31 Jul Agronomy Update – July 30

Some welcome (and perhaps unexpected) rainfall this afternoon!  As I write this (2:30 pm Thursday), there has been some heavier showers in the Eastern half of PEI, but the radar looks promising to get at least 5-10 mm across most of the province, perhaps more in places.

I’ve been on the road doing trial work much of this week in West and East Prince. Some comments from my travels, as well as conversations with growers across the province:

• The crop generally looks quite healthy and vigorous, with most of the fields I visited having very little in the way of foliar disease or CPB damage. Some fields near the south shore on sandier soils and not sheltered from the wind were showing mild symptoms of water stress on Monday/Tuesday.
• Colorado potato beetle (CPB) pressure is high in certain fields/communities, with definite indications of resistance to in-furrow insecticides becoming evident.  In other regions, CPB are not present.
• There are a few reports of early blight, brown spot and grey mold; however, foliar disease reports are limited.
• Many growers have one or two targeted fungicide applications on for Alternaria, ahead of row closure.
• Tubers and stems per plant appear to be above average, no doubt because of more physiological age of seed.
• Some evidence of tarnished plant bugs on field margins requiring attention.
• Aphid numbers trending downward.
• European corn borer largely now past the window for control in most of the province.

Colorado Potato Beetle Control (reshare from last week):

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, particularly in East Prince
• Grey mold spores continue to remain relatively low but did register higher on Friday of last week.

Aphid Alert:

• Aphid numbers remain at a similar level to last week, at a much lower level than earlier in the season.
• Weekly aphid number per sample have decreased for five 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)