence that corn rootworm numbers were up substantially over 1998, even though Pherocon sticky traps had measured relatively low counts. Was it the new rootworm phenotype? "We aren't sure," Murrell says, "but we saw about an 11-bu./acre increase in cornfields following soybeans that were treated with a soil insecticide, compared to untreated. That pays for the $16 to $17/acre cost of application and then some. In some fields not treated, we saw a lot of goosenecking and lodging, although not all had yield reduction."

This year? "We're getting a lot of questions about beetle counts," Murrell says. "Some growers who decided that cutting back on insecticides was the least risky place to shave costs will likely reconsider."

Secondary pests threaten Secondary soil pests are enough reason in some cases to justify the cost of a soil insecticide, thinks professional farm manager David Englund, Farmers National Company, Hastings, NE. "Our overall use of soil insecticides has gone down during the last three or four years because we've gone away from continuous corn to rotations. But we still see a frequent need to control wireworms. And cutworms are a threat when we plant corn into wheat stubble in eco-fallow programs," he says.

"I've been saying all along that secondary pests are doing more damage than we thought," agrees Murrell. "A few years ago some entomologists thought we could cut back to two-thirds or three-fourths recommended rates on insecticides and still control rootworm. But what we didn't realize is that while we might be getting the rootworms, we may have been sacrificing control of certain secondary pests.

"In one study we applied a soil insecticide in a field that had been in wheat and pasture, so we were confident there were no rootworms," Murrell continues. "But we still got a 4_1/2-bu. yield increase. The question becomes, If you don't use an insecticide, will the secondary pests become more of a problem over time? It seems likely."

Count the bugs Summer scouting is the best way to help you make the soil insecticide buying decision for the following year, say entomologists. Steffey explains that the economic threshold for treating first-year corn fields is 5 rootworm beetles/trap/day measured in soybeans the previous season. He says it will not pay to spray insecticides on soybean fields this summer to control rootworm beetles, and it could lead to resistance problems.

A rule of thumb: If you didn't scout fields last year but noticed lodging in first-year corn, the decision to buy a soil insecticide is more likely to be the right one this year, the insect experts say.

Shopping for product in 2000 Fortunately, there is plenty of ammunition available for corn rootworms and other soil insects. The lineup, in fact, has grown during the past few years. Granular soil insecticide formulations for rootworm and secondary pests include Aztec 2.1G, Counter CR, Force 3G, Fortress 2.5G and Lorsban 15G. Regent is a liquid formulation launched in 1998. Warrior T, an aqueous formulation also introduced in 1998, is primarily for control of cutworms and above-ground pests. ProShield, a seed-delivered formulation of new Force ST, was launched this year. Although the older organophosphates (Counter, Lorsban and others) are in the first group of pesticides to be reviewed and reregistered by the EPA under the Food Quality Protection Act, it looks like they could be around for years to come (see sidebar).

"Look around," says farm manager Englund. "We're seeing some good prices because of the cutbacks in insecticide usage, and the new products are triggering competition." Here's how manufacturers are positioning their products for 2000.

DowAgro Sciences. Look for a reduction of about $1/acre in the cost of Lorsban 15G. "That drops the price to between $15 and $16/acre for control of rootworms, cutworms and secondary pests," says product manager Susanne Wasson. "In addition, we've seen fungistatic properties that lead to healthier, higher-yielding corn in multiple midwestern university studies," she says.

You can pick up a $100 savings bond rebate if you buy 16 bags of Lorsban, enough to treat 100 acres.

American Cyanamid. Counter CR Lock'n Load continues to be priced at $16 to $17/acre, says product manager Todd Frazier. "Counter CR is well known for control of corn rootworm, white grub and wireworm, but corn nematode control is what separates it from the competition," he says.

Corn nematodes have become a costly problem beyond the sandy areas of Nebraska and Kansas, Frazier claims. "We did extensive testing and found economic levels of nematodes from the Colorado, Kansas and Nebraska corner to Iowa, Minnesota, Wisconsin, Michigan, Illinois and Indiana. In 51 Cyanamid yield trials across the country where we knew nematodes were present, plots with Counter banded over the row outyielded other insecticides by 3 to 7 bu./acre," he says.

Bayer. Aztec 2.1G is priced competitively with other soil insecticides but offers two modes of action, says Scott Welge, insecticide marketing manger. "Aztec contains a newer generation organophosphate in combination with a pyrethroid controlling rootworm, wireworms, cutworm, white grub and other damaging soil insects. This allows for a low active ingredient required per acre with options to apply in-furrow, T-band or conventional band. Another advantage is the favorable worker and environmental safety characteristics.

"Because we see a lot of uncertainty regarding GMOs [genetically modified organisms], and because growers will continue to be faced with multiple pests, we feel there is a future need for soil insecticides, including Aztec," Welge says.

Aventis CropScience. "Regent is a broad-spectrum liquid soil insecticide," Mike Eade, northern region sales manager, says. "In addition to corn rootworm control, Regent provides excellent control of the first-generation European corn borer, wireworms and other secondary pests. Regent works well on Bt refuge acres to assist with corn borer resistance management programs, due to its different mode of action."

Eade says the 1-Pass liquid in-furrow applicator is simple to use and eliminates handling bags or closed system planter boxes. "We recommend mixing Regent with liquid pop-up fertilizer, which is why some of our first areas of adoption were in northern Illinois, Wisconsin and Nebraska where liquid starter is more common. We've been expanding market throughout the Corn Belt during the past eighteen months," Eade explains. Regent is comparably priced with other soil insecticides.

For 2000, Aventis is offering a $2/acre rebate program for installing a 1-Pass in-furrow sprayer with either RHS or Redball planter systems. The rebate can be spread over two years' purchases.

Zeneca. "Force 3G will continue to be offered at a competitive price per acre for control of rootworm, cutworms and other secondary insects, including wireworms, white grubs and seed-corn maggots" says Dr. Caydee Savinelli, Zeneca technical crop lead.

"Both Force and Warrior T are new-generation pyrethroids that give broad-spectrum control at lower use rates than older chemistries," Savinelli continues. "Warrior T provides 45 to 60 days control for cutworms when applied in a band before, during or after planting. A water base makes it compatible when tank mixed with fertilizers or herbicides. Warrior T also offers improved applicator safety since the microencapsulated active ingredient isn't released until it contacts plant or soil moisture. Both insecticides are harmless to birds and earthworms," she adds.

Novartis Seeds. "ProShield's patented seed-coating system allows Force ST to be applied to each seed, ensuring uniform performance against corn rootworm, wireworm, white grub and seed-corn maggot," Dr. David Dornbos, Novartis research and development director, explains. Novartis has exclusive rights for the 2000 planting season for Force ST, formulated by Zeneca for the seed delivery system. It will be offered on three NK-brand YieldGard hybrids and two conventional numbers. "We'll have limited availability of ProShield seed in Nebraska, Indiana and Illinois for 2000," Dornbos says.

He adds that root ratings and yields in fields planted with ProShield seed compared favorably with crops treated with soil insecticides. Cost per acre will be about equal to conventional seed plus insecticide.

AMVAC Corporation. California-based AMVAC Chemical Corporation announced last December that it had purchased the Fortress insecticide business from Dupont. "We'll be adding personnel in the Midwest to handle sales and technical service for 2000," reports Glen Johnson, director of business development. Fortress has been marketed as a 5G formulation and applied with the SmartBox closed delivery system.

What's coming? Although the situation for soil insecticides seems to be static for now, many industry experts believe that will change, probably within three to five years. First off, there's the uncertainty of the EPA's reregistration process for the organophosphates, although, as mentioned, there's no sign yet that labels for corn will be affected.

Even so, new technologies will be here soon to cut into insecticide market shares. Already, nearly 30% of all corn planted is biotech. Monsanto expects to market GM hybrids with genetic corn rootworm control in 2001, and other seed companies will surely follow with their own offerings. Even newer ventures are well into development.

"Dow AgroSciences is committed to offering growers choices for insect control, either traditional products like Lorsban 15G or through the development of insect-resistant seed varieties," Wasson says. "We are collaborating with Pioneer Hi-Bred International on research efforts to bring rootworm resistant hybrids to the marketplace," she adds.

Bayer has announced a joint venture called GenOptera with Exelixis Pharmaceuticals, Welge says. He explains that GenOptera is expected to be a platform for future discovery of new generations of insecticides and nematicides with novel modes of action.

"While we believe the broad-spectrum control and low use rates will keep Force a strong product for years into the future, Zeneca's biotech arm, Zeneca Plant Science, is also moving ahead with second-generation, non-Bt insect control technology," says technical lead Savenelli.

Gustafson LLC expects EPA approval for Gaucho insecticide seed treatment for use on hybrid corn seed by mid-2000. Product development manager Bill Hairston explains, "A primary use for Gaucho will be to protect genetically enhanced seed from secondary insects."

A couple years ago, Congress passed the Food Quality Protection Act (FQPA), authorizing the EPA to add new dimensions to a review and registration process that had been in effect since 1988 for hundreds of crop protection products, including organophosphate (OP) insecticides. FQPA set entirely new ground rules, changing the way EPA regulates pesticides. Now a new safety standard - reasonable certainty of no harm - must be applied to all pesticides used on food.

Manufacturers, farmers and commodity associations have worked hard to help decision makers in Washington, DC, understand that OP insecticides are needed to help sustain economic yields, at least until other insect control products are proven effective, especially where no viable alternatives now exist.

Because of the magnitude of the review process, the most significant impacts of FQPA have yet to be seen. Some restrictions have been placed on a few products, including methyl-parathion and Guthion. But, overall, it appears that legislators handed the regulators more than they could handle with the time, budgets, personnel and science currently available.

In fact, the EPA has yet to produce a cumulative exposure assessment for any chemical or chemical class. "This is largely due to the enormous scientific challenges imposed by the act," says Dow AgroSciences spokesperson Garry Hamlin, "because the scientific methodology to conduct cumulative exposure assessments required under the FQPA is still being developed.

"We have more than 3,000 studies and reports supporting use of chlorpyrifos [Lorsban]," Hamlin continues. "Our analysis of that extensive database shows no ecological issues and no food residue issues, so we eventually hope to come through the reregistration process with minimal impact to our business. We expect that registrants will have to make label changes on a number of crops, but we don't look for any significant changes for chlorpyrifos on field corn."

Gregg Storey, Bayer's product stewardship manager and FQPA specialist, says his company has been instrumental in helping to set protocols for companies working with EPA on OP assessment and review. "It is going to take longer than originally scheduled to process all of the products on the agency's list, but eventually everything will be reviewed, with the older products first, followed by newer chemistries," Storey says. "We have worked diligently with grower groups, the USDA and EPA to help put a more accurate focus on the real-world uses of these products. At this point, I don't anticipate major changes on any of the soil insecticide labels for corn."

Cyanamid looks for similar results from the agency's review of Counter. Todd Frazier, Counter product manager, says the company expects to hear from the EPA regarding registration eligibility by mid-April. He states, "We do not expect important issues regarding product use on field corn."