By Mark A. Ritenour
Modern production practices for fresh fruits and vegetables usually include the use of various preharvest and postharvest chemicals, some of which are pesticides. Legally, these materials must be labeled for use on specific crops and may only be used according to label instructions. Chemical residues on fruits and vegetables are monitored by industry and regulators to assure compliance. Therefore, the United States and other countries set maximum residue limits (MRLs) on fresh produce for various chemicals.
U.S. MRLs are rarely exceeded when the label instructions are followed. However, when MRLs set by importing countries are lower than U.S. MRLs, then the use of these pesticides often must be discontinued or modified to keep from exceeding import tolerances. Except for Canada, that defaults to a 0.1 parts per million (ppm) tolerance for unlisted materials, any detectable residue will usually violate tolerances when no tolerance is stated.
The limit of detection for chemical residues is often around 0.01 ppm, depending on the testing laboratory and chemical of interest. Take note when considering which blocks are suitable for shipping to markets with low or missing MRLs because pesticide residues can remain detectable in crops for several months after their application, depending on the chemical.
Violations of a country’s MRLs will lead to rejected product, possible additional requirements for future shipments, and potential increased market restrictions for all growers/shippers of the product in the same state or country. In addition, individual buyers may set their own more restrictive standards. Similar to buyer-imposed food safety standards, buyer-imposed MRL standards, especially from large buyers, can significantly impact how pesticides are used in the field and packinghouse.
NO GLOBAL STANDARD
Once, it was hoped that the Food and Agriculture Organization of the United Nations would set global MRLs through its Codex Alimentarius. However, most developed nations have abandoned this and developed their own MRLs, which may be dramatically different from those of other countries. The European Union (EU) tends to maintain the lowest MRLs for fresh produce.
Of particular concern over the past year, Korean MRLs for numerous pesticides expired at the end of 2021. This is especially true for grapefruit, with the MRLs of about 30 compounds dropping to essentially the level of detection. The registrants for some of these materials have submitted applications for Korean import tolerance, but it is unclear when such MRLs will come into effect. Unfortunately, some registrants have indicated they will not apply for a Korean MRL because of the cost or other factors.
Keeping track of these constant changes is a challenge. Most problems occur when importing countries lower their MRLs and notification of the changes do not reach the relevant growers or packinghouse managers. Thus, it is critical for growers and packers wishing to export their product to have ready access to current MRLs for the materials they use. Furthermore, because MRLs for various export markets change frequently, growers and packers are encouraged to keep up to date with such changes through their respective trade group and through one or more web resources.
To assist with this, the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) developed and maintains a Postharvest Resources Website dedicated to helping the industry stay current on changing MRLs. This website includes a list of MRLs (in ppm) for various chemicals specifically used on fresh Florida citrus destined for the United States and important export markets. This website also includes links to MRL databases for select countries and to BCGlobal, which provides a comprehensive list of MRLs for all commodities and markets. Because MRLs for the various export markets are continually changing, this information is intended as an initial reference source and no guarantee can be made to its accuracy. Always verify these values with other knowledgeable sources within specific markets of interest.
With continued public interest in pesticide usage on fresh produce, knowledge of current MRLs, judicious use of pesticides based on label instructions and the use of integrated pest management practices will maximize not only production but also the marketability of Florida’s high-quality citrus.
Mark A. Ritenour is a professor at the UF/IFAS Indian River Research and Education Center in Fort Pierce.
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