Here is some additional information to supplement the March 2016 article of Tracy Shinners-Carnelley, “Bacterial soft rot:  new name, new pathogen, new problem? It is sourced from Amy Charkowski’s presentation at the 2016 Ontario Potato Conference held in Guelph on March 1. She is a seed potato researcher with the University of Wisconsin-Madison.
   

Dickeya dianthicola, the new blackleg pathogen has the ability to remain dormant in tubers when temperatures are low e.g. at harvest time and in seed storages. Infected tubers look healthy at planting, but the disease develops when soil temperature increases. Seed tubers may rot in the soil (poor emergence) or infected plants emerge, which eventually die but also can spread the disease to neighbouring plants.
     

The point is that growers should have the seed tested for Dickeya because if the disease is dormant, tubers would look fine at planting but there could be serious losses.
    

Charkowski’s presentation on Dickeya is available at the University of Wisconsin-Madison website. 

How seed is handled can make a difference in emergence as well as marketable yield. That’s the conclusion of New Brunswick’s Potato Industry Transformation Initiative and a recent report by Loretta Mikitzel. She’s a potato physiologist with the New Brunswick Department of Agriculture, Aquaculture and Fisheries who spoke at the Ontario Potato Conference.

After two years of trials, there was a positive difference of 21 cwt per acre when seedlots were warmed before planting, especially in less than ideal conditions. With climate change, that’s a difference worth noting.  There was more rapid and uniform emergence, higher yields and greater value. Some seedlots don’t benefit from warming, Mikitzel warns, so know the condition of your seedlot in late spring. \

In trials conducted in 2014 and 2015, seedlots were received in early March and stored at 4°C. The seed was evaluated for physiological age by sprouting tubers in the dark at 18°C.  

For the stored warm treatment, in early May, half of each seedlot was cut into seed pieces, treated with Maxim and stored at 7-10°C until planting.  For the stored cold treatment, half of each seedlot was stored at 4°C until late May then cut and treated, and stored at 10° until planting.  Planting occurred in processing fields on June 2 (2014) and May 25 (2015).  

Differences in seedlot emergence were visually apparent.  

A seedlot warming demonstration was conducted at the McCain Research Farm, Greenfield, New Brunswick, in 2015. It was evident that the Russet Burbank variety benefited from precutting and warming when stored at 10°C for 26 to 33 days before planting. The Innovator variety was shown to perform best when precut and stored at 10°C for 19-33 days before planting.  

Mikitzel concluded that the highest yields and crop value were achieved with precut seed.  The lowest yields and crop value were recorded when seed was held at 4°C until planting, and warmed for only six days before planting.

“Don’t have the tubers sweat,” she reminded growers when warming tubers. “Warm gradually over a week or so.” 

She confirmed that if warmed seed was planted into cold soil, growers would have a rot problem.