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Pale Cyst Nematode (PCN) Eradication Program - Idaho Falls, Idaho

2023 4th Quarter Report (October 1st – December 31st) 

PROGRAM UPDATES AND NEW INFORMATION: 

• The current Pale Cyst Nematode (PCN) regulated area, which spans portions of northern Bingham 

and southern Bonneville Counties, is 6,495 acres (3,538 acres of infested fields and 2,957 acres of 

associated fields). The PCN infestation is limited to an area with an 8.5-mile radius and represents 

less than 1% of Idaho’s total potato production areas. 

ERADICATION ACTIVITIES

• The PCN program contracted with a licensed chemical applicator to fumigate seven PCN-infested 

fields (approximately 754 acres) with the nematicide Telone II® (1,3-dichloropropene). Fumigation 

was completed on the seven fields in October 2023. 

REGULATORY DATA

Table 1. Number of Pieces of Equipment Treated by PCN Program by Treatment Type 

Treatment type 4th Quarter 

of 2023 

2023 Year 

to Date 

Since Program 

Inception (2006) 

Pressure washed 302 1,375 35,035 

Steam Sanitized 19 197 5,676 

Total 321 1,572 40,711 

Table 2. Number of Pieces of Equipment Treated by Stakeholders Participating in the SelfCertification Program

Treatment type 3rd Quarter 

of 2023* 

2023 Year 

to Date* 

Since Program 

Inception (2006) 

Pressure washed 32 74 5016 

*Self-certification data lags all other program data as stakeholders have three months after the end of each quarter to self-certify. 
 

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Table 3. Regulatory Documentation Issued by PCN Program

Documentation type 4th Quarter 

of 2023 

2023 Year 

to Date 

Since Program 

Inception (2006) 

Active 

Certificates (PPQ* 540) 99 542 15,667 ** 

Limited Permits (PPQ 530) 31 140 4,515 ** 

Compliance Agreements (PPQ 519) 1 16 406 34 

*Plant Protection and Quarantine (PPQ); **Not applicable

SURVEY DATA

• To date, the PCN program has collected 539,543 soil samples in Idaho outside of the 32 known 

infested fields. 

Table 4. Soil Samples Collected in Idaho

Type of 

Survey

 4th Quarter 

of 2023 

2023 Year 

to Date 

Since Program 

Inception (2006) 

Detection 88 317 247,133 

Delimiting 1,218 1,855 298,519 

Eradication 5,861 6,691 206,419 

Total 7,167 8,863 752,071 

LABORATORY DATA

• Since 2009, the PCN program has collected and screened 89,379 soil samples in support of the Idaho 

State Department of Agriculture’s (ISDA) post-regulation monitoring survey of fields deregulated 

by the Animal and Plant Health Inspection Service (APHIS). Note: this data stays static, because the 

ISDA no longer conducts post-regulation monitoring surveys. 

• Since program inception, the PCN laboratory has screened 107,496 soil samples collected in other 

potato-producing states. There have been no PCN detections in the United States outside of Idaho. 
 

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Table 5. Samples Processed by the PPQ Idaho Falls PCN Laboratory 

Type of Survey 4th Quarter 

of 2023 

2023 Year 

to Date 

Since Program 

Inception (2006) 

Detection 8 7,197 296,334 

Delimiting 136 637 288,687 

Eradication 3,800 4,484 203,146 

Total 3,944 12,318 788,167 

Table 6. Historic Info: Samples Processed at Other Idaho Laboratories 

Type of Survey Idaho Food Quality Assurance 

Laboratory (2006-2009, now closed) 

Idaho State Parma Research and 

Extension Center (2006-2009) 

Detection 52,670 69 

Delimiting 10,227 896 

Total 62,897 965 

ERADICATION MONITORING AND PROGRESS

• Since its inception in 2006, the PCN program has used a staining technique to analyze the viability 

of nematode eggs in 1,081 cyst samples. The cyst samples are composited from subsamples of cysts 

collected from infested field-monitoring grids before and after fumigation treatments. Viable 

nematode eggs have not been detected in 22 of the 32 infested fields, which advances those 22 fields 

to the next phase of evaluating eradication progress, the greenhouse bioassay. 

Table 7. Viability Cyst Stain Results Summary as of December 31, 2023 

Location Total number of 

infested fields

Total number of infested fields with 

no viable PCN detected by stain

Idaho Falls PCN Laboratory 32 22* 

*One Infested Field in Bingham County has proceeded to Infield Greenhouse-Bioassay since no cysts have been collected in following 

surveys.

• Greenhouse bioassay is a test of the nematode’s ability to hatch, feed, and reproduce when cysts are

placed in proximity to a growing host plant. Currently 20 of the 22 fields have successfully 

completed the greenhouse bioassay test. Two remaining fields are currently in greenhouse bioassay 

testing, results are expected in spring 2024 for one field and the other field in the spring of 2025. 
 

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• The PCN program continues to monitor and regulate fields after successful completion of 

greenhouse bioassay testing, but with reduced sanitation requirements. Fields that have passed the 

greenhouse bioassay test are also eligible to return to potato production at the landowners’ 

discretion.

Table 8. Greenhouse Bioassay Results Summary as of December 31, 2023 

Greenhouse bioassay 

location 

Fields that advanced to 

greenhouse bioassay testing

Fields that passed 

greenhouse bioassay testing

University of Idaho, Moscow 21 20 

Bingham County 1 0 

Total 22 20 

• The PCN program requires infested fields that return to potato production to undergo full-field 

surveys following each of three subsequent potato crops to check for viable PCN populations. If 

viable nematodes are found after a survey, the program reinstates prohibitions on growing potatoes, 

and full sanitation treatments for equipment and vehicles leaving the field (i.e., pressure washing and 

steam treatment). 

Table 9. In-field Bioassay Results Summary as of December 31, 2023 

Fields that have passed one

round of in-field bioassay 

(viable nematode eggs not

detected following harvest)

Fields that have passed two

rounds of in-field bioassay 

(viable nematode eggs not

detected following harvest)

Fields that did not pass in-field 

bioassay (viable nematode 

eggs were detected following 

harvest)

5 4 7* 

*Viable nematodes detected in five fields on second deregulation iteration and two on the third deregulation iteration. 

Table 10: Eradication Progress Summary as of December 31, 2023

 

*No cysts have been detected since 2015 in a Bingham County field (149.6 ac) following the litchi tomato trap crop. In the spring of 

CY2023 potatoes were planted only in the monitoring grids for the first round GH bioassay test. The rest of the field was planted to wheat.

Field Status

Number 

of 

Fields

Acres

Passed Greenhouse Bioassay Test: Eligible to Return to Potatoes and 

start the In-Field Bioassay Test (See Table 9 for in-field bioassay 

results summary)

20 2,220.0 

Passed Viability Test: Greenhouse Bioassay Test in Progress 2* 225.9

Viable PCN: One or more Telone treatments 9 1,016.0

Viable PCN: No Treatment to Date 1 76.8

Total 32 3,538.7
 

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IMPACTS ON COMMERCE

In response to the initial PCN detection in 2006, Canada, Mexico and Korea shut off importation of 

potatoes from Idaho, while Japan cut off importation of potatoes from the entire United States. The 

Mexico and Canada export markets have both been re-opened except for potatoes from PCN-regulated 

areas. Both require PCN soil surveys from origin fields. The Korea market was reopened in June 2010 

except for potatoes originating from Bingham and Bonneville Counties, Idaho. Japan reopened the 

market for all except Idaho potatoes in February 2007 and to Idaho potatoes in September 2017. This 

action represented a major milestone for the Idaho potato industry and the PCN program, the full 

restoration of all markets lost due to the original 2006 PCN detection. Because of extensive field surveys 

conducted throughout production areas in Idaho, all of which have been negative beyond the twentynine infested fields, the general opinion by trading partners is that potatoes produced outside regulated 

areas do not pose a risk for spread of PCN. 

PUBLIC OUTREACH

Pale Cyst Nematode program information is available via the USDA APHIS Stakeholder Registry. The 

Registry allows anyone to subscribe and receive alerts by email or by text message when new 

information about PCN or other topics of interest are announced. Subscribing is simple and you can 

unsubscribe or change your selections at any time. For PCN program announcements, select Plant 

Health in the U.S. (Domestic), then Pest Management, and finally Potato Pests and Diseases. To sign up, 

visit https://public.govdelivery.com/accounts/USDAAPHIS/subscriber/new

More PCN program information can be found at:

https://www.aphis.usda.gov/aphis/ourfocus/planthealth/plant-pest-and-disease-programs/pests-anddiseases/nematode/pcn

If you have additional questions, contact the PCN program office at (208) 522-2431, 

Monday through Friday, 8:00 AM to 4:30 PM (Mountain Time), excluding federal holidays.