Aug 7, 2015 - Potato Disease Report #9

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

Crops are doing quite well throughout the province. In a few early emerged fields frost injury early in season had set the crop back by a few days. Scattered hail damage has also been reported.

No late blight has been reported in the province yet. Growers are diligently spraying their crops with contact and systemic fungicides.

With continued rainfall the risk for late blight is high these days. The weekly accumulation of DSVs for most of the province suggests moderate late blight risk conditions. However, rains and thunderstorms are forecast for many areas in the province in the coming 2 days. Thunderstorms can carry the spores over long distances. It is important to scout for late blight after thunderstorms. It may be helpful to check local rain forecast and decide if contact fungicide will suffice or consider using translaminar/ systemic products that could provide coverage to new or within canopy foliage.

In our neighbourhood, late blight has been reported in Wisconsin, Ontario and Alberta. There is no report yet from Saskatchewan, ND or MN. Scouting for the disease in wind sheltered areas of the fields is very critical – e.g. areas close to shelter-belts or low lying spots in the fields.

Other diseases like early blight and white mold are showing up in places, but are at low levels.

If soils remain wet and warm, growers will have to consider management of pink rot disease, which is favoured in these warm and wet soils. Phosphorus acid fungicides have shown good activity in reducing the disease. The fungicide can be sprayed on foliage and also as post-harvest treatment on tubers as they are being put into storage.

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