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JULY 16, 2020

Prepared by Lorraine MacKinnon, Potato Industry Coordinator
For any issues related to content, please contact Lorraine MacKinnon at 902-314-1607.

This Pest Update combines information from a variety of sources to provide growers and field staff with general pest levels reported on a weekly basis.  The dashboard is NOT intended as a decision tool for spraying on its own; rather growers are encouraged to use integrated pest management strategies specific to their own fields. 


  • Fields across PEI are at or near row closure; generally excellent crop development.
  • Some herbicide injury has been noticed.
  • No volunteer weather stations on PEI reported greater than 1.5 mm on July 15.
  • Periods of HIGH LATE BLIGHT RISK (based on weather alone) are upcoming in some locations.  See table below.
  • Spore trapping services have detected Alternaria solani (early blight) spores in several areas across Prince County, but NOT east of Pownal.  
  • Botrytis spores have also been detected in several locations around the Island. 
  • NOTE:  Spore trapping collections were interrupted by weather in central PEI (between Kinkora and Pownal) on July 15.
  • No late blight spores have been trapped on PEI, NB or Maine.
  • Regional spore trapping services provided by AirSpore (Lab'Eau-Air-Sol).
  • Late blight spores have been trapped in Alberta.
  • Colorado Potato Beetle life stage is advanced compared to last year - populations mostly at 3rd and 4th instar stage.
  • Weed control has been a challenge.
  • NEXT POTATO FIELDWORKER MEETING:  7:30am JULY 28 (email for link to online webinar)


  • Submit suspect plant samples to  the PEI Analytical Labs.  Sample submission form here 
  • Disease samples should always first be submitted to PEI Analytical Labs, and can be sent on for further testing from there.
  • PEIDAL staff & local researchers seek insect and weed samples for further study - Colorado Potato Beetle, European Corn Borer, resistant weed populations.  Contact Lorraine @ or 902-314-1607 for instructions on submitting samples.
  • For integrated pest management strategies, click here
  • For the 2020 Potato Pest Control Guide, click here.
  • For Potatoes in Canada magazine's scouting resources, click here.

  July 9-16  
Mount Royal 4.7  
Tyne Valley 11.6  
Kensington 10.4  
Tryon N/A  
New Glasgow 16.2  
Harrington 14.4  
Johnston's River 0.6  
Souris N/A  
Dover 140.3*  
*Volunteer weather stations nearby have reported significantly less rainfall.


Sample submission to date has identified the following diseases:  bacterial blackleg, brown spot (alternaria alternata), fusarium and calico virus.
Several samples were submitted as a result of poor emergence.  A variety of issues were identified - fusarium, physiologically aged seed, blind sets, bacterial rot, and multiple sprouts.  


Predicted Pest Levels & Events for July 16-21.  For explanation, see notes below.

  Late Blight¹ European Corn Borer² Colorado Potato Beetle Aphids - July 13 collections      
East Point HIGH July 18-19
MED July 20-21
July 21 July 11 5.3 other aphids; slight increase noticed this week across PEI.

Some Potato Aphids found, low numbers.
Souris HIGH July 18-19
MED July 20-21
July 19 July 9      
Dover HIGH July 19-21 July 20 July 10      
Johnston's River HIGH July 19-21 July 18 July 9      
Charlottetown HIGH July 19-21 July 18      July 8      
Harrington MED July 18-21 July 18 July 9      
New Glasgow MED July 19-21 July 18     July 8      
Baltic MED July 19-21 July 18 July 9      
Kensington MED July 19-21 July 17 July 8      
Tryon MED July 19-21 July 18 July 8      
Maple Plains MED July 19-21 July 17 July 8      
Summerside MED July 19-21 July 16 July 7      
Tyne Valley LOW July 16-21 July 18 July 9      
O'Leary MED July 19-21 July 20 July 10      
North Cape MED July 19-21 July 20 July 10      
1BlitecastModel assumes June 15 emergence and is purely based on weather conditions. 
2Predicted date of 5% eggs.  Unknown dates indicate event will occur later.  
3Predicted date of 85% 1st & 2nd instar Colorado Potato Beetle.  This event has already occurred.  

IMPORTANT:  Ratings are based on a combination of reported cases, trapped spores, and weather conditions conducive to disease.  ECB, CPB and late blight ratings were generated using CIPRA software (Agriculture and Agri-Food Canada, Saint jean sur Richelieu, QC), and Blitecast.  For more detailed information on pest modelling and other monitoring tools contact Sebastian Ibarra, 902-314-0388 or
Insect ratings are based on growing degree models specific to that pest; actual observations reported in Fieldworker meeting summary below.

The July 14 potato fieldworker meeting captured the following observations:
  • Reports of volunteers in non-potato fields.  These need to be watched; glyphosate may not be effective at getting rid of volunteers, and there is a risk of pest infestation (Colorado Potato Beetle) and disease spread (late blight, PVY) to nearby potato fields.
  • Lots of fields at row closure now; some in blossom.
  • Variable rainfall across the Island.
  • Several reports of Colorado Potato Beetle damage.  Some samples sent for insecticide resistance.
  • European Corn Borer egg masses have been found in West Prince and areas just east of Charlottetown.  REMINDER:  The threshold for ECB is cumulative for the season; so if you found 2 egg masses per ten plants last week and 1 per ten plants this week then you are at 3.
  • Some Tarnished Plant Bugs found but damage not as bad as other years.  
  • Any cull piles need to be reported and destroyed immediately. Call Dwight Thompson (902-620-3119) to assist in destruction.


Our mailing address is:
PEI Department of Agriculture & Land
11 Kent Street, 5th Floor Jones Building
Charlottetown, PEI
C1A 7N8

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Prince Edward Island Department of Agriculture & Land · 11 Kent Street · 5th Floor, Jones Building · Charlottetown, Pe C1A 7N8 · Canada

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