25 Jul Agronomy Update – July 25th

Hi everyone,

A mostly dry week so far, with some showers in the forecast but not a lot of substantial rain likely to be coming right away.  Folks that have been doing soil moisture testing in both West and East Prince have shown values not too far from wilting point, so there will likely be some irrigation starting right away.  It appears to be particularly dry in parts of West Prince and much of Kings County.  Hopefully some evening showers manifest in the next few days.

Overall, the crop appears to be looking good.  A stretch of sunny days with cooler evening temps and lower humidity should be a great recipe for lower disease concerns and greater photosynthesis by the plants.  Many varieties are already starting to shift into tuber bulking, and based solely on the subset of plants I’ve been pulling, the average number of tubers per plant appears to be average or higher.  I hope that Mother Nature cooperates to help us capitalize on a great start with a great finish to the growing season.

Aphid Alert:

Aphid numbers have not dropped significantly two weeks in a row, down to 1 aphid per trap this week.  As well, we still have not found any Green Peach aphids so far this season, which is welcome.  Seed growers can keep this in mind when deciding whether to apply aphicides with their next spray.  We are at almost an even split between potato aphids and other aphids at the moment.  A very small number of tarnished plant bugs have been trapped.

Spore Trapping:

• No late blight spores were detected in PEI this week.  No spores were detected in either NB or Maine as well.
• Grey mold (Bortrytis) spores were very high in about half of the Spornado samples this week, without a clear pattern across the province.  As these spore traps collect spores continually through the week, it is quite possible that these numbers will be higher than for Airspore, which only collects at a point in time 3x per week.  Grey mold spores have started to increase now that canopies are mostly at row closure.  Given the mostly dry and warm weather forecast, I wouldn’t be as concerned about grey mold yet on a widespread basis, but we should keep an eye on it as we get into August.
• Foliar late blight has been confirmed in Ontario.  The strain has been identified as US-23.

• Early blight spiked late last week and early this week with high spore levels in some areas but has largely decreased by mid-week.  Brown spot is mostly at zero in most samples, except for a few individual samples.  From Airspore, grey mold spore samples are still relatively low.
• If you have observed early blight or brown spot in any fields and would like to submit a sample for resistance testing, please contact me!  You can either drop off samples at the office, or we can arrange to collect samples.

Pest/Disease Update:

• There are a few growers dealing with high numbers of Colorado potato beetles that have survived neonic treatments at planting.  More on that below.
• Early blight is starting to show up more now that we have seen a change in weather.  High spore numbers are indicative of the second spike of early blight.  I was in a number of fields this week that have obvious infection on the lower leaves but look pretty healthy for the rest of the plant.  Particularly for susceptible varieties (Dakota, Targhee, Ranger), keep an eye on your fields and mix in a suitable product if you deem it necessary.
• As we start to lose flowers on a lot of fields, be on the lookout for white mold (Sclerotinia).  Grower experience indicates that Mountain Gems are a bit more susceptible to white mold than other varieties.
• It sounds like scouts aren’t finding any more corn borer egg masses for now.  We’ll keep an eye out to see if a second generation appears this summer.
• Tarnished plant bugs and leafhoppers are also being reported by scouts and growers.  These insects may be present but may not cause much damage.  Consult with your agronomy team to assess whether the number of insects observed reaches the threshold for application.

Colorado Potato Beetle control:

Lots of questions this week about options for Colorado potato beetle control.  As I have shared with you in the past, we have documented evidence of increase resistance/shortened time of efficacy for the neonic treatments at planting (Actara/Titan).  More and more, growers are having to come back with at least one foliar treatment. As always, resistance management is key to keeping tools in the toolbox to combat CPB.

Some of the insecticides in the different groups are: (this is not an exhaustive list, but a list of commonly used options)

• Group 6 + 28:  Minecto Pro (Syngenta)
• Group 3:  Decis 100 EC (Bayer), Pounce (FMC) and Perm-Up (UPL) (used for aphids as well)
• Group 5:  Delegate, Success, Entrust (Corteva) – has shown some level of resistance
• Group 28: Coragen (FMC), Exirel (FMC), Harvanta (Belchim), Vayego (Bayer)
• Group 15: Rimon (UPL)
• Group 30:  Cimegra (BASF)

Do not apply the same product or products from the same class twice in a row.  Mix up groups to try and keep ahead of insecticide resistance and get a good kill on beetles.

Looking for Fields for PVY robot:

I am looking for a few fields for the research team at UPEI to take their AgriScout PVY detection robot into early next week.  What I’m looking for:

• Commercial fields planted at 0.5 to 1.5% PVY
• Varieties:  Mountain Gem, Russet Burbank, Targhee Russet, Caribou, Alverstone Russet
• Not sprayed with Sencor/Prism or any other herbicide that may mottle the leaves.
• Ideally fields that are wider than long (so the robot doesn’t have to go 500 m before turning around)

If you think you might have candidate fields, please call/text/email me!

Crop Update Meeting #3 – Tuesday, July 30^th – 8:00 am

Based on feedback from the survey I circulated last week, there are still a lot of people that like having the option of an in-person crop update meeting, but the majority would like to see a hybrid meeting format return, so we will be adding that option starting next Tuesday at our next meeting in Charlottetown at the Potato Board office.  You are welcome to join us in person or via Zoom (please contact me for the Zoom link).

I hope you all have a great end of the week.

Ryan