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Best practices at planting

Another important issue related to seed for the 2012 season is fungicide resistance that’s been detected for Fusarium sambucinum, the main Fusarium species causing dry rot. Banks says that because F. sambucinum has developed some resistance to fludioxonil (Maxim) and to thiophanate-methyl (Senator) – fungicides commonly used as seed treatments to control dry rot – losses due to the fungus causing poor potato plant emergence are increasing. To minimize dry rot losses, Banks says it is critical to purchase seed that has as little dry rot as possible, so inspect seed carefully upon receipt. (See sidebar on testing availability below.) She also advises warming seed tubers to at least 10 degrees Celsius (50 degrees Farenheit) before handling and cutting to minimize injury and promote rapid growth, as cold tubers are very prone to bruising.

In addition, Banks cautions growers to thoroughly clean and disinfect their seed storage areas before receiving seed. “Also disinfect seed-cutting and seed-handling equipment often and clean up well between seed lots,” she says “Grade out obviously rotted tubers before they reach the cutter – and make sure the knives on the cutter are very sharp, so that you get smooth cuts that heal easily.”

The next step is to treat seed pieces with an effective seed treatment to help control seed decay. “Then, plant any seed that has a Fusarium problem in warm soil and cover with as little soil as is practical,” Banks concludes. “Coarse-textured soils warm up faster and are better drained than fine-textured soils. This allows the seed pieces to tuberize quickly and helps the plants become established.”

Chris Denys, seed care technical lead (Eastern Canada) for Syngenta Canada, also thinks growers need to put extra effort into making sure their potatoes tuberize properly in 2012. “We have seen some Erwinia Soft Rot recently that could have been prevented,” he says. “It’s caused by a lack of oxygen to cut-and-treated seed potatoes, when there is not enough ventilation and the temperature is too warm.” Denys recommends that if you are storing potatoes after cutting and treating the piles is no higher than 1.8 metres, with good ventilation and a maximum storage temperature of 10 degrees Celsius. “Erwinia can also occur with planting into saturated soil,” he adds, “so if you’re not set up to store properly and have heavier soils, do your cutting and treating just before you have ideal planting conditions, and plant immediately.”
To manage resistance of Fusarium and other fungal diseases, Denys says seed growers should go over their strategy to make sure they are using multiple modes of action to reduce carryover of resistance in seed stocks. “Seed growers must use a secondary mode of action (in addition to Fludioxonil, Maxim Liquid and Cruiser Maxx Potatoes), such as a mancozeb-based product like MaximMZ (dust formulation) or a straight mancozeb product if using a liquid seed treatment, such as Cruiser Maxx Potatoes.” Processor and table growers should use a mancozeb product if their seed stock is confirmed to have Fusarium species that are insensitive to common fungicides.

Vanessa Currie says growers will always have environmental stresses to worry about, but if they are growing a range of high-quality, diverse varieties, then every year they can have a successful crop. “I also suggest they consider growing the new lines being offered by Agriculture and Agri-Food Canada,” says Currie, a breeding technician in the University of Guelph’s Department of Plant Agriculture. “Whether you produce chipstock, tablestock or french fry, there are new varieties available which can enhance competitiveness and profitability.” She would also like to see more growers get involved in research in 2012, and attend more meetings to learn what research has to offer.

“Research is a co-operative and collaborative process and we welcome the involvement of potato growers,” she notes. 

SIDEBAR

Disease and resistance testing options for 2012

Agricultural Certification Services Inc. (ACS) based in Grand-Falls, New Brunswick, is a testing laboratory accredited by the Canadian Food Inspection Agency to perform testing on potatoes for various pathogens, including viruses. ACS provides services to growers and potato industry personnel in New Brunswick, Prince Edward Island, Nova Scotia, Quebec, Ontario, Manitoba, Alberta, the United States and other countries. In Prince Edward Island, the industry-operated Potato Quality Institute in Charlottetown does virus testing for potato growers.

Starting in early 2011, the Prince Edward Island Department of Agriculture and Agriculture and Agri-Food Canada (AAFC), with support from Syngenta, began offering a new free service to P.E.I. and Canadian potato growers to test potato seed lots for Fusarium dry rot. The lab is located in Charlottetown and is operated by AAFC researcher Dr. Rick Peters. If found, the Fusarium species are tested for sensitivity to commonly used fungicides, with results generally available within three weeks. The service will be offered again in 2012 and will help growers ensure they are using a fungicide that is effective against any Fusarium species that may have affected seed lots, says Brian Beaton, potato industry co-ordinator with the department.

In taking samples, growers are advised to collect 10 to 15 tubers. “Any tubers that are showing disease symptoms should be included in the sample especially if they have cuts or cracks,” Beaton says. “Tubers that are completely rotted should not be included. Place the samples in a sealed plastic bag and send them immediately.”

Syngenta Canada’s Chris Denys believes growers must be especially careful in taking samples. “Keep in mind that lab tests can produce ‘false negative’ results due to poor sampling,” he says. “Infected potatoes could be missed, so take your time to get a representative sample. It’s worth the effort.”