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

2023 1st Quarter Report (January 1 – March 31)

PROGRAM UPDATES AND NEW INFORMATION:

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

and southern Bonneville Counties, is 6,568 acres (3,542 acres of infested fields and 3,026 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 five PCN-infested 

fields (approximately 454 acres) with the nematicide Telone II® (1,3-dichloropropene) in August 

and September 2022. Soil samples were collected from the fields following fumigation and will be 

analyzed in the laboratory to determine fumigation effectiveness against encysted nematode eggs. 

The results of one field are expected by June 2023.

REGULATORY DATA

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

Treatment type 1st Quarter 

of 2023

2023 Year 

to Date

Since Program 

Inception (2006)

Pressure washed 3 3 33,662

Steam Sanitized 0 0 5,479

Total 3 3 39,141

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

Treatment type 4th Quarter 

of 2022*

2022 Year 

to Date*

Since Program 

Inception (2006)

Pressure washed 12 114 4,942

*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 1st Quarter 

of 2023

2023 Year 

to Date

Since Program 

Inception (2006)

Active

Certificates (PPQ* 540) 3 3 15,127 **

Limited Permits (PPQ 530) 1 1 4,376 **

Compliance Agreements (PPQ 519) 0 0 ** 34

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

SURVEY DATA

• To date, the PCN program has collected 542,912 soil samples in Idaho outside of the 32 known 

infested fields. 

Table 4. Soil Samples Collected in Idaho

Type of Survey 1st Quarter 

of 2023

2023 Year 

to Date

Since Program 

Inception (2006)

Detection 0 0 246,248

Delimiting 0 0 296,664

Eradication 0 0 199,727

Total 0 0 742,639

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 106,187 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 1st Quarter of 

2022

2023 Year 

to Date

Since Program 

Inception (2006)

Detection 6,037 6,037 295,174

Delimiting 0 0 288,050

Eradication 476 476 199,138

Total 6,513 6,513 782,362

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 1,055 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 March 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 24

• 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. Twenty-two of the 24 fields have successfully 

completed the greenhouse bioassay test. Of the two remaining fields currently in greenhouse 

bioassay testing results are expected in late 2023.

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

discretion.

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

Location Fields that advanced to 

greenhouse bioassay testing

Fields that passed 

greenhouse bioassay testing

University of Idaho, Moscow 24 21

• 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.

• Between 2015 and 2023, potatoes were planted on eleven eligible fields, which were the first potato 

crops grown since PCN was first found on those fields. 

• Viable nematodes were found in soil samples collected from three of these fields following potato 

harvest. As a result of finding viable nematodes on these five fields, the program reinstated 

prohibitions on growing potatoes, and full sanitation treatments for equipment and vehicles leaving 

the fields (pressure washing and steam treatment). 

• No viable nematodes were found in soil samples from the other six fields, making them eligible to 

grow another potato crop, which is at the landowners’ discretion. Of these six fields, five have 

successfully completed one round of in-field bioassay, and one field has successfully completed two 

rounds of in-field bioassay.

• Potatoes were planted on three eligible fields in 2022. This is the first round of in-field bioassay for 

two of the fields and the second round of in-field bioassay for the third field. Soil samples were 

collected from the fields following potato harvest and viable nematodes were found on all three 

fields. As a result of finding viable nematodes on these three fields, the program reinstated 

prohibitions on growing potatoes, and full sanitation treatments for equipment and vehicles leaving 

the fields (i.e., pressure washing and steam treatment).

Table 9. In-field Greenhouse Bioassay Results Summary as of December 31, 2022

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)

4 1 6*

*Viable nematodes detected after one crop on four fields, and after two crops on two field.
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ERADICATION PROGRESS SUMMARY AS OF MARCH 31, 2023

This pie chart summarizes eradication progress for the 32 infested fields (3,542 acres) detected in Idaho 

since program inception in 2006.

* One field planted with a multi-year alfalfa crop in 2020, and one field detected in November 2021 that 

received its first treatment in September 2022 (results not available until June 2023).

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 U.S. 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 twenty-nine infested 

fields, the general opinion by trading partners is that potatoes produced outside regulated areas do not 

pose a risk for spread of PCN.

Passed viability and greenhouse 

bioassay tests; also passed round 1 of 

in-field bioassay (5 fields, 473.2 ac)

Passed viability and greenhouse 

bioassay tests; also passed round 

2 of in-field bioassay (1 field, 

119.7 ac)

Passed viability test; 

greenhouse bioassay testing 

in progress (1 fields, 147.5 

No treatment data to date 

(2 fields, 173.4 ac)*

No cysts found since 2015, 

following litchi tomato (1 field, 

149.6 ac)

One or more Telone treatments, 

viable population remaining (7 fields, 

734.1 ac)**

Passed viability and 

greenhouse bioassay tests; 

eligible to return to potatoes 

(15 fields, 1,795 ac)
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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.