Jun 17, 2016 - Potato Disease Report #2

Dr. Vikram Bisht
Potato & Horticultural Crops,
Manitoba Agriculture, Foods and Rural Development

The crops in general look very good. The early planted crops appear to be about a week ahead of last year. Many of these fields have crop canopy nearly closed between rows, and have 1/2” to 3/4” tubers. Some of the later planted crops are between hooking and pea-size tuber size stage.

Wide spread and well distributed rains have helped the potato crop in Manitoba grow very well. Today’s rains (including overnight) have been also wide spread, and amounts reported range from ¼” to 1.5”. There are reports of scattered hail in central potato growing areas of the province. There is a forecast for rains on Sunday. The conditions appear to be favourable to late blight disease development. It is important that the crops be protected against late blight with protectant fungicides in fields nearing row closure. This is especially true for crops close to cull piles with volunteer potatoes growing in the cull pile.

Disease Severity Risk Values (DSVs) for late blight are currently low across the province.

An early incidence of late blight disease has been reported from Walla Walla County, Washington state on Jun 1 (USAblight.org), late blight strain US #8 (metalaxyl resistant strain).

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