Aug 28, 2014 - Potato Disease Report #17

By Vikram Bisht and Xiaowei Guo
Potato & Horticultural Crops, Manitoba Agriculture, Foods and Rural Development


The early planted seed potato fields are starting to be desiccated from the last week.

The commercial potato fields were still being irrigated. Between Aug 20th to 26th there has been 44 mm, 67 mm and 81 mm rainfall recorded in the Winkler, Portage LaPrairie and Carberry areas, respectively. There has been a break in rains for 2-3 days, but rain forecast for end of week.

The recent rain quickly increased the 7-day DSVs; they ranged from 9 to 12 in the southern region, 8 to 12 in the central regions, and 8 to 11 in the western region. However, there is no late blight reported or found so far in MB. Field scouting and a 7-day schedule of fungicide application are still recommended.

Now, it is time to think about harvest and managing potatoes in storage. In some areas fields may be wet, and prone to pink rot issues. The pink rot is favoured by wet soils and warm temperatures. Post-harvest treatment with phosphorus acid products on potatoes going into storage has shown good results in many instances. Pre-harvest inspection of potatoes for pink rot in areas tending to be wet longer, like low lying patches or near centers of pivots could help determine pink rot risk. If risk is high, such patches could be scheduled for harvest so that the potatoes are easily accessed if rot issues develop in storage.

Pre-harvest inspection and sanitation of equipment and storage should be considered for long term storage.

Early blight is easily found in the most fields at the current stage, but it is not a major concern at this late stage of the crops. Other diseases, like blackleg and verticillium wilt are scattered at low levels in a few fields.

Late blight was found in a processing field sown to Russet Burbank in Hanson County, Minnesota. Its genotype has not been identified. No report from North Dakota.

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