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Potato farmers could easily envy the winemaker. It must be wonderful to make a product that gets better with age.

Spuds are as good at harvest as they’re ever going to be. The same is true of other fresh vegetables of course, but potatoes are often stored for months. Growers can only hope that the crop will maintain its quality until marketed.

A properly functioning storage building can help growers achieve that goal. Now is the time to get storages in shape.

“The most important thing is to have it clean and ready to go,” said Nora Olsen, Extension potato specialist with the University of Idaho.

As a first step, producers should remove all soil and debris from potato handling equipment and all interior storage surfaces that will come into contact with tubers, Olsen says. A good pressure washing with some type of detergent is recommended, followed by a disinfectant. Thorough coverage of all surfaces is needed — including the plenum, duct pipes, storage bay and fan house.

Approved disinfectants include quaternary ammonium, copper quinolinolate, hydrogen peroxide and a variety of hypochlorite formulations. It’s important to keep disinfected surfaces wet for at least 10 minutes in order to kill pathogens, experts say.        Growers also need to make sure that everything is working properly. That means a complete check of all electrical and mechanical systems, including air ducts, louvers, doors, humidification and refrigeration equipment.

These aren’t new recommendations; you’ve heard them before. But there’s been an increased focus on storage management issues in recent years.

The re-emergence of diseases such as bacterial ring rot (BRR) is one reason. BRR can survive up to three years on hard surfaces and up to seven years on wood surfaces, experts say.

Another reason for the increased focus on storage management is USDA’s Good Agricultural Practices (GAP). GAP applies not only to farm fields, but to packing, handling and storage facilities.

Growers must keep storages free of foreign material and animals to pass a GAP audit. No more eating lunch in the cellar or locking the barnyard cat inside to take care of the mice.

“I do think GAP has changed things. I think people are getting their storages cleaned and disinfected more,” Olsen says. “I think too with the increased quality expectations and current disease situations that we are hitting it a little harder than we have in the past.”

What to do about those dirt floors?

Growers can scrape them out and put down a granular cleaner, but that may not always be enough.

Olsen recommends that when they can, growers remove the top inch or two of the dirt floor and replace it with non-potato soil.

“Ideally, it’s a good thing to do every year, especially is you’ve had any bacterial issues,” Olsen said.

“Let’s say that you have a perennial problem with silver scurf in your storage. You should absolutely scrape the top inch off the floors and make sure that everything is cleaned and disinfected,” Olsen said.

Silver scurf can survive on foam insulation and soil floors for at least nine months and in plywood and sheet metal for three months, University of Idaho researchers have found.

An increasing number of new potato cellars are being built with concrete floors and under-floor air distribution systems. Suberizer just completed one in Othello, Wash. and is building eight for J.R. Simplot-Australia in Tasmania.

“It’s easy to sanitize because it’s all concrete,” owner Robert Hesse said of the company’s Air Everywhere system, which can be used to store bulk potatoes or onions in pallet bins.

The middle of harvest is no time to discover that something is wrong with a spud cellar, yet it’s surprising how often problems come up, said Nathan Oberg with Agri-Stor.

“Too often we see that storages are not properly checked out and ready to go for storage,” Oberg said.

Agri-Stor offers a pre-season checkup service that includes everything related to storage climate control. A partial list of items checked include:

  • Inspection and calibration of fresh air doors
  • Lubrication of louver joints, a check of settings and any necessary adjustments
  • Inspection of fan motors and propellers
  • Inspection and cleaning of humidifiers and Climacell
  • Check of the control panel for calibration and proper functioning

“For us the preseason check is critical,” Oberg said. “We want to make sure that from the minute the spuds go into storage the climate control system is ready to work correctly.”

Growers can also hire out the cleaning and disinfection of their storages. Potato Services of Idaho has been in the business since 1994.

“We go in and presoak the walls with (catholyte) soap to help reduce the biofilm on the storage walls,” company co-owner Terry Mortensen said. “We prewash with that and then we pressure wash the walls with soap. We mechanically wash the plenum pipe inside and out.”

There are a number of disinfectants available, but Mortensen prefers to use hydrogen peroxide products mixed with peroxyacetic acid.

“They’re more effective; they don’t gas off as easily,” he said. “They’re safer to use.”

Mortensen’s company certifies the storage as GAP compliant when it’s finished.

There’s nothing to be gained by waiting to prepare a storage for another season, Mortensen said, especially if a problem like silver scurf was present the year before.

“That silver scurf will grow through the summer in the storage and it can be a worse problem come harvest time,” he said.

When should growers get started?

“The sooner the better,” Mortensen said. 

— By Dave WIlkins, Spudman Correspondent

Originally posted Thursday, Jul. 25, 2013

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