Agronomy Update – July 7th

Hi everyone,

Finally, some sun and warmth to dry up some of the moisture we got last weekend.  I’m sure everyone is well aware of how much rain we got, but it seemed to range mostly between 60 and 85 mm of rain from Sunday to Tuesday of this week.  Some areas of the province have now had more than 200 mm of rain since June 1st.  More on the weather a little later on.


Spore Trapping Update:

This week was the first collection for late blight spore traps through the Spornado program that we’ve worked with the last two years.  This year, we are operating 12 collectors across the province in partnership with the PEI Agri-Watershed Partnership and some individual watershed groups.  Samples will be collected on Tuesdays, with the aim of having results to you on Thursdays.

This week, no late blight spores were detected from 11 sites across the province.  There was Bortrytis spores (grey mold) detected at 3 out of 11 locations, which is early for grey mold.  Spornado is doing some calibrations on these counts and I’ll have more to share by next week.

Airspore sampling also started this week across the province, also with no late blight spores detected in PEI.  There was a detection of late blight spores in the Grand Falls region of New Brunswick on July 5th (Wed) this week from the Airspore network in NB.


Crop Update:

The first Crop Update Meeting of the season was held on Tuesday in Kensington.  We had a strong turnout, given the wet weather.  Some of the key points raised:

  • Until the Canada Day weekend, emergence was slow but not too many reports of set rot or drown-outs. Following the Canada Day weekend rain, this has increased, particularly in West Prince.
  • There is a lot of worry about the amount of PVY inoculum around this year. Growers are advised to be very diligent with oil and aphicide applications very soon after emergence and consistently through the rapid growth phase.  Many reported that those potatoes that are fully emerged are growing quickly, so oil application every 4-5 days is warranted to keep up with new growth.
  • We do not have complete results from the first week of Aphid Alert; however, reports are that total aphids numbers have been relatively low so far. Some of the first collections were compromised by the Monday/Tuesday rain.
  • There has been a report of Green Peach Aphids being found already in Maine, which is super early to find GPA.
  • There were a few reports of adult Colorado Potato Beetles here and there, but no reports of significant damage thus far.
  • One person reported large number of click beetles being evident in the last week. Click beetle egg-laying may have been delayed somewhat this year by some of the cooler conditions in April and May.
  • With the wet weather making it hard to get protective fungicides applied, there is of course worry about late blight. While we have not had late blight in PEI in several years now, it can travel here through imported seed, home garden potatoes or tomatoes, or on the wind from other areas.  There was discussion about checking up with garden centres to assess tomato transplants for signs of blight.
  • Lots of issues with weeds this year, particularly grasses. Lots of people getting grass herbicides on.  Also several reports of volunteer potatoes, particularly near hedgerows/sheltered areas.  Be on the lookout for volunteers, as they can be great reservoirs for blight and PVY.


June Weather Report:

In looking just at June:

Table 1: Rainfall amounts for the month of June (current year 2023 vs historical records 1981-2010)

  Rainfall (mm)
Location June 2023 Historical
Difference Cumulative
May + June


May + June
O’Leary 2 121.2 84.8 36.4 157 187.7
Summerside 1 94.4 91.7 2.7 127.4 190
Charlottetown 1 128.4 98.8 29.6 128.4 189.8
Souris 2 116 100.9 15.1 185.2 194

1:  Environment Canada Station   2:  PEI Department of Agriculture Station


June rainfall was 143% of normal in O’Leary and 130% of normal in Charlottetown in June.  Rainfall amounts in Summerside and Souris were closer to historical averages.  Additional rainfall in June did not make up for the lack of precipitation in May in most of the province (except Souris).  However, significant rains over the Canada Day long weekend have made for damp conditions in most of the province.

Growing Degree Days (GDD) for June:

Temperature data was gathered from the same weather stations as rainfall. The following formula was used to calculate the growing degree days (GDD – Base 5C) as shown below:

Table 2: Growing Degree Days for the month of June (current year 2023 vs historical records 1981-2010)

  Growing Degree Days (GDD)
Location June 2023 Historical 1981-2010 Difference Cumulative
May + June
May + June
O’Leary 2 282 284 -2 438 408
Summerside 1 262 285 -23 395 428
Charlottetown 1 277 286 -9 392 424
Souris 2 281 273 +8 388 410

1:  Environment Canada Station   2:  PEI Department of Agriculture Station


GDDs were very close to the historical average across the province.  The most different reading was in Summerside, with an 8% reduction in GDD.  Generally, GDD accumulation is slightly ahead of normal in West Prince, while slightly below normal in the rest of the province.

So with the rain so far in July, we’ve likely caught up to the normal amount of rainfall to this point in the growing season…unfortunately in a short period of time.


My take home messages as we finish this week:


  • As we deal with spore trapping services just getting up and running, I would recommend growers to be conservative and get up to date on protective fungicides as soon as they can, especially as potatoes are in rapid growth phase. Band spraying is of course recommended for early-emergence fields.
  • Seed growers: Pound the oils and aphicides as soon as the plants are out of the ground.
  • The earlier the better for getting grass herbicides applied. Be aware of harvest interval restrictions on some of these herbicides.
  • Keep an eye out for Colorado Potato Beetles and don’t let them get ahead of you. We know that Titan/Actara is starting to have reduced control on CPB, so pay attention and plan accordingly for foliar sprays to control them.


Have a great weekend!