Agronomy Update – July 6th

Hi everyone.  Great to see some more much needed rain today.  Once again, amounts are quite variable.  The highest totals so far today appear to be in West Prince (over 30 mm at West Cape) and around Charlottetown (~10 mm so far), while totals in East Prince are closer to 5 mm.  The forecast also look favourable to some more rain on Wednesday…here’s hoping that indeed arrives!

Morgan and I were out to check on a bunch of trial fields last week, as well as visiting with some growers.  Generally, the crop looks quite promising across the province, and most growers I talked with are happy with how things are progressing.  Of course, some more rain will be essential as we start to move toward tuber initiation.  Adequate soil moisture is essential at tuber initiation to get good tuber numbers as well as minimize common scab incidence.

A few things to think about as you’re checking your fields this week.

  1. Colorado Potato Beetles:  I’ve found CPBs in multiple fields over the last week despite use of in-furrow or seed piece neonic treatment.  That being said, none of the levels of damage were huge…but worth keeping an eye on.  Have seen adults and larvae in the same field, so definitely multiple generations in play.  Keep an eye out for beetle, larvae and egg masses and consult with your agronomist to decide if it makes sense to follow up with an insecticide.  I’ve had a few growers note that when it’s dry early in the season they can see some CPBs chewing on plants, but after the soil moisture catches up and plants get into rapid growth stage, the beetles are pretty much gone.  However…follow up with your scouts and assess your own fields before making a decision to spray.
  2. Weeds: Still lots of weedy fields around.  Pre-emerge herbicides were limited in effectiveness in many communities due to the lack of soil moisture.  I’m not seeing quite as much problem with grass and more with broadleaf weeds like redroot pigweed, lamb’s quarters, and wild buckwheat, among others.  Some growers are going in with a follow-up application of Sencor/Prism at the moment.  Be forewarned that while Prism (rimsulfuron) can be effective on some weeds, it has limited effectiveness on lamb’s quarters.  A number of growers are doing some additional passes with hillers/cultivators to keep the weeds under control.
  3. Additional Insects. According to the table below (Table 1), we are about 50 to 70 growing degree days ahead of the historical average, and far ahead of last year when we had a cool June.  Therefore, we would expect a number of insect species (aphids, European corn borer, tarnished plant bug) to also be ahead of schedule.  Keep up scouting activities to inform your IPM strategy.  Watch for Pest Updates from the Dept of Ag in the near future with more on this.
  4. Emergence.  Overall, I’ve been very pleased with what I’ve seen on emergence.  Very little evidence of unemerged seed pieces or “ragged” emergence from what I’ve seen.  Have seen a couple of examples where seed pieces are starting to break down a bit early, but they already have a plant up and through the ground now.  Last year there were a lot of later-season reports of blackleg that ended up being problematic in storages.  Keep a close eye on your crop throughout the season and watch for any blackleg symptoms.  Some of the newer strains of blackleg thrive in hot and dry conditions and cause issues later in the plant’s lifecycle, enabling infected plants to set tubers and either infect seedlots or produce tubers that will break down in storage.  If you have any suspect plants that you feel should be tested, be sure to submit samples to the Provincial Pathology Lab.

Hopefully everyone gets a decent amount of water this week.  As always, feel free to call if you have any questions or comments.


PS:  Thanks to Morgan for her help collecting the weather data again this month!

Table 1: Growing degree days (GDD) comparison of June 2020 to historical records

Location June 2020 GDD (>5oC) Historical June GDD (>5oC) Difference (oC)
North Cape 341.1 283.6 +57.5
Summerside 340.4 285.2 +55.2
Charlottetown 338.6 285.5 +53.1
St. Peter’s 332.4 257.6 +74.8

Table 2: Rainfall amounts comparison of June 2020 to historical records

Location Rainfall Amount for June 2020 (mm) Historical Rainfall Amount (mm) Difference (mm)
North Cape NA 82.1 NA
Summerside 16.7 91.3 -74.6
Harrington/Charlottetown 29.5 98.8 -69.3
St. Peter’s 23.3 100.9 -77.6

Note:  Rainfall data for North Cape (Environment Canada) was unavailable for June.