23 Jul Agronomy Update – July 23

Hello everyone,

After being out of the province last week, I came home to many potato fields in blossom with partial or full row closure. Most plants are growing rapidly, with many fields now at tuber initiation. I pulled a few plants on Tuesday in potatoes planted mid-May that now have potatoes larger than a toonie.

Most of the Island received between 10-15 mm of rain yesterday, and most of the province has now received 25-30 mm in the last 7 days. Some areas got isolated thundershowers yesterday with higher totals, particularly in Queens County. The long-range forecast doesn’t currently have a lot of moisture it in, but long-range forecasts don’t seem to be very accurate this year. The soaking rain of yesterday and last Saturday night should hopefully set up a strong week of growth.

Crop Update:

At the second Crop Update meeting on Tuesday afternoon:

• Attendees reported that the crop generally looks quite healthy and vigorous.
• There are some reports of significant Colorado potato beetle (CPB) pressure in certain fields/communities, with definite indications of resistance to in-furrow insecticides becoming evident.
• According to PEIDA GDD models, the end of this week should see peak CPB larvae numbers in most of the province (not Kings Co.).
• There are reports of European corn borer (ECB) that have hatched and moved into plant stems already. According to PEIDA GDD models, this week should be the peak of EUR moths in most of the province.
• There are a few reports of early blight, brown spot and grey mold; however, foliar disease reports are limited.
• Most growers are battling windy conditions to match ideal timing windows for certain products.
• Many growers have one or two targeted fungicide applications on for Alternaria, ahead of row closure.
• There are some reports of red-headed flea beetles in Prince County requiring attention.
• Tubers and stems per plant appear to be above average, no doubt because of more physiological age of seed.
• Due to low attendance at the Crop Update meetings, I am considering discontinuing these meetings.  If you see value in these meetings and would like to see them continue, please contact me and I can make a final decision on whether to hold a meeting on Aug 4^th.

Colorado Potato Beetle Control:

 As we start to see more CPB adults and larvae in fields across the country, some growers are asking about CPB control options.  A few things to share:

• Primary insecticide options include:
  • Group 5:  Delegate, Entrust, Success
  • Group 6:  Agri-Mek SC
  • Group 28:  Vayego, Coragen, Exirel, Verimark, Harvanta
  • Group 30:  Cimegra
  • Group 6 + 28:  Minecto Pro
  • Group 15: Rimon (larvicide only)
  • Some of these products may not be locally available. Check with your sales representative for availability and pricing.
  • I have not included the foliar neonic products (Group 4) because if using Actara or Titan at planting, it is not recommended to use these products foliar.
• In a 2025 AIM trial, we saw similar levels of control between Cimegra, Minecto Pro, Vayego and Coragen. Control levels from Delegate were not as long-lasting, but it performed well as a 2^nd application.  A follow-up trial is underway this year.
• Do not use the same product or products from the same group for consecutive treatments. This is a recipe to build insecticide resistance.
• If you have fields in close proximity to other potato growers, it is recommended to consult with your neighbors and consider a “community” approach to CPB. For example, plan to spray all fields in an area with the same chemistry for the first spray, and then everyone another, different treatment for a second spray, if needed. This will reduce the likelihood of building resistant populations in your community.

Spore Trapping Results:

• No late blight spores have been found in PEI or NB.
• We are seeing higher early blight and brown spot spores than earlier in the month. None detected in West Prince.
• Grey mold spores continue to remain low.
• Due to the rain yesterday, there were only samples collected at 3 sites yesterday. Very low numbers of spores detected at those 3 sites.

Aphid Alert:

• Aphid numbers have decreases by more than half in the first part of this week compared to last week.
• Weekly aphid number per sample have decreased for four weeks in a row.
• Numbers of colonizing aphids are quite low, with only one Green Peach aphid found so far this week, and none last week.
• Growers are encouraged to keep up with oil sprays during rapid plant growth, but lower aphid numbers are welcome for aphicide rotation.

Additional Resources:

• PEI Dept of Ag Plant Health – Pest Monitoring
• PEI Dept of Ag Weather Stations
• AgIntel Weather Dashboard (note: some stations not accurate/functional)
• OMAFA Crop Protection Hub (for pesticide labels/details)

Have a great rest of the week!

Ryan