Although many have started harvesting potatoes, I thought it be wise to share some tips again to ensure the best quality that we can put into storage this year!  I know that hot, dry conditions really limited yield and size this year, but all in all what I’ve seen out there for a crop has been encouraging.

So far this year I’ve heard Potato Virus Y or PVY (Figure 1) has been rearing its ugly head, especially in Yukon Gold.  I also wouldn’t be surprised to see some internal necrosis from heat stress and probably some hollow heart in areas that might have gotten those sought-after rain showers in July and August!  Here again is a review of best management practices for Irish potato harvesting:

1.)  Be sure vines are dead prior to harvest.  Minimally vines should be dead or killed 2-3 weeks before harvest to ensure the tubers set their skin, making the tubers more resistant to skinning and bruising. Vine killing can be done many different ways including flail mowing, flaming and chemical desiccants.

2.) Irish potatoes should not be harvested if the pulp (internal tissue) temperature of the tubers is less than 40 O F. Pulp temperatures below that can increase bruising and internal issues like black spot. I find using a soil thermometer or even a meat thermometer that goes low enough works well to determine pulp temperatures.  If pulp temperatures are cold, hold off digging until late morning/early afternoon to allow the soil to warm up a bit.

3.)  Maintain fungicide applications as long as there is green tissue left exposed including those stumps of vines from flail mowing. These tissues are still susceptible to diseases such as Late Blight.

4.)  Make sure that tubers are not falling from heights greater than 6 inches (this includes digging and handling). This will also help reduce the potential for bruising and black spot (a result of bruising).

5.)  Do not put harvested potatoes directly into a cold storage. Potatoes should go in a dark area and allowed to cool down gradually in order to heal and cure before going into storage— cuts and bruises heal best under high relative humidity (90%) at 50 – 60°F for 2 – 3 weeks after harvest.  Curing at higher temperatures will only encourage diseases and shrink while lower temperatures slow curing.  Cooling them down rapidly could result in condensation that can increase rot organisms that might already be there. I know this might be contrary to what most of us think, but carrying a little bit of moist soil into the bins or whatever you are harvesting into is not a terrible thing –and I don’t mean tons of soil, but enough that it provides some of the humidity needed to help properly cure your potatoes.

6.)  After this healing/curing period they can be moved into storage and cooled slowly to 40 F maintaining a high relative humidity of about 90 –95%.This should help reduce the shrinking that happens in storage.

7.)  Do not wash potatoes before putting them into storage, but rather wash what you need as you need them. Do not put warm potatoes into wash water that is 10 degrees colder as this will increase bacterial breakdown. For that matter, you should follow this rule for all produce that is washed!

8.)  Don’t dig and plan on storing tubers from wet areas of a field. If possible, keep them separate and plan to market those immediately to reduce the chance of brining disease into the storage.

9.)  Cull hard! Do not put any potatoes that do not look healthy into your storage, and when it doubt, don’t put it in!

 

Image: M. BALDAUF , S. M. Gray, and K. L. Perry . Department of Plant Pathology, Cornell University, 334 Plant Science, Ithaca, NY 14853, USA and USDA-ARS, PPRU, Ithaca, NY 14853, USA.