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PLANT SCIENCE
INTEGRATED PEST MANAGEMENT IN WINTER CANOLA
Introduction
Integrated pest management or IPM uses all the tools available for controlling
pests. The goal of using IPM is to achieve effective management of pests by
using all of the tools that are available in the safest manner possible and in a way
that enhances the economic viability of the farm. This includes chemical,
cultural, mechanical and biological tools. It means not exclusively relying on one
technique (e.g., using herbicides exclusively for weed control or tillage
exclusively for disease control).
The challenge for growers is to tie them all together for a complete program that
maximizes the effectiveness of their pest management. Most of any canola IPM
program takes place in the timeframe before seeding canola. One estimate of
the resources needed for IPM shows that about 70% of the work comes in the
seasons leading up to the seeding year. This is because the IPM approach
requires forward planning, good knowledge of pest life cycles and is less oriented
toward quick fixes.
Canola is a management-responsive crop. Weather certainly plays a role in
canola yields, but management makes the difference between average and
above average yields. Canola should not be planted in the fall and ignored until
harvest in June. Effective canola production requires hands-on involvement with
the crop.
Weed Management
Weed management is a key component of any winter canola production system.
In the southern Great Plains, winter canola is commonly grown in rotation with
wheat, sorghum, and corn.
Winter canola has difficulty competing with established weeds at emergence.
Planting winter canola into a weed-free seedbed is essential. Weed control
before seeding can be obtained with tillage, herbicides, or a combination of both
methods. If planting winter canola after wheat, it is critical to control volunteer
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cereals and cool-season winter annual grasses, but attention must be given to
previous herbicide applications.
Once plants are established, winter canola suppresses and out-competes most
annual weeds if good management practices are followed. Spring weeds
become a problem when canola stands are poor and areas of the field are left
open.
The most common mistake with canola weed control is waiting too long in the fall
to control weeds. If volunteer wheat or grassy weeds are present, a herbicide
should be applied by 4 to 6 weeks after seeding. Waiting for additional rain to
germinate more weeds is usually a serious mistake.
Winter canola varieties with the Roundup Ready (glyphosate tolerance) trait are
currently available in the Great Plains region that have been developed for
seeding in the fall and harvesting the following spring/summer. Roundup Ready
winter canola varieties contain in-plant tolerance to Roundup agricultural
herbicides, enabling growers to apply Roundup agricultural herbicides over the
top of winter canola anytime from emergence throughout pre-bolting. Do not
apply any herbicides once canola has entered the flowering growth stage. This
system provides nonselective control of winter annual grasses and broadleaf
weeds. The introduction of the Roundup Ready trait into winter canola varieties
assures growers of unsurpassed weed control, crop safety and maximum yield
potential. Roundup Ready winter canola will offer growers an important option as
a rotational crop in traditional monoculture winter wheat production areas.
Introducing crop rotation is an important factor in reducing pest cycles, including
weed and disease problems Apply 1 to 1.5 pints of glyphosate per acre to
Roundup-Ready canola from emergence through the 6-leaf stage of growth.
Common weed pests to canola in the southern Great Plains include henbit,
common chickweed, cheat grass, rescue grass, Japanese brome, jointed
goatgrass, Italian rye, wild oat, volunteer wheat, several various mustards,
flixweed, field pennycress and shepherdspurse.
Canola is very sensitive to SU (Sulfonylurea) herbicides typically used in wheat
production; therefore, all equipment must be thoroughly cleaned. Herbicides
currently labeled for weed control in winter canola include Treflan, Stinger Select,
Assure II, and Roundup Ultra Max II on Roundup Ready winter canola varieties.
Diseases
Diseases can attack canola at any stage of development. They can be soil
borne, seed borne, or airborne. Only a few major diseases are likely to be of
concern in the southern Great Plains. The occurrence of major diseases in the
Great Plains is low, but will likely increase as winter canola acres increase.
These include blackleg, Sclerotinia stem rot, powdery mildew, Alternaria black
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spot, and aster yellows. Currently labeled fungicides include Abound, Curalan,
Ronilan, Quadris, Endura, M-Pede, and Trilogy.
Blackleg
The blackleg fungus, Leptosphaeria maculans, is common
worldwide and infects canola and related crops. Blackleg
is the most serious threat to canola production. There are
both mild and aggressive strains of the fungus.
The blackleg fungus survives in infected seed, stubble, and on certain weeds.
Long-distance spread of the disease occurs when over-summering spores,
known as ascospores, are released from infested stubble. Ascospores can travel
on air currents for many miles. On newly infected plants, a second spore type
called conidia, are released from small, black, pimple-like structures known as
pycnidia and are responsible for infecting neighboring plants and seed pods.
Blackleg is introduced into new areas with infected seed.
Infections from the mild strain usually occur much
later in the season than those from the aggressive
strain. Shallow white to gray lesions will form on
the leaf or stem, but stems are usually not girdled.
Only a few pycnidia are formed. In contrast, the
aggressivee strain can infect early and produce
leaf spots as well as stem lesions. Leaf spots are
round to irregular in shape and are usually tan to
buff in color with many pycnidia present. Stem
infections are usually first observed as inconspicuous bluish lesions at a petiole
scar near the soil line. Later, these lesions develop into an elongated, light
brown sunken area with a purplish or black margin.
The most important management method to control blackleg is excluding it from
an area. This is accomplished by planting only disease-free, certified seed that
has been treated with a fungicide that is effective against blackleg. Several see
treatment products are registered for control of blackleg.
Sclerotinia Stem Rot
Sclerotinia stem rot is caused by the fungus Sclerotinia
sclerotiorum. It is a serious problem in many areas
throughout the world and is present in the Great Plains.
Sclerotinia, also known as white mold, is most severe when
warm wet conditions occur during the flowering period. A
wide range of field crop hosts exists including dry beans,
sunflowers, and soybeans.
,
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The first noticeable symptom of Sclerotinia stem rot is the presence of
prematurely ripened plants. Under high moisture conditions, a white moldy
growth may develop on the surface of
stems and pods. Stems become bleached
and tend to shred. Hard black structures
known as sclerotia appear in or on he
stems near the soil line as well as on
infected pods. Sclerotia fall to the ground
at harvest or when the stems break from
lodging. During the spring, sclerotic near
the soil surface germinate to produce small
golf-tee shaped structures known as
apothecia. Apothecia release ascopores
during wet weather and periods of heavy dew. Spores are carried on air currents
and infect flower petals. Infected petals fall on leaves or stems, which in turn
become sites for the fungus to invade the plant. Symptoms of stem rot appear
approximately 10-14 days after infection. Sclerotia remain dormant in the soil or
8 or more years and can be brought near the surface by cultivation. To reduce
the incidence of conditions favorable for Sclerotinia infection, use lower plant
densities to facilitate air movement, light infiltration, and drying.
Alternaria Black Spot
The fungal disease known as Alternaria black spot is widespread and is worse in
wet years when seed yields can be significantly reduced by pods splitting or early
death of the plants. All aboveground parts of the plant are susceptible. Black,
brown, or gray spots on the leaves,
stems, and pods are the most common
symptoms. Often the spots are
surrounded by a light green or yellow
halo.
Alternaria survives in infested crop
residue, on infested seed, and on some
alternative weed hosts. Infested seed
either rots in the soil or produces infected
seedlings. Wind-blown spores
germinate, penetrate plant tissues, and
cause lesions within a few days. These lesions produce more spores, which
cause new infections on the same or neighboring plants.
Downy Mildew
The downy mildew fungus, Peronospora parasitica, causes yellow, irregular
patches on upper leaf surfaces, giving the leaf a stippled appearance.
Undersides of the leaves exhibit yellow patches with a white, granular
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appearance. Sparse webs of fungal growth occasionally occur on stems and
pods. Little damage is caused by spring infection, but occurrence of the disease
on the fall reduces winter survival. Losses from this disease are rare to the Great
Plains.
Powdery Mildew
The powdery mildew fungus, Erysiphe curciferarum, causes a white, dusty
growth on aboveground plant parts. The disease is favored by moderate
temperature, high humidity, excessive nitrogen fertilization, and excessive
canopy density. In some production areas, powdery mildew results in serious
yield losses.
Aster Yellows
Aster yellows is caused by a phytoplasm (a bacteria-like,
plant pathogenic micro-organism). This organism has a wide
host range and infects about 300 species of pants. Plants
infected with aster yellows fail to set pods, producing bluegreen, sterile, hollow bladders in place of normal pods.
Infected plants remain in a vegetative state during the entire
growing season and remain greener and taller than
uninfected plants at harvest. Aster yellows is spread from
plant to plant by the aster leafhopper in the fall or spring.
Aster yellows is common throughout the southern Great
Plains.
Insects
Several insect species can damage winter canola. Because winter canola
production in the region has been limited, these pests have not posed a large
threat or problem. Starting in November and continuing through harvest,
scouting should be done on the field to identify insect infestations. Canola pests
can cause problems throughout the entire growing season. Some insects reduce
yields by defoliating plants or attacking buds or seedpods. Other insects carry
plant pathogens such as yellow asters. Some insects exist on canola and
mustards only, whereas some are found in other cole crops and still others have
an even wider host range.
Labeled insecticides include Helix (seed treatment), Capture, Warrior T, Confirm,
methyl and ethyl parathion as well as several others. Chemical pesticides should
not be used as a substitute for good agronomic practices or as “preventative
insurance” because it is rarely economically or environmentally justifiable. Some
canola pest problems can be avoided by following good cultural practices
planting at an optimal date and providing proper fertilization and weed control.
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If spraying of insect pests is necessary, select insecticides carefully and consider
options that would protect pollinating insects as well as predatory insects.
Cultural practices such as crop rotation, killing volunteer canola, spraying ditches
and fencerows for wild mustard, and incorporating plant residue into the soil are
important means of insect control. As the number of acres of canola increases in
the region, insect problems will likely increase, but so will the availability of
management options.
Insects causing serious problems in the southern Great Plains over the past 10
years include flea beetles, cabbage seedpod weevils, cabbage worms, alfalfa
looper, diamond moth larvae, and aphids.
Flea Beetles
Generally, flea beetles are less of a problem with
later plantings of winter canola. Flea beetles attack
the cotyledons at emergence and the first true
leaves of the seedlings producing pits or shot holes
in leaves. Plants withstand 50 percent damage to
the cotyledons without suffering any loss of yield
potential. Overwintering flea beetles attack canola
in the spring, but foliage is abundant and potential
damage needs to be severe for treatment to be
economical.
Aphids
Aphids have become the most important insect pest of canola in the southern
Great Plains. The turnip and green peach aphids have been frequently observed
to colonize fields during fall growth, survive mild winters, and increase to
damaging levels during the early spring. Green peach and turnip aphids feed on
the underside of canola leaves. Cabbage aphids colonize the terminal buds late
in the season.
Predatory and parasitic insects such as
Ladybugs, contribute to aphid population
control. During and following mild winters,
aphid populations are sometimes high
enough to cause significant stand decline
and reduce seed production. The frequency
of fall aphids and their potential for damage
clearly suggest that a seed treatment should
be considered as an important preventative
management approach. Scouting is the best
method to ensure effectiveness of seed
treatments during the fall and determining if
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treatment is necessary on emerging spring infestations. If populations are high
from January through March, an insecticide treatment may be necessary. It is
important to note that canola can recover from aphid infestations following timely
insecticide applications.
During flowering, cabbage aphids reproduce on the stalk inside the cluster of
flower buds making it difficult for ladybugs to penetrate this cluster and eat
aphids. Pushing the flower cluster open with your fingers is often necessary to
find these aphids. Damage to flower buds and flowers prevents pod set and can
reduce yields severely.
Cabbage aphids can reproduce and spread
quickly so it is important to scout your fields
for these aphids several times during
flowering.
For every aphid per plant, 0.5 pound of
seed yield is lost. Before flowering begins,
canola can handle large numbers of aphids
before a costly insecticide is justified. It is
important to delay insecticide use until aphids approach economic levels.
Diamondback Moth Larvae
Diamondback moth larvae may cause serious problems
in the southern Great Plains. Scouting canola fields for
diamondback moth larvae should begin following
emergence. In the fall, diamondback moth larvae and
aphids arrive earlier if a seed treatment was not used.
Diamondback moth larvae often attack larger canola
that was seeded early. Diamondback moth larvae will
overwinter and feed in the crown of canola plants. If infestations in the crown are
high, they can be very destructive and stand loss may occur before spring.
Larval infestations of the crown can easily be mistaken for winter kill. To scout
for the larvae, pull up a few plants and tap the crowns on a piece of white paper.
Root Maggots
Root maggots can be a problem on canola
during cold, wet growing seasons. Plants
infestedd with maggots may easily lodge,
have feeding damage inside the stem at the
soil level, and are often infected with
secondary fungi.
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Cabbage Worms and Alfalfa Loopers
Cabbage worms and alfalfa loopers defoliate canola plants in
the spring and summer. Damage is usually minor and yield
loss is minimal if the plants are healthy and growing
vigorously.
False Chinch Bugs
False chinch bugs can occur in large numbers
during mild, dry winters. Research shows that
severe damage can occur if false chinch bugs infest
racemes during bloom and early pod fill. It is
suggested that fields should be treated if five to 10
false chinch bugs occur on flowering racemes, and
if 10 to 20 false chinch bugs occur on racemes
during early pod set. Fall infestations of false
chinch bugs could cause stand losses. False
chinch bugs are common in ripe fields of canola, but
damage rarely occurs.
Summary
Using an integrated approach to managing weeds, diseases, and insects in
canola needs to make sense from a financial standpoint as well as an
environmental point of view. Although many of these pests have not posed a
serious problem for canola producers in the region, as canola acres begin to
increase it will be the responsibility of all growers to keep the problems under
control. The first step is knowing what to look for, knowing the management
options, and making knowledgeable decisions. Together, southern Great Plains
canola producers can grow high quality, pest free winter canola.
References
Great Plains Canola Production Handbook, Kansas State University, March 2009
www.canola .okstate.edu/index.htm
greatplainscanola.com/
www.canola-council.org/
www.uscanola.com/
www.northerncanola.com/
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SUGGESTED STUDENT ACTIVITIES
FILL IN THE BLANK: Complete the following statements.
Scouting
Tools
Insecticides
Spraying
Management
Mechanical
Disease
Pesticides
Chemical
Identification
1. Integrated pest management uses all ____________ available for
controlling pests.
2. The goal of using IPM is to achieve effective _______________ of pests
by using all tools available in the safest manner possible.
3. IPM includes using chemical, cultural, _____________, and biological
tools.
4. _____________ can attack winter canola at any stage of development.
5. _____________ should be done on winter canola fields to identify insect
infestations.
TRUE/FALSE: Circle the “T” if the statement is true or “F” if the statement is false. If
false, correct the statement to make it true.
T
F 6. Weed management is not a key component of any winter canola
production system.
T
F 7. Winter canola easily competes with established weeds at
emergence.
T
F 8. Field history of previous herbicide use is not important.
T
F 9. Once established, winter canola suppresses and out-competes
most annual weeds.
T
F 10. The most common mistake with canola weed control is waiting
too long in the fall to control weeds.
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MULTIPLE CHOICE: Write the letter corresponding to the correct answer in the blank
provided.
_____ 11. Which of the following is not a weed affecting winter canola?
a)
b)
c)
d)
Wild Oats
Henbit
Duck Weed
Volunteer Wheat
_____ 12. Which of the following does not cause damage to canola
plants?
a)
b)
c)
d)
Lady bug
Cabbage Worm
Aphids
Flea Beetle
_____ 13. Which of the following insects causes damage to the buds
during flowering?
a)
b)
c)
d)
Turnip Aphids
Flea Beetle
Cabbage Aphids
Alfalfa Looper
_____ 14. The first noticeable symptom of Sclerotinia stem rot is the
presence of
a)
b)
c)
d)
Seed production
Prematurely Ripened Plants
Black Leaf Spots
Golf-Tee Shaped Structures
_____ 15. Canola is very sensitive to ________________ herbicides
typically used in wheat production.
a)
b)
c)
d)
Sulfonylurea
Roundup Ready
Generic
Select
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_____ 16. Do not apply any herbicide once canola has entered the
__________ growing stage.
a)
b)
c)
d)
_____ 17.
Ripening
Rosette
Seeding
Flowering
Insects reduce yields in canola by
a)
b)
c)
d)
Defoliation
Attacking Flower Buds
Carrying Plant Pathogens
All of the Above
_____18. ____________ is the most serious threat to canola production.
a) Root Rot
b) Blackleg
c) Aster Yellows
d) Downy Mildew
_____ 19. _____________will overwinter and feed in the crown of canola
plants.
a)
b)
c)
d)
False Chinch Bugs
Aphids
Diamondback Moth Larvae
Flea Beetles
_____ 20. For every aphid per plant, ____ pound of seed yield is lost.
a)
b)
c)
d)
0.5
1.0
0.25
1.5
SHORT ANSWER/LISTING: Answer the following question or statement in the space
provided.
A local first time canola grower has noticed problems with some of the plants in
each of his three winter canola fields. He knows that you have been learning
about canola in your agricultural classes and has decided to hire you to help find
out what is wrong with his crop. Use the following scenarios to determine what
pest or pests are causing the grower problems in each field.
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21. Field 1-The grower informs you that the field is in the flowering stage. He
also mentions that the weather has been unusually warm and wet for this time of
year. At first you notice a white moldy growth on the surface of the stems. Near
the soil line on the stems of several plants in the area you notice hard black
structures you think may be sclerotia. Upon further inspection you notice some
prematurely ripened plants.
22. Field 2- The grower informs you that this canola was seeded earlier than the
rest. After walking through the field you notice several shot holes in the leaves.
You notice that the crowns appear to be damaged from winterkill. Given that this
winter was rather harsh it makes sense. However, you decide to pull up a few
plants and tap the crowns onto a white sheet of paper. After a few taps you
notice that several worm like insects have fallen on the paper.
23. Field 3-Shallow white to grey lesions have formed on the leaves and stems
of a few plants. You notice a few black-pimple like structures. As you scan the
field you notice another potential problem. It appears that some foliage damage
has occurred on some the neighboring plants. You decide to take a closer look at
the underside of the leaves and locate groups of tiny insects feeding on the
underside of the leaves.
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ADVANCED ACTIVITIES
1. Have the students create their own sweep net to use out in the canola
field.
Supplies:
1 Pillow Case
2 Wire Hangers
Duct Tape
1 piece of wood about 3 feet long for the handle
Scissors for cutting the pillow case
Step 1: Turn your 2 wire hangers into
similar circles. Then tape them together in
several places, leaving the open end opened.
Step 2: Now cut two holes on either side of the seam
where there are two layers of pillow. Then put the wire through
the pillow. Straighten out the ends sticking out for the handle.
Step 3: Now heavily tape the four wire pieces hanging
out of the pillow to your handle. Make sure its sturdy because
it’s used to sweep through high grasses, alfalfa, clover, and canola.
2. Create an insect collection. Collect and identify insects common to canola
and your area. List the insects you collect as pests or beneficial insects.
Combine all individual collections to create a large classroom display.
3. Interview winter canola farmers in your area and develop a winter canola
IPM journal. Include the techniques they use to control pests, any
success stories or barriers they have encountered, and any other valuable
information. Share your stories with the class.
4. Photograph or collect pictures of the different pests (weed, disease, and
insect) you encounter while out in the field. Create a collage of your
findings. Develop an IPM program for the local participating farmer.
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SUGGESTED STUDENT ACTIVITIES (KEY)
FILL IN THE BLANK:
1.
2.
3.
4.
5.
TOOLS
MANAGEMENT
MECHANICAL
DISEASE
SCOUTING
TRUE/FALSE
6. T
7. F-HAS DIFFICULTY COMPETING
8. F-IS VERY IMPORTANT
9. T
10. T
MULTIPLE CHOICE
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
C
A
C
B
A
D
D
B
C
A
SHORT ANSWER/LISTING
21. SCLEROTINIA STEM ROT
22. DIAMONDBACK MOTH LARVAE
23. BLACKLEG; TURNIP APHIDS
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