The Right Level

Published online: Jan 19, 2022 Articles Matt Lantz
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This article appears in the January 2022 issue of Potato Grower.

What is an MRL?

Maximum residue levels (MRLs) are a trade standard that represent the amount of a pesticide that can appear on a food product to indicate the food was produced using Good Agricultural Practices. MRLs are not food safety standards, but they are often confused for them by consumers.

In the United States, pesticide MRLs are established by the EPA after a thorough review of data. EPA registers a pesticide for use and then sets the MRL for a particular commodity. For growers, meeting domestic MRLs is not difficult. Correctly following the label for pesticide application will result is residues well below the established U.S. MRL. The challenge begins when U.S. growers and processors seek to export their potatoes and potato products to other markets. 

Why do MRLs matter for exports?

Since 1999, numerous markets have modernized their food safety systems, and such an overhaul often involves establishing their own set of pesticide MRLs. At times, those foreign MRLs differ from U.S. standards. Foreign governments with national MRL standards often then test imported products for pesticide residues. Should a violation be detected, severe consequences can occur. These can include rejection of shipments, resulting in destruction or re-export of the product. Violations can also result in future expanded testing for the shipper or even the entire supplying industry.  Repeated MRL violations have the potential to close the entire market to a U.S. industry. 

What issues do U.S. growers face with foreign MRLs?

U.S. potato exporters face several challenges when exporting. These include:

  • Missing MRLs: Sometimes a foreign market will not have a potato MRL established for a pesticide used for potato production in the U.S. In these cases, the foreign MRL may be zero (no residue can be present) or set at a low default tolerance of 0.1 or 0.01 parts per million (PPM). Having a residue present when the foreign country does not have an MRL established is considered a violation.
  • Restrictive MRLs: Sometimes a foreign MRL has been established for potatoes, but the level is more restrictive than the U.S. MRL. Although the product would be legal in the U.S., exceeding the more restrictive foreign MRL is still considered a violation by the importing country.
  • Customer interest in the issue: With new MRL systems in place, foreign buyers are more frequently asking U.S. potato suppliers what pesticides have been applied and whether the shipment is compliant with their market’s MRLs. At times, customers will insist on pre-shipment residue testing. These requests can be expensive and burdensome.

MRLs are a growing trade challenge for U.S. potato exporters. Growers and shippers need to be aware of what pesticide residues are allowed and not allowed in a market.

How can I find potato MRLs for different countries?

Potatoes USA provides a complete list of U.S. and foreign potato MRLs in key export markets in its Global Trade Regulations Database at ( Users will need to make a one-time request of a password to set up their account to access the information.

Once in the global database, navigate to “Global Review Database” at the top of the page.   Then, under “Select Countries and Categories,” choose the market of interest and “Chemical Residue Levels (MRLs).”  This will generate a report on the U.S., foreign country, and international Codex potato MRLs.

If growers are not sure what active ingredient is associated with the trade name for a pesticide (i.e., glyphosate for Roundup), Potatoes USA provides a comparison chart that links trade names with chemical names on the same website. 

Which markets are active on MRL issues?

While any country can decide to begin establishing MRLs and testing for residues, below is a summary of key markets for U.S. potato exports where pesticide MRLs play an important role.

  • Canada maintains its own national MRL list. Many of its MRLs are similar to the U.S. MRLs. When no MRL exists in Canada, a 0.1 ppm default standard applies. Canada is in the process of canceling the use of several pesticides that U.S. potato growers use over the next several years. Growers and shippers will want to track Canadian MRLs and determine if the withdrawal of use of these products results in the loss of Canadian MRLs.
  • Traditionally, Mexico has unofficially deferred to U.S. MRLs. This has allowed trade to flow without issue. In the last year, however, Mexico has begun discussing eliminating the use and MRLs for several substances, including glyphosate. The U.S. government is engaging with Mexico on its pesticide policies to ensure they are not trade-disruptive.
  • Japan has a large MRL list that includes many potato MRLs. The U.S. potato industry worked hard leading up to the introduction of Japan’s new system in 2006 to ensure potato MRLs were established.  Still, it is important for shippers to check Japanese potato MRLs versus U.S. MRLs, as there can be differences. Japan has a 0.01 ppm default tolerance if no MRL exists. A pesticide residue violation in Japan is a significant event involving loss of the shipment and additional future testing not only for the shipper, but possibly for the entire U.S. potato industry.
  • South Korea introduced a national MRL list in 2009 and will remove all current temporary MRLs on Dec. 31, 2021. Korea has a 0.01 ppm default tolerance. The U.S. potato industry has worked for several years to establish as many potato MRLs as possible in Korea. Exporters should confirm Korean MRLs against U.S. MRLs, as there can be differences. Korea actively tests for pesticide residues and will take immediate action against the shipper if a violation occurs. U.S. potato violations have occurred in Korea.
  • Taiwan has maintained its own MRL list since 1999. Taiwan does not use a default tolerance. Taiwan has many potato MRLs, and they should be compared to U.S. MRLs prior to exporting, as differences do exist. Taiwan actively tests for pesticide residues, and violations result in rejections and increased testing for the shipper, and often for the entire industry. U.S. agriculture has frequent challenges with Taiwan MRLs.  Potato residue violations have occurred.
  • Hong Kong has a limited list of MRLs established in 2014. The U.S. potato industry sought as many potato MRLs as possible at that time. No new MRLs have been established since. Hong Kong tests against its existing MRL list. It remains to be seen whether Hong  Kong will establish additional MRLs or begin  using  Chinese  MRLs.
  • China has a limited list of pesticide MRLs. All U.S. commodities, including potatoes, are missing MRLs in China. Establishing additional MRLs in China is challenging, and new Chinese laws are being drafted to make seeking an MRL in the market easier. To date, China has not aggressively tested imported  product  for pesticide residues, but it has the capacity to do so should its policies change.
  • Costa Rica maintains a national list that uses international Codex MRL standards in the absence of an established national MRL. When  there  is  no  established  national or Codex MRL, U.S. and EU MRLs are compared, and the highest (least  restrictive) MRL is applied. U.S. potatoes have been rejected in Costa Rica for pesticide residue violations.


With the growing opportunities for U.S. fresh and processed potato exports in international markets, it is important for growers, shippers and processors to be aware of and comply with foreign regulatory requirements. Increasingly, pesticide MRLs play an important part in that effort. Potatoes USA and the National Potato Council have dedicated significant resources to opening new markets for U.S. potato exporters and  toward establishing as many harmonized potato MRLs as possible. Pesticide residue violations are costly not only for the shipper, but for the entire industry. 

Matt Lantz is vice president for global access at Bryant Christie, Inc., a firm that offers assistance on market access and foreign government affairs to shippers of various commodities. This report was originally provided to Potatoes USA for distribution to the U.S. potato industry.