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ISSUE 14 AUGUST 5, 1999



    One very important management aspect of growing canola is estimating the correct time to swath
and harvest. A canola grower must attempt to maximize yield and yet maintain quality with as little
green seed content as possible in the threshed oilseed.

    Swathing canola at the optimum stage of ripening reduces green seed problems and seed shatter
losses, and ensures the quality required for top grades and prices.

    Field inspections should be every "two to three days" when there is some color change in the first
formed pods on the bottom of the mains stem.

    To determine when a field of canola is ready to swath, plants from different parts of the field must
be examined. The stage of maturity in an evenly maturing field will vary from plant to plant and from
area to area within the field. When examining the plants, take into account varying soil types, low lying
areas, available soil moisture and exposed early ripening areas.

    Examine only those pods on the main stem. Seeds in pods on the "bottom third" of the main stem
were formed earlier and will turn color much sooner than seeds in the pods on the top third of the plant.
When the overall moisture content of seed from the total plant averages 30 to 35 percent, about 30 to
40 percent of the seeds in pods on the main stem only will have changed color or have started to change
color. Seeds with only small patches of color should be counted as color changed. Remember, the color
of the seed is more important than the overall color of the field in determining the stage of maturity.

    Most of the seeds that have changed color will be from the bottom third of the stem. When seeds in
the bottom pods slightly turn color, seeds in the top, last-formed pods are filled or nearly filled. At this
time, most of the seeds will be firm and roll, as opposed to break, when pressed between the forefinger
and thumb.

    Seeds in all pods on a plant complete filling (physiological maturity) at about 40 percent moisture and
then slowly turn from green to light yellow, or reddish brown to brown, depending on the variety. Once
filled, the seeds rapidly lose moisture at about 2 to 3 percent or more per day, depending on the weather.

    Green Seed Problem: Temperatures at maturity is an important factor in chlorophyll breakdown.
Cool temperatures and light frosts in August and September slow the enzyme activity that breaks down
chlorophyll. Frosts from 32 to 33 degrees F disrupts that system, more specifically it can reverse it and
restart the synthesis process. This is very sensitive in the seed development stage, and the window is very
narrow. This can cause differences between adjacent fields that are only days apart in maturity, or differ
in uniformity of maturity. Even canola swathed four to six days before a frost will retain relatively high
levels of chlorophyll. Two or more germination flushes and growth stages result in immature seed at
swathing and green seed at harvest. Thin stand counts can result in plants with more branching and
more variability in seed maturity and are more likely to have immature seed at swathing. Late seeded
canola may be impacted by all these situations. When looking at uneven stands, its suggested that one
do a count early on the ratio of early emerged canola which is bolting or starting to flower and the late
emerged flush of young more immature plants.

    If one knows the ratio of early to late emerged canola plants, a better decision can be made as to how
soon to swath or wait until the later crop catches up. If the stand is on 20-25% early and 75-80% late,
then waiting to cut later may be the best strategy to reduce the amount of green seed.

    Research was conducted in 1996 and 1997 to study the effects of canola color change at swathing on
yield and percent green seed.

Table 1. Canola Swathing Research Results

Seed Color at Swathing (% change)

Number Seeds/lb

Seed Yield (lbs/A)

Green Seed (%)

Oil (%)
















Locations Averaged - 1996-97, Langdon, Minot, Carrington, ND and Roseau, MN 

    The research results suggest that swathing of canola can start when a minimum of 15-20 percent seed
color change has occurred. This management practice will help ensure maximum yield potential, acceptable
green seed content and percent oil. The early start is particularly important when large acreage of one
variety of Argentine canola is involved or all the crop was seeded over a short period of time.

    The average green seed at the 0-5 seed color at swathing time resulted in 3.5% green seed content
which is higher than the 2% allowed in the market place before a discount will occur. Approximately 180
lbs/A of yield gain was noted when swathing was delayed to the 15-20 percent seed color change.

    Another sign of canola being very near the swathing stage is the natural yellowing and senescence of
leaves and leaf drop. When canola plants consist only of stems, stem branches and pods, it is probably
very near the optimum time for swathing.

    Canola should be allowed to cure and ripen from ten to 14 days in the swath before combining. If
combined too early, the chance of increased green seed in the harvested crop is much greater.

    "Be in a hurry to swath on time and prevent shattering, but take your time in moving the combine
into the field to ensure maximum drying, maturation and quality of your harvested canola."

Duane R. Berglund
Extension Agronomist



    Late season problems in soybeans are usually very limited; however, there are some cases where a
few diagnostics can help point you in the right direction or jog your memory for other, related ideas
toward determining the causes for field conditions. While by no means complete, perhaps the following
conditions and probable causes will help you investigate your soybean fields more closely from bloom
to harvest.

A. Plants are dead or wilted
    1. dead plants with no evidence of disease
        a. plants are broken off at the ground but secondary root system was in place; however, callus
            tissue is seen on the plant
            * alfalfa hopper
            * lesser cornstalk borer
            * surface applied dinitroaniline herbicide
            * hail damage
        b. dead areas across the field show plants that are scorched looking
            * spider mites
        c. a circular pattern of dead plants are seen in the field
            * lightning
    2. Plants are dead but roots show disease problems
        a. white fungal growth is seen with sclerotia (large, black, irregular structures inside and outside
            the stem)
            * Sclerotinia rot (white mold)
        b. stem is discolored with minute, black fruiting structures
            * charcoal rot
        c. stem is discolored with reddish fruiting structures present
            * black root rot
        d. stem is discolored but no fruiting structures are present; however, cankers are seen near the
            stem nodes
            * stem canker
        e. roots with galls, cysts, root proliferation or stubbiness
            * nematode (usually not present in ND)
B. Flowers are not present due to damage or because they are eaten off
    1. flowers were fed on or eaten off
            * corn earworm
            * bean leaf beetle
    2. flowers fell off or were not present
            * drought damage
            * boron deficiency
            * zinc deficiency
C. Pods are damaged or lost
    1. pods show insect damage
        a. pods show that the seed cavity has been fed on
            * corn earworm
            * grasshoppers
        b. pods show on superficial feeding
            * bean leaf beetle
            * a late season caterpillar
        c. pods are completely cut off the plant and lying on the ground
            * a late season caterpillar (following very heavy defoliation only)
    2. pods are stunted, discolored or shriveled
        a. fruiting bodies are present on pods
            * pod and stem blight
            * anthracnose
        b. pods have fallen off the plant but were not fed on
            * drought damage
            * boron deficiency
        c. pods are shriveled with one or more aborted seeds
            * stink bugs
            * pod and stem blight
            * anthracnose
        d. pods are hardened, knotty and show spots on the outer covering and the seed are smaller
            than normal (may be shriveled)
            * stink bug
        e. pods are abnormal, distorted and small (one or no seed per pod)
            * bud blight virus
            * phenoxy or benzoic acid or pyridine misapplication or drift
    3. pods are split along the midline
            * pod is too small for developing beans (can occur during the season with alternating
                wet and dry conditions, especially on certain varieties)
D. Physical damage to the leaves or stems is seen on the soybeans
    1. leaves show insect feeding
        a. leaves are skeletonized or lacy looking
            * bean beetle
            * Japanese beetle
            * catepillars
        b. leaves show holes or leaf margins show feeding damage
            * beetles or catepillars
        c. leaves show a mottled, yellow appearance or may appear scorched
            * spider mites
        d. leaf tips and upper leaf margins are yellow with possible cupping
            * potato leafhopper
    2. leaves are hanging down, shriveled/collapsed petioles or stems
        a. insect damage is suspected
            * alfalfa hopper
    3. the stem terminal hangs from the plant
        a. insect feeding injury is seen
            * corn earworm
    4. soybean plants easily snap or lodge when touched or blown during wind or heavy rains
        a. breakage along any part of the plant
            * alfalfa hopper (old damage)
            * cornstalk borer (old damage)
            * dinitroaniline injury (old, surface application)
            * paraquat injury (old post-directed injury--rarely seen/used)
            * phenoxy injury (old post-directed or drift injury)
            * old hail damage
E. discoloration or stunting of leaves or stems
    1. interveinal chlorosis remains on upper leaves
        a. disease present
            * black root rot
            * stem canker
            * brown stem rot
            * Phytophthora rot
            * Sudden death syndrome (not currently present in ND or MN)
    2. near maturity, stems appear blighted with fruiting bodies present
        a. soybeans show effects later in the season
            * pod and stem blight
            * anthracnose
            * black root rot
            * Sclerotinia rot
    3. plants show cankers from the lower to the mid-section of the main stem
        a. most cankers are near the axils of the branches
            * stem canker
    4. leaves are discolored, spotted or blighted
        a. many diverse causes may be contributing to the problem
            * frogeye leaf spot
            * bacterial blight
            * aerial blight
            * downy mildew
            * brown spot
            * sudden death syndrome (not yet seen in ND or MN)
            * sunburn
            * purple seed stain
            * brown stem rot
            * Fusarium spp.
            * air pollution
    5. leaves have a white, powdery growth on the upper-side
        a. disease is apparent
            * powdery mildew
    6. areas within the field appear scorched
        a. damage is not known to be due to insects
            * spider mites
            * chlorine toxicity
    7. leaf yellowing is followed by a silver-gray discoloration of the lower stem
        a. disease is suspected
            * charcoal rot
    8. stem is tunneled making plants wilt or die
        a. insect damage is noted
            * stem borer
    9. roots are fed on or cut off
        a. insect damage is suspected
            * white grubs
            * wireworms
F. the entire plant appears stunted and may exhibit abnormal growth
    1. leaf crinkling, mottling or distorting is seen
            * viruses
            * phenoxy, benzoic acid or pyridine injury
            * manganese toxicity
    2. leaves yellow and roots have galls, cysts, proliferation or stubbiness
            * nematode (not currently found in ND)
    3. leaves are yellow with some plants stunted
        a. look for damage to roots and stems
            * white grubs
            * beetle larvae
            * stem borer
G. Some plants within the field remain green past the remainder of the field
    1. few pods present, otherwise plant appear normal but green
            * stink bugs
    2. some leaves are crinkled but few pods are present, of which many only have one-bean or
        appear in clusters
            * bud blight virus
            * phenoxy, benzoic acid or pyridine injury
    3. pods mature in color but stems and petioles remain green
            * green stem condition (suspect stink bugs or varieties with certain environmental stresses;
               some viruses and growth regulator drift damage can also cause stems to remain green)
H. Seed is discolored or damaged
    1. brown or black streaks from the hilum (bleeding hilum)
            * viruses
            * genetic
    2. purple color patterns on the seed
            * purple seed stain
            * stain of crushed black nightshade berry juices
    3. moldy, dark or deformed seed
            * any one of various diseases (such as pod and stem blight, anthracnose, downy mildew)
    4. seed coat is split
            * excessive rainfall with high humidity, often following a drought
    5. small and shriveled seed
            * stink bugs (puncture marks may be visible)
            * various diseases (charcoal rot, brown stem rot)
            * drought damage
    6. orange to brick red or light brown seed
        a. as damage increases, seeds are more shriveled
            * stink bugs
    7. small, shriveled, green seeds
            * frost damage

Denise A. McWilliams
Extension Crop Production Specialist

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