Potatoes: Organic Production and Marketing

1. Potatoes: Organic
Production and Marketing
A Publication of ATTRA—National Sustainable Agriculture Information Service • 1-800-346-9140 • www.attra.ncat.org
By Rex Dufour, This publication outlines approaches to organic and sustainable potato production. Practices
Tammy Hinman and include fertility and nutrient management; organic and biorational pest management for insects,
Jeff Schahczenski diseases and weeds; and storage and marketing.
NCAT Agriculture
Specialists Introduction organic potato sales appear to be strong,
© 2009 NCAT This publication outlines many of the it can be difficult to enter wholesale mar-
practices used in organic and sustainable kets due to storage complications and
potato production. While organic potato market control. These factors are
Table of Contents production can yield a premium price discussed in greater detail as well.
Section I: for your product, the production consid- Because each farm is a unique combi-
Organic production erations are significant. This publication nation of soil, climate, environment,
overview ...................................1
discusses organic soil and pest manage- management and marketing techniques,
Fertility and nutrient
management ..........................3 ment strategies that help ensure growth it is important to plan and assess which
Organic matter ...................4 of healthy and vigorous plants. Strategies practices described here are appropriate
Rotations ...............................4 include choosing potato varieties suitable for a particular farm. There are numerous
Section II ..................................9
for the area and intended use; using dis- potato production manuals that are spe-
Weed management .............9 ease-free seed potato sources; appropri- cific to regions within the United States.
Nematode management ...9 ate soil fertility and management; weed, For further information on region-specific
Disease management ...... 10 disease and insect control; harvesting and potato production in general, within
Insect management...........14 methods and crop storage. your region, consult your local Coopera-
Section III ............................. 21 Economic and market evaluation are tive Extension Service or call the ATTRA
Harvesting ............................ 21 equally important topics in organic information line at 1-800-346-9140 for
Storage................................... 23
Economics and marketing
potato production. While direct-marketed county extension office contacts.
of organic potato
Section I
production ........................... 23
Profile of organic potato
grower: Gene Thiel ......... 26
Profile of organic potato
grower: Mike Heath........ 30 Organic production overview analyses and nutrient crediting help pro-
ducers avoid excess fertilizer applications.
References .............................31 Organic farmers adhere to certification
Further resources ............... 33 Sustainable farming methods also include
guidelines that exclude the use of syn-
thetic fertilizers and pesticides. Producers
using these techniques are able to market
their products as organic if they have gone
through a certification process. If you are
interested in becoming certified organic,
ATTRA—National Sustainable ATTRA has many publications that can
Agriculture Information Service
(www.ncat.attra.org) is managed
help you through the transition process.
by the National Center for Appro- The ATTRA publication Guide to ATTRA’s
priate Technology (NCAT) and is
funded under a grant from the
Organic Publications will help you get off
United States Department of to the right start.
Agriculture’s Rural Business-
Cooperative Service. Visit the
NCAT Web site (www.ncat.org/
Organic production practices maximize
sarc_current.php) for the use and recycling of on-farm nutri-
more information on
our sustainable agri-
ent sources, including animal and green Potato plant. Photo by Dianne Earl. Courtesy of the
culture projects. manures. Techniques such as accurate soil National Education Network.

2. soil-building and -conserving practices interested in transitioning to organic
such as adding organic matter and potato production.
minimum-tillage approaches. Biointensive
The National Organic Program certi-
integrated pest management is also a sus-
fication standards require producers
tainable farming method.
to grow potatoes from organically certified
The primary goal of biointensive IPM seed potatoes. The limited availability
is to provide guidelines and options for of organic potato seed stock may limit
the effective management of pests and the selection of specific varieties and
beneficial organisms in an ecological context. larger quantities.
The flexibility and environmental compati-
Related ATTRA bility of a biointensive IPM strategy makes it
Publications
Zuseful in all types of cropping systems. Organic seed potato stock must be sourced
Sustainable Soil See the ATTRA publication Biointensive for certified organic production unless
Management Integrated Pest Management for more infor- organic seed stock is not available in the
same quality, quantity or form as nonorganic
Biointensive mation on this subject.
stock. Examples of the quality, quantity and
Integrated Pest
Management Two important factors that contribute to form clauses are:
developing a sustainable and profitable farm- Quality: The same quality, such as non-
Guide to ATTRA’s ing system are willingness to experiment with certified seed or disease-free seed, of potato
Organic Publications
new or different farming practices and the seed is not available .
Farm-Scale Composting ability to observe how management practices Quantity: The desired variety is not available
Resource List influence the farm ecosystem. Talk with as in commercial quantities.
Overview of Cover growers experienced in using sustainable Form: The same variety that you typically
Crops and Green techniques to find what methods will work in grow is not available.
Manures your region. This publication includes three
Intercropping Principles
profi les of growers throughout the country
and Production who are producing organic potatoes. There If you source nonorganic seed due to any
Practices is also a list of experienced organic grow- reason listed above, you must document that
ers in the Further resources section of you researched at least three different seed
Principles of Sustainable
this publication. These growers agreed to sources to fi nd organic seed and that the
Weed Management
for Croplands
be a resource for new farmers or farmers same quality, quantity or form is not avail-
Flame Weeding for
able from those sources. Also, all non-cer-
Agronomic Crops tified seed must be sourced as untreated if
organic seed is not commercially available
Nematodes: (King, 2006).
Alternative Controls
Colorado Potato Beetle:
Another consideration when buying seed
Organic Options is ensuring that the seed is certified as
disease free (Charlton, 2008). If certi-
Farmscaping to fied disease-free seed is not available in
Enhance Biological
the organic form, seed can be purchased
Control
from a nonorganic source as allowed in
Notes on Compost Tea the quality stipulation of the National
Organic Program (NOP, 2006).
An excerpt from the National Organic
Program regulations states:
§ 205.204 Seeds and planting stock
Organic potato stock is required by the National practice standard
Organic Program unless you demonstrate the same
variety, quantity or quality is not available from an
(a) The producer must use organically
organic seed supplier. Photo by Neva Hassanein, grown seeds, annual seedlings and plant-
courtesy of Community Food and Agriculture Coalition. ing stock, except that,
Page 2 ATTRA Potatoes: Organic Production and Marketing

3. (1) Nonorganically produced, untreated has been granted in accordance with
seeds and planting stock may be used to § 205.290(a)(2);
produce an organic crop when an equivalent
(4) Nonorganically produced planting stock
organically produced variety is not commer-
to be used to produce a perennial crop may
cially available, except that organically pro-
be sold, labeled or represented as organi-
duced seed must be used for the production
cally produced only after the planting stock
of edible sprouts;
has been maintained under a system of
(2) Nonorganically produced seeds and organic management for a period of no less
planting stock that have been treated with than one year; and
a substance included on the National List
(5) Seeds, annual seedlings and planting
of synthetic substances allowed for use in
stock treated with prohibited substances
organic crop production may be used to
may be used to produce an organic crop
produce an organic crop when an equiva-
when the application of the materials is a
lent organically produced or untreated vari-
requirement of federal or state phytosani-
ety is not commercially available;
tary regulations (2006).
(3) Nonorganically produced annual
seedlings may be used to produce an Fertility and nutrient
organic crop when a temporary variance
management
Potatoes have high nitrogen and potas-
sium requirements. These can be met
Certified seed and certified organic by using manures, compost and crop
seed stock: What’s the difference? rotations, which are detailed in the later
The Western Organic Potato Pest Manage- sections. You can assess soil nutrient
ment Strategic Plan offers clarification to levels with a soil test. If nutrient levels
some confusion about certified disease-free are deficient, apply organic amendments.
seed. This excerpt from the plan explains the
difference between certified disease-free Most organic potato growers should
seed and certified organic seed stock: consider producing their crop with 120
pounds of nitrogen, 25 pounds of phosphate
Certified disease-free seed stock: and about 140 pounds of potash per acre
“It is important that organic potato growers (Sideman and Johnson, 2006).
plant high-quality, early generation, certi-
fied seed to manage diseases. Certification
of seed does not guarantee that the seed
Seed sources for organic potato production
potatoes are disease free, but that the dis-
ease levels fall within certain tolerable levels. This is only a partial list. Your local organic certification organization
Certification means that the seed potatoes may know of local seed sources.
have met the standards of a grower-sup- Wood Prairie Farm (207) 872-8317 FAX Notes: Organic potatoes,
49 Kinney Road www.fedcoseeds.com garlic and onions
ported state certification agency. Seed pur-
Bridgewater, ME 04734 Order: Mail, fax
chased from different states and countries Catalog: Online, print Healthway Farms
are subject to different certification rules. As 1-800-829-9765
request through Web site PO Box 49
1-800-300-6494 FAX or send $2.
such, each certification agency has its own Malin, OR 97632
orders@woodprairie.com Quantity: Retail and
set of tolerances, or allowable amounts, for wholesale (541) 723-4725
www.woodprairie.com
each disease.” scott@healthwayfarms.com
Order: Online, e-mail,
fax, phone Ronnigers Potato Farm www.healthwayfarms.
Certified organic seed stock: Catalog: Online, print 2101 2135 Rd, com/index.html
“Certified organic seed is not necessarily certified Quantity: Retail and Austin CO 81410 Order: E-mail, phone
at the same specifications required for certified wholesale (877) 204-8704 Catalog: Online, print
Notes: Organic seed Quantities: Smaller
disease-free seed that meets stringent disease and potatoes
info@ronnigers.com quantities of certified
virus-free specifications and other physiological www.ronnigers.com potato and organic
requirements. Certified organic potato seed is FEDCO Seeds/Moose Order: Online, e-mail, fingerling seeds up to
fax, phone 10 pounds.
grown in accordance with the National Organic Tubers Catalog: Online, print
Program regulations (Miller et al., 2008).” PO Box 520 Quantities: Up to 50
Waterville, ME 04903 pounds available
www.attra.ncat.org ATTRA Page 3

4. Note that nutrient requirements vary by ble to other soil amendments, but no cur-
potato variety and yield goals. Lowering the rent studies support this claim. Com-
soil pH will help prevent common potato post that is available on the farm should
scab problems, but not powdery scab. A soil be considered as a soil amendment.
pH of 5.0 to 5.2 is recommended for pre- The ATTR A publication Farm-Scale
venting scab, but this pH level may affect Composting Resource List has more
other crops in the rotation, as well as nutri- information about this topic.
ent availability (Charlton, 2008).
Sulfur is an organically acceptable way Rotations
to lower soil pH. Contact your local Coop- The most important step in organic potato
erative Extension Service office to deter- production is planning a crop rotation
mine the correct quantities to apply based scheme that allows a few years between
on your current pH, soil type and region. potato crops on the same land. For
Before purchasing any sulfur amend- organic production, a lengthy rotation
ment, contact your certification agent from four to seven years generally assures
to obtain a list of organically accept- good plant and soil health. A lengthy
able sulfur amendments. Some amend- rotation also reduces long-term reliance
N
utrient
requirements
ments have inert ingredients that are not on expensive inputs and increases the
acceptable by NOP standards. percentage of marketable potatoes.
vary by
potato variety and The ATTRA publication Sustainable Longer rotations can be thought of as a
yield goals.
Soil Management provides information form of crop insurance because the rota-
about nutrient management and ref- tions help prevent plant pathogens in the
erences that are useful to the organic
soil from building up to economically dam-
grower. Please contact ATTRA at 1-800-
aging levels. Growers must consider rota-
346-9140 if you would like a copy of this
tion plans with crops that are not hosts for
publication or search the ATTRA Web
potato pathogens or insects. The key con-
site at www.attra.ncat.org.
sideration for the long-term viability of
organic production is preventing problems
Organic matter through maintaining good soil quality.
You can organically manage nutrient
requirements with animal manures and Rotat ions that include cover crops
composted materials. Annual application have the advantage of adding organic
of these materials can provide a well-bal- matter and nitrogen to the soil. This
anced, stable form of nutrients and help generally will reduce input costs over
build organic matter in the soil. time. Organic matter helps soils resist
compact ion, a l lows for better root
In a multiyear study of sustainable penetration, stores more soil moisture
potato cropping systems, researchers and allows more water penetration. Cover
from the University of Maine demon- crops and green manures may include
strated yield increases with the applica- legumes, sudan grass and mustards.
tion of 10 tons of compost per acre. The Mustards also have been shown to play
researchers also studied the economic a positive role in soil pest management
considerations of applying compost and (McGuire, 2003).
determined that buying compost would
require a price premium on potatoes to Useful characteristics for a cover crop
make the compost purchase cost-effective or green manure in a potato rotation
(Porter, 2002). include:
This study predates recent increases • The abi l it y to tolerate frost
in conventional fertilizer prices. The and grow well under cool fall
cost of compost may now be compara- conditions;
Page 4 ATTRA Potatoes: Organic Production and Marketing

5. • The ability to quickly produce
substantial amounts of biomass as a
weed suppressant;
• The ability to fix nitrogen and
suppress soilborne potato pests;
• A compatibility with the manage-
ment requirements of other crops
in the rotation;
• The availability of seed and a
lack of planting restrictions, such
as the restriction of rapeseed
production in canola districts; and
• The ability to avoid producing
and shedding seed, which leads to
problems with volunteer plants.
A good rotation includes crops that are
not hosts to common potato pests. A good
rotation also includes green manures
that add nutrients and organic matter to
the soil (Hutsinger, 1995). Mustards used in a rotation can be a disease and
nematode management strategy. Photo by
The ATTRA publications Overview of Cover Peggy Greb, courtesy USDA/ARS.
Crops and Green Manures and Intercrop-
ping Principles and Production Practices second year, Porter uses an adapted
provide more detailed information about potato planter to scrape the clover from
these subjects. Small grains, corn and sor- the ridge and plants potatoes from 2 to
ghum sudangrass may benefit a potato crop 3 inches deep. One week later, he kills
that follows. In Maine, some growers have the clover with a f lail chopper to pre-
used Japanese millet as a cover crop in the vent competition with the potatoes. Only
year prior to potatoes in an effort to reduce
one hilling is required, occurring six
Rhizoctonia. The skin of potatoes with
the Rhizoctonia fungus appears to weeks from planting time. A second cover
be covered in dirt that won’t wash off crop could be seeded at this time,
(Grubinger, 2005). In parts of the West, although harvesting operations are not
producers rotate potatoes with mustard refined to assure survival of a cover
cover crops to prevent root knot nematode (Porter, 2006).
and Verticilium outbreaks. More informa-
Porter estimates that he saves from
tion about using mustard as a disease and
nematode suppressant is provided in the $50 to $60 per acre in energy costs as
Nematode management section below. a result of reduced tillage. His research
also assesses the nutrient savings that
Dr. Gregory Porter at the University of result from the nitrogen-fixing legume.
Maine developed a two-year reduced- He mentioned that wheat could be
tillage rotation for potatoes and barley.
substituted for barley. For more information
The rotation uses red clover as a cover
crop. Porter builds planting ridges in the on Porter’s research, see the final report of
spring of the fi rst year of the rotation and their Sustainable Agriculture Research and
then seeds the entire field to barley and Extension Project Report, Soil Amendment
red clover. He harvests barley in the fall and Crop Rotation Effects on Productivity
and allows the red clover to continue as a and Soil Properties within Potato Production
winter cover. In the spring of the Systems under Further resources.
www.attra.ncat.org ATTRA Page 5

6. Table 1: Potato rotation chart
Location Rotation sequence Comments Contact/reference
Pacific 7-year crop rotation: Year 1-3: Alfalfa; This rotation works well under Mike Heath
Northwest Year 4: Row crop*; Year 5: Grain; organic production practices. (208) 539-4107
Year 6: Row crop*; Year 7: Grain Buell, ID
* Dry beans, squash, potatoes and field
corn are row crop options depending
on market
Michigan 2-year rotation: Year 1: Potato and Research in MI has shown that poul- Annual report (2005) of the
then rye planted as winter cover; try compost added to the soil under Southwest Michigan Research
Year 2: Snap bean. these two-year conventional rota- and Extension Center.
3-year rotation: Year 1: Potato and tions in combination with use of www.maes.msu.edu/
then rye/vetch planted as winter cover crops can increase soil quality swmrec/publicationsfolder/
cover; Year 2: Corn; Year 3: Wheat and at least maintain yields com- Annualreports/05annualrpt/
and then clover pared to no cover crops. The three- snappenvfriendveg.pdf
year rotation had a marketable yield
nearly the same as the two-year
rotation for comparing single har-
vest years, but less than half of the
scab of the two-year rotations.
Maine 4-year rotation: Year 1: Potatoes; This rotation is used for organic Jim Gerritson
Year 2: Spring wheat or oats, under- seed potatoes. Wood Prairie Farm
sown with clover or timothy grass; www.woodprairie.com
Year 3: clover sod, plowed down,
year 4); Year 4: Buckwheat, plow
down and then plant rapeseed as
biofumigant
Maine 3-year rotations, various crops : This research on various three-year Robert P. Larkin and
Year 1: Soybean/sweet corn/green rotations that all included potato C. Wayne Honeycutt
bean/canola; Year 2: Canola/soy- found that continuous potatoes U.S. Department of Agricul-
bean/sweet corn/ barley and then decreased soil microbial activity. ture – Agricultural Research
clover; Year 3: Potato Overall microbial activity were high- Service, New England Plant,
est following barley, canola and Soil and Water Laboratory
sweet corn. Potato crops following Orono, ME 04469
canola, barley or sweet corn provided (207) 581-3367
the lowest levels of Rhizoctonia dis- bob.larkin@ars.usda.gov
ease and best tuber quality, whereas (207) 581-3363
potato crops following clover or soy- wayne.honeycutt@ars.usda.gov
bean resulted in disease problems in
some years.
3-year rotations: These rotations are used on a 200- Igl Farms
Wisconsin Year 1: Potato; Year 2: White oats acre organic farm. Antigo, WI
underseeded with clover; Year 3: *Peas are determinant grain pea, not a (715) 627-7888
Field peas*; forage pea, and can be used directly as iglfarms@verizon.net
or animal feed without processing.
Year 1: Potato;
Year 2: Oats underseeded with
clover; Year 3: Alfalfa
Canada 2-year rotation:
Year 1: Potato and then rye planted
as winter cover; Year 2: Spring cereal
with legume underseeding, legume
incorporated before potato
Page 6 ATTRA Potatoes: Organic Production and Marketing

7. It is important to note that legumes such simply because there are so many fac-
as peas, beans and crimson clover are tors that influence the choice of rotations,
hosts to some races of Rhizoctonia (Cer- including economics of the crops in the
esini, 1998) and can encourage scab in rotation, available land, weather and
certain regions. Red clover may be a host climate, farmer skills and knowledge,
of Rhizoctonia as well. pest management and soil quality goals.
As often happens in agriculture, there Since many of these factors are moving
is no clear-cut answer to the question of targets, implementing a good crop rotation
what rotation a farmer should use. It is a is as much an art as a science because so
matter of evaluating the costs and ben- much depends on the knowledge, skill and
efits of a particular practice or combina- creativity of the farmer.
tion of practices. In this case, producers
must weigh the risk of these crops host- When making rotation decisions, it is
ing and possibly increasing Rhizoctonia helpful to have additional information
against the soil fertility advantages and from local experts — be they farmers,
other benefits of planting a legume. extension agents or researchers — who
Table 1 (page 6) provides some exam- know about the pest pressures and soil
ples of potato rotations used around the and climate considerations for your
country. It is not meant to be exhaustive, particular region.
www.attra.ncat.org ATTRA Page 7

9. Section II
Weed management
Organic potato producers control weeds
largely by cultivation. Good field preparation,
timely pest control and proper seed spac-
ing provide a satisfactory stand that can also
reduce weed competition. In areas with lots of
weed pressure, farmers should choose specific
potato varieties that put on a canopy quickly.
Hilling, either with an implement or by hand,
is a good way to control weeds and is a neces-
sary component of potato production. In larger
operations, an implement called the dammer- Root knot nematodes are common in Western organic
potato systems and are the leading cause of soil fumi-
diker hills and cultivates at the same time. gation in commercial potato production in the North-
Complete all hilling by the time the plants are west. Photo by Jack Kelly Clark. Courtesy University of
Contents 10 inches high (Sideman and Johnson, 2006). California-Davis Statewide IPM Program.
Section II: Your chances of stolon pruning are high after
Weed management .............9 the plant reaches 8 inches. Stolon pruning is a et al., 2005). For more details on these
Nematode management ...9 condition that causes the underground stems techniques, refer to the ATTRA publi-
Disease management ..... 10
Early blight ....................... 10
to die-back, reducing yields and increasing cations Principles of Sustainable Weed
Late blight .........................11 disease incidence. (Charlton, 2008). Management for Croplands and Flame
Rhizoctonia ........................12
Cover cropping is also a good way to Weeding for Agronomic Crops.
Insect management...........14
Colorado potato beetle14 reduce weed populations in your soil and
Potato leafhopper ..........18 add soil organic matter. Results from the Nematode management
Neem ...................................18 Maine Potato Ecosystem Project demon- Nematodes are microscopic roundworms
strate that cover cropping with red clo- found in many habitats. Nematodes are
ver and adding soil amendments such as the most abundant multicellular organ-
compost and manure reduced weeds and isms on Earth. Most are beneficial
enabled the potato crop to better compete members of their ecosystems, but a few
with weeds (Porter, 2002). Fast-growing are economic parasites of plants. The
cover crops such as buckwheat and sor- Columbia, stubby and northern root
ghum sudan grass add organic matter and knot nematodes are common in Western
compete with weeds. For smaller farmers, organic potato systems and are the lead-
mulching with clean straw is an option that ing cause of soil fumigation in commercial
builds soil organic matter and helps with potato production in the Northwest.
weed populations.
Root knot nematode feeding reduces the
Flame weeding is another technique used vigor of plants and causes blemishes on
by some growers. Flaming is also used in tubers (Westerdahl, 2007). Infection of
management of the Colorado potato beetle. tubers by the Columbia and stubby root
Stale seed bedding draws down the weed knot nematode often results in the for-
seed bank. Irrigate or wait until after a rain mation of galls that appear as knobs or
to let weed seeds germinate, and then flame swellings on the tuber surface and affect
weed or cultivate. Crop rotation is another marketability. Root knot nematode lar-
measure that helps keep weed problems vae invade roots or tubers, establish
from becoming severe (Gallant, 1998). feeding sites and develop into the adult
Producers can also significantly reduce stage. Adult females are swollen, seden-
weed populations by using a drip irriga- tary and lay eggs in a gelatinous matrix
tion system combined with bed planting on or just below the root surface. These
instead of sprinkler irrigation (Mirabelli eggs hatch and larvae invade other roots
www.attra.ncat.org ATTRA Page 9

10. and tubers. Feeding by root knot nema- these varieties, see the ATTRA publication
tode eliminates the possibility of expor- Nematodes: Alternative Controls.
tation since infected potatoes are banned
in many countries. Disease management
There are recent promising develop- Organic management of viral, bacterial and
ments with biofumigation using bras- fungal diseases begins with using certified
sica mustard cover crops in a rotation seed, employing proper sanitation prac-
before potatoes. Brassica crops such as tices, controlling other plant and insect
rapeseed and mustard contain active vectors and using crop rotations. The two
chemicals called glucosinolates. The integrated pest management (IPM) guides
breakdown of these chemicals has been listed in the Pest management portion of
shown to suppress some soilborne dis- the Further resources section cover these
eases, nematodes and weed seeds. The topics. What follows is a brief summary of
best strategy for the ultimate suppres- the diseases that are the most troublesome
sion of soilborne diseases and nema- to organic potato growers and some preven-
todes is selecting a species of mustard tative and control measures.
that produces large amounts of biomass
and glucosinolates. Also, before incor-
porating, chop the green manure with
Early blight (Alternaria solani)
a rotary mower or a high-speed f lail Early blight is basically a disease of
chopper. The breakdown of the biofu- older plants or plants that experienced
migant seems to be better in moist soils, stress, such as infection by some other
so irrigate following incorporation or plant pathogen or deficiencies of nitrogen
time incorporation to occur with a rain or water. Excessive irrigation can also
(McGuire, 2003). cause susceptibility. The lower leaves
of the plant are generally infected fi rst.
Jack Brown, a plant breeder specializing Early blight may appear early in the
in brassicas at the University of Idaho, season, but the rate of infection accel-
has released two biofumigant varieties:
erates rapidly after f lowering. Tomato
Humus rapeseed and IdaGold mustard.
and other solanaceous plants are hosts
Each variety contains elevated levels of
to early blight. The disease has also
glucosinolates. For more information on
been reported on other plants such as
some brassicas. There are several races
of this pathogen. Some races are highly
pathogenic while others are saprophytic
and live in the soil on dead organic mat-
ter. The pathogen can survive on crop
debris, as a saprophyte in the soil, in
infected tubers and on other hosts.
The most severe damage generally
occurs on early maturing potato variet-
ies. However, some varieties within each
maturity group have greater resistance
to foliar infection by early blight. Infec-
tion begins as small dark brown spots on
lower leaves. As the infection spreads,
the spots are restricted by the leaf veins
and take on an irregular, angular look.
Severe early blight symptoms. Photo by Cynthia M. Ocamb, courtesy Oregon State Close inspection of the infection will
University. reveal a series of dark, concentric lines
Page 10 ATTRA Potatoes: Organic Production and Marketing

11. within the infected area. These lesions Table 2: Susceptibility to early and late blight.
will enlarge and may coalesce as the
disease progresses. Tubers may also Highest Lowest
susceptibility susceptibility
become infected and will have irregular-
shaped, sunken lesions with somewhat *Note: Certified seed for some of these varieties may not be available.
darker borders. The infection is shallow Early- and mid- Late-season Very late
and causes a brown discoloration of the season cultivars cultivars cultivars
tuber flesh. These lesions can increase in Norland Russet Butte
size during storage and reduce the mar- Redsen Burbank Nooksack
ketability of the crop. Lesions are most
troublesome on white, red-skinned and BelRus Kennebic Ontario
chipping varieties. Norchip Katahdin
Norgold Rosa
Growers should select a marketable
cultivar with the greatest resistance to Russet
early blight. Table 2 lists the suscepti- Early Gem
bility of several cultivars. The cultivar Superior
should also fit in with other aspects of Monona
an IPM program. Water management for
LaChipper
early blight prevention walks a thin line.
Too much water will leach soil nitrogen. Atlantic
Nitrogen and phosphorus deficiencies Table adapted from: (Stevenson, 1993).
can create susceptibility to early blight, Lowest
but too much nitrogen can reduce crop susceptibility
yields and delay maturity. to early and
late blight
Growers should closely monitor soil
ferti lity, especially nitrogen levels.
This can be done with petiole analysis. compost extract prepared in a 1:5 ratio
Insufficient soil moisture will stress the of compost to water (volume: volume)
plant and cause early senescence. This provided a level of early blight control
is a condition conducive to early blight similar to that of copper fungicide treat-
development. Overhead irrigation cre- ments (Lahkim, 1999). It should be noted
ates ideal situations for infection and the that compost teas can be highly variable
spread of foliar pathogens such as early and inconsistent. Commercial compost teas
and late blight. Pay close attention to the may provide more consistency. For more
frequency, duration and timing of irri- information on making compost tea on your
gation during possible infection peri- farm, see the ATTRA publication Notes on
ods, since too much water can lead to Compost Tea.
early and late blight. Overhead irriga-
tion should be timed so plants dry prior Late blight
to dew formation in the late evening and
early morning. Also, the plants should (Phytophthora infestans)
also be allowed to dry early in the morn- Late blight is the most serious fungal
ing, prior to the start of irrigation. disease of potatoes worldwide, according to
the authors of Integrated Pest Management
A 1994 study concluded that compost
for Potatoes in the Western United States
teas can be as effective as copper fun-
(Strand, 2006).
gicide treatments to reduce disease
symptoms. The study examined the use New, more virulent strains of late blight
of compost teas for controlling early cause serious losses in potato varieties
blight. Results of this study indicate previously considered resistant to the fun-
that spraying the plants with 14-day-old gal disease. Late blight is usually of little
www.attra.ncat.org ATTRA Page 11

12. blight. Recent studies from the OSPUD
farmer participatory research project at
Oregon State University show promising
late blight management using compost
teas and Oxidate, a hydrogen dioxide and
peroxyacetic acid product from BioSafe
Systems, a manufacturer of biodegrad-
able disease-control products.
Some commercially available U.S. potato
varieties that demonstrate resistance to
late blight are the New York 121, a mid- to
late-season variety; two Hungarian Sarpo
varieties: the Sarpo Mira, a medium- to
late-tablestock and the Sarpo Axona,
a processor potato; and Remarka, an
a l l-pu r pose potato ( Per r y, 20 02 ).
Defender is a new late blight-resistant
Late blight in potato tuber. potato cultivar that was released in Idaho,
Photos by Neil C. Gudmestad, Oregon and Washington by the Tri-State
courtesy North Dakota State Potato Variety Development Program in
University.
2004. Useful levels of fi eld resistance
to both late blight and early blight were
observed in Defender in the absence of
fungicide sprays and reduced fungicide
input programs (Stevenson et. al., 2007).
Rhizoctonia (Black scurf, Stem
canker, Rhizoctonia solani)
Rhizoctonia is a pathogen present in all
potato-growing areas. Most damage occurs
concern in the western United States,
during the early part of the growing sea-
except in the coastal valley regions where
son, particularly when infected tubers are
late blight occurs regularly. Its occur- planted. Cold, wet soils can increase prob-
rence in other regions of the United States lems with this disease.
is dependent on both the presence of
the pathogen and cool, damp weather. The fungus survives in the soil either as
Blight forecasting still occurs quite mycelia associated with decomposing plant
regularly to help alert growers when residues or as sclerotia, the dirt that won’t
conditions are conducive to the disease. wash off unharvested tubers. Soilborne
For more information on blight fore- infections, known as the chronic phase
casting, contact your local Cooperative of the disease, generally will not infect
Extension System office. sprouts. Instead, soilborne infections cause
a decrease in tuber quality and yield by
Sanitation is the best defense against pruning tubers and causing reddish-brown
late blight. Eliminate all cull piles and lesions that may develop into cankers.
control volunteer potato sprouting the
following spring in areas where there was Tubers may also be malformed, cracked,
an incidence of late blight. pitted or display stem-end necrosis.
Young plants that develop from infected
Copper products are currently allowed by seed pieces are most severely affected.
NOP standards and are the most effective Sprouts may be completely girdled by
means of controlling and preventing late lesions and killed. Partially girdled stems
Page 12 ATTRA Potatoes: Organic Production and Marketing

13. will slow growth and development and may
result in stunting and rosetting of plant tops;
purple pigmentation of leaves; upward leaf
roll; and chlorosis, which is usually most
severe at the top of the plant.
Potato growers can manage Rhizoctonia with
monitoring. It is useful to keep good records
of the existence and severity of black scurf
problems in each field. This way, fields with
economically damaging levels of black scurf
can be managed through appropriate rota-
tions and other methods.
Cultural controls
Avoid growing sugar beets prior to pota-
toes because sugar beets tend to increase Rhizoctonia (Black Scurf) in tubers of potato. Photo by Neil C. Gudmestad, courtesy
Rhizoctonia problems. Avoid a rotation North Dakota State University.
with buckwheat before potatoes because
Rhizoctonia colonizes mature buckwheat surface of tubers under cool, moist condi-
stems (Leach and Specht, 1987). Crop tions, usually after the vine starts to die.
rotation to nonhost crops such as cere-
als for at least two years can reduce Biological management options
disease incidence. A three- to fi ve-year
Research in greenhouses and in the
rotation away from potatoes is recom-
field shows that dusting seed pieces with
mended if disease incidence is severe
fungal antagonists of Rhizoctonia can
(BASF Canada, 2005).
significantly reduce stem canker and
It should be noted that recent protein- and black scurf (Beagle-Ristaino and Papavi-
DNA-based studies of Rhizoctonia found zas, 1985). This reduces Rhizoctonia
considerable genetic diversity in Rhizocto- infection and decreases the viability of
nia and its hosts (Ceresini, 1998). Grow- sclerotia on the potato. The commercially
ers should be careful when selecting rota-
tion crops. Generally speaking, cereals are
a safe bet. Crops closely related to potatoes, Cultural management options
such as tomatoes, eggplants and peppers, for Rhizoctonia:
along with volunteer potatoes, may host Rhi- • Plant potatoes when soil
zoctonia and should not be used in a potato temperature is above 60
rotation. Likewise, related weeds such as degrees Fahrenheit.
black nightshade and Jimsonweed should • Avoid irrigation before the
be kept out of the field. expected harvest.
Planting certified seed significantly • Plant seed pieces no more
reduces poor stands and sprout death than 2 inches deep. The
associated with Rhizoctonia. For a defi ni- temperature of the soil is
tion of certified seed, see the box on page warmer at this depth.
three. However, using certified seed will • Harvest potatoes as soon as
not eliminate Rhizoctonia problems since skin set occurs after vine kill to
the fungus survives in the soil either as avoid development of sclerotia
mycelia associated with decomposing plant on mature tubers in the soil
(Rowe et al., 1995).
residues or as sclerotia on unharvested
tubers. The sclerotia may form on the
www.attra.ncat.org ATTRA Page 13

14. available fungal antagonists featured Insect management
in the study include Trichoderma viride
and Trichoderma virens. There is a list Colorado potato beetle
of commercial products formulated with (CPB, Leptinotarsa decemlineata)
fungal antagonists of Rhizoctonia, as
well as contact information for manufac- Many insect pests are associated with potato
turers of the microbial pesticides, in the production. Because the Colorado potato
Fur ther resources section of this beetle (CPB), Leptinotarsa decemlineata, is a
major insect problem in potatoes, we focus
publication. The ATTRA publication
on acceptable approaches to control this pest
Biointensive Integrated Pest Management
in organic production. The ATTRA publica-
has more information on using fungal
tion Colorado Potato Beetle: Organic Control
antagonists.
Options provides more detail about managing
Many scient i f ic invest igat ions have this pest. ATTRA also has information about
examined various aspects of biologi- control techniques for other pests, such as
cal control of Rhizoctonia (Jager and the blister beetles and aphids.
Velvis, 1986; Lewis and Papavizas, 1987;
Howell, 1987). More recent research
shows that some readi ly ava i lable
commercial biocontrol products reduce
the development of stem lesions in
the field, with control comparable to
that of a standard chemical treatment.
However, no treatments, including chemi-
cal control, substantially reduced black
scurf on potato tubers. Some treatments
resulted in higher total yield, as well as
Immature Colorado potato beetle. Photo by Tom Murray.
higher yield of larger potatoes. Although
no treatments effectively controlled black
scurf, all biocontrol treatments controlled
stem canker and some resulted in greater
overall yield and larger potatoes (Larkin
and Talbot, 2002).
Recent studies in Washington show that
mustard green manures may offer farm-
ers an equally effective but less expen-
sive alternative to fumigants for control Adult Colorado potato beetle. Photo by Tom Murray
of soilborne pests (McGuire, 2003). The
fi ndings from this study suggest poten-
tial for mustard green manures to replace
the fumigant metam sodium for potato
production in some cropping systems.
The practice can also improve water
infi ltration rates and provide substantial
savings for farmers. While Rhizoctonia is
not mentioned in the above study, another
Colorado potato beetle eggs are bright orange and
recent study found that mustard biofumi- typically located on the undersides of leaves.
gants reduced incidence of Rhizoctonia in Photo by Whitney Cranshaw, courtesy Colorado
a greenhouse setting. State University.
Page 14 ATTRA Potatoes: Organic Production and Marketing

15. The CPB is native to the United States. Its A combination of several strategies can help
original range was restricted to the east- keep CPB populations under control. Crop
ern part of the Rocky Mountains. In the rotation, preferably with field corn, wheat
Rockies, the beetle fed on buffalo burr, or some other crop that can tolerate a pH
a plant of no economic importance. Once of 6.0, can delay CPB population buildup.
the potato was introduced to this region, Ideally, rotated fields should be isolated
the beetle moved to the crop and spread from the previous year’s potato planting.
eastward from potato patch to potato patch
and reached the East Coast by 1874. The Cultural techniques to manage
beetle is now found throughout North Amer- the CPB
ica, except in parts of Florida, Nevada, The effect of crop rotation on populations
California and eastern Canada. By 1935 of CPB and on the incidence of early blight
the CPB was established in France and is caused by Alternaria solani is quantified in
now widespread in Eurasia. a 1994 study (Weisz). The study noted that
The CPB is the most economically threat- infestations of both pests are inversely related
ening pest of potatoes in the northeastern to the distance between rotated fields and the
United States. If left uncontrolled, this pest nearest location where potatoes were planted
T
he
can completely defoliate a potato crop by late in the previous season. In other words, the
Colorado
July (Hollingsworth et al., 1986). Although farther you plant this season’s potatoes from
last season’s potato field, the fewer pest prob- Potato Beetle
the potato is its favorite food, the beetle may
also survive on tomato, eggplant, tobacco, lems will occur. is also the most
pepper, ground cherry, thorn apple, Jimson- economically
Research at Cornell University demon-
weed, henbane, horse nettle, belladonna, strated the efficacy of flame technology in threatening pest
petunia, cabbage, thistle, mullein and other controlling overwintering CPBs. The most of potatoes in the
plants (Metcalf and Flint, 1962). The CPB effective time for flaming is between plant northeastern
is resistant to most registered pesticides, emergence and when the plant reaches 8 United States.
making the beetle one of the most difficult inches in height. Taller plants are less heat
insect pests to control in cultivated crops tolerant and their canopy shields many
(Hollingsworth et al., 1986). of the pests. The best control is achieved
on warm, sunny days when beetles
The life cycle of the beetle varies accord-
are actively feeding on top of the plants. In
ing to where it is found. In northern Maine,
trials, flaming provided 90 percent control
the CPB completes one generation per year. of overwintering adult CPBs, contrasted
Farther south, the CPB completes three with from 25 to 50 percent with chemi-
generations per year. The adult beetle over- cal insecticides. Flaming also reduced egg
winters in the potato field, from 12 to 18 hatch by 30 percent (Moyer, 1992).
inches below the soil surface and in pro-
tected sites around the field. The beetles The CPB ca n be excluded f rom
emerge in late spring, move to the field and crops with the use of floating row covers.
mate once established on a plant. Females Floating row covers are thin fabrics spun
lay egg masses on lower leaf surfaces in from a synthetic material. The product
batches of approximately 25 eggs. A single allows air and moisture to pass through
female may lay up to 500 eggs. Because the while preventing pest species access to
eggs are laid in clumps, the larvae tend to the plants. The floating row covers should
be found in clumps rather than randomly be put on either shortly after planting
throughout the field (Hollingsworth et al., or emergence.
1986). You can fi nd good life cycle infor- Straw mulch of wheat or rye in potato
mation for the CPB in the book Destructive fields may reduce the CPB’s ability to
and Useful Insects, by Metcalf and Flint, locate potato fields and alter the microen-
1962. The book is available from most vironment in favor of CPB predators (Brust,
agricultural libraries. 1994). In the fi rst half of the season, soil
www.attra.ncat.org ATTRA Page 15

16. predators — mostly ground beetles — climb field borders or by planting insectary strips
potato plants to feed on second- and third- in the field can increase the effectiveness
stage instar larvae of the CPB. In the sec- of these biological controls. ATTRA has
ond half of the season, lady bird beetles more information on this technique in
and green lacewings are the predominant the publication Farmscaping to Enhance
predators and feed on eggs and fi rst and Biological Control.
second instars. The increased number of Several plants, such as tansy and catnip,
predators in mulched potato plots com- are reported to repel the CPB. Two jour-
pared to non-mulched plots resulted in sig- nal abstracts from The IPM Practitioner
nificantly less defoliation from the CPB and discuss interplanting trials conducted at
one-third higher tuber yields. Rodale Institute Research Center in coop-
eration with USDA researchers (Olkowski,
Varietal resistance to the CPB et al., 1992). The experiments show tansy
Some potato varieties, such as Russet and catnip were from 58 to 100 percent
Burbanks, seem to be more tolerant to effective in repelling the CPB from pota-
S
ome potato
varieties, the CPB, but no varieties are completely toes. However, a European study shows that
resistant. The April 1989 issue of National companion planting did not significantly
such as Russet reduce plant defoliation by the CPB. In the
Gardening highlighted research on planting
Burbanks, seem to be
early maturing varieties that develop potato European study, companion plants were
more tolerant to the tubers before CPB populations explode. smaller than the potatoes in the begin-
CPB, but no varieties It listed seven varieties that mature from 75 ning of the season. The study’s authors
are completely to 88 days. The varieties are the Caribe, speculated that more mature companion
Norland, Pungo, Redsen, Sunrise, Superior plants might be more effective (Moreau et
resistant.
and Yukon Gold. The issue also illustrated al., 2006). In 1992, The IPM Practitio-
the growth stages of the potatoes and how ner published a special report specifically
the stages coincide with CPB emergence addressing potato IPM for the CPB. The
and larval development (Ruttle, 1989). This issue can be ordered as a photocopy from
the publisher. See the Further resources
practice of using early maturing varieties
section for ordering information.
may prove beneficial to growers in northern
regions of the United States, where cooler Parasitic nematodes are another con-
temperatures slow insect development. trol option. Commercial formulations of
Heterorhabditis species are available and
Biological controls of the CPB have been shown to be more pathogenic
(Berry, et al., 1997) to the CPB than Stein-
There are several natural enemies of the
ernema species, which is also commercially
CPB, but these enemies are rarely seen available. The Ohio State University Web
in commercial potato fields because of site portal for beneficial nematodes, avail-
heavy pesticide use. Even under organic able at www.oardc.ohio-state.edu/nematodes,
growing conditions, when natural enemies provides helpful information on how to use
are abundant, the beetle can still cause and where to obtain beneficial nematodes.
defol iat ion. The genera l predators,
such as lady bird beetles, lacewings and Biorational controls for the CPB
stink bugs, provide some control of the
CPB, as do several parasites. Dorypho- Commercially available M-One is a prod-
rophaga doryphorae and D. coberrans, two uct manufactured by the Mycogen Corpora-
species of fly that invade the larvae; and tion of California. See contact information in
Edovum puttleri, a wasp that parasitizes the Further resources section for order-
ing information. This biopesticide is made
CPB eggs; were recently introduced and
from Bacillus thuringiensis (Bt) var. ‘San
are commercially available.
Diego’, a naturally occurring bacterium,
Increasing habitat for natural enemies by and is effective for controlling CPB with-
providing pollen and nectar sources along out disrupting beneficial organisms. It is,
Page 16 ATTRA Potatoes: Organic Production and Marketing

17. however, a genetically engineered product materials will work best in situations with
and is not acceptable in organic certification moderate to high relative humidity.
programs.
Entrust is a new formulation of Spinosad
Some research indicates that sprays of manufactured by Dow AgroSciences. It is
Bacillus thuringiensis species tenebrionis registered for use on organically managed
(Bt) will cause significant mortality of CPB farms to control the CPB and is popular with
larvae upon emergence from their eggs. organic farmers. The contact information to
This is because the beetles gnaw out of find a distributor near you is listed at the end
the eggs and continue eating the shells of this publication in the Further resources
afterward, therefore also ingesting Bt section.
particles (Ghidiu et al., 1994). Several neem-derived products are
Mycotrol-O, a formulation of the parasitic registered for use against the CPB.
fungus Beauveria bassiana, is available from Soft-skinned larvae of CPB are reportedly
Laverlam International, based in Butte, killed on contact. In a two-year study of vari-
Mont. This product is an effective control of ous organic techniques for controlling CPB
the CPB by itself or when used in combina- in the United Kingdom, a 2-percent formula-
tion with Bacillus thuringiensis var. tenebri- tion of Neemix increased yield and lowered
onis (Jones, 1999). Some formulations use beetle densities and the occurrence of defo-
different strains of B. bassiana. Each strain liation significantly.
has the greatest efficacy against a slightly The ATTRA Biorationals: Ecological Pest
different group of insects, so be sure to read Management Database, available at www.attra.
the label or ask a sales representative about ncat.org/attra-pub/biorationals/biorationals_
which formulations are most effective against main_srch.php, lists several organically accept-
the CPB. Since these are all formulations able biorational pest management materials for
with a fungus as the active ingredient, the the CPB. Several of these materials are listed
Table 3:
Reduced Risk Pest Management Manufacturer Active ingredient OMRI listed*
Agroneem Agro Logistic Systems Azadirachtin Yes
AgroneemPlus Agro Logistic Systems Azadirachtin Yes
Ecozin AMVAC Chemical Corp. Azadirachtin
Ornazin AMVAC Chemical Corp. Azadirachtin
Biorin Biotech International Beauveria bassiana
Azatin XL Plus Certis USA, LLC Azadirachtin
Neemix 4.5 Certis USA, LLC Azadirachtin Yes
Diatect V Diatect International Diatomaceous Earth (Sili-
con Dioxide)
Conserve sc turf and ornamental Dow AgroSciences LLC Spinosad
Entrust Dow AgroSciences LLC Spinosad Yes
Spintor 2sc Dow AgroSciences LLC Spinosad
Success Dow AgroSciences LLC Spinosad
Fortune Aza Fortune Biotech Limited Azadirachtin
Pyola Gardens Alive!, Inc. Pyrethrins
Anti-pesto-o Holy Terra Products, Ltd. Azadirachtin
* OMRI is the Organic Materials Review Institute. If a product is OMRI approved, it is allowed for use in certified organic sys-
tems. Contact your certifier before using any organic pesticide to ensure it is approved by the National Organic Program.
www.attra.ncat.org ATTRA Page 17

18. above in Table 3. The database also provides selective. Anagrus species of trichogrammatid
information about using cultural controls to wasps might be available at a local insectary
prevent pest problems. and are effective against leafhopper eggs in
inundative releases.
Potato leafhopper
Even if this particular species is not avail-
(Empoasca fabae)
able, you might consider an inundative
The potato leafhopper, Empoasca fabae, does release of a generalist Trichogramma egg
not overwinter in the northern United States parasite, as Trichogramma species tend
and must migrate annually. The potato leaf- to parasitize whatever eggs are available.
hopper is one of several closely related leaf- Make sure you check with the insectary
hoppers in this genus. The potato leafhop- about parasite host ranges. Other benefi-
per feeds on more than 200 cultivated and cial insects are green lacewing, lady beetle,
wild plants including beans, potatoes, egg- minute pirate bug, assassin bug, syrphid fly,
plant, rhubarb, celery, dahlia, alfalfa, soy- hover fly, robber fly, spiders, damsel bugs
beans, clovers and sweet clover. A high
and big-eyed bugs.
migration rate and wide host range make
control of the potato leafhopper difficult. The Department of Pesticide Regulation,
part of the California Environmental
Both nymphs and adults feed on the under-
Protection Agency, publishes a booklet
sides of potato leaves. By extracting the sap,
called Suppliers of Beneficial Organisms
potato leafhoppers cause stunting and leaf
in North America. The most recent
curl. Potato leafhoppers also bring on hop-
version, from 1997, lists 143 commer-
perburn, a disease caused by the injection
of a toxic substance. Hopperburn is charac- cial suppliers of more than 130 beneficial
terized by a yellowing of the tissue at the tip organisms used for biological control. It is
and around the margin of the leaf. The yel- available for free download at www.cdpr.
lowing increases until the leaf dies. Symptoms ca.gov/docs/ipminov/bscover.htm.
are sometimes confused with drought stress
(Bennett et al., 2007).
Neem
Neem works best when ingested by pests
The ATTRA publication Farmscaping to and is effective for controlling leaf-eating
Enhance Biological Control describes how to pests. Although neem is not effective for
design your farm to favor predatory organ- controlling sucking insects such as leafhop-
isms. These techniques can be integrated in pers, it appears that it still could be part
a biointensive IPM program and can help of a biocontrol strategy targeted against the
make your cropping system friendlier to insect. Neem shows considerable anti-feed-
beneficial organisms. ant and growth-regulating effects on leaf-
Biological control hopper nymphs (National Research Coun-
cil, 1992). Neem is primarily an insect
Leafhoppers have several growth regulator and should be applied
parasites and predators. early in the crop cycle. It is essential to get
The mirid bug, Cyrtorhinus good leaf coverage and to see that the neem
species and specifically product adheres to the leaf surface. If not,
Cyrtorhinus lividipennis, the nymphs, which feed on the undersides
is an effective predator. of the leaves, will not contact the active
Some members of the ingredient. The nymphs should be targeted
wasp family are parasites because leafhoppers are most vulnerable in
of leafhopper eggs. Some this stage.
species of Trichogramma
Potato leafhoppers cause hopperburn, a disease are generalist egg para- The IPM Practitioner notes that gar-
with symptoms that are sometimes confused
with drought. Photo by Art Hower, courtesy
sites and have a wide host lic sprays can signif icant ly reduce
Pennsylvania State University Department of range. Other species of leaf hopper populations, although the
Entomology. Trichogramma are more resulting numbers are still unacceptably
Page 18 ATTRA Potatoes: Organic Production and Marketing

19. high. Garlic may increase the efficacy of these interspecies crosses, including King
other leafhopper pest management strat- Harry, protect themselves from pests by
egies. Insecticidal soap penetrates the arming their leaves and stems with hairs
insect’s cuticle, disrupts the cell mem- fi lled with sticky fluids. These trichomes
branes and causes death by dehydration. explode when touched, miring small insects
This method is likely to work best against such as leafhoppers and flea beetles in
nymphs (Olkowski et al., 1992). Efficacy is goo. The trichomes also ruin the appetites of
variable with this method as well. hungry Colorado potato beetles, reducing or
eliminating the need to use other pest control
Alternatively, a water spray directed at the measures (Pleasant, 2007). King Harry
plant, especially under the leaves, will seed potatoes are available in limited quan-
wash off the insects. This treatment is not tities from Wood Prairie Farm in northern
recommended in humid weather because of Maine. See the Potato seed stock box on
possible disease problems. Take care not page 3 for more information.
to use excessive force. Spray early in the
morning, especially in hot weather (Bradley
and Ellis, 1992). Other physical controls
include the use of floating row covers dur- OSPUD
ing the first month to keep leafhoppers out. A new kind of research and
Pyrethrin, rotenone and sabadilla are rec- information sharing
ommended only as a last resort. Rotenone is Eleven organic farmers in Oregon and Washington are working
not approved by the NOP standards and has closely with Oregon State University faculty members to improve
heavy restrictions from the Environmental potato quality and profitability through a participatory learning
Protection Agency. process and on-farm, farmer-directed research.
A new variety of potato called King Harry, This project encourages an exchange of existing knowledge of
integrated management techniques and promotes farmer inno-
and the earlier Prince Harry, are the result
vation. OSPUD’s goal is to learn more about the wide variety of
of three decades of work by Cornell Uni- management issues, including soils, nutrients, insects, diseases,
versity potato breeder Bob Plaisted. The weeds, tuber quality and profitability, facing small organic potato
potatoes have shown resistance to small farmers in the Northwest.
insects such as leafhoppers and flea beetles. This project has generated a number of useful publications for
Starting in the late 1970s, Plaisted began organic potato production. For more information and access to
crossing Katahdin and other mainstream these publications, visit http://ospud.org.
varieties with Solanum berthaultii, a wild
potato from Bolivia. The most successful of
www.attra.ncat.org ATTRA Page 19

21. Section III
Harvesting from Market Farm Implement Company at
www.marketfarm.com/index.cfm. The Spedo
Timely vine killing is essential for good tuber
Potato Planter is a cup-type potato planter
separation from stolons, tuber skin set, and
that automatically plants cut or graded seed
efficient harvest. But many farmers do not
potatoes and other similar-size tubers. It is
prematurely kill vines (Vales, 2004). Harvest-
imported from Italy. The Spedo Potato Planter
ing procedures for organic potatoes require
plants the tubers from 6 to 13 inches apart in
alternatives to chemical desiccants. Mechan-
the row and hills the row at the same time. It
ical destruction is one method and flaming
is available as a one- and two-row model. Row
technology is an alternative. Flame weeding is
spacings are adjustable from 26 inches plus.
used successfully to top-kill the potato vines.
Woody Gerritsen of Wood Prairie Farm does US Small Farm, formerly Afiveplus, from
two passes with a propane flame weeder to Torrington, Wyo., is also a source for
top-kill the potato vines before harvest. Many small- to medium-scale potato planting and
growers also use a flail chopper that, if the harvesting equipment. In 1998 Afiveplus
Contents equipment is present on your farm, can reduce began manufacturing and selling small-scale
Section III:
Harvesting ............................ 21
propane costs associated with flaming. potato equipment. Owners Larry and DeeDee
Anderson, along with their son Eric, make
Profile of organic potato
Immediately after harvest, healthy potatoes
grower: Ivy Donovan ..... 22 potato planters specifically suited for the small
should be cured by holding them for 10 to
Storage................................... 23
farm. After the first year of digging their own
Economics and marketing 14 days at 50 to 60 degrees and high rela-
of organic potato potatoes, the family developed a small dig-
tive humidity with good air movement to per-
production ........................... 23
ger to add to the product line. Smaller prod-
Evaluating economics mit suberization and wound periderm for-
and markets ..................... 23 ucts developed over the years include a small
mation, or the healing of cuts and bruises.
Organic potato table-model seed cutter and hilling discs.
industry ........................... 24 Although wound periderm formation is most Contact information is listed in the Further
Emerging organic market
structure ........................... 25
rapid at about 70 degrees, lower temperatures resources section of this publication.
Market segments .......... 25 are recommended to reduce decay. Curing
Marketing difference ... 25 reduces subsequent weight loss and decay by
Price premiums and preventing the entry of Fusarium, soft rot and
cost of production ......... 26
Profile of organic potato other decay organisms. The relative humidity
grower: Gene Thiel ........ 26 should be about 95 percent (Vales, 2004).
Two comparative studies
of organic and
conventional potato
Seed cutters, planters, harvesters, washers
production costs ........... 28 and storage rooms make large-scale potato
Estimating costs and
profitability for organic
production a significant financial commitment
potato production ....... 29 for any larger-scale grower. The Igls family,
The emerging processed
organic potato
who farms 43 acres of potatoes in Antigo,
industry ............................ 29 Wis., customized and adapted almost all of
Profile of organic potato
grower: Mike Heath ...... 30
their equipment to refine their organic oper-
References .............................31 ation (Padgham, 2002). Most medium-scale
Further resources ............... 33 mechanized organic producers have one or
two pieces of used equipment; potato dig-
The Spedo brand has a potato digger that is a two-
gers are most common. Auctions and dealers row, three-point hitch-mounted digger for tractors
located in traditional small-scale potato pro- (above left). This model straddles two rows of hilled
duction areas, such as south of Montreal, are potatoes. The potatoes must be grown in a hill for the
digger to work properly. Also, the Zaga Potato Digger
good sources for equipment. Increased mech- (above right) is a one-row, three-point hitch-mounted
anization allows farmers to grow on more power-take-off (PTO) powered digger. It is designed
acres. That often, but not always, reduces the for use on tractors that straddle one row of potatoes
centered under the tractor since the digger cannot be
unit cost of production (Caldwell, 1999). offset. It will only dig hilled potatoes because the shoe
cannot be adjusted to go below ground level.
Some mechanical options for planting and Photos courtesy of Market Farm Implement,
harvesting on a medium scale are available www.marketfarm.com
www.attra.ncat.org ATTRA Page 21