AgronomyOntario Potato Crop Update

Ontario Potato Crop Update


As heat and drought continue across the province, irrigation has been the order of the day.  Many fields are in the tuber setting stage, a stage that requires adequate soil moisture for an optimum tuber set.  Fields with closed rows and vigorous canopies keep the soil cool, which reduces stress.  Potatoes suffer when soils get hot in direct sun.  Many fields still have open canopies, the result of late planting.  Unfortunately, a nice, steady rain is not in the forecast for this coming week.

Crop problems that were detected this week include:

● Long stolons with shoots at the tips instead of tubers. Varieties with low tolerance to heat, like the old processing variety Snowden, react this way when day temperatures are above 30 C and at night temperatures are above 22 C.

● Fusarium wilt:  Fusarium is a soil-borne fungus that enters potato plants through the roots and restricts water flow to the plant. The disease can be confused with Verticillium wilt, but Fusarium wilt usually spreads through the stem while Verticillium wilt is restricted to the vascular system and does not cause much rotting of the stemFusarium wilt is difficult to manage because it can persist in the soil for many years.  It also causes stem-end browning and internal browning of tubers, which reduces market quality.

   Fusarium wilt of potato plants in Ontario. Photo: Eugenia Banks

● Low incidence of leaf burning caused by high temperature combined with high humidity.

● Fiddlehead stems:  This distortion is due to herbicide drift, 2,4-D or other auxin herbicides.  Such injury may result in tuber malformations.

Good control of early blight is noticeable. As expected, late blight spores were not detected this week.






Fusarium Wilt Photo: Eugenia Banks
2,4-D injury. Photo: Eugenia Banks

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