By Heather Curlett
Every day in ports around the country, USDA’s Plant Protection and Quarantine (PPQ) and U.S. Customs and Border Protection (CBP) officials decide the fate of hundreds of agricultural imports based on inspection. What they find—or don’t find—determines whether a shipment will be allowed to enter our country, or whether it must be treated, destroyed, or sent back because it is infested with plant pests or animal diseases.
For the last 100 years, the United States has relied on these port-of-entry inspections to protect our Nation’s agriculture and natural resources against the introduction of invasive pests and diseases. Today, PPQ is developing a risk-based sampling strategy that will fundamentally change—for the better—how the United States inspects agricultural commodities for pests.
Despite being the most commonly applied plant health (phytosanitary) measure around the world, inspection is not necessarily the most efficient tool for keeping pests out of the country because it’s simply not possible to find every pest or disease. In addition, most countries, including the United States, typically inspect by sampling a flat percentage (for example, 2 percent) of every incoming shipment. While this approach is simple and widely used, it does not produce a consistent pest detection rate.
Consider: When an inspector samples 2 percent of a large shipment, detection rates can be inflated because a large number of samples are taken. When the inspector samples 2 percent of a small shipment, detection rates can be underestimated—especially if infestation rates are low—because so few samples are taken. As a result, inspectors invest a lot of time and effort with variable results.
To make inspection a more effective safeguarding tool, PPQ scientists have been exploring new ways to collect and use data about imported shipments of live plants intended for planting. Their goal: Analyze the data and identify higher-risk imports for increased focus—without increasing the inspection effort or resources. To accomplish this, PPQ inspectors have been using a specially designed online tool for the last 18 months. It calculates a statistically appropriate number of units to inspect from each incoming shipment arriving at one of PPQ’s 16 Plant Inspection Stations.
“In a way, we are reverse engineering the inspection process,” explained National Operations Manager Dave Farmer. “We set the pest detection rate, and the tool tells us how many boxes to look at based on the shipment’s size and the number of sample units and plant taxa it contains.” Now PPQ inspectors detect pests at a consistent level because they know exactly how many boxes they need to sample to confidently determine if there is a problem with an incoming shipment of plants or cuttings.
With every inspection, PPQ scientists collect more information about commodities and pest interceptions that they feed back into their analyses. “We’re using the results of our statistically designed inspections to better estimate pest approach rates for specific plant material types,” explained Pest Exclusion Analysis Coordinator Barney Caton. “Our next step is to use those results to develop sampling strategies that better focus inspections on shipments which are more likely to be infested.”
Going forward, Caton and Farmer, along with their colleague Ron Komsa, will lead a PPQ work group to consider different types of risk-based sampling plans, including ratings-based sampling and continuous sampling. Ratings-based sampling plans adjust inspections based on a commodity’s analytically derived risk ranking. Continuous sampling plans reduce inspections after an importer achieves a predetermined number of sequential pest-free shipments.
The work group will carefully evaluate how these plans might work in PPQ’s Plant Inspection Stations and explore other options, including variations or combinations of these strategies, based on operational feasibility. The group will also be working with CBP to implement similar risk-based inspections of agricultural commodities at U.S. ports of entry.
In June, PPQ and the North American Plant Protection Organization (NAPPO)—a regional plant protection organization whose members include the United States, Canada, Mexico—welcomed 122 participants from 27 countries to the first-ever International Symposium for Risk-Based Sampling. PPQ and NAPPO put together this Symposium to help drive a global conversation about the use of data- and statistics-driven inspection practices not only here in North America, but around the world.
During his opening remarks, PPQ Deputy Administrator Osama El-Lissy underscored the value of risk-based sampling. “I am an adamant supporter of this approach,” he said, “because it brings us closer to reaching our overarching goal of making risk management decisions based on evidence of risk, not just perception of risk. This concept is central to the achievement of our shared vision of a safe, fair, predictable, rules-based trade system.”
PPQ experts, alongside their counterparts from U.S. and foreign government agencies, industry representatives, and other scientists, spoke during the 5-day event. Through this exchange of technical information and best practices, they helped lay the foundation for worldwide understanding and harmonization of risk-based sampling concepts and practices while encouraging greater adoption of international standards for inspection.
On the last day of the event, a smaller group of participants met to develop the framework for an international risk-based sampling manual. “We purposefully structured the event to introduce participants to the concept of risk-based sampling and then step them through the scientific, technical, and social aspects of implementing data- and statistics-driven inspections,” explained Christina Devorshak, National Science Programs Coordinator and Co-Chair of NAPPO’s Risk-Based Sampling Steering Committee. “We then carried all that we learned into the last day of the event, where we mapped out the contents of a risk-based sampling manual.”
Once developed, the manual will provide practical guidance to countries that are interested in implementing risk-based inspections in their ports of entry. NAPPO will coordinate the development of the manual during the coming year and will open participation to countries outside its member organizations.
As the volume of international trade continues to grow and government budgets remain static or shrink, advances in risk-based sampling are especially timely and crucial. By using risk-based sampling, policy makers and inspectors will be able to more readily identify riskier imports and adjust resources and policies to maximize the effectiveness of inspection.
The result is a win-win for importers and regulators. Higher-risk shipments will receive more intensive inspections, and we will be able to more confidently detect low-level pest infestations in other shipments. Low-risk shipments will clear faster, and importers will have a financial incentive to present clean, compliant commodities. In the end, agriculture and natural resources will benefit from overall better pest risk management.
To learn how risk-based sampling works, take the online training available on the NAPPO web site.