EPA stops use of effective insecticide carbofuran

A broad-spectrum insecticide, considered to be among the sunflower producers best friends against the crops enemies, has lost its registration with the U.S. Environmental Protection Agency, leaving producers scrambling for alternative products that arent close to being as effective and developing growing strategies as a work-around to the loss of this effective product.

After years of legal wrangling, the EPA registration of carbofuran (better known by its trade name of Furadan, manufactured by FMC) was cancelled as of Dec. 31, 2009. Carbofuran was considered the product of choice by sunflower producers because of its efficacy against stem weevils--perhaps the top enemy of the sunflower.

Another plus was its being labeled for control of several other insects including banded moth, sunflower (head) moth, seed weevil, sunflower beetle and grasshoppers.

Whats daunting to growers is that carbofurans window of use is fairly limited to mostly sunflowers. Why EPA would want to target their industrys only effective tool is a mystery--particularly in light of EPAs denial of a full review of the reasons behind the de-registration.

"EPAs unprecedented attempt to deny any review of its science deprives the registrant and the growers who use carbofuran the right to prove that the product is safe and represents a bold abuse of power in contradiction of the agencys earlier commitments to transparency and good science," said Michael Morelli, Ph.D., director of global regulatory affairs, FMC Agricultural Products Group.

"Additionally, EPAs attempt to link carbofuran food residues to symptoms of potential poisoning in children is particularly unwarranted."

EPA announced the cancellation of the registration for carbofuran last May, but the lead-in to the cancellation began three years earlier in August 2006, when EPA published a series of risk assessments against the product, stating that no uses were eligible for re-registration.

Since then, FMC voluntarily canceled 22 carbofuran uses, but according to Larry Kleingartner, executive director of the National Sunflower Association, EPA showed "the elimination of these uses was not sufficient to allow the Agency to make a finding that combined dietary exposures to carbofuran from food and water are safe."

Both the grower group and the manufacturer say that carbofuran meets all safety standards and that no residues exist in food or in imported crops, but that EPAs only concern is with drinking water.

FMCs Morelli said EPAs only alleged concern--drinking water worries--is based on an incorrect assumption that 100 percent of crops are treated with carbofuran, when in most cases only one percent or less is treated.

"Without exaggerated assumptions, carbofuran residues are well within safe levels," Morelli said.

Next stop: appeals court

Because of this attitude, FMC is taking EPA to court, since EPA has denied an administrative hearing on the Agencys action to revoke the food tolerances for carbofuran.

Whats really upsetting to Kleingartner is that he believes the EPA decision circumvents the normal re-registration process under the Federal Insecticide, Fungicide and Rodenticide Act. EPA has not taken action to cancel carbofuran registrations, which continue under FIFRA.

"This has been a battle for four years now. Weve testified at over a dozen different hearings and attended countless meetings with EPA on this," Kleingartner said. "The EPA pulled the rug out from under the sunflower producer by doing an end run on using the product on food items.

"It just seems to me that this item was going to be pulled from the shelves no matter what we did. We could have been in a position that this product could, heck, save mankind, and I dont think it would have made any scientific difference to these people."

Besides American Sunflower, the U.S. Department of Agriculture and the National Association of State Departments of Agriculture have gone on record supporting a continued but very limited use of carbofuran where there are no alternative products, such as in sunflowers and corn rootworm rescue.

"EPA remains closed-minded about mitigation measures, even though FMC proposals have clearly demonstrated how such mitigation is possible, and indeed allows product use to meet the EPA safety standard even under the Agencys worse case assumptions," said Morelli.

FMC contends that current law clearly mandates that growers and registrants be provided a right to a timely and neutral hearing when there are "obvious and genuine factual issues" between EPA and those parties over safety of a pesticide. EPA has chosen to disregard the legal requirements, said Morelli.

To that end, in late October 2009, FMC filed a request with the U.S. Court of Appeals for the District of Columbia for an expedited review of their challenge against EPA to hold that hearing to contest the revocation of all carbofuran tolerances. The court granted the request Dec. 14, setting a March 22 date for oral arguments to be heard.

"The appeals court then has to decide if FMC was improperly denied a hearing on the revocation," Morreli said. "If the court makes a final ruling that EPA must hold a hearing, the matter will be assigned to an administrative law judge for a full hearing where the safety of carbofuran can be evaluated in an expeditious and neutral manner."

Kleingartner said American Sunflower is joining in assisting FMC with anything it needs, to move the case forward through the appeals process.

What next?

While the legal wrangling goes on, the question remains: What does a sunflower producer do for insect control, for this season, and if carbofuran continues to be no longer registered with EPA, into the future? While research into seed genetically enhanced to be resistant to stem weevils and other pests is going on, what does a grower do now?

"The alternatives growers have are second best, at best," Kleingartner said. "We are working with producers on helping producers understand when stem weevils are emerging in their area. The Extension services in all the growing states will be putting the word out that growers whose crops are vulnerable will have to use some topical application of product."

The problem is stem weevil is hard to scout for, Kleingartner said.

J.P. Michaud, Ph.D., associate professor of entomology at the Kansas State University Agricultural Research Center-Hays, agreed.

"Its almost impossible, even with experience, to find them. Stem weevils hide in the little dried up cotyledons next to the base of the stalk. Theyre really tiny and at the base of the stalk," Michaud said.

"They see you, and they hide and run around to the other side of the stalk. Theyll fall off of leaves, lay on the ground and play dead. Theyre extremely hard to scout. Even if you do get a count, theres really no way of telling if the count is accurate and therefore no way of telling what kind of problem youll have at the end of the growing season."

The problem is producers have no integrated pest management formula for stem weevils because theres no good economic threshold established for them," Michaud said.

"If the plants are very healthy, they can resist the development of a lot of larvae. So even if you have lots of adults, you wont necessarily have a serious problem. But if the plants are stressed--either by being too dry (worse) or too wet--that seems to reduce the plants resistance to stem weevil."

The other complication for stem weevil foliar treatments, Michaud said, is that "weve never really established a threshold number of larvae and said, OK, you start having significant yield loss with X number of larvae per stalk." Sunflower stalk size can vary significantly, depending on plant spacing and other factors.

"So when dealing with an insect whose numbers can be more than 100 per stalk, we really should be expressing the threshold as number of larvae per unit of stalk diameter or volume."

Michaud suggests that on an "averaged-sized" oilseed sunflower plant, an economic threshold would be "more than 40 larvae per stalk." Again, he emphasizes, no actual recommended threshold has yet been developed for stem weevil.

"But if you have fewer than 40 per stalk, youre probably not going to see any yield loss," Michaud said.

Extra care ahead

In looking at producing sunflowers for now, Michaud said, a producer will have to face the task with some extra vigilance--not that the producer didnt already.

"Sunflowers are a crop you really have to pay attention to, to begin with," Michaud said. "You have to watch them. You will have to step up your mindset. You can get good control on stem weevils with alternative products, but it has to be timed right because you are killing adults on the plants rather than getting systemic control."

Michaud offered a short list of products that are currently labeled for the same insects including: beta-cyfluthrin (Baythroid XL), chlorpyrifos (e.g., Lorsban 4E, Warhawk, Yuma 4E), chlorpyrifos + gamma-cyhalothrin (Cobalt), cyfluthrin (Tombstone), deltamethrin (Delta Gold), esfenvalerate (Adjourn, Asana XL), gamma-cyhalothrin (Proaxis), lambda-cyhalothrin (e.g., Silencer, Taiga Z, Warrior) and zeta-cypermethrin (Mustang Max EC). All these products also are labeled for cutworm control in sunflower. Like carbofuran, most of them are restricted-use pesticides.

"Furadan was a good product," Michaud said. "It would give you a nice, white stalk with nothing in it. It was a reference material for every other product on the market. Certainly, with that particular product, youll find no equal right now. The best time to apply the product is in the vegetative growth stage when there are eight to 10 leaves, and follow it with irrigation or rainfall if picks it up."

"Nothing else really works. Seed treatments are wonderful for about two weeks-- then most stem insects attack after that. Theres really no equivalent for it."

That said, Michaud said he is "actually wary of advising people to spray for stem weevil."

Why?

"We knew we had better control against Phoma with Furadan than we did with a fungicide. That is how important stem weevils are to letting Phoma get to the plant. It definitely had an effect on fungal deterioration of the plant," Michaud said.

"The one insect it didnt do a good job on was the stem girdler, but it actually delayed that insects doing its damage early in the season--so even offered some control on the insect it didnt fully protect against."

That statement is contingent, though, on the absence of stalk-weakening diseases like Phoma black stem.

"If you have a lot of Phoma, [stem weevils or other stalk insects] exacerbate the disease infection. They initiate it," Michaud points out. "But Phoma development also is contingent, to a large degree, upon the survival of insect larvae" because the disease proliferates by following the insect tunnels within the stalk.

The KSU entomologist says, "The real problem with Phoma and stem weevil together is if they occur early, youre going to have premature ripening, and if its later in the plant cycle, youll have lodging problems."

New trait research

While specific management recommendations for sunflower stem weevil are in short supply, there is good news from the breeding front: Host-plant tolerance to stem weevil does exist and is being exploited. Screening and selection for tolerance to stem weevil and other sunflower insects has been going on for several years in a cooperative project among USDA Agricultural Research Service entomologists and university researchers in Kansas, Nebraska, Colorado, South Dakota and North Dakota.

In a 2008 trial at Colby, Kan., investigators found significant tolerance to stem weevil in several breeding lines. In one group of tested lines, for instance, per-stalk larval counts ranged from two to 40. Of the 83 lines tested, 13 had fewer than 10 stem weevil larvae per stalk.

Until commercial sunflower hybrids possessing good tolerance hit the market, however, growers must continue to rely upon rotation, planting date and/or a foliar insecticide. Michaud notes that stem weevil populations are most likely to manifest in rotations where sunflower is grown in tighter rotations. The insect does not travel well (as opposed to the banded sunflower moth, for example).

"It can barely fly, and if it has a host plant, it doesnt move," Michaud said. "So if you have a history of stem weevil problems in a certain field, you may want to consider treatment at around the six- to eight-leaf stage" as an insurance policy.

A later planting date goes a long way toward avoiding stem weevil problems altogether. For High Plains sunflower fields planted after the second week in June, "Id say, dont worry about it," Michaud said. "Where you want to be concerned is with early-planted fields in areas with a history of intensive [sunflower] cultivation and weevil-induced lodging."

Meanwhile, people like Kleingartner await new lines of sunflowers resistant to stem weevil to come online.

"There is some good stuff out there," Kleingartner said. "It just takes time to find the right genetic material suitable for use to create that resistance."

Don Lilleboe of the National Sunflower Association contributed to this report. Larry Dreiling can be reached by phone at 785-628-1117, or by e-mail at ldreiling@aol.com.