potato newsletter

Brian N. Craig bncraig at BUD.PEINET.PE.CA
Thu Oct 6 16:41:43 EST 1994

This is a new Newsletter for potato netters to subscribe to:


        October 1994                      Volume 1, No. 2

This is a newsletter to provide information on extension technology that
may be useful to the agriculture sector for potato production.  The
information will provide ideas and information useful to potato production
in the North Eastern parts of North America.  As this is a Canadian potato
newsletter, the information on products will be those registered for use
in Canada.  Foreign products will be mentioned to provide the agriculture
sector with new technology. 

Please feel free to read the articles and comment on the content.  The
Newsletter is designed to help individuals to stay up dated on events and
technology.  Only through comments will the newsletter be able to provide
information that will suit your needs. 

This issue of the Potato Newsletter will focus on Potato Storage 
Buildings, Post Harvest Potato Treatment,  Potato Seed Field Inspection 
Standards, Items Wanted To Purchase, Products and Services For Sale.


Potato storage buildings should be thoroughly inspected to ensure the
potato stores well.  The storage building must be able to protect the
tubers from freezing while held at low temperatures.  The building must be
capable of maintaining high levels of humidity to keep the potato from
loosing moisture. Because the tuber is "living", the storage must be able
to move air and the humidity through the piled tubers. 

Storage buildings should be inspected each year.  What should you check
for?  Here are a few things to check: 

1.  Insulation - Insulation can be damaged over the years.  If they are
not kept under control, rodents can cause major damage to the insulation. 
Therefore check the storage doors, ceilings and walls to ensure all of the
insulation is still intact.  Keep in mind that the walls of the storage
building should have an insulation factor of R-30 while the ceiling should
have an insulation factor of R-40.  This level of insulation will keep
condensation from collecting on your walls and ceilings.  Moisture
collecting on the building and falling down onto tubers creates ideal
conditions for bacterial soft rot to develop. 

2.  Vapour Barrier - Check the vapour barrier covering the insulation. 
With high humidity requirements to store potatoes at, the vapour barrier
protects moisture from entering the insulation.  If moisture enters the
insulation, the insulation ability of the potato storage will be reduced. 
Make sure the vapour barrier is still in good repair to keep moisture from
soaking into the storage insulation. 

3.  Equipment (Fans & Humidifiers) - High quality storage buildings use
fans to circulate air through the stored potato tubers.  Stored tubers
must have frequent air exchanges to remove heat, carbon dioxide, and
excess water vapour.  Fans must be in top working order to ensure even
temperature and water vapour is evenly distributed throughout the piled
potato tubers. 

Humidifiers may be required to ensure the relative humidity remains
between 90-95%.  Each year always consider if the fans and humidifiers are
matched to meet the greatest demand the storage will be faced with.  Will
there be more tubers to store this year than last year?  If the answer is
yes, will the equipment handle the extra harvested tubers this year.  Will
the fan capacity deliver one (1) cubic foot of air per minute per cwt
(hundred weight) of tubers.  This should be your minimum fan capacity in
your storage building. 

Make sure all equipment is in good repair.  Check bearings, belts and
lubricate the equipment before filling the storage. 

When the potato storage building is filled, make sure that the storage is
moving air uniformly throughout the building.  A good potato storage
building must remove excess condensation from the ceilings and walls. 

4.  Duct System - The duct system that the fans and humidifiers are
connected to should be checked.  Check to ensure that none of the ducts
are plugged or broken.  This can be very crucial to ensure air movement is
well distributed through the piled potato tubers.  Once the potatoes are
placed in storage it becomes extremely difficult to repair or clean a duct
system.  Keep in mind that the duct system has to be properly sized to the
fan and humidifier system to ensure proper air flow through the stored
potato tubers. 

5.  Doors - This is one area that causes many producers problems.  Storage
building doors must function the same as the walls of the building.  They
require the same insulation and vapour barriers as the walls have.  When
the doors are closed, they must seal "tightly".  There is more heat lost
in storage buildings because of doors not closing tight and providing a
good quality seal.  Doors are very prone to damage.  Trucks, tractors and
unloader have caused what would be consider small damage but results in
major storage losses such as frozen tubers.  Check and keep doors in top

6.  Control Panel - This is the "brains" of the storage.  If the control
panel is not functioning properly, the whole storage could be quickly
lost.  The control panel is connected to thermocouple which should be
checked carefully to ensure they are in good repair and are working
properly.  Be sure that the thermocouple are placed properly in the
storage building and replace andy malfunctioned ones. 

Before filling the storage make sure the control panel operates the
dampers and damper motors to ensure the inside environment will be
maintained at the levels required to store the harvested tubers. 


Potato harvesting usually brings with it the risk of storage diseases.  To
keep these diseases well under control a potato tuber treatment is
recommended.  MERTECT (thiabendazole) is the standard treatment to
consider for treating tubers going into storage. 

Mertect controls tuber diseases: Dry Rot (Fusarium spp.), Pocket Rot
(Phoma spp.), Silver Scurf (Helminthosporium spp.), Skin Spot (Oospora
spp.) and Black Scurf (Rhizoctonia spp.).  Mertect will provide a higher
quality potato to be marketed as table stock.  Through the use of Mertect
seed potato producers will be able to preserve potato seed vigour, reduce
seed decay and keep the five diseases mentioned above under control. 

The processing potato will benefit from Mertect.  Processing potatoes are
stored at a higher temperature than seed and table stock tubers.  Warm
temperatures are more favourable to disease infection than tubers stored
at cooler temperatures. 

Mertect is sold in Canada as a 45% thiabendazole flowable product.  When
mixed with water, Mertect disperses easily in the water.  The product is
applied directly to the tubers as a mist as the potato moves over the bin
piler.  It is also recommended that tubers for seed and table stock be
retreated at time of grading to help protect the tubers during shipment
and storage at their destination. 

Mertect Application : 
1.  Shake the container of Mertect well. 

2.  Mix 8 litres of Mertect in 170.21 litres of water.  Be sure to add the
    Mertect to the water.  Do NOT add water to Mertect.

3.  Keep the solution agitated in the holding tank at all times.  This
    prevents the Mertect from settling out.

4.  Apply 2 litres of the suspension per metric tonne of potatoes.  Be
    sure the potatoes are rotating over the conveyor line to ensure total
    tuber coverage. 

5.  An ideal nozzle pressure for applying the Mertect mist is 80 to 100
    psi.  This allows a fine mist that will minimize product run-off on
    the potato tuber. 

6.  Always try to mix up a new solution of Mertect each day.  Do not let
    the mixture to stand over night.

7.  Always follow the labelled directions on the Mertect container. 

Mertect Applicator: 
A minimum of equipment is required to apply a Mertect solution.  A small
motor and pump is needed that will provide 80 to 100 psi of pressure.  A
holding tank for the Mertect solution with an agitator system, a pressure
regulator (with shut-off valve) and a return bypass hose, a pressure gauge
and three hollow cone nozzles (8 to 10 inches from the potatoes) that
operate on a swivel to set the spray pattern. 

The applicator system should be installed at a point on the conveyor where
the potatoes are falling or turning over.  One good place for the spray
system is on the bin piler where the potatoes drop onto the boom conveyor
form the dirt eliminator or sizing chain.  The potatoes both tumble and
fall through the mist at this point.  The spray equipment can also be
watched carefully by the bin piler operator. 

Be very careful in locating the Mertect treater where the spray mist will
cover canvas-backed belts.  Canvas belts tend to shrink or separate if
they become wet.  Use belts that are completely rubber coated. 


Pre-Elite:  During the growing season, the fields are inspected 3 times by
Agriculture Canada Potato Inspectors.  With each field inspection, the
potato plants must be visably free from any varietal mixture and free from
visible symptoms of viruses or other diseases that could affect the
quality of the seed.

Elite I:   During the growing season, the fields are inspected 3 times by 
federal agriculture inspectors.  The potato seed fields must be planted 
in tuber units - whole seed or cut seed.  The first 2 inspection have a 
tolerance for viruses - there must not be any more than 0.1% visible 
symptoms of viruses.  During the last inspection no visible viruses must 
be observed.  For varietal mixture, there is a zero tolerance during each 

Elite II:   Durinng the growing season, the fields are inspected 3 times 
by federal agriculture inspectors.  The potato seed must be planted in 
tuber units - whole seed or cut seed.  During the first 2 inspections 
there must be no more than 0.1% visible symptoms of viruses with no 
symptoms visible during the last inspection.  For varietal mixture, there 
is a zero tolerance during each inspection.

Tolerances for field inspections of Elite III, Elite IV, Foundation and 
Certified are as follows:  

Elite III: Inspection 1   .25% Total Viruses; .5% total viruses, wilt, 
				blackleg; .1% Foreign Varieties.
	   Inspection 2   .1% Total Viruses; .25% total viruses, wilt,
				blackleg;  0% Foreign Varieties.
	   Inspection 3   .1% Total Viruses; .25% total viruses, wilt, 
				blackleg;  0% Foreign Varieties.

Elite IV: Inspection 1    .5% Total Viruses; 1.0% total viruses, wilt, 
				blackleg; .1% Foreign Varieties.
	  Inspection 2    .1% Total Viruses; .25% total viruses, wilt, 
				blackleg;  0% Foreign Varieties.

Foundation: Inspection 1  .5% Total Viruses;  1.0% total viruses, wilt, 
				blackleg;  .1% Foreign Varieties.
	    Inspection 2  .2% Total Viruses;  .5% total viruses, wilt, 
				blackleg;  .05% Foreign Varieties.

Certified:  Inspection 1   1.0% any one virus;  2.0% Total Viruses; 3%
				total viruses, wilt, blackleg;  3% Foreign 
	    Inspection 2   .5% any one virus;  1% Total Viruses; 2% total 
				viruses, wilt, blackleg;  .1% Foreign Varieties.




Any one wishing to sell Russet Norkotah this year?  I have Prince 
Edward Island buyers who are looking for major sources of this variety.  
For sales please contact this Newsletter.


I have suppliers of new potato varieties.  All seed is Nuclear stock or
Pre-Elite.  The varieties that are for sale include over 80 potato 

These varieties include:  ATLANTIC, AC NOVACHIP, AC DOMINO, ALLEGANY, 

A hot new variety A7961-1 is also available.  

For further information on any of these varieties please contact this 

Genetic Engineering:  If you have specific genes in bacteria you wish to
introduce into other potato varieties, this newsletter has listings of
companies who have the technology and abilities to commercialize this 
opportunity for you.

Confidentiality will be maintained with any genetic requests made by 
cooperating individuals.


If you have products or services that would be of interest to the potato 
sector, please contact this Newsletter.

Comments or suggestions for future Newsletters are welcomed.

bncraig at bud.peinet.pe.ca

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