Organic Pest Managment

1. Organic
Pest Management
Debbie Roos
North Carolina Cooperative Extension
www.growingsmallfarms.org

2. Outline
Insect
Management
Disease
Management
Weed
Management

3. What the NOP Says
about Pest Management
When cultural, mechanical, and biological strategies are
insufficient to prevent or control crop pests, a biological
or botanical substance or a substance included on the
National List of synthetic substances allowed for use in
organic crop production
(www.ams.usda.gov/nop/NationalList/FinalRule.html)
may be applied to prevent, suppress, or control pests,
weeds, or diseases
The conditions for using the substance must be
documented in the organic system plan

4. Organic farming is all
about building
healthy soil and
using optimal
cultural practices to
prevent insect,
disease, and weed
problems
The emphasis is on
biodiversity and a
systems approach

5. Organic Pest Management
Approach
 pests are indicators of how far a production
system has strayed from the natural
ecosystems it should imitate
 pests are attracted to a plant that is weak or
inferior
 in a well-balanced system, massive pest
outbreaks are rare due to the presence of
natural predators, parasites, and disease
agents

6. Organic Pest Management
Approach
prophylactic, holistic approach vs. remedial approach
not just treating symptoms
pest problem usually indicates sub-optimal growing
conditions and imbalance
emphasis on biodiversity and optimal cultural practices

7. Soil Fertility
Rotations
Field Planting Decisions
Labor
Weed Control,
Irrigation, Trellising
Harvest
& Postharvest
Pest
Management
Peregrine Farm

8. Organic Pest Management: Example
Conventional approach: spray insecticide to control
caterpillars, which often results in a secondary
outbreak of aphids or spider mites because beneficial
insects such as lady beetles and other predators are
also killed
Organic approach: enhance habitat for beneficial
insects to increase population, reduce stress on crop
plant, use adapted varieties, and use non-chemical
methods to control pests (Bt, hand-picking, row
covers, alternating planting dates, traps, etc.)

9. NOP Hierarchical Approach
to Pest Management
Level 1: Systems-based Cultural Practices
Level 2: Mechanical and Physical Practices
Level 3: Materials (Pesticides)

10. Cultural Controls
Physical Controls
Biological Controls
Organic Pesticides

11. Insects

12. Cultural Controls
The goals of cultural practices:
1. reduce initial pest levels
by making the crop environment
unfavorable for pest development
2. produce favorable conditions for natural enemies
3. increase the plant host's ability to withstand pest damage
In organic systems, cultural practices that prevent
pest problems are the first line of defense for farmers

13. Cultural Controls
Resistant cultivars
Crop rotation
Companion planting
Timing of planting
Sanitation
Soil Management
Mulches
Composting
Tillage
Flaming
Vacuuming
Trap crops

14. Resistant Cultivars
Some varieties may be less attractive to
pest species or tolerate more damage
than others
Plant size, shape, coloration, leaf hair,
cuticle thickness, and natural chemicals
(attractants and repellents) can all affect
pest susceptibility

15. Resistant Cultivars
Morphological characteristics
include those plant structures
that interfere with insect
movement, feeding, or
reproduction associated with
that plant
Examples include color,
thickness of the cell walls and
plant tissue, surface wax,
spines and trichomes
waxy cabbage
leaf
edamam
e
bean leaf beetle
stink bug

16. Resistant Cultivars
Physiological defenses include plant-
produced compounds that deter certain
pests – e.g., pyrethrum, is derived from the
blooms of an African chrysanthemum
Some plants have specific color-related
resistance
Most insects are attracted to leaves in the
yellow-green color range. Healthy, dark
green leaves are less attractive than
yellowing plants under stress
pyrethrum pesticide

17. Crop Rotation
Insects overwinter in soil and debris, reinfest new crop if susceptible
and build up populations
3 questions to consider when deciding whether crop rotation will help
manage a pest:
How long can the pest persist in the field without any host
How capable is it of invading from other areas
How well does it survive on other hosts when the crop is
not present
Design your rotation plan to present a non-host to pest insects
Crop rotation is effective for pests such as nematodes, CPBs, corn
rootworm, squash vine borer
Also, design your rotation to include lots of cover crops which will
help build soil food web which helps control pests

18. Sample Farm Rotation
Plan

19. Companion Planting
Attractant crops - small-flowered - carrot family, daisy
family, mint family - catnip, caraway, dill, fennel, hyssop,
lemon balm, parsley, rosemary, thyme, yarrow, etc.
Repellent crops - catnip and tansy repel aphids, Artemesia
repels flea beetles???
Lots of recommendations out there with little scientific
evidence; need more study before recommending; some
companion plants increase pest populations

20. Timing of Planting
Keep notes to record pest and disease outbreak patterns - the first
date you see a problem and the coinciding phenological events
Adjust planting schedule accordingly to avoid peak pressure
Experiment with different planting dates - e.g., to avoid corn
earworm or flea beetle or squash bug
Plant crops susceptible to nematodes early or late while soil
temperatures are cooler

21. Timing of Planting:
Pickleworm Problem
winter squash is
planted before June 1
to reduce pickleworm
damage
pickleworm
larva
adult moth

22. Method of Planting
The method of planting – direct-
seeded vs. transplants – can
also affect a crop’s ability to
resist pests
Direct-seeded crops require the
right conditions to emerge
quickly and grow fast
The use of transplants when
possible can speed crop
development
Plants struggling to survive or
under stress will be more
attractive to insect pests and
more affected by damage

23. Sanitation
The goal is to prevent the introduction of pests from off
the farm, prevent the movement of pests within the farm,
and to remove overwintering or breeding sites for pests
on the farm
Start with healthy plants & inspect plants brought in from
off-farm
Remove and destroy infested plants as soon as possible

24. Sanitation
When working in an infested area clean equipment and
clothes before going to another area of the farm
Remove crop debris and culls promptly to reduce
overwintering sites for pests
Exclude pests with barriers, screens, etc.
Eliminate alternate hosts, but be careful about timing

25. Soil Management
Healthy soils high in OM and with a biologically diverse
food web support plant health and nutrition better than
soils low in OM and species diversity
Healthy plants are generally less susceptible to pest
damage
Approximately 75% of insect pests spend part of their
life cycle in the soil. Healthy soils contain many natural
enemies of insect pests, including insect predators,
pathogenic fungi, and insect-parasitic nematodes

27. Tillage
Disrupts life cycle of pests and
beneficials
Can expose pests to predators,
the elements
Till before planting to control
weeds that harbor armyworms,
cutworms, plant bugs, aphids
Till in the fall to destroy
overwintering sites for flea
beetles, corn borers, squash
bugs, etc.
Balance with need to maintain
groundcover and not burn organic
matter

28. Soil Management
A soil’s physical condition – its level of
compaction, water-holding capacity, and
drainage – all affect soil and plant health
The chemical aspects of soils – pH, salt
content, availability of nutrients, etc. – can
affect crop health and pest susceptibility

29. Strategies for Improving Soil Health
Increase soil organic matter
Keep soils covered with cover
crops and/or crop residue to
reduce erosion and protect
from extremes of moisture and
temperature
Plan tillage operations
carefully

30. Example
of Soil Management
Affecting Pests
crimson clover
cover
crop next to
beds
wilted broccoli
plant
seedcorn
maggots feeding
on root ball

31. Nutrient
Management
Both the type and amount of
fertilizer can have a significant
impact on a crop’s susceptibility to
pests.
Increasing soluble nitrogen levels in
plants can decrease resistance and
increase pest numbers and crop
damage.
Research has shown that organic
systems that rely on more slow-
release nutrient sources tend to be
less susceptible to insect pests.
One example from California found that organically
fertilized broccoli developed lower populations of flea
beetles
and cabbage aphids than conventionally fertilized
broccoli.

32. Mulches
Plastic mulches that speed
early season crop growth
can enhance plant’s ability to
withstand insect feeding
Reflective mulches can
reduce thrips and aphid
populations in crops
Straw mulch can reduce
problems with Colorado
potato beetle

33. Composting
Helps control pests above-
and below-ground
Improves structure, moisture-
holding capacity, nutrient
content, beneficial organisms

34. Flaming
Technique aimed at
overwintering Colorado potato
beetle
Propane burners used to quickly
pass a flame over young potato
plants when beetles are on top
Does little harm to the crop when
the plants are less than 4-5” tall

35. Vacuuming
Sizes range from tractor-
mounted to handheld
Some pests too adept at hiding
for it to be effective
Used successfully for CPBs,
Harlequin bugs, flea beetles
Research has shown that
vacuuming has little negative
effect on beneficial populations

36. Trap Crops
A trap crop is a crop that is planted to lure insect pests away from
the cash crop.
Successful use of trap crops can be challenging. Trap crops are
not effective against pests that are weak fliers (e.g., aphids) or
are wind-dispersed (e.g., spider mites).
In organic systems with fewer insecticidal options, pests in trap
crops are often killed through crop destruction. But the timing of
crop destruction is critical.

37. Trap Crop in Organic Broccoli
in NC
Harlequin bugs
striped flea
beetles
mustard trap crop

38. Farmscaping to Attract Beneficials

39. ambush bug on Monarda punctata

40. Physical Controls

41. Physical Controls
Manual controls
Physical barriers
Baits, traps, and lures

42. Manual Controls
Hand-picking
Mowing
Pruning
Shaking
Water sprays

43. Physical Barriers
Bagging fruit
Copper strips
Crawling pest
barriers
Cutworm collars
Floating row covers
Mulches
Trenches
Trunk bands

44. Baits, Traps, and Lures
Bait traps
Japanese beetle traps
Pheromone traps
Slug and snail traps
Sticky boards
Trap crops
Water traps

45. Biological Controls

46. Biological Controls
Beneficial animals and insects
Beneficial microorganisms - Bt, milky
spore, Beauveria bassiana (fungus),
Nosema (protozoan)

47. Biological Control in Action
Augmentation
increase population through purchase & release
Conservation
increase existing populations through habitat
conservation & other means

48. Beneficial Organisms
Predators: larva or adult hunts, attacks, and
consumes prey; examples include lady
beetles, lacewings, praying mantids, syrphid
flies, assassin bugs, minute pirate bugs,
spiders, and predatory mites
Each one eats many insects in its lifetime
Not picky eaters

49. Predators: Examples

50. Wheel Bug
wheel bug nymph
nymph feeds on
Colorado potato
beetle larva
wheel bug molting

51. Lady Beetles
seven-spotted lady beetle
aphid dinner
pink-spotted lady
beetle
convergent lady
beetle
larva and eggs
larvae
hatching
larva feasting on
aphid

52. Predatory Flies
robber fly
syrphid fly
syrphid fly
larva
long-legged fly
syrphid fly
pupa

53. Other Predators
eggbig-eyed bug
lacewing
larva
tiger beetle
predatory stink
bug
minute pirate
bug
spider

54. Beneficial Organisms
Parasitoids: immatures develop on or inside a
host, killing it as they mature; they emerge as
adults and continue the cycle; examples
include parasitic flies and wasps
Each one eats only one insect in its lifetime
Usually very picky eaters

55. Parasitoids: Examples

56. Braconid Wasp
on Hornworm

57. Trichogramma wasp
on tomato hornworm egg
parasitized egg

58. More Parasitic Wasps
Scelionid wasp parasitizing stink bug egg cluster
Aphidius just emerged from aphid mummy

59. Tachinid Fly
Tachinid fly egg laid
on spined soldier bug!

60. Beneficial Organisms
Pathogens: colonize and kill host; examples
include nematodes, bacteria, viruses, fungi
and protozoa
Weed Feeders: weeds can be attacked by
arthropods, vertebrates, and pathogens
(fungi, viruses, bacteria, and nematodes)

61. Insect Pathogens
fungus on loopers
fungus on fly
nematodes on larva
fungus on soldier
beetle

62. Organic Pesticides:
Rescue Treatments

63. Organic Pesticides
for Insect Management
Botanical pesticides
Microbial pesticides
Inorganic pesticides

64. Botanical Pesticides
Plant-derived materials such as neem, pyrethrum, rotenone,
ryannia, and sabadilla
Characteristics of botanical insecticides:
break down rapidly in the environment
some are more toxic (mammalian) than synthetic pesticides
broad spectrum
must be used carefully
many are not approved for organic production; only neem
and pyrethrum, and they are regulated and to be used only
as a last resort after other strategies have failed

65. Toxicity of Botanical Pesticides
Insecticide LD50
Parathion 18-50
Sevin, Nicotine 246-283
Ryania 1,200
Aspirin 1,200
Rotenone 1,500
Pyrethrin 1,500
Malathion 2,800
Table Salt 3,320
Sabadilla 5,000
Neem, pyrethroids >5,000

66. Botanical Pesticides
Pyrethrum - extracted from a flower in the chrysanthemum family; a
contact poison with quick “knock down”; little residual effect; OMRI-
approved products include Pyganic®
broad-spectrum insecticide that is highly toxic to honey bees and other
beneficials
Insects controlled: aphids, beetles, caterpillars, thrips, true bugs
Neem (azadirachtin) - extracted from the fruit of a tree grown from India to
Africa; acts mainly as an insect growth regulator, repellant, stomach
poison and some fungicidal properties have been reported; it is relatively
non-toxic; OMRI-approved products include AZA-Direct®, Neemix®
Neem products have little to no negative effect on adult beneficials
Insects: CPB, Mexican bean beetle, squash bugs, aphids, and more

67. Neem
Frequent applications are more effective than single sprays
because neem does not persist well on plant surfaces
Use against immature insects
Begin applications before pest levels are high
Works best under warm temperature conditions
Neem’s systemic properties suggest that applying it to transplants
just before planting to the field could be an effective and
inexpensive way to control certain pests

68. Microbial Pesticides
Microbials tend to not be as toxic as botanicals and are
more selective and softer on beneficials
Bacillus thuringiensis (Bt)
parasitic fungi - e.g., Beauveria bassiana
parasitic nematodes – e.g., Heterorhabditis
Spinosad

69. Microbial Pesticides
Limitations of microbials
Slow host death
High dosages required
Need favorable environment
UV light and temperature affect persistance

70. Bacillus thuringiensis (Bt)
Bacillus thuringiensis (Bt) – contains a toxin made by a
soil bacterium; choose appropriate formulation for the pest
Because Bt must be eaten by the insect to be effective, it
is very important to apply the spray to the parts of the plant
where and when the insect is feeding;thorough coverage
is required
Young larvae more susceptible
Sprayed formulations sensitive to UV light; best applied
late in the day
Several OMRI-approved formulations

71. Parasitic Fungi
e.g., Beauveria bassiana
The spores of the fungus germinate
once they come into contact with
the insect pest, then the fungus
must penetrate the cuticle and
infect the body cavity to kill the pest
Effective on many insects including
aphids, thrips, whiteflies, and
grasshoppers
Work best when applied at onset of
infestation; takes a week or more
after application to see evidence of
control
OMRI-approved formulations
include Mycotrol®, Naturalis L®
Fungal spores are
readily killed by solar
radiation and infect
best in cool to moderate
temperatures

72. Parasitic Nematodes
Naturally occur in soil
Semi-aquatic; live and move in soil
water
Sensitive to UV radiation and
desiccation
Heterorhabditis (Hb) for control of
deep-dwelling lethargic pests like
Japanese and June beetles
Steinernema (Sc) nematodes for
control of shallow-dwelling active
pests such as fungus gnat larvae,
shore flies, etc.

73. Parasitic Nematodes
Application - spray or irrigation; drip, fertigation; aerial,
watering can; application should be followed by
irrigation; don’t apply during hottest part of day but soils
should be >60º
Soil physical properties affect efficacy
Works well in labs; poor understanding of why failures
occur in field
Important to follow instructions

74. Spinosad
Spinosad gets its name from the microbe that produces it, a
soil-dwelling bacterium called Saccharopolyspora spinosa.
Controls beetle larvae, caterpillars, thrips, etc. Most effective
when ingested rather than as a contact insecticide
Fast-acting, better than Bt on caterpillars; supposedly not as
soft on beneficials so use in targeted areas
Entrust® - Formulation approved for organic production in
many vegetables

75. Inorganic Pesticides
Diatomaceous earth
Kaolin
Insecticidal soap
Horticultural oil

76. Diatomaceous Earth
Diatomaceous earth (silicon
dioxide) - finely milled fossilized
remains of diatoms; product can
scratch insect exoskeleton or
puncture gut lining (if ingested);
can be used as a desiccant; can
be put on wet foliage to get it to
stick
Insects: aphids, mites, caterpillars

77. Particle Film
Barrier
Kaolin - clay material ground to a uniform
size; when sprayed forms a particle barrier
on plant surfaces that is effective for both
insects and some diseases; must be
sprayed ahead of time on a 7-14 day
schedule; washes off easily & must be
reapplied after rain; agitation is required to
keep it suspended
A proven product, just need to sort out what
it works on
Residue can pose a problem for some
vegetables and is not useful on flowers
because it can’t be washed off
OMRI-approved product: Surround®

78. Insecticidal Soap
Soaps smother soft-bodied pests
and disrupts their cuticle layer. In
order to be effective, it is necessary
to thoroughly coat the pest.
Soap products are most effective
when they dry slowly, so spraying
in the evening or at night is best
Can help control aphids, some
caterpillars, scale crawlers,
leafhopper nymphs, mealybugs,
thrips, whiteflies
OMRI-approved formulations
include M-Pede®, Safer®

79. Most (Un)Wanted Insect Pests
(and how to control them!)

80. Flea Beetles
Row covers
Sanitation to control weedy hosts
Trap crops
Crop rotation
Timing of planting
Organic pesticides: insecticidal soap,
Spinosad, neem, pyrethrum,
particle film barrier?
Hb nematodes
striped flea beetle
eggplant flea beetle

81. Harlequin Bugs
Sanitation
Trap crops
Vacuuming
Pesticides:
Insecticidal soap,
pyrethrum

82. Colorado
Potato Beetle
Crop rotation
Control Solanaceous
weeds
Early maturing resistant
varieties
Straw mulch
Flaming, vacuuming
Trenches
Row covers
Spinosad, neem
Parasitic Hb nematodes?

83. Caterpillars
Spinosad, Bt, neem
provide control
Good idea to rotate
pesticides with different
modes of action to avoid
resistance
Corn earworm: oil + Bt
mixture applied to silks

84. Squash Bug
Hand-pick
Trap crops
Delay planting
Prune vines to remove
egg-laying sites?
Trap boards
Row covers
Sanitation
Neem, Surround®,
insecticidal soap

85. Squash Vine Borer
Crop rotation can help delay problems,
although adults are strong fliers and can find
fields
Use pheromone lures to monitor arrival of
adults and start of egg-laying; remove eggs
laid at base of stems and leaves in April and
May
Use row covers early in season and remove at
flowering
Extract borers from infested vines
Post-harvest tillage will prevent late borers
from completing life cycle
Some farmers have tried injecting either Bt or
parasitic nematodes into the stem with a
syringe; effectiveness not documented

86. Mexican Bean Beetle
Row covers
Neem
Pyrethrin
Release parasitic wasp
Pediobius foveolatus
Vacuuming??

87. Fire Ants
Boiling water – need ~3 gallons per mound;
reported 60% success rate; works best after
a rainfall when fresh mounds are present
Mound drench – ideal if few mounds are
present because doesn’t affect native ants
(which help keep fire ant populations in
check)
Baits – apply to individual mounds instead of
broadcasting
Biological control – nematodes, Beauveria
baits, Phorid flies, protection of native ant
species!

88. OMRI-listed Fire Ant Products
Mound drenches:
Entrust®
Monterey Garden Insect Spray
Safer Brand Fire Ant Killer®
Baits:
Greenlight Fire Ant Control with
Conserve®
Come and Get It!
Research has not shown boric acid or
diatomaceous earth to be very effective

89. For More Information on
Organic Fire Ant
Management…
http://www.ces.ncsu.edu/chatham/ag/
SustAg/fireants.html

90. For More Info on Pest Management…
Photos and Fact Sheets
of NC Insects Pests and Beneficials:
http://chatham.ces.ncsu.edu/
growingsmallfarms/insects.html

91. Diseases

92. Address the Three Conditions
Required for Pathogens
Susceptible host plant –
avoid with resistant and
tolerant cultivars, crop
rotation
Presence of inoculum –
reduce through sanitation
Environmental conditions –
limit with cultural practices

93. Site Selection Considerations
Soil type and associated drainage
patterns
Field layout and exposure
Soil compaction

94. Plan for Diversity over Time
Rotation - soil inhabitant or soil invader
Crop-free periods - obligate parasites
Sowing dates and harvest time can be
adjusted

95. Plan for Diversity over Space
Most small farms are
already diverse!
Use variety mixtures
Employ intercropping

96. Plan for Genetic Diversity
Host plants
Soil microbial
communities
Use of cover crops,
no-till
broccoli with rye/vetch
cover crop

97. Exclusion and Evasion
Use of plant quarantines
Don’t import diseases on seeds or in soil
Control weeds and alternative hosts
Evade problems by growing seed plants in areas
of low or no disease pressure for that particular
plant

98. Variety Selection
Disease resistance vs. disease
tolerance
Select cultivars that have disease
resistance/tolerance characteristics
that are appropriate for your climate
Local/regional heirloom varieties have
often evolved with particular disease-
resistant characteristics
Keep good records of a cultivar’s
performance and the disease pressure
for each season

99. Resistant Varieties
Host resistance is the easiest, cheapest,
safest, and most effective means of
managing diseases!
Especially important for soil-borne diseases
such as fusarium wilt, verticillium wilt,
bacterial wilt, nematodes, Phytophthora
crown and root rot of peppers

100. Sanitation to Reduce Inoculum
Start with clean seed
Hot water treatment
Disease-tested certified seed
Western-grown

101. Transplant Production
Buy from a reputable producer
Use clean, sterile containers and
growing structures
Use soilless mix
Provide good air movement,
temperature control and optimal germinating conditions
Keep seedling flats up off the ground avoiding contact with soil-
borne pathogens

102. General Strategies
Rogue isolated infected plants from the
field during the growing season
Increase air movement by staking,
pruning, and using wide-row spacing
Use drip irrigation to minimize leaf
wetness period
Use mulch to prevent soil splashing onto
foliage and fruit
Avoid working in the field when foliage is
wet to reduce the spread of inoculum

103. General Strategies
Use tunnels or greenhouses to reduce
moisture on foliage and soil splashing

104. Vegetable Grafting
It started in Japan and Korea in the 1920s to control
soil-borne diseases in the greenhouse – watermelon
grafted onto gourd
Today almost 95% of the watermelons, oriental
melons, cucumbers, tomato and eggplant crops are
grafted before being transplanted to the field or
greenhouse in Japan
Grafting can give the best of both worlds: it allows the
grower to combine the good genetic disease-
resistance of hybrid rootstock without hindering fruit
quality

105. Benefits of Vegetable Grafting
Disease resistance
Improved stress tolerance
Salt-tolerant
Extreme moisture
Season extension
Improved yields – vigorous rootstock varieties
can improve water & nutrient uptake

106. North Carolina State University
Grafting Research
Dr. Frank Louws and grad students Cary Rivard
and Suzanne O’Connell are grafting heirloom
tomato varieties onto hybrid disease-resistant
rootstock

107. Tomato
Grafting
stem is cut
before grafting
scion graveyard
grafting clip
healing tent
graft union

108. General Strategies
Use raised beds to improve drainage
Cultivate carefully to promote healthy root growth
Use floating row covers and reflective mulches to
reduce insect vector activity
Harvest gently to minimize cuts and bruises on the
produce
Cool produce rapidly after harvest to slow microbial
activity; store at cool temperatures

109. General Strategies
Optimize NPK fertility to reduce stress
Rotate crops and incorporate crop residues to reduce
inoculum buildup
Plow, disk or roto-till immediately after harvest to
speed up the decomposition of plant tissue
Wash equipment frequently to reduce the spread of
inoculum

110. Organic Pesticides
for Disease Management

111. Organic Pesticides
for Disease Management
Copper & Sulfur
Plant Extracts
Biofungicides
Microorganisms
Particle Film Barrier
Peroxides & Bicarbonates
Compost Tea

112. Some of North Carolina’s
Most Wanted Vegetable Diseases
(and how to control them!)

113. Use crop rotations of at
least 3 years to non-hosts
Use early maturing
varieties (avoidance)
Early Blight
Provide optimum growing conditions and fertility (low N and
early senescence aggravates EB)
Use drip irrigation to keep the period of leaf wetness to a
minimum
Allow for good air circulation
High tunnels?

114. Early Blight
Stake or cage plants to keep fruit and foliage away from
soil
Disinfect stakes or cages with an approved product each
season before using
Treat seed at 122°F for
25 minutes
Apply mulch to help
prevent splashing of
spores from soil up to
lower leaves

115. Early Blight: Pesticides
Serenade® - Bacillis subtilis
Trichoderma products
(e.g., PlantShield®) applied as a drench at
planting
Copper?

116. Southern stem blight on pepper; note white
mycelium and sclerotia at soil line
Remove and destroy infected fruit
Prevent excessive moisture
Stake plants to prevent the fruit from
touching the ground
Deep disking will bury host plant debris
and sclerotia
Soil solarization
Crop rotation – grass crops reduce
inoculum
Southern Stem Blight

117. Southern Stem Blight
Biorationals: Trichoderma®
products
Gliocladium products:
SoilGard® sprayed against
base of young plants
provides some protection

118. Bacterial Wilt
Resistant varieties
Water management
Avoid problem areas
Grafting!

119. Local Crop Problems
on GSF Website
www.growingsmallfarms.org

120. Weeds

121. Weed Management
What is a weed?
any plant growing where it is not wanted
usually causing economic or aesthetic loss
a plant whose virtues have not yet been
discovered
Ralph Waldo Emerson

122. Organic Weed Management:
Philosophy
control weeds to prevent seed rain and to prevent
establishment of noxious or poisonous species
understand and appreciate the potential benefits of
weeds:
beneficial insect habitat
trap crop
nutrient cycling
reduce erosion and improve soil structure
alternative crop?

123. Cultural
Control Strategies

124. Sanitation
Clean machinery so you don’t introduce root
parts from an infested section to a clean
section
Be sure that all manure used in your fertility
system has been hot composted to 140º F to
kill weed seeds and pathogens
Use certified seed to decrease likelihood of
planting weeds

125. Reducing the Weed Seed Bank
The longevity of weed
seed, together with the
large numbers of seeds
produced by individual
plants, can lead to the
long-term build-up of
enormous seed banks in
the soil
Anything you can do to
remove weeds prior to
seed production will help
reduce weed pressure in
subsequent seasons
one barnyardgrass
plant can produce
1,000,000 seeds!

126. Optimizing Planting Date
Later planting date means warmer soils
so crops germinate quicker; allows for
pre-germination of weeds

127. Increasing Crop Competitiveness
Examples of competitive vegetables:
potatoes, beans, squash, cucumbers,
pumpkins, sweet corn, and sweetpotatoes
Examples of non-competitive vegetables:
garlic, onions, carrots, asparagus

128. Increasing Crop Competitiveness
Transplanted crops vs.
direct-seeded crops
Seeding rate and plant
spacing can affect
competitiveness
Try and choose
varieties that germinate
and develop rapidly

129. Water and Nutrient Management
Nitrogen plays a role in
breaking weed seed
dormancy, and the source of
N can affect weed
germination and growth
Use of drip irrigation and
banding or side dressing of
fertilizer may help to deprive
weeds of resources

130. Mulching
Use clean mulch to avoid importing weed seeds
Benefits of organic mulches: suppress weeds,
conserve water, moderate soil temperature, keep
crops clean, prevent soil crusting, and increase
penetration of rain or irrigation water
Inorganic mulches: black plastic, clear plastic, IRT
plastic, landscape fabric
Cover crop residue

131. Mulching

132. Crop Rotation
To effectively
break the life
cycles of various
weeds, crop
rotations should
include cold and
warm weather
crops, legumes
and grasses

133. Crop Rotation
Rotate weed suppression activity and crops
where weeds can be mechanically controlled
Rotate difficult to cultivate crops after crops
where effective control can be achieved
Rotating perennial crops or winter covers
may disrupt the life cycle of weeds present

134. Stale Seed Bed
Takes advantage of the weed
seeds’ light requirement for
germination
Method: prepare seed bed two
weeks ahead of planting date
for crop; encourage weed seed
germination then eradicate
weed seedlings by flaming or
shallow cultivation
Useful especially when
planting direct-seeded and
noncompetitive crops like
carrots, parsnips, lettuce

135. Cover Crops
Living cover crop vs. dead cover crop mulch
Can reduce germination of weeds by
preventing adequate light penetration
Can reduce soil moisture and temperature
which may affect weed germination

136. rye cover crop with
beans
rye cover crop residue with
beans
Cover Crops

137. Allelopathic Cover Crops
Rye residue contains generous amounts of
allelopathic chemicals; when left on the soil
surface, these chemicals leach out and
prevent germination of small-seeded
broadleaf weeds for about 30-60 days
Other allelopathic crops include sorghum-
sudangrass, sunflower, rapeseed

138. Smother Crops
Starve weeds of water, light, and fertility
Warm season examples: buckwheat,
Japanese millet, sorghum-sudangrass,
sunflowers
Cool season examples: rye, oats, field pea,
ryegrass

139. Intercropping
The practice of creating multiple
crop layers that may include
planting a cover crop along with
a cash crop
Benefits include weed
suppression, reduction of soil
erosion, and reduction of wind
injury to the cash crop; care must
be taken to avoid competition
with the cash crop
French beans
intercropped with
cilantro

140. No-till Production
The production of high residue cover is crucial to
successful weed control in no-till system
Benefits of high residue include moisture conservation,
weed suppression, erosion control, increased soil
organic matter, food and habitat for soil organisms; if a
legume is used as a cover crop the benefits include
biologically fixed N
Follow-up methods of weed control are hand-pulling,
high-residue cultivators, weeder geese, hand-hoeing

141. Soil Solarization
Covering soil with clear plastic for 5-6 weeks during the hottest,
sunniest months has been shown to kill weed seeds, pathogens
and nematodes
Soil temperatures should be 140º F at 2 inches and 103º F at 18
inches of soil depth
Solarizing soil after the
addition of composted manure
may be effective in reducing
annual dicots
Weed seeds sensitive to
solarization include winter
annual grasses, black nightshade,
cocklebur, chickweed, redroot
pigweed and velvetleaf

142. Mechanical
Control Strategies

143. Mechanical
Control
Strategies
Hand-weeding
Hoeing
Mowing
Flaming
Hot Water
Tillage

144. Evolving Strategies

145. Biological Control Strategies
Biological control involves the use of a living
agent – insect, fungus, bacteria, animal, plant -
to control another living agent (weed, insect
pest, disease)
So far biological control of weeds has been
achieved in only 30% of the cases reported
Two successful examples:
Weevils to eat the seeds of musk thistle
Rust disease to control yellow nutsedge

146. Biological Control Strategies
Cover Crops
Bio-herbicides
Herbivores

147. Bio-herbicides
Limited effectiveness of organically
acceptable herbicides
Examples of bio-herbicides include
corn gluten, acetic acid, citric acid,
herbicidal soap
Note: Certified organic growers
should consult their certifying
agency before applying any bio-
herbicide

148. Herbivores
Grazing herbivores is an excellent way to
control weeds
Grazing prevents the invasion of aggressive
species
Grazing ruminants can improve the health of
land base by increasing plant diversity

149. Herbivores
Chicken tractors
Pigerators
Weeder geese

150. Grower Resource List
on the Growing Small Farms Website
http://chatham.ces.ncsu.edu/growingsmallfarms/resourcelist.html
Books and publications
Organic seeds
Fertilizers and soil amendments
Equipment & supplies for season extension,
pest management, cut flowers, etc.
Transplants, plants, & bulbs
Livestock & pastured poultry
Beekeeping