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Reducing residues

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Growers are working to lower residues of the growth regulator maleic hydrazide (MH) in their leaf.

Brandy Brinson

Cigarette manufacturers, especially those in Europe, are growing ever more strict on levels of residual chemicals in leaf. Regulatory bodies around the world are increasingly imposing limits on residues, and manufacturers are working diligently to meet these limits. Manufacturers are also cracking down on levels of pesticides as they pursue social responsibility goals. Philip Morris International, for one, says it is committed to minimizing the impact of agrochemicals on the environment and enhancing practices that ensure growers’ safety.

Manufacturers are doing this by working with growers to make sure they do not overapply chemicals or use unapproved chemicals. A major concern has been with residues of maleic hydrazide (MH), which is used for sucker control. MH residues are particularly high in flue-cured tobacco grown in the U.S., where the chemical is most commonly used. U.S. growers are now being told they must lower their levels if they want their tobacco to be more marketable.

“Some of our biggest export customers have concerns over MH residues in U.S. flue-cured tobacco,” says Loren Fisher, Extension tobacco specialist at North Carolina State University (NCSU). “Therefore, everything growers can do to keep their MH residues low, including using as little as necessary, helps the marketability of their crop.”

Trade mission
The issue came to light during a recent tobacco trade mission, when U.S. growers traveled to Europe to meet with cigarette manufacturers to discuss how U.S. tobacco could be more marketable. During the meetings, manufacturer representatives expressed their concerns about chemical residues to the growers.

Nicolas Denis, director of leaf agronomy for Philip Morris International, says, “PMI supports minimizing pesticide residue levels for tobaccos that we buy. We want to work with our suppliers for implementation of sound integrated pest management practices with growers. For the U.S., we see opportunities for improvement on residue levels of maleic hydrazide and certain compounds used to control pests. We are not against the use of these compounds, but we would like to see them used in alignment with our Good Agriculture Practices guidelines. These products should be applied in a way that minimizes residue levels.”

In response to these concerns, tobacco leaders, the North Carolina Department of Agriculture and NCSU are increasing efforts to educate growers on the importance of reducing residues.

North Carolina Agriculture Commissioner Steve Troxler says, “The end of the tobacco quota system has opened up international opportunities for tobacco farmers, and in today’s tobacco environment, exports provide the best opportunity for growth. Like in any competitive business, in order to seize these opportunities you have to know what your customer wants and be able to provide it. In meetings with representatives of European tobacco companies earlier this year, we heard about their desire to purchase tobacco that is within the tolerances for residues and is clean and free of twigs, leaves and other debris. [We are] helping to educate North Carolina growers about what these potential international customers want and need. I want North Carolina to continue to be seen as the premier supplier of high-quality tobacco. We’ve all got to do our part to ensure we have a premier product that meets the needs of international customers.”

U.S. residues higher
U.S. tobacco tends to have the highest levels of MH in the world. MH has been widely used in the U.S. for sucker control since it was introduced more than 50 years ago.

“Residue analysis programs show that MH residues of U.S. tobacco are often higher in comparison with tobacco from other countries,” says Denis. “There are a very few countries that occasionally produce tobacco with higher-than-normal MH levels.”

Bill Collins, coordinator of tobacco programs at NCSU, says, “There’s nothing wrong with MH—the residues have not been shown to cause health problems—but it’s a problem because our chief competitors, Brazil and Zimbabwe, do not use MH. Canada, which is not as big a competitor, doesn’t use MH either.”

Other countries are not using MH as extensively as in the U.S. because many of their farms are small operations, where suckering is done by hand.

In Brazil, for example, there are many small farms that employ hand operation. Brazilian farmers do use some sucker controls such as alcohols and Prime Plus, but not MH.

In the U.S., where farms are much larger, sucker control by hand is not possible. “We can’t do hand suckering here in the U.S. because the labor requirements are too high,” says Collins.

The U.S. tends to have more of a problem with suckers, which Collins says is actually the result of a good situation. “In the U.S., growth of the tobacco is good, so sucker growth is good.”

How to reduce MH
Reducing MH residues is not difficult; it just takes more effort by growers and in some cases, a little more money.

Collins says that while steps can be taken to reduce the use of MH, the chemical will continue to be important for growing tobacco. “In the U.S., it’s an essential pesticide that growers need to control suckers. MH is foolproof in controlling suckers. It’s easily applied and stops cell division. The goal is not to do away with it but to reduce it,” he says.

Sometimes Mother Nature can help reduce MH levels. “If there’s heavy dew or rain irrigation before harvest—that can lower MH levels,” says Collins. Counting on Mother Nature alone isn’t going to cut it for U.S. growers, but there are several other options to reduce MH residues.

Properly applying MH is one example. Growers should make sure that they use the proper pump pressure and appropriate nozzle arrangements when spraying sucker controls, says Collins.

Another practice to reduce MH residues is to lower the pressure of the pump when spraying the chemical. Collins says this would decrease MH residues dramatically. Some growers think they have to turn the pressure up high to soak the plant top to bottom, but this isn’t necessary, he says.

Farmers should also avoid applying MH late in the season because that raises the risk of high residues.

The overall goal is to reduce reliance on MH. Collins says, “Growers can lower MH levels by applying less of it. There are also several other types of chemicals that don’t leave the residues that MH does. Growers can include these chemicals in their sucker control programs. This will reduce overall MH levels.”

For example, they can use alternative products on the lower stalk. Collins says growers can also use nonresidue products in the early season, and the first and second harvest will be MH free.

There are two types of chemicals that can be used to reduce MH residues—contacts, also called fatty alcohols, and local systemic chemicals such as flumetralin and butralin.

“It’s important for growers to use everything they have for sucker control, including contacts and flumetralin or butralin,” says Fisher. “They should use contacts up front and then follow that by labeled rates of MH in combination with flumetralin or butralin. That way, growers can use minimal rates of MH because they are relying on other non-MH products for sucker control.”

He adds, “I would say 80 percent or more of our acres in North Carolina are treated with flumetralin (the active ingredient in Prime Plus). Sucker control with a labeled rate of MH and Prime Plus provides better sucker control and longer residual control than MH alone.”

Incorporating Prime Plus into a sucker control program has been shown to reduce MH residue. Trials conducted at NCSU demonstrated that two contact applications—one made at button and another 3 to 5 days later, followed by a tank mix of MH and Prime Plus at 5 to 7 days—provided superior sucker control when compared with two contact applications followed by MH alone.

This research led Fair Products, a major producer of MH and sucker control agents for use on tobacco, to package its sucker control product FST-7 with Syngenta’s Prime Plus. The company is touting this combination as the most effective way to control suckers with the lowest MH residues possible.

FST-7, for contact and systemic sucker control, is a combination of MH and fatty alcohol. Frank Grainger, president of Fair Products, says it is a more highly concentrated material, offering sucker control but with decreased residues.

FST-7 has been around for quite some time. However, “Farmers have been reluctant to use it because it costs more, and farmers tend to use whatever costs the least,” says Grainger.

With the raised awareness of MH residue issues, Grainger says demand for the product is growing, thanks to the new strategy of selling FST-7 with Prime Plus in the co-pack.

“Interest in the product did increase last year. Offering FST-7 and Prime Plus together gives the farmer a set package. The farmer just mixes 0.5 gallon[s] of Prime Plus with 3 gallons of FST-7. It’s hard to mess up—all the farmer has to do is mix them together,” says Grainger.

Not only does this combination result in decreased MH residue levels, but Grainger says using these two products together actually offers increased sucker control. “On-farm test research consistently shows that this combination offers the best sucker control possible.”

As a result of the new marketing strategy, sales of both FST-7 and Prime Plus have increased. “Farmers have responded very positively to it,” says Grainger. “We’ve been real pleased with the marketing and sales of the co-pack.”

Fair Products is doing its part to educate farmers about the MH residue issue. “We are taking the time to educate growers. We’ve held meetings and written letters working to educate farmers all over the U.S. on how they can lower MH residues,” says Grainger. The company is also discussing the MH issue with tobacco companies. “We’ve also met with companies and shared all the agronomy info so they can consciously make efforts to reduce MH.”

Burley
The MH residue issue is mainly a problem for flue-cured tobacco. MH residues are not nearly as high in burley tobacco as they are in flue-cured.

Gary Palmer, Extension tobacco specialist in the Department of Plant & Soil Sciences at the University of Kentucky, says, “We do have an MH residue problem in burley, but not to the extent that they do in flue-cured tobacco. Since we typically have more time between application and harvest, less residue is left. We have changed our application method by reducing MH from 2 gallons per acre to 1.5 gallons per acre, added either Prime Plus or butralin and changed to coarse nozzles. This has a two-fold impact. It has improved grower confidence, which in the past was lacking and often led to excessive rates or a second application, which increased residues. By reducing the MH and applying so that droplets were more likely to run off of the leaf and down the stalk where the sucker buds are, residue declined. We are now seeing residues consistently in the low 30 parts-per-million range instead of occasionally seeing over 100.”

However, he says, “This seems not good enough since some buyers are seeking a true MH-free burley tobacco. Although the demand is not yet high, if they are willing to offer a premium, then some producers may try to supply MH-free tobacco. We have conducted a lot of trials to assess mechanical application of alternative sucker control chemicals and have yet to find a workable solution that allows [a] producer to use comparable labor but achieve acceptable control. A question still remains concerning alternative chemicals that might have actual residue concerns versus perceived residue problems, as is the case with MH.”

Legal limits
Manufacturers want MH residues reduced mainly for regulatory and social responsibility reasons rather than for health reasons, as MH residues have not been shown to carry a health risk.

The U.S. Environmental Protection Agency has conducted evaluations on the potential risk associated with MH residue and has not identified negative health effects. Collins says, “Lots of studies have been done on MH, and no health effects have been found. Had [researchers] found anything wrong with it, it would’ve been banned.”

Nevertheless, countries are imposing limits on the chemical. Various countries in the European Union are now enforcing a maximum level of MH residues at 80 parts per million (ppm) on tobacco products. Others are expected to pass similar tolerances in the near future.

Denis says it is especially important that growers reduce residues as various countries mandate limits. Tobacco must meet the requirements for all 160 countries where PMI sells its products. “MH itself is not a concern. But it should be applied so that residues are not higher than appropriate levels,” he says. “We want to be able to use U.S. tobacco in all countries where our products are sold. We have a comprehensive sampling and testing program in place. It’s our responsibility to make sure we comply with local regulatory requirements.”

Collins says the issue is “serious enough that last year and the two previous years PMI paid a premium for MH-free tobacco.”

So far, tobacco companies have not formally declared their own limits. “I don’t know of any companies that have externally announced levels,” says Collins.

Up to this point, Grainger says, “No one has issued an ultimatum and no one has said there can be absolutely no MH residues. The companies haven’t issued limits, but I’ve worked long enough in this industry to know that anything can happen.”

He says growers are smart enough to act now to reduce residues before guidelines are issued. “So far, the companies have tried not to dictate what the farmers must do. But the farmers have figured out on their own that they need to lower the levels, and they are consciously trying to reduce residues of all types.”

PMI has thus far not issued its own limits, but the company is following the limits set by these various countries. Denis says, “Regulatory authorities set maximum residue levels for MH, and we follow these regulations.”

He says it’s important that U.S. growers reduce residues, as U.S. tobacco is important to PMI. “High-quality, American-grown tobacco remains critical to the success of PMI’s brands. At the same time, we want to work with our Tobacco Farmer Partnering Program (TFPP) growers, and others, to find solutions to this important issue. In 2005, we initiated, through PM USA, an incentive program to promote the tobacco production without MH, and we continue to offer this program to TFPP growers in 2006. We also work with our TFPP growers to focus on integrated pest-management implementation, and we support research at land-grant universities to evaluate safer and more environmentally friendly crop protection agents.”

Rather than wait for companies to dictate limitations, U.S. growers must work to reduce MH levels for fear that buyers will turn elsewhere. This will be key to ensuring the future success of U.S. tobacco. Collins says, “The benefit of lowering MH is that it makes our tobacco more competitive and results in more interest from buyers.”

For more information:
For more detailed instructions on how to control suckers while minimizing MH residues, see Fisher’s “Maximizing Sucker Control and Minimizing Residues with MH” in chapter 7 of the North Carolina Flue-Cured Tobacco Production Guide (available online at: http://ipm.ncsu.edu/Production_Guides/Flue-Cured/2005/chptr7.pdf) or to “Alternative Sucker Control Methods” by Gary Palmer, University of Kentucky Extension Tobacco Specialist (available online at: http://www.uky.edu/Ag/TobaccoProd/FactSheets/HTML/Tob-04-05.htm)

For a history of burley residue levels, go to: http://www.uky.edu/Ag/Tobacco/
Archive/Archive.htm Look for the “MH Residue Figures for 2004 Crop Year with Comparisons to Previous Years” link below the test plot data table.