Organic Apple Production in Iowa

New and experienced organic apple growers will find recommendations in this guide for managing insect pests, diseases, and weeds.
Midwest

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2010

Organic Apple Production
I N

I O WA

Marketing Opportunities
The best system for organic apple production in
the Midwest uses apple cultivars that are resistant
to apple scab plus integrated approaches—
including mechanical, cultural, and biological control
methods—to manage destructive insects.

Midwest organic apple growers have two likely markets for
their produce—the large natural food grocery chains and/
or local consumers.
Selling to the national chain stores is challenging
because their buyers expect organic apples to be
cosmetically similar to conventionally produced apples.
The high humidity that is typical in the Midwest often
meansgrowers do not need the irrigation systems required
by growers in other parts of the country. However, the
humidity also can encourage problems with disease,
weeds, and insects. When disease-resistant cultivars are
planted and careful management techniques are used, an
organic apple grower can effectively produce marketable,
aesthetically appealing fruit for national grocery chains.

Because commercial production of organic apples is
relatively new in the Midwest, most information for
growers comes from New York and California (see
References).

The second opportunity for Midwest organic apple
growers is to market their produce directly to consumers
who prefer small-scale, locally produced, synthetic
chemical-free and third-party verified, organically-raised
food.

Get the most from your
ORGANIC ORCHARD
MAXIMIZE PROFITS with timely harvests.

Growers can take advantage of this niche market through
on-farm sales, participation at farmers’ markets and sales
to local grocery stores (see “Using Organic Agriculture
and Sustainable Crops and Livestock in the Local Food
System” PM 1995).

PRACTICE GOOD SANITATION by picking up and/or
destroying all fallen or rotten apples.

By carefully developing this market, growers can maintain
an adequate profit margin while personally connecting
with consumers.
An additional strategy for organic growers is to expand
their marketing to include “value-added” products—such
as cider, preserves, pies, and other prepared goods.
On-farm processing requires special equipment and
compliance with health regulations (see References).
Alternatively, a grower can work with other orchard
owners who have processing capabilities.

AVOID PROBLEMS with E. coli and other human diseases by
only using apples picked off trees.
CONSIDER USING chickens and guinea hens to clean orchard
floors of infested apples.
BE EXTREMELY AGGRESSIVE in managing disease and insect
problems to reduce damage and crop loss. To be effective,
the producer must continuously monitor for insect or disease
problems and develop a timely management plan.

Michigan State University’s
Fruit Ecology and Management
Manual discusses the
importance of viewing
the orchard as an
entire eco-system
(see References).

SEEK ADVICE and help from professionals, such as extension
specialists.
VISIT WITH OWNERS of neighboring conventional orchards
and assure them that you will use sound and proven
sustainable practices to manage insects and diseases so as
not to negatively impact their orchards.

2

Managing Insect Pests

grubs (larvae) tunnel into the fruit’s central seed cavity
where feeding commences until development is completed
in about three weeks.

PLUM CURCULIO
The most devastating apple insect pest is the plum
curculio, a small, brown, snout-nosed weevil native to
most apple production areas in the eastern U.S. This beetle
injures fruit in multiple ways:
•
•
•
•

The larvae generate and release pectin enzymes that
trigger the host fruit to drop prematurely. The grubs then
chew through the fallen fruit and enter the soil to pupate.
A combination of several cultural control methods can be
useful in reducing damage.

Scarring caused by surface feeding and egg depositing
Internal damage caused by burrowing larvae
Premature fruit drop
Punctured fruit caused by adults feeding in late summer
and fall

Visual observation of the adults and their egg deposition
marks is the best way to detect beetle activity. It is
important to check the perimeter apple trees at bloom.
“Trap trees” of plum trees can be used for early detection
because the crescent signature appears earlier on plums
than apples. Additionally, USDA Agricultural Research
Service scientists have developed pheromone traps that
attract adult beetles and allow a grower to capture the
insects when they first arrive in the orchard.

Avoiding this pest is difficult because the adult weevil over
winters in woodlots, fencerows, and hedges. If your
orchard is near a maple woodlot, planting one or two rows
of conifers along the woodlot edge will discourage plum
curculios from entering in the fall. Abandoned orchards
and neighboring fruit trees—including crabapple, wild
apples, pears, plums, cherries, peaches, and apricots—also
can harbor plum curculio beetles.

Infested fruit typically drop before the larvae complete
their feeding. Prompt gathering and disposal of the
dropped apples before the larvae exit the apple to enter
the soil can reduce the number of emerging adults. Boiling,
burning, or soaking in oil should destroy the larvae in the
dropped apples. Infestation may be greater in the outside
two or three rows of trees than in the rest of the orchard.
Not all dropped apples are caused by plum curculio. Other
causes are heavy fruit set and poor pollination.

The weevils move into the orchard during bloom to feed
on young flowers. After mating, the female adult beetle
bores a small hole into the skin of the developing fruit,
deposits a single egg, and then makes a crescent cut below
the hole to protect the egg from being crushed by the
rapidly expanding fruit tissue. The female lays an average
of 150 to 200 eggs, which hatch 2 to 12 days later. The

“Tree jarring” limbs with a padded board can knock
adults from a tree to a waiting tarp placed below. This
should be done in the early morning while it is still cool to
prevent beetles from flying away. Captured beetles must
be destroyed immediately. For significant control to be
achieved by this method the trees should be jarred every
morning for four to six weeks beginning at blossoming.

During the cocoon stage or pupal period a mechanical
disking of the top inch of soil where pupation occurs can
be an effective control. Disking should begin about three
weeks after the infested fruit starts to drop. This should be
done on weekly intervals for several weeks. Do not start
too early. If the cocoon is broken before pupation occurs,
the larvae make another cocoon.

Plum curculio adult weevil

Parasitic wasps are likely to be attracted by a diverse
array of ground vegetation with small flowers. Flowers
should blossom after apple trees to avoid attracting bees
that attack plum curculio larvae.
Mixing poultry feed with the soil under the trees can
encourage free-ranging fowl (such as chickens, ducks and
geese) to scratch for larvae and adult weevils. Mobile
chicken coops also could be moved along the edge of the
orchard. Hogs also have been employed to consume fallen
infested apples.
Cresent-shaped markings of the plum curculio

3

CODLING MOTH

a protective powdery
film on the surfaces of
leaves, stems and fruit.
Tiny particles of the clay
become attached to an
insect as they come in
contact with the film,
acting as an irritant. The
film-coated plants and
fruit are unsuitable for insect feeding and egg laying.
The film is white and highly reflective–making the tree
unrecognizable to certain insects as a host.

Coddling moth larva and damage
The codling moth is present throughout North America.
In the warmer parts of the Midwest, there may be two or
three generations per season. Several acceptable cultural
and biological control methods are available.

Surround™ is reported to be an effective deterrent against
plum curculio, codling moth, leafrollers, leafhoppers,
mites, stink bugs, and apple maggot. Other reported
effects include reduction of heat stress, fruit drop and
sunburn, improvement of color, and greater return bloom
in certain cultivars. Iowa State University trials in 2000
produced a 50 percent reduction in codling moth damage
with the use of kaolin particle film (see References). Since
these trials, organic apple growers are relying more on
CMGV and spinosad for more effective codling moth
management.

Mating disruption is considered mandatory in organic
apple orchards. Females release pheromones that signal
their location to males during the mating period. Codling
moth’s mating cycle can be disrupted by releasing mass
quantities of pheromones into the orchard through dispenser
strips tied on trees or through “puffer” systems. Since
treeless spaces and taller trees interrupt pheromone spread,
for best results, trees should be evenly spaced and of equal
heights. Mating can occur in the air above the dispensers
so the ties should be placed as high in the trees as possible.
An aerosol dispenser, nicknamed the “puffer,” uses a timer
to periodically spray specific amounts of pheromone at the
recommended rate per acre into the orchard. When codling
moth populations are high, an organic grower can combine
mating disruption with black light traps. Both male and
female moths are attracted to black light.

Woodpiles, boxes, and bins can be a major source of
re-infestation of codling moth and should be routinely
cleaned and kept away from the orchard.

MITES, APHIDS, SCALE, LEAFHOPPERS
These so-called minor pests primarily feed on apple stems
and foliage. They can be tolerated in much higher numbers
than direct fruit pests until their occurrence is high enough
to seriously weaken the tree, resulting in reduced quality
and quantity of fruit or even tree death.

Bacillus thuringiensis (Bt), a naturally occurring
bacterium, can be used with limited results against codling
moth. Dipel™ is an example of a product formulated with
this bacterium. Other organic insecticides used against
codling moth include a spinosad fungus, Entrust™, and
codling moth granulosis virus (CMGV), commonly sold as
Cyd-X™.
Adult Trichogramma wasps feed on insect eggs, nectar,
pollen, and honeydew. Border plantings of good nectar
and pollen food sources—such as alfalfa, sorghum,
sunflower, corn, clovers, and wildflowers—will increase
wasp parasitism of codling moth eggs.
Codling moth larvae can be intercepted as they descend
the trunk to pupate by wrapping the trunks with corrugated
cardboard. The cardboard provides an artificial pupation
site and should be removed and destroyed about a month
after the first larvae have moved down to pupate.

Kaolin particle film
(Surround™) was introduced in 1999 for use against apple
pests. Surround™ is a liquid spray that dries to leave

4

Beneficial organisms—such as aphid midges (Aphidoletes
aphidimyza), pink spotted lady beetles (Coleomegilla
maculata), green lacewings (Chrysoperla spp.), predatory
mites (Galendromus occidentalis, Galendromus pyri,
Neoseiulus fallacies, Zetzellia mali), and spined soldier bugs
(Podisus maculiventris)—generally keep minor pests below
damage-inducing thresholds. The natural bacteria, Bacillus
thuringiensis (Bt), can be used for any leaf-eating caterpillars
on the trees. If mites or scale insects are present (not
normally a problem in Iowa), horticultural oils (vegetablebased) can be used. Oils should not be used in conjunction
with sulfur or within 30
days of sulfur applications.
A combination of the two
can cause leaf burning.
Organic growers who
rely on frequent sprays of
non-selective botanicals
like pyrethrum may be
inducing minor pest
problems.
Apples can be protected with Fuji bags – paper bags individually
placed around each apple to prevent insect attack.

Tips on Spraying

BORERS
Several species of borers also may be pests in apple tree
cultivation. Trees that are stressed by drought or disease
are much more susceptible to borers. Borer development
takes one to two years to complete.

Growers should follow label rates and application
recommendations for all spray treatments.

Conventional spray equipment with some form of

A primary control method is to remove serviceberry trees
(the preferred hosts of the round head borer) from close
proximity to the orchard. Flatheaded and roundheaded
borers emerge from late April through early May and
start laying eggs beneath the bark scales of the fruit tree.
A favorite egg-laying location is the graft union of a tree.
When the larvae hatch they burrow under the bark to feed
on the cambium tissue. Trees with good vigor are able to
drown invading larvae with sap.

agitation is ideal for use in commercial organic apple
orchards. Full coverage of the material on the foliage,
branches and trunk is important. A fan-type sprayer that
blows the leaves around works well for this purpose.
A spray program for plum curculio and first-generation
codling moth should start at first petal fall and continue
for 6 to 8 weeks or until the infestation is over. Spraying
should be done every 5 to 7 days to achieve a high level of
suppression.

The dogwood borer feeds primarily on burr knot tissue
on clonal rootstocks. These clusters develop on the above
ground portion of some rootstocks. To prevent dogwood
borer attack, plant so that the graft or bud union is within
an inch of the soil. This should inhibit development of burr
knots. Dogwood borer damage is generally less damaging
than that caused by the flatheaded or roundheaded types.

Using white Surround™ film may increase photosynthesis
by keeping the tree cooler longer on hot days. Studies
show that trees sprayed six to eight weeks after petal fall
had increased yields and red color. Fruit trees in hot areas
benefit from marked reduction in sunburn. If spraying is
discontinued after eight weeks, little or no residue will
remain at harvest because of rain and wind. Residue left
on the fruit at harvest might be considered unsightly, but is
not a problem for processing. Although the residue is not
harmful, if a full season spraying program is used to
suppress apple maggot or other late season pests a
scrubber/washer will need to be used to remove any dust
remaining on the fruit at harvest for the fresh market. A
Michigan State University study reported increased return
bloom where Surround™ had been used the previous year
(see References). Combining Surround™ with other
available cultural pest controls is key to an effective
program for producing high quality fruit.

For all species of borers use a wrap or paint to cover the
bottom 12 to 14 inches of the trunk. The wrap material can
be window screen, metal, fiberglass, or nylon secured at
the top with a twist tie that should be loosened once a
year. This will help prevent entry, but is not as effective on
roundhead borers because they attack near ground level.
All types of borer larvae can be removed from the trunk
with a jackknife or piece of wire. Routine checks during
the spring and summer will help identify signs of borer
damage—such as frass mixed with sawdust at the pest
entry hole. By September, the borer may have burrowed
beyond the range of manual removal.

APPLE MAGGOT
Apple maggot can be a
serious pest in certain years
in Iowa. The apple maggot
remains in a pupal stage
underground throughout
Apple maggot adult flies
the winter and, in June or
(larvae attack fruit)
July, flies will emerge from
a few inches below the soil surface. Female flies lay eggs
and once they hatch, tiny larvae begin to tunnel through
the fruit. Apples will rot internally once bacteria develop
from larval tunneling, causing apples to drop from the tree
in severe cases. Adult flies can be trapped by placing one
red sphere covered with a sticky coating per tree. The flies
also are susceptible to pyrethrum and diatomaceous earth
sprays.

Pruning and trellising apple trees helps open air spaces within the
canopy, which aids in disease management.

5

FIRE BLIGHT
This disease is caused by the bacterium Erwinia amylovra.
Warm, wet conditions are conducive to bacteria production.
Wind, rain, bees, aphids, and other insects spread bacteria
throughout the orchard. Large numbers of new infections
can occur within minutes after rain or heavy dew.
Infections gain entry to the tree through blossoms or lush
new growth then spread internally through the stems
working towards the roots. Affected branches appear as
if scorched, wither, and turn a brownish black. Resistant
varieties are rarely invaded beyond young wood (Empire,
Liberty, and Priscilla varieties are moderately resistant).

Apple scab management is best achieved by planting resistant varieties.

Managing Diseases

Once infected, the only treatment is to remove infected limbs
to minimize damage. Cutting damaged branches during
the growing season should be done only high in the tree
when the central tree stem is threatened and the job can be
completed quickly. Make cuts only into two year old or older
wood and at least four to five inches short of the next healthy
branch union.

APPLE SCAB
The most serious apple disease worldwide is apple scab.
The seriousness of infections depends on a combination of
factors: rain, longevity of leaf wetness, and temperature.
Spores germinate and cause infection when leaves have
been wet for 48 hours at temperatures from 32° to 40°F.
However, germination occurs after only nine wet hours
when temperatures are 58° to 76°F.

An unfortunate characteristic of this bacterium is its
ability to be present in healthy tissues far ahead of visible
symptoms. These are not visible because high levels of
reserve carbohydrates in living bark tissues deny bacteria
water and limit development of symptoms. If healthy looking
branches are cut, the natural defense provided by the reserve
carbohydrates is breached and cankers will form around
the site of infection. Bacteria will remain at the canker site
through the off-season and will survive to infect more trees
the following year.

If primary infections are not controlled they can erupt
into secondary infections later in the season. Secondary
infections weaken the tree and blemish and deform
the apples. During wet periods, secondary infections
develop when summer spores germinate in lesions on
leaf and bud tissues and spread throughout the tree. The
warmer the weather, the more quickly summer spores
developfollowing a primary infection.

For prevention, cankers that form around the cut can be
removed during the regular dormant pruning season
during the winter. All blighted twigs, branches, and cankers
should be cut out about five inches below the last point of
visible infection burn. After each cut, the shears should be
dipped in a strong bleach solution (1 part bleach to 4 parts
water) to avoid transmitting the disease from shears to
branch. Because fire blight favors young succulent tissues,
cultural practices that favor moderate growth (such as
low fertilization and limited pruning) are recommended.
Streptomycin is an antibiotic produced by cultured fungi,
and has been the most common commercial control since
the 1950s. Organic growers should check with their certifier
to identify organically acceptable mixes of streptomycin.
Application is made just before rain or heavy dew is
expected during early bloom, when the average temperature
is 60°F or higher. If rainy conditions persist, repeat spraying
within four days. Unnecessary overuse of streptomycin could
induce resistance in the pathogen population. Streptomycin
should never be used when burned branch tips are present.
Copper formulations, such as Bordeaux mix, sprayed at
green tip stage provide some protection from infection. For
best results, copper formulations should be applied to the
entire orchard. Streptomycin sprays should not be used in
combination with copper sprays.

Planting scab-resistant varieties is the best long-term
strategy for the organic grower; examples include
Jonafree, Redfree, Liberty, Freedom, Dayton, William’s
Pride, Gold Rush, Enterprise, Priscilla, Nova Easygro, and
WineCrisp.
On susceptible varieties, timely sprays of sulfur, lime-sulfur,
or Bordeaux mixture (copper sulfate plus lime) are effective
against scab spores if applied before the spores have a
chance to germinate. Trees must be sprayed before, during,
and after every rain from the time of bud break until all the
spores are discharged. These fungicides can be harmful to
foliage or blossoms so label instructions must be followed.
If primary infections are prevented, it may not be necessary
to spray during the rest of the season. Otherwise, spraying
will have to continue through the season.
The scab fungus over-winters on fallen apple leaves. By
raking and destroying (burying, burning, or composting)
the fallen leaves, a grower can control and for the most
part eliminate the primary scab inocula. Animals (hogs
and sheep) also can be used for cleaning the orchard floor
of infected apples. However, for the best results, a grower
should establish an orchard with scab-resistant fruit trees.

6

Conclusion

Powdery mildew
Primarily a foliar disease, powdery mildew can affect the
fruit if the infection is severe. For example, infections that
curl, distort, and discolor leaves reduce photosynthesis
and affect overall tree health. Mildew can be controlled
with sulfur compounds, such as elemental sulfur and limesulfur, or Bordeaux mixture.

The organic apple orchardist can build an economically
and ecologically sustainable business, but potential
pitfalls related to disease and insect management require
attention to infection periods and timely applications of
organic-compliant treatments. Despite the increase in
large-scale organic apple production and the abundance of
organic apples from Washington state and New Zealand,
most organic consumers prefer locally produced fruits
and vegetables, which will help secure markets for Iowa
organic apples.

Cedar apple rust
The responsible fungus moves between Eastern red cedars
(junipers, not true Midwest cedars) and apple trees; it
spends part of its life on an Eastern red cedar. Incidence
can be reduced by eliminating junipers within a given
area; however, spores can travel up to three miles, making
eradication impossible. If spray controls are used, the
grower should time sulfur fungicide sprays to coincide
with the springtime appearance of orange gelatinous
“horns” on the galls on the cedar. This bizarre-looking
fruiting stage releases spores that infect the apple trees.

No endorsement of products or firms is intended, nor is criticism
implied of those not mentioned.
This research project was partially funded by
the Leopold Center for Sustainable Agriculture
at Iowa State University and the USDA-IFAFS
Organic Agriculture Consortium. Thanks are
expressed to James Boes and Maury Wills for
advice and information for this publication.

Summer rots
When summers are warm and humid, black rot, bitter rot,
and white rot can be problematic. Cultural practices that
can help suppress these organisms include pruning out
diseased wood, removing fruit mummies, pruning for
light penetration and air circulation, and avoiding poorly
drained sites when planting new orchards.

For complete reports on all organic ag projects,
visit extension.agron.iastate.edu/organicag
Prepared by Kathleen Delate, extension organic agriculture
specialist and Victoria LeBeaux, graduate student, Iowa State
University Department of Horticulture.

Photo credits

Managing Weeds

p.2 Eco-pie graphic by Steve Deming, Michigan State University

Mulching and mowing are primary methods for weed
management in an organic orchard. Mulches can be
wood chips, bark, paper, plastic, or straw. Research has
demonstrated the durability and protectiveness of bark
and wood chips over other choices. Some orchardists use
a Weed Badger™to cultivate around trees but damage to
roots and trees can occur if care is not used.

p.3 Plum Curculio reproduced with permission from Mid-Atlantic
Orchard Monitoring Guide, NRAES-75, published by NRAES,
the Natural Resource, Agriculture, and Engineering Service,
Cooperative Extension, 152 Riley-Robb Hall, Ithaca, New York
14853-5701, U.S.A. (607) 255-7654.
p.6 Apple Scab photograph by Alan R. Biggs. Reproduced
with permission from Mid-Atlantic Orchard Monitoring Guide,
NRAES-75, published by NRAES, the Natural Resource,
Agriculture, and Engineering Service, Cooperative Extension, 152
Riley-Robb Hall, Ithaca, New York 14853-5701, U.S.A. (607) 2557654.

Periodic mowing along with planting a cover crop of grass
with some legumes (e.g., clovers) for beneficial insect
attraction is recommended over fallow ground.

p.7 Field photograph by J. Reganold, Washington State University
All other photographs by Kathleen Delate

Organic fruit operations may include animals to maintain vegetation
once trees or vines are of an adequate size

7

References
Bessin, R.T., P.S. McManus, G.R. Brown, J.G. Strang
(editors). 1998. Midwest Tree Fruit Pest Management
Handbook. University of Kentucky Extension. Lexington,
KY.
Delate, K., J. T.S. Walker, R. Volz, J. Johnston, A. White, V.
Bus, R. Turnbull, D. Rogers, L. Cole, N. How, S. Guernsey,
and A. McKern. 2008. “Organic apple systems: Constraints
and opportunities for producers in local and global
markets.” HortScience 43(1):6–11.
Delate, K., A. Martin Schwarze and J. DeWitt. 2007. Local
Foods in Sustainable and Organic Agriculture. Extension
PM 1995, Iowa State University, Ames, IA
Domoto, P., M. Gleason, and N. Zriba. 1999. “Growth and
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C. Feldhake. 1999. “Hydrophobic particle films: A new
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Greene, C., C. Dimitri, N. Richman. 2001. “Organic
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know what you’re eating? An analysis of U.S. government
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February 1999. Yonkers, NY.
Landis, J. (editor). 2002. Fruit crop ecology and
management. Michigan State University Extension
Publications, East Lansing, MI.
Phillips, M. 1998. The Apple Grower. Chelsea Green
Publishing Company, White River Junction, VT.
Reganold, J.P., J.D. Glover, P.K. Andrews, and H.R. Hinman.
2001. “Sustainability of three apple production systems.”
Nature 410: 926-929.
Swezey, S.L., P. Vossen, J. Caprile, W. Bentley. 2000.
Organic Apple Production Manual. University of California.
Publication 3403. Santa Cruz, CA.
Thomas, A. 2000. Evaluation of Kaolin-Based Particle Film
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Organic Farming Research Foundation (OFRF). Santa Cruz,
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This institution is an equal opportunity provider. For the full non-discrimination statement or accommodation inquiries, go to
www.extension.iastate.edu/diversity/ext.
Jack M. Payne, director, Cooperative Extension Service, Iowa State University of Science and Technology, Ames, Iowa.
PM 2085

February 2010