Sep 13, 2019 - MB Potato REPORT #16 - Disease & Insect

Dr. Vikram Bisht

Potato & Horticultural Crops, Manitoba Agriculture

In the website www.mbpotatoes.ca checkout “10-day weather forecast” for temperatures and rainfall - Click on Maps – Weather – then double-click the site you are interested in, and you get the Temperature and rainfall historical data & graphs. 

Rainfall in the week (Tue, Sep 2 to Monday, Sep 8) was extensive in distribution in the province, but not as heavy as last week.  Though only a few sites recorded close to 1” rainfall, most fields don’t need anymore rain.   The max temperatures were generally warm, but the minimum temperatures gone below zero in a few sites!

Table1. Weather Data - Sep 2 (Tuesday) to Sep 8 (Monday), 2019. (MB Ag Weather Network)

Potato harvesting is progressing, but has been slowed or interrupted in some places due to rains. Most RB fields have started senescing naturally.  Early blight disease is more severe now in some fields (Fig 1). Stressed or senescing plants are more prone to early blight and No fungicide is recommended at this late stage.  Early dying – Verticillium affected plants, appears to be less extensive than last year.

The 10-day forecast indicates a break in rainfall for over a week, beginning Saturday (Sep 14).

Due to frequent rain and substantial rain events and based on cumulative DSVs for the week, (up to Sep 5) – for the week the risk for late blight has been medium to high in MB; however, NO late blight disease has been reported from anywhere in Manitoba. 

In the last 10 years, 2nd week of September (in 2015) was the latest first report of late blight disease.

In the Simplot Research project Late Blight spores were NOT trapped in any of the three sites, in RMs of Cornwallis, North Cypress & Dufferin. It is still important to scout diligently in low-lying or wind-protected areas in the fields.

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