Agronomy Update – July 15th

Good afternoon,

Another damp and cool day in PEI.  It does not appear we are going to get much rainfall accumulation this week, as most weather stations are reading less than 1 mm so far yesterday and today.  The long range forecast appears to be favourable for some rain the first of next week…but we all know that the forecast that far out is subject to significant change.

The rain last week appears to have been most significant west of Portage and east of Hunter River.  Between Tyne Valley and Hunter River, rainfall amounts were generally lower and more sporadic.  At the same time, crops generally look healthy around the province, with a lot of potatoes now achieving row closure and blossoming.  I hope that you all continue to get some timely rainfall through the next couple of months to facilitate a good crop.  Early reports from growers indicate that there appears to be a good set started under some varieties.  I hope to dig a few plants myself before the weekend to assess this for myself.

Dealing with Volunteers:

There are lots of reports that there are a lot of volunteer potatoes this year.  The consistent snow cover through the winter as well as a lack of freeze/thaw events in the spring resulted in a lot of tubers surviving the winter.

Many volunteers will be taken care of by Colorado potato beetles, which are also quite abundant so far this year.  In fields with more significant numbers of volunteers, waiting for beetles to take care of them may not be enough.  You don’t have a lot of options with herbicides.  The option with the most consistent effect is glyphosate (Round-Up), but even it is not terribly effective on a mature potato plant.  One plus is that even if the glyphosate doesn’t completely kill the potato plant, it can often sufficiently impair any tubers that it sets from growing next year.

If you have a forage crop in that field, you can achieve some level of control with mowing; however, C4 grasses like sudangrass or pearl millet won’t regrow if mowed too close to the ground.

Why are we worried about volunteers?  Primarily, we are worried about their ability to host and spread diseases like late blight, early blight, and PVY.  We have been fortunate not to have a large number of volunteers in the last couple of seasons.  Keep an eye on your rotation crops and consider what are the best options for you to reduce the risk of disease spread through volunteer potatoes this season.

Pest and Disease Round-up:

The Department of Agriculture will have a more complete Pest Update this week (contact Lorraine to get on the mailing list if you’re not on it already), so I won’t try and cover all of that ground myself.  However, here are a few points to consider based on what I’ve seen recently or heard from other agronomists/scouts:

  • Colorado potato beetle reports seem to be higher this year.  1st and 2nd instar larvae are being reported as well as adults.  With earlier emergence this year, there is more likelihood of multiple generations of beetles this year.  If you have significant numbers of adult CPBs and would like to submit beetles for an insecticide efficacy trial with AAFC, please contact me, Lorraine MacKinnon or Sebastian Ibarra with the PEI Dept of Ag in the next week or so.
  • Sebastian and Steven Hamill are also collecting samples of European corn borer (ECB) for a resistance trial.  If you are seeing ECB egg masses and would like to submit samples, talk to Sebastian.  There are lots of reports of ECB egg masses, primarily from Charlottetown to the east.  According to Dr. Christine Noronha, the cumulative threshold for ECB is around 3 egg masses per 10 plants.  Timing of insecticide application is crucial (when they start turning black) to make sure you get control.  Eggs normally hatch within 3 to 7 days, depending on temperature.
  • Also hearing reports of damage from tarnished plant bugs in potatoes and flea beetles in brassica crops.
  • This week is PRIME weather for late blight.  We have had no reports of late blight spores in PEI (or elsewhere in Eastern Canada or the Eastern USA) but late blight models based solely on weather indicate the potential for infection events.  Keep an eye on your crop and your spray schedules.
  • I’m posting a table for early blight (Alternaria solani) and grey mold (Bortrytis cinerea) spore trapping results from last Friday and this past Monday, courtesy of AirSpore.  As noted before, getting your targeted fungicides on before row closure is encouraged.  A dose of prevention is always preferred over battling to control a disease all summer.  So far, early blight spores have mostly been found in the western half of the Island, while grey mold (Bortytis) spores have been found all over.

Spore Trapping Results for Friday, July 10 and Monday, July 13

Community Fri, July 10
Early Blight
# of spores
Fri, July 10
Grey Mold
# of spores
Mon, July 13
Early Blight
# of spores
Mon, July 13
Grey Mold
# of spores
Elmsdale 13 18 22 62
O’Leary 93 0 0 44
Wellington 13 0 31 116
Summerside 0 4 0 44
Kinkora 22 49 0 22
Meadowbank 4 4 0 0
New Glasgow/Rustico 0 44 0 22
Oyster Bed/Winsloe 4 0 0 84
Souris 0 0 0 9
Elmira 0 44 0 27
Dundas 0 18 0 13
Stratford 0 18 13 49


PAA Virtual Meeting Presentations – July 20-22nd

For anyone interested in viewing this year’s Potato Assoc. of America (PAA) scientific presentations, they are being held online this year due to the physical meeting in Montana being cancelled.

You can register to view these presentations at  There is a registration fee of $50 USD that covers all three days of presentations.  The first two afternoons (Monday and Tuesday) are more agronomy-focused, while Wednesday is primarily breeding and genetics.  I will be presenting on our AIM ethylene trial (in partnership with AAFC) on Tuesday afternoon at 4:35 pm, if that is of interest.


For those unfamiliar with PAA, this would provide a good taste of the type of presentations that are usually shared at these annual meetings.  The PAA Annual Meeting is scheduled to take place here in PEI next July…hopefully we’ll be able to still host that meeting!  Stay tuned for more in the coming months about PAA 2021 in PEI.

Have a great rest of the week.  As always, feel free to contact me with any questions.  If it’s something that I don’t have the answer to off the top of my head, I’m happy to help dig for the right answer with you!