Oct 6, 2022 - MB Potato Report #21

Dr. Vikram Bisht
Potato & Horticultural Crops, Manitoba Agriculture

The week Sep 26 – Oct 2 had practically no rainfall, amounting to a max of 0.4 mm.  (Table 1).

So far, the cumulative rainfall at many more sites is now closer to 100% of normal (Cypress River, St. Claude, Treherne, Carman, Morden), while Austin, Bagot and Rivers are around 140% of the 30-year normal (Table 1).  https://www.gov.mb.ca/agriculture/weather/weather-conditions-and-reports.html http://www.gov.mb.ca/agriculture/weather/pubs/percent-normal-precipitation.pdf  

The week’s Crop Water Demand (CWD) at various weather station sites ranged from 20.2 to 27.2 mm (>3/4 to 1 inch) across Manitoba potato areas. But there was no rainfall to cover the CWD (Table 1). http://mbpotatoes.ca/cwd.cfm.  

Daytime temperatures for the week (Sep 26 to Oct 2) were slightly warmer that the previous week. The average of high temps at the selected sites was around 25OC vs 20OC last week. The nighttime temperatures became generally colder and ranged from 0.3 to -2.8OC (Table 1) at various weather station sites.

After minor frosts on Sep 21 and Sep 26/27 another frost is forecast for Oct 6/7 in most potato areas, with temperatures as low as -5OC in different areas.

Accumulated Potato heat units (useful heat 7OC to 30OC) from June 6 –Oct 2 across the potato growing areas of Manitoba range from 875 to 920). This is close to or just above normal so far, 105 to 120% of normal.   https://www.gov.mb.ca/agriculture/weather/pubs/total-acc-p-day.pdf 


Based on water holding capacity, the soil moisture in the top 30cm soil zone is generally in optimal ranges, but there are larger pockets of very dry soils and fewer areas with wet soils in potato growing areas (Fig 1). https://www.gov.mb.ca/agriculture/weather/pubs/soil-moisture-30cm.pdf.  

Late Blight: 

The 7-day cumulative DSVs up to Oct 3 indicated low risk conditions for late blight disease throughout the province if late blight inoculum was present.  Late Blight (mbpotatoes.ca)  http://mbpotatoes.ca/dsv.cfm .  In the absence of late blight in Manitoba or neighbouring production areas – there is low risk of the disease. The late blight forecast was stopped on Oct 3.

Harvest (for storage) is now in full swing with good harvesting conditions. In 2022 the fields in general have lower early dying. There is still plenty of healthy green crop (Fig 2) being harvested.

Estimates of harvested acres to-date range from < 60% to 100% in various farms; the overall average could be around 80-90% for the province as per different estimates. By the end of this week many more farms are expected to finish harvest for the season.

However, there is a forecast for frost on Thursday/Friday Oct 6/7 with projected temperatures as low as -6OC in pockets. After this frost there is another week of good harvest weather in the forecast.

Tuber Diseases at Harvest and in Storage:

Potatoes are coming in dry and clean from most fields. Low spots and wet fields have some tuber rot incidence.  Such areas with higher-than-normal incidence should be targeted for careful monitoring in storages and probably should be placed for early access for processing or shipping.

This report is compiled using information from potato growers and agronomists. Please contribute if you have some information or photos to share.