Quarantine Use of MeBr in United States

The amount of methyl bromide used specifically for quarantine work in the United States is a number that is going to become increasingly important in the next few years, since quarantine use is exempt from the coming phaseout. But the number is not as simple to calculate as might be supposed, according to plant pathologist Sally Schneider, who is putting together a report on methyl bromide use in quarantine for the Agricultural Research Service.

“If the U.S. is going to have enough methyl bromide for import and export during the phaseout and afterward, we need a pretty solid idea of how much is being used now for those purposes,” Schneider says. “If manufacturers don’t have a good idea of how much methyl bromide is needed for quarantine use, how will they know how much they will be allowed to manufacture?”

Historically, there has been no requirement in the United States for separate, detailed record- keeping of how much methyl bromide is used for quarantine, explained Schneider, which is one reason why coming up with a total is complicated. Methyl bromide is also used in different circumstances in quarantine work: on imports, exports, and in some intra- and interstate shipping of commodities, particularly citrus.

Schneider is still gathering data for the report, particularly about export use. She has been collecting information from commodity groups; shippers and packers; federal, state, and county agencies; and as many other sources as she can identify. “And I would welcome information from anyone else,” she adds.

On the import side alone, methyl bromide is used as a preventive treatment on specific commodities where required by regulation to prevent the entry of a pest from a particular country; it is used where a pest has been found in a specific shipment even when there is no country-by-country requirement; and it is used to fumigate nonagricultural imports if pests are suspected of being present in pallets, shipping material, or equipment.

But calculating the comprehensive amount of methyl bromide used on importss has been less involved because one agency—USDA’s Animal and Plant Health Inspection Service (APHIS)—monitors compliance with quarantine reg-ulations on agricultural commodities and suspicion of pest infestation in other imports. The agency also maintains a database of fumigant use, Schneider explains.

Import

In 1996, APHIS recorded a total of 402,465 pounds of methyl bromide used on imports, of which 49 percent was used on fruit imports, mainly grapes from Chile. Other fruit imports from Chile included kiwis, peaches, nectarines, lemons, and plums. Cotton was second on the list with 22 percent of methyl bromide use, and vegetables third with 9 percent. Almost 17,000 pounds of methyl bromide were recorded as being used on imports where wood borers were suspected or spotted, mostly in packing material.

Total import use of methyl bromide in 1997 was 357,193 pounds according to APHIS, with 58 percent used on fruit, again mainly from Chile, 11 percent on vegetables, 10 percent on cotton, and 6 percent on imports that could be harboring Khapra beetle. In 1998, the total was 281,274 pounds of methyl bromide with 62 percent used on fruit, 14 percent on vegetables, 6 percent for wood borer, and 5 percent on Khapra beetle.

“Obviously, the amount of methyl bromide used on imports changes each year based on pest outbreaks, discovery of new pests, and new trading partners. Agricultural imports vary each year due to many factors including the quality and yield of a crop at home and abroad,” Schneider says. “All of these factors affect the amount of methyl bromide needed each year, but we can get an idea of the average amount being used.”

Export

Determining the amount of methyl bromide used to fumigate exports is much more difficult because no one agency keeps general records, and there are no definitive standards for what information should be kept.

For example, in California, it is the county agricultural commissioners who certify fumigation chambers and record methyl bromide use. “Some keep the data by commodity and destination; some keep track only of the amount used, but not by commodity or destination,” Schneider says. “Information on commodity and destination is necessary to determine if the fumigation was a required quarantine treatment covered by the exemption or a nonquarantine precautionary treatment.” In the Pacific Northwest, much of Schneider’s information is coming from the commodity groups because most fumigation is on apples, cherries, and stonefruit.

Another factor that makes it hard to project average use on exports is that some record sources refer only to the pounds of a commodity that had to be treated to meet the receiving countries’ quarantine regulations. This doesn’t translate directly into the amount of methyl bromide used, since the amount needed to achieve the required concentration depends on the size of the fumigation chamber and not whether the chamber is completely full or half empty.

“Really, the question is how many times was the fumigation chamber used, not simply how many tons of fumigated fruit were shipped each month,” Schneider explains. Ballpark estimates on the amount of methyl bromide used for export quarantine treatment of fruit and nuts are 143,000 pounds in 1996, 175,000 pounds in 1997, and 137,000 pounds in 1998. Oak logs are a significant export user of methyl bromide for quarantine purposes, but data on the amount used each year is still being gathered. So Schneider is piecing together a widely spread picture of methyl bromide fumigation on exports.

One surprise that she has run into is that methyl bromide for fumigating dunnage—pallets and other packing materials used to crate exported products—may end up proving to be a much larger percentage of quarantine use than suspected. “All those pallets and skids that are made of wood can harbor insect pests that are of concern to our trading partners, so a lot of it ends up needing fumigation,” she explains. Information from one port alone, indicated that more than 45,000 pounds of methyl bromide per year was used to fumigate dunnage.

With data still accumulating, Schneider is not ready to put even preliminary numbers on total export use. But she expects to have a draft report “with a pretty good handle on the amount” ready this summer.

Interstate and Intrastate

The third category of methyl bromide use in the United States is for federal domestic quarantines, state exterior quarantines, and state interior quarantines, which affect interstate and intrastate shipping of some commodities. Gypsy moths on trees, shrubs, and mobile homes are subject to federal domestic quarantine. Exterior pests on citrus and blueberry maggot on fresh blueberries can be treated with methyl bromide to meet California exterior quarantine requirements. Mediterranean fruit fly is an example of a pest that is subject to within-state quarantine in California.

“It can be hard to put together all the numbers to get a complete picture of methyl bromide use in this category because there are different agencies in each state keeping track, and each one is keeping the information in a different way,” Schneider says.

Is This So Important?

Methyl bromide, or effective alternatives, is an essential part of the quarantine process that allows international agricultural trade, Schneider points out. “One of the standards on which the free flow of agricultural trade depends is the assurance that nonnative pests can be prevented from entering a country along with commodities and other imports. The United States must be able to prevent the introduction of foreign pests that would threaten the security of U.S. agriculture. And other countries want to be sure that what the United States is shipping is free from threatening pests,” she explains.

The United States certainly cannot do without agricultural trade, Schneider adds. Not only are agricultural commodities a major export for the United States, but U.S. consumers have come to expect and depend on the year-round availability of fresh fruits and vegetables. To maintain such abundance requires that agricultural commodities continue to be importable, but without creating a risk of allowing in new pest problems that could threaten the country’s crops and landscape plants.

“There is also the possibility, if not the probability, that new insect invaders will emerge in the future that will require fumigation of commodities. How do we estimate the amount of methyl bromide needed to meet new pest problems?” Schneider asks.

Right now, methyl bromide is the fumigation method of choice for many commodities, Schneider says. But there are potential alternatives, and research is continuing to pursue the possibility of still others. “Irradiation, controlled atmospheres, temperature treatments, other chemicals—there are a number of alternatives being looked at,” she says. “Even if quarantine use is currently exempt from the phaseout, we don’t want all of our eggs in one basket. It would be nice to have other choices if we need them. A change in the Clean Air Act gave us the quarantine exemption. Another change could revoke it. We need to continue our research to develop viable alternatives.”

Last Updated: July 1, 1999