Guide to Commercial Cabbage Production

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					                                           A L A B A M A     A & M    A N D    A U B U R N    U N I V E R S I T I E S

                                           Guide to Commercial
                       ANR-1135            Cabbage Production
Historical Perspective                     Planting                                  germination of the seed; otherwise,
                                                                                     seed will be lost to rotting and
     Cabbage (Brassica oleracea L.         Recommendations                           damping off, resulting in poor, un-
var. capitata) is a member of the
Brassicaceae (Mustard) family                                                        even stands. The optimal range for
                                           Planting Dates, Seeding,                  germination is between 45°F and
(Figure 1). This family includes
                                           and Transplanting                         95°F.
broccoli, brussels sprouts, cauli-
flower, kale, mustard (greens), and              Cabbage is a cool-season crop             Some growers opt to produce
collards. Collectively, these crops        generally requiring 60 to 100 days        their own transplants in field beds
are referred to as cole crops or           from sowing to reach market matu-         where seed is scattered over a pre-
crucifers.                                 rity, depending on the variety.           pared area and then transplants are
                                           Cabbage can be grown as a spring          dug 5 to 7 weeks later. One ounce
                                           crop as well as a fall crop in            of cabbage seed will produce about
                                           Alabama. Although it can be direct-       5,000 transplants.
                                           seeded, most cabbage production                For a spring crop, transplant in
                                           relies on the use of transplants.         late December through early
                                           Ideal monthly temperatures for            January in South Alabama or in late
                                           optimal growth and development            January through early February in
                                           ranges from 60°F to 65°F.                 North Alabama. The fall crop
                                                Temperatures over 75°F can in-       should be field-seeded during the
                                           duce “bolting” in cabbage, but vari-      first half of August in South
Figure 1. Well-formed head of cabbage      eties differ in their susceptibility to   Alabama and during the last half
                                           this disorder. Bolting is the process     of July in other areas. If using trans-
     Early Greek and Roman litera-         in which the plant switches from          plants in the fall, plant about 1
ture refers to the cultivation of cole     vegetative growth (heading) to re-        month later than if field-seeding.
crops for their perceived medicinal        productive growth (formation of                Prepare the land early by turn-
properties as well as a source of          flowers and seeds). This switch be-        ing the soil so that any crop residue
food. Belief that these crops re-          comes evident when seed stalks            is fully decomposed before trans-
lieved such conditions as gout,            appear, making the heads unmar-           planting or direct-seeding is done.
deafness, and headaches furthered          ketable. The presence of a seed           Space plants 12 to 15 inches apart
the spread of cole crops from the          stalk is not always apparent from         in 36- to 42-inch rows. This will
Mediterranean through the Old              examining the exterior of the cab-        produce heads that range from 2 to
World.                                     bage; the head may have to be split       3 pounds. When larger heads are
     Now, cabbage and many of the          to see the seed stalk forming from        desired, increase the spacing
cole crops are cultivated through-         the base of the plant. Many vari-
out the world for use fresh and in         eties differ in their tolerance to
processed products. Nutritionally,         higher temperatures that induce
1 cup of raw cabbage contains 93           bolting. More information on vari-
percent water and is a good source         ety selection is discussed in the
of dietary fiber as well as vitamins        Variety Selection section of this
A and C. Worldwide, China is the           publication.
leading producer and consumer of                Direct-seeding of cabbage re-
cabbage. In the United States,             quires using a precision seeder to
80,000 acres of cabbage valued at          place single seeds at the desired
almost $280 million was harvested          plant spacing. Soil temperatures
                                                                                     Figure 2. Characteristic symptom of
in 1997.                                   must be above 40°F to ensure
                                                                                     tipburn on exterior (top) cabbage head

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Figure 3. Diamondback moth cater-           Figure 7. The cross-striped cabbage-      Figure 11. Several aphid species, includ-
pillar larvae are smaller than other        worm is easy to identify by the black     ing cabbage aphids, infest cole crops.
caterpillar pests of cole crops; mature     and white transverse stripes down the     Large numbers of aphids may kill small
larvae are green, 1⁄ 3 to 5⁄ 8 inch long,   back.                                     plants, and their feeding can distort
and tapered at both ends.                                                             leaves of older plants, causing leaf curl.

Figure 4. Mature cabbage looper lar-        Figure 8. Beet armyworm larvae are        Figure 12. Closely related to the
vae grow as large as 11⁄ 2 inches in        light green to dark olive green and may   stinkbug, the harlequin bug is a brightly
length and have only three pairs of         have longitudinal stripes on the back     colored, shield-shaped bug with red
fleshy prolegs in the rear.                  or sides of the body.                     and black markings and piercing-suck-
                                                                                      ing mouthparts.

Figure 5. Green larvae of the import-       Figure 9. Cutworms are dark gray-         Figure 13. Flea beetle adults are
ed cabbageworm can be distinguished         brown in color with a greasy appear-      small, dark-colored beetles with en-
from other caterpillars by the dense        ance, and they often curl into a C        larged hind legs that enable them to
coating of fine hairs that give the lar-     shape at rest or when disturbed.          jump great distances.
vae a velvety appearance.

Figure 6. Cabbage webworm larvae            Figure 10. Seed and root maggots are      Figure 14. Vegetable weevil adult
are 3⁄ 4 inch long when mature and are      the immature, or maggot, stages of
gray in color with five dark stripes.        flies that are attracted to decaying
                                            organic matter.

2 Alabama Cooperative Extension System
between plants within a row.              and lime required to successfully         (besides 10-10-10) can be used to
Another option is to use double           produce a crop of cabbage. The            supply equivalent amounts of nutri-
rows (two rows of plants within           best strategy is to have a soil test      ents. Fertilizer applied before plant-
each bed). Using double rows will         performed yearly. Timely and ap-          ing or transplanting should be well
increase your yields from 30 to 50        propriate applications of fertilizer      mixed into the soil to prevent any
percent or more. Plants in double         can make a significant difference in       chance of plant injury.
rows compete better with weeds            the quality and quantity of cabbage
and produce a more uniform crop.          harvested. Collect soil samples from      Variety Selection
     Use Table 1 to determine the         each area that you intend to crop,
                                                                                          Cabbage varieties can differ in
number of plants per acre required        and have a soil analysis performed
                                                                                    terms of head size, density, shape
at the various spacings. To deter-        on each sample. Apply recom-
                                                                                    (globe, round, flat round), color
mine the number of plants required        mended lime 2 to 3 months be-
                                                                                    (green, red, blue-green), leaf tex-
per acre for any spacing, divide          fore planting because it takes time
                                                                                    ture (smooth or savoyed), and mar-
43,560 (number of square feet in 1        for lime to raise the soil pH. Failure
                                                                                    ket maturity as well as tolerance to
acre) by the product of the desired       to properly lime your soil can ulti-
                                                                                    bolting. Read variety descriptions in
spacing between plants and the            mately cause your crop to have a
                                                                                    seed catalogues, variety trial re-
spacing between the rows. For ex-         major nutritional problem that is
                                                                                    ports, and other publications to de-
ample, a 12-inch between-plant            not easily corrected. Often, by the
                                                                                    termine whether a particular variety
spacing on 36-inch centers would          time a nutrient disorder is visible, it
                                                                                    meets all the requirements for your
require 14,520 plants per acre: (12       is too late to salvage the crop, es-
                                                                                    growing area, season of produc-
in. x 36 in. or 1 ft. x 3 ft. = 3 ft.2;   pecially if that disorder has resulted
                                                                                    tion, and intended market. Most va-
then divide 43,560 by 3 = 14,520          from very low soil pH. Contact
                                                                                    rieties indicate whether they are
plants per acre). For double rows,        your county Extension agent for
                                                                                    suited to spring and/or fall produc-
simply double the number of plants        information about how to collect,
                                                                                    tion. This is an indication of how
required for single-row production.       submit, and interpret the results of
                                                                                    susceptible that variety is to bolting.
                                          your soil test.
Table 1. Number of Plants Required
                                                                                    In Alabama, bolting tends to be
                                                The general recommendation          more problematic in the spring
at Various Spacings                       for cabbage is to apply enough fer-       when temperatures commonly fluc-
            Number of plants required     tilizer to furnish 120 pounds each
            per acre at two spacings
                                                                                    tuate above 75°F. For a spring crop,
                                          of nitrogen (N), phosphorus               choose a cabbage variety that is
Between-                                  (P2O5), and potassium (K2O) per           less sensitive to bolting.
row spacing 36 inches 42 inches           acre. This can be done by applying
                                                                                          Disease resistance/tolerance is
  12 inches      14,520       12,446      800 pounds of 10-10-10 per acre by
                                                                                    also important. The disease black
  15 inches      11,616        9,957      broadcast or band placement meth-
                                                                                    rot (described in the Controlling
                                          ods before planting. Also apply 10
Soil and Fertility                                                                  Diseases section) can be devastat-
                                          to 20 pounds of Borax per ton of
                                                                                    ing to cabbage because it can be
     Cabbage can be grown on a            fertilizer. If boron is not applied
                                                                                    difficult to control. Use cabbage va-
wide range of soil types. A well-         with preplant fertilizer, spray 10
                                                                                    rieties that are tolerant of the dis-
drained sandy loam soil with good         pounds of Solubor per acre or 2
                                                                                    ease, especially for plantings that
organic content is preferred. Avoid       quarts of N-Boron per acre directed
                                                                                    will be placed into fields that have
soils that tend to dry quickly. Adjust    at the base of young plants. Cole
                                                                                    produced cabbage or any other
soil pH to between 6.0 and 6.5.           crops have a higher demand for
                                                                                    cole crop in the past 2 to 3 years.
Plow under cover crops at least 1         boron than many other vegetable
                                          crops do. A boron deficiency can                 Tolerance to a physiological
month before planting to allow suf-
                                          manifest itself as a condition called     condition called tipburn is also de-
ficient time for the cover crop to
                                          “hollow heart” in cabbage. With           sirable. Tipburn is related to a calci-
decompose. To avoid potential soil-
                                          hollow heart, the pith of the head        um deficiency in developing tissue.
borne disease and nematode prob-
                                          (center) becomes cracked and              The condition is favored by exces-
lems, do not plant cabbage in soils
                                          brown as the cabbage reaches              sive or rapid growth due to overfer-
that have produced a crop of cab-
                                          maturity.                                 tilization, or it can be caused by
bage, broccoli, collards, or any
                                                                                    low soil pH. High relative humidity
other cole crop in the past 2 to 3              Sidedress with 20 to 25 pounds
                                                                                    also favors the development of tip-
years. Crop rotation can be an ef-        of N per acre 2 weeks after trans-
                                                                                    burn. Symptoms of tipburn are not
fective means of decreasing disease       planting or 4 to 5 weeks after di-
                                                                                    always detectable on the exteriors
severity or incidence.                    rect-seeding. Sidedress again with
                                                                                    of heads (Figure 2). Often, it is not
     Soil testing is essential for de-    another 20 to 25 pounds N per acre
                                                                                    apparent until a head is cut in half
termining the amount of fertilizer        3 weeks later. Other fertilizer grades
                                                                                    and the internal tissue is examined.

                                                                             Guide to Commercial Cabbage Production      3
Tissue inside the head turns black,      maintained to maximize yields. In        Controlling Weeds,
especially the tissue that surrounds     cabbage, the most critical period
the growing point of the head.           for irrigation is following direct-
                                                                                  Insects, Diseases,
Once tipburn develops, it cannot         seeding or transplanting and during      and Other Pests
be reversed, and the head is un-         head development. Any stress relat-           Contact your county Extension
marketable. To prevent or limit the      ed to a lack of water during these       agent or consult Extension publica-
development of tipburn, grow only        periods can lead to small head size      tion ANR-500A, Alabama Pest
tolerant varieties and avoid exces-      (reduced yields), growth cracks, or      Management Handbook—Volume
sive fertilization. Soil test and lime   tipburn. Any of these problems will      1, for current information on strate-
with dolomitic or calcitic lime to a     result in the production of poor-        gies to control pests (fungi, bacte-
pH of 6.0 to 6.5. Apply calcium if       quality heads, reducing their mar-       ria, nematodes, insects, weeds) and
necessary as indicated by the soil       ketability and value.                    for materials used to control these
test. Sprays containing calcium can                                               pests in cabbage. Always confirm
also be used to supply extra calci-      Production on                            that what you are applying will
um, especially under stressful           Plastic Mulch                            control the target pest(s). If you
growing conditions. These sprays,                                                 are unsure, contact your county
however, are not a substitute for             Using polyethylene (plastic)
                                                                                  Extension agent.
proper soil pH and an adequate           mulch offers several advantages.
                                         Plastic mulch increases soil temper-          Since cabbage is related to
soil calcium level.                                                               broccoli, collards, cauliflower, and
                                         ature, which accelerates plant
     Contact your county Extension       growth and development. It also          other cole crops, it is a host for
agent for a copy of the latest edi-      conserves soil moisture and re-          many of the same pests that attack
tion of the report entitled “Fall        duces several problems including         these other cole crops. Planting re-
Vegetable Variety Trials” from the       compaction and crusting of soil,         lated crops year after year in the
Alabama Agricultural Experiment          leaching of fertilizer, drowning of      same area will increase pest pres-
Station at Auburn University. In the     crops, evaporation of soil moisture,     sure in that area. Eventually, you
report, you will find information         and competition from weeds. At           might not be able to produce a
about the performance of selected        harvest, wrapper leaves are cleaner,     marketable crop of cabbage. To
cabbages in trials at several loca-      requiring less washing, which            avoid this, rotate to crops in other
tions throughout Alabama.                greatly facilitates field packing.        plant families (such as the Cucurbit
Although there are a large number                                                 family—cucumbers, watermelons;
of commercial varieties available,            Although using mulch increases
                                                                                  or the Solanaceaous family—toma-
grow only those that are adapted to      production costs, those costs can
                                                                                  toes, bell peppers, eggplant).
Alabama. It is advisable to grow a       be offset by earlier and larger yields
                                         of high-quality heads. In order to            The use of cover crops can also
small trial plot of several varieties                                             be used in a rotation. Crop rotation
each year to determine which vari-       spread increased costs over two
                                         seasons, growers can plant another       is one of the most effective pest-
eties are best suited to your specific                                             management strategies that a grow-
growing conditions, management           crop (double cropping) into plastic
                                         mulch before or after the cabbage.       er can use. Locate fields for cab-
practices, and marketing outlets.                                                 bage production away from areas
                                         Care must be taken throughout the
                                         growing season not to tear or oth-       where any related crops were
Irrigation                               erwise damage the mulch. Double-         grown the previous season. The
     Irrigation is an essential ele-     cropping will spread your produc-        longer the rotation, the more effec-
ment of a successful vegetable pro-      tion costs over two crops, decreas-      tive the pest control will be (3 to 4
duction operation and is critical to     ing the risk associated with higher      years is ideal).
the consistent production of quality     preharvest costs. In the fall, grow-
produce. Cabbage is a fast-growing,      ers in Alabama commonly double-          Controlling Weeds
shallow-rooted crop whose roots          crop cabbage following such crops             Weed management in cole
penetrate only 12 to 15 inches into      as watermelons and tomatoes or           crops in Alabama usually begins
the soil. Although cabbage is rela-      preceding such crops as tomatoes,        with some form of tillage before
tively drought tolerant, adequate        bell peppers, and watermelons in         seeding or transplanting to destroy
soil moisture levels should be           the spring. On plastic, use double       emerged weeds. Nonselective her-
                                         rows of cabbage plants spaced 12         bicides such as Gramoxone Extra
                                         to 14 inches apart between rows          (Zeneca) or Roundup Ultra
                                         within the bed. Contact your coun-       (Monsanto) can be used in place of
                                         ty Extension agent for more infor-       tillage to destroy emerged weeds if
                                         mation about using plastic mulch.        the crop is planted no-till. Most her-
                                                                                  bicides registered for use in cole

4 Alabama Cooperative Extension System
crops are designed to provide con-           Goal 2XL (Rohm and Haas) at        Scouting Fields
trol of annual grasses such as annu-    1 to 2 pt./acre. Goal should be ap-          The most important tool in pest
al bluegrass and crabgrass and          plied to the soil surface before        management is regular (at least
small-seeded broadleaf weeds such       transplanting. Transplanting should     weekly) scouting of fields to cor-
as chickweed, henbit, lambsquarter,     be done with the least amount of        rectly identify pests and to deter-
and common purslane.                    soil disturbance possible. DO NOT       mine if their numbers and potential
     Avoid locations with heavy         use on direct-seeded crops. Use a       for damage warrant treatment.
weed pressure, especially areas         low rate on sandy soils. Goal con-      Growers who monitor their fields
with perennial weeds such as            trols small-seeded broadleaf weeds.     are able to make treatment deci-
nutsedge. If nutsedge is a problem,     Use with a grass herbicide to obtain    sions based on knowledge of pest
consult Extension publication ANR-      adequate annual grass control.          conditions, and they can avoid hav-
1073, “Nutsedge Control in              Crop rotation restriction: see label.   ing to make unnecessary pesticide
Commercial Vegetables.”                      Prefar 4E (Gowan) at 5 to 6        applications. Most insect pests
     Mechanical cultivation between     qt./acre. Prefar should be applied      found on cole crops have parasite
rows is a valuable tool for use in      preplant-incorporated or preemer-       and predator natural enemies that
cole crops. Cabbage is a shallow-       gence to soil after transplanting for   are often able to keep pests below
rooted crop, so cultivation should      control of annual grasses and small-    damaging levels. Because natural
not extend any deeper than 2 inch-      seeded broadleaf weeds. Prefar will     enemies are very sensitive to syn-
es into the soil. On small areas,       not control emerged weeds. Irrigate     thetic insecticides, particularly those
using organic or plastic mulch will     with overhead sprinklers immedi-        with a broad target range, it is best
help suppress many weeds. The           ately after preemergence applica-       to use insecticides only when nec-
herbicides currently registered for     tion. Crop rotation restriction: 4      essary based on scouting informa-
use in cabbage, broccoli, and cauli-    months for crops not specified on        tion. When scouting plants, it is im-
flower are listed below. These           the label.                              portant to correctly identify pests
products must be used according to           Poast 1.5E (BASF) at 0.5 to 1.5    because incorrect identification
label directions and applied with       pt./acre. Poast should be applied       may result in false estimates of the
the proper equipment calibrated to      over-the-top for control of emerged     potential for damage or improper
apply correct rates.                    annual and perennial grasses. Poast     selection of pesticides for control.
     Dacthal 75W (ISK Biosciences)      will not control broadleaf weeds.            When scouting, it is helpful to
at 6 to 14 lb./acre. Dacthal should     Two pints of crop oil concentrate       divide each field into four quad-
be applied preplant-incorporated or     per acre should be added to all         rants. Scouting should be done in a
preemergence to the soil surface        Poast treatments. Poast should not      zigzag pattern across the field to
after seeding or transplanting. This    be sprayed within 30 days of har-       ensure that all quadrants of the
product requires rainfall or over-      vest. Crop rotation restriction:        field are covered. Approximately 10
head sprinkler irrigation for activa-   none.                                   sites should be sampled in the
tion to control annual grasses and           Trifluralin 4E (several manu-       field, with 5 adjacent plants sam-
small-seeded broadleaf weeds.           facturers) at 1 to 1.5 pt./acre.        pled at each site for a total of 50
Dacthal will not control emerged        Trifluralin should be applied pre-       plants per field. The plants should
weeds. Crop rotation restriction: 8     plant-incorporated before seeding       be selected at random—do not se-
months for crops not specified on        or transplanting for control of an-     lect plants because they are large or
the label.                              nual grasses and small-seeded           look damaged. Sample field edges
     Devrinol 50DF (United Phos-        broadleaf weeds. Crop rotation          and areas with poor stands sepa-
phorus) at 4 lb./acre. Devrinol         restriction: 5 months for crops not     rately; some insect infestations start
should be applied preemergence to       specified on the label.                  at and may be limited to these
soil after seeding or transplanting.                                            areas. At each plant, count and
This product requires rainfall or       Controlling Insects                     record caterpillars before sampling
overhead sprinkler irrigation for ac-                                           for aphids or other pests. Keep
                                            Cabbage and the other cole          written records of pest observa-
tivation to control annual grasses      crops share many of the same in-
and small-seeded broadleaf weeds.                                               tions. It is helpful to develop a
                                        sect pests. Although the informa-       printed format and make copies to
Devrinol will not control emerged       tion presented here was developed
weeds. Crop rotation restriction: 12                                            use on each sampling date. Keep
                                        specifically for cabbage, broccoli,      separate records for each insect
months for crops not specified on        and cauliflower, the majority will
the label.                                                                      species because many insecticides
                                        apply to all cole crops grown in        are not equally effective against all
                                        Alabama.                                species.

                                                                         Guide to Commercial Cabbage Production      5
Determining When to                      natural enemies. For best results,       completely through the leaf, giving
Treat for Insect Pests                   all insecticides should be applied       the damage a “windowpane” ap-
     For pest management purpos-         using a boom sprayer equipped            pearance. Large larvae can chew
es, plant growth can be separated        with swivel-type drop nozzles            completely through leaves, creating
into the following three stages: (1)     arranged with one nozzle over            holes. Larvae may also feed on the
seedling development, or prethin-        each row and adjacent nozzles on         developing heads, causing head
ning stage (seed to 6 inches), (2)       drop tubes between plants. This          deformation and providing entry
preheading or precupping stage           way, the spray is directed over the      for disease. DBM pupae are green
(from thinning to head formation),       tops of the plants and also outward      and enclosed in netlike cocoons at-
and (3) heading or cupping stage         and upward into the plants. The          tached to the foliage.
(heads forming).                         top nozzle should be approximate-             Because DBM populations can
     The extent of economic dam-         ly 9 to 12 inches from the top of        increase rapidly at temperatures
age caused by insects depends on         the plant, and the drop nozzle           above 80°F, at least twice-weekly
crop growth stage, so treatment          should be within 3 inches of the         scouting is recommended. Heavy
thresholds change as the plants          ground or bed between rows. One          rains may reduce populations dra-
grow. Small seedling plants (stage       nozzle directly over the row is suf-     matically. Bt insecticides are usually
1) are very susceptible to insect        ficient during the stage 1 growth         effective and should be applied at
damage, and large numbers of in-         phase. For complete coverage, the        the first sign of worm activity (see
sects that migrate into fields can de-    sprayer should be operated at 150        treatment thresholds below). Sprays
stroy plant stands. Plants in stage 2,   to 250 pounds per square inch (psi)      may need to be applied at 5-day in-
between thinning and head forma-         with 80 to 120 gallons of spray vol-     tervals when populations are high.
tion, can tolerate moderate insect       ume per acre. Because cole crops         A combination of Bt and pyrethroid
populations. Because most leaves         have a waxy layer on the leaf sur-       insecticides (e.g., Asana, Ambush,
and stems grown during this time         face, a spreader-sticker product         Pounce) may be used if increased
do not go to market, moderate            should be included in the spray          activity is needed. DBM pupae suf-
damage will not cause economic           tank to inhibit the formation of         fer natural mortality from native
loss as long as it does not stunt        large drops and to ensure even           parasitoids, and parasitized pupae
plant growth and delay maturity.         wetting of the spray on the foliage.     can be recognized by the presence
Treatment thresholds must be low-        Refer to Extension publication           of a broad white stripe around the
ered during stage 3 because insect       ANR-500A, Alabama Pest Manage-           pupa. Disking after harvest to de-
damage or contamination during           ment Handbook—Volume 1, for a            stroy crop debris will prevent
head formation will reduce the           complete listing of recommended          buildup of DBM and migration to
market value of the crop. There-         insecticides.                            plants in adjacent fields.
fore, when scouting for insect                                                         Cabbage Looper. The cabbage
pests, it is important to consider the   Foliage-Feeding Caterpillars             looper (CL) is most active in early
plant growth stage in determining             Diamondback Moth Caterpillar.       summer and fall. Mature larvae
whether treatments are necessary.        Diamondback moth (DBM) has be-           grow as large as 11⁄ 2 inches in
Crop-maturity-based action thresh-       come a serious worldwide pest of         length and have only three pairs of
olds for several insect pests have       cole crops because it has been able      fleshy prolegs in the rear (Figure
been developed and are listed            to develop resistance to insecti-        4). The larvae loop their bodies
below.                                   cides. The caterpillar’s name comes      when they move and grasp the
                                         from the diamond-shaped markings         plants tenaciously when handled.
Applying Insecticides                    on the adult moth. DBM caterpillars      Their green color blends well with
     Adequate spray coverage is          are most active in spring and early      the foliage, and their dark frass, or
critical to successful pest manage-      summer, producing as many as ten         excrement, is often detected before
ment in cole crops because leaves        generations during the growing           the larvae are seen. CL pupae are
grow close together and insects          season. DBM larvae are smaller           green and are attached to the leaf
seek protected areas underneath          than the larvae of other caterpillar     undersides. They are twice as large
and between leaves. Good spray           pests of cole crops. Mature larvae       as DBM pupae. CL larvae chew
coverage is particularly important       are green, 1⁄ 3 to 5⁄ 8 inch long, and   complete holes in the leaves, and
when using Bacillus thuringiensis        tapered at both ends (Figure 3). A       more mature, larger larvae con-
(Bt) insecticides because caterpil-      larva wriggles violently when dis-       sume great amounts of plant mater-
lars must eat the treated foliage to     turbed and often dangles from a          ial. Because large larvae are less
ingest the toxin. The advantage of       leaf by a silken thread.                 susceptible to insecticides than
Bt insecticides is that they are non-         Larvae feed on the leaf under-      young larvae are, sprays should be
toxic to humans and most insect          sides. Small larvae do not chew          applied when larvae are still in the

6 Alabama Cooperative Extension System
early growth stages. Bt insecticides    Table 2. Chart for Conversion of Caterpillar Counts to Larval Units
are moderately to highly effective      (1)Insect and Size           (2)Total         (3)Conversion         (4)Larval
and may be combined with                                             Counted              Factor              Units
pyrethroid insecticides (e.g., Asana,   Large CL                    ________      x           1        = _________
Ambush, Pounce) for increased ac-       Small CL                    ________      x          2⁄ 3      = _________
tivity if needed.                       Large ICW                   ________      x          2⁄ 3      = _________
                                        Small ICW                   ________      x         1⁄ 10      = _________
     Imported Cabbageworm.
                                        DBM Larvae                  ________      x         1⁄ 10      = _________
Imported cabbageworm (ICW)
moths are white to yellowish-white      Multiply the numbers in column 2 by the appropriate conversion factor (column 3) to
butterflies with black spots on their    calculate the larval units (column 4). Next, add all the larval units together, and divide
                                        the total by the number of plants sampled to get the average number of larval units per
wings. Unlike nocturnal CL moths,       plant.
ICW moths are often seen flying          Total larval units ÷ no. plants sampled = larval units per plant
around plants during the day. The       _____________ ÷ _______________ = _________________
green larvae can be distinguished
from other caterpillars by the dense    Finally, consult Table 3 to determine if treatment is necessary.
coating of fine hairs that give the      Table 3. Treatment Thresholds for DBM, CL, and ICW*
larvae a velvety appearance (Figure
5). The mature larva has a faint or-    Plant Growth Stage                     Treatment Thresholds (avg. larval
ange stripe down the back. The lar-
vae chew irregular holes in the         1. Seedling to 6 inches                              0.50
leaves, bore into heads, and conta-     2. Preheading or precupping                          1.30
                                        3. Early to late head or cup formation               0.50
minate leaves and heads with fecal
material. Damage is similar to that     *Thresholds developed by the New York State IPM Program and validated in cabbage
                                        trials in Alabama.
caused by the CL. ICW is effectively
controlled with the same insecti-       with five dark stripes (Figure 6).                are light green to dark olive green
cides recommended for the DBM           The head capsule is black with a                 and may have longitudinal stripes on
and CL.                                 distinct white V-shaped mark.                    the back or sides of the body (Figure
     Treatment Thresholds for DBM,      Cabbage webworm is an occasion-                  8). There is a black spot above the
CL, and ICW. Because these three        al pest of cole crops and feeds in               second pair of true legs just behind
worm species cause similar dam-         areas around buds. The caterpillars              the head. Recommended insecticides
age, they should be considered to-      produce webbing that can protect                 should be applied if egg masses or
gether when making treatment de-        them against insecticide contact.                larvae are found on 2 to 3 percent of
cisions. Because different types and    Insecticides for other caterpillars              the plants.
sizes of worms cause varying levels     will provide control of webworms
of feeding damage, their impor-         as long as the bud areas are ade-                Other Insect Pests
tance should be weighted accord-        quately covered by spray.                             Cutworms. Cutworms are cater-
ing to the following chart. After            Cross-Striped Cabbageworm.                  pillars that rest beneath the soil
field scouting is conducted, add the     The cross-striped cabbageworm                    during the day and feed at night,
total number of each of the worm        (Figure 7) is easy to identify by the            causing damage to stems and fo-
species found on all the plant sam-     black and white transverse stripes               liage. They are dark gray-brown in
ples, and fill in column 2 of Table 2    down the back. It is controlled with             color with a greasy appearance,
below.                                  Bt and other insecticides recom-                 and they often curl into a C shape
     If the average number of larval    mended for caterpillar control in                at rest or when disturbed (Figure
units exceeds the thresholds in         cole crops.                                      9). Cutworm larvae overwinter in
Table 3, treatment is warranted. If          Beet Armyworm. Beet army-                   fields and therefore may be present
the number is below the specified        worms may infest fall plantings of               at the time of planting, particularly
thresholds, treatment is not needed.    cabbage and other cole crops. They               in fields with high organic matter
If numbers are just below or at         may move into cole crops in large                from previous crop residue. Cut-
threshold, repeat sampling during       numbers as other crops die or are                worms can be detected when land
the next 48 hours to determine if       harvested, so it is important to moni-           is prepared for planting, and a pre-
larval unit numbers are increasing      tor late summer/fall plantings care-             planting or at-planting soil insecti-
(treatment is needed) or decreasing     fully and to apply insecticides when             cide can be applied if necessary. If
(treatment not needed).                 infestations are first detected. The              cutworm damage is observed after
     Cabbage Webworm. Cabbage           moths lay egg masses on the under-               planting, insecticide sprays directed
webworm larvae are 3⁄ 4 inch long       sides of leaves and cover the eggs               to the base of the plants may
when mature and gray in color           with white, fuzzy scales. The larvae             achieve some control.

                                                                               Guide to Commercial Cabbage Production                7
     Seed and Root Maggots. These       ance. Like aphids, whitefly adults        reductions in young plantings, par-
are the immature, or maggot, stages     and nymphs suck plant sap with           ticularly in early fall and spring
of flies that are attracted to decay-    piercing-sucking mouthparts, and         plantings. Treatment is recommend-
ing organic matter (Figure 10). The     they produce sticky honeydew on          ed if more than 5 percent of the
maggots feed on young roots and         leaves where they are feeding.           stand exhibits damage.
stems and may severely reduce           Black sooty mold often grows on
plant stands. Damage usually oc-        the excreted honeydew. Insecti-          Controlling Diseases
curs during cool, wet spring condi-     cides are not highly effective
                                                                                     There are a number of plant
tions when plants grow slowly. The      against whiteflies, so prevention is
                                                                                 diseases that can limit cabbage pro-
best approach to preventing mag-        the best approach. Make sure that
                                                                                 duction in Alabama, including
got damage is to plant seed or          transplants are free of whiteflies,
                                                                                 black rot, black leg, Alternaria leaf
transplants when weather condi-         and plant fields as far as possible
                                                                                 spot, wirestem, and downy mildew.
tions are favorable for rapid plant     from other whitefly-infested crops.
growth. Planting when conditions        Destroy weeds and previous crop
                                                                                 Black Rot
are cool and wet increases the risk     residues that may harbor whitefly
of maggot damage.                       populations.                                  Black rot, caused by the bac-
                                                                                 terium Xanthomonas campestris, is
     Aphids. Several aphid species,          Harlequin Bug. This insect is
                                                                                 a problem on cole crops worldwide.
including cabbage aphids (Figure        closely related to the common stink
                                                                                 Black rot is considered to be the
11), may infest cole crops. Cool, dry   bug. It is a brightly colored, shield-
                                                                                 most important disease affecting
weather is most favorable for aphid     shaped bug with red and black
                                                                                 cabbage production in Alabama and
development. Aphids do not usually      markings and piercing-sucking
                                                                                 the Southeast. It is not uncommon
infest seedlings but may build up       mouthparts (Figure 12). It feeds in
                                                                                 to lose an entire crop to black rot.
after thinning or transplanting have    the veins of leaves, causing leaves
been done. Large numbers of             to wilt. Harlequin bug eggs are bar-
aphids may kill small plants, and       rel-shaped and laid in clusters on
their feeding can distort leaves of     leaves. The eggs are white, and               Seedling infection first appears
older plants, causing leaf curl.        each has two black bands around          as a blackening along the margins
                                        the circumference. Treatment             of the cotyledons. Cotyledons shriv-
     Often, the most serious prob-
                                        thresholds developed in Georgia          el and drop off. Infected seedlings
lem associated with aphids is cont-
                                        recommend treatment if one bug           are often stunted and yellowed and
amination. Aphid colonies in the
                                        per ten plants is found.                 may eventually wilt and die. Seed-
heads of cabbage, broccoli, and
                                                                                 ling infection can be difficult to di-
cauliflower are almost impossible             Flea Beetle. Flea beetles are
                                                                                 agnose since only a few plants in a
to remove before marketing.             most common in the spring and in
                                                                                 lot may be infected.
Natural enemies can provide con-        fields that are weedy or are sur-
trol of aphids, but they usually do     rounded by weeds. The adults are              On older plants, the disease is
not build up fast enough to keep        small, dark-colored beetles with en-     easily recognized by the presence
heavy aphid populations below           larged hind legs that enable them        of yellow V-shaped or U-shaped
damaging levels. Use of broad-          to jump great distances (Figure 13).     areas extending inward from the
spectrum insecticides like              They feed on the undersides of           margins of the leaves (Figures 15
pyrethroids can increase aphid          leaves, causing numerous small,          and 16). As the disease progresses,
numbers by eliminating natural en-      round, or irregular holes often re-      the yellow lesions turn brown and
emies; therefore, these insecticides    ferred to as “shot-hole damage.”         the tissue dies (Figure 17). Veins
should be used sparingly early in       Flea beetles are of most concern         darken and the midrib of leaves
the season and only when neces-         during the seedling stage and do         turns black within the affected leaf
sary to control other insect pests.     not usually cause economic dam-          area. This vein discoloration pro-
                                        age to mature plants.                    gresses toward the base of the leaf.
     Sweetpotato or Silverleaf
                                                                                 Eventually, the bacteria spread into
Whitefly. Adults are tiny, winged             Vegetable Weevil. The vegetable
                                                                                 the main stem. When infected
insects about 1⁄ 16 inch long with      weevil adult is 1⁄ 4 to 3⁄ 8 inch long
                                                                                 stems are cut in cross-section, a
white bodies and yellow heads.          with a stout snout (Figure 14). It is
                                                                                 black vascular ring may be evident
Although small, they are easy to        brownish gray with two light-col-
                                                                                 where bacteria have moved into
detect on the undersides of leaves      ored marks on the wing covers.
                                                                                 the water-conducting vessels. This
or when they fly off plants when         Larvae are legless grubs. Adults
                                                                                 vascular discoloration extends from
disturbed. They lay eggs on the un-     and larvae feed on the foliage and
                                                                                 the stem to the upper leaves and
dersides of the leaves where the        stems of plants and cause the most
                                                                                 down into the roots. In later stages
immobile nymphs develop. The            damage when feeding on seed-
                                                                                 of the disease, all central tissues of
nymphs are scalelike in appear-         lings, causing significant stand
                                                                                 the main stem turn black. This

8 Alabama Cooperative Extension System
symptom can be confused with             through natural openings or              winter. A copper-containing prod-
Fusarium yellows disease; however,       wounds. From the infected leaves,        uct such as Kocide will reduce
discoloration caused by Fusarium is      the bacteria move through the            damage from black rot. Begin ap-
dark brown rather than black.            water-conducting vessels to the          plying the material when weather
     Cabbage heads infected with         main stem, down into the roots,          conditions favor disease develop-
black rot often do not reach full        and up into the leaves. Plant-to-        ment. Apply the material at 7- to
size, and their lower leaves fall off.   plant infection in the field occurs       10-day intervals. Be aware that cop-
Frequently, symptoms are more            through the hydathodes at leaf mar-      per-containing products may cause
severe on one side of the head.          gins. Bacteria can also enter            plant injury.
Diseased plants may rot quickly be-      through insect feeding wounds.
fore or after harvest, owing to sec-     “Clipping” of oversized transplants      Black Leg
ondary, soft-rotting bacteria. Soft-     with rotary or flail mowers also               Black leg, caused by the fungus
rotting bacteria commonly invade         promotes spread of the disease if        Phoma lingam, can cause serious
heads of black-rot-infected plants       the bacterium is present. Root in-       losses in cabbage production. Black
and turn them into slimy, foul-          fections can occur through wounds        leg and black rot are the two most
smelling masses of tissue (Figure        and are most common when infest-         serious diseases of cabbage.
18). Late infections from black rot      ed soil is saturated with water.
may simply result in leaf spots or            The disease develops best           Symptoms
smaller heads.                           under warm, wet conditions.                   Symptoms of black leg are usu-
     Black rot is usually most severe    Growth of the bacterium is favored       ally first seen in the field as an
in low, wet areas of fields or along      by temperatures of 80°F to 86°F.         oval, sunken, light brown canker,
windbreaks where plants remain           Free moisture in the form of rain,       often with a black or purple margin
wet for long periods of time. Black      dew, or fog is required for infection    near the base of the stem. The
rot can also be seen moving down         to occur and for the disease to          canker enlarges until the stem is
rows as the bacterium is spread          develop.                                 girdled and the plant wilts and dies.
during cultivation. However, distrib-                                             Foliar symptoms first appear as
ution of the disease often is quite      Control                                  pale, irregular-shaped spots on
uniform across production fields.              Purchase and plant certified,        leaves. These spots gradually en-
                                         disease-free transplants only.           large, becoming circular with gray
Transmission and Persistence             Always examine plants thoroughly         centers. Small, black, pepperlike
     The black rot bacterium can be      before purchasing them. Plants that      spots (pycnidia) can be seen within
carried over from year to year in or     are discolored, have visible lesions,    the leaf spots. These are the spore-
on the seeds of infected cole crop       or appear unhealthy should not be        producing structures of the fungus,
host plants, on overwintering cru-       purchased. Grow plants in fields          which can also be seen within stem
ciferous weeds, or in partially de-      that have not held cole crops for at     cankers. Severely infected plants
cayed, infected plant material in the    least 3 years. Rotate with plants        are stunted. Infected plants eventu-
soil. The bacterium can persist in       from other plant families that are       ally wilt and then turn a dull blue-
plant residue for 1 to 2 years or as     not hosts of the disease. Plant only     red color. With black leg, it is not
long as the plant debris remains in-     in areas that provide good soil          uncommon for plants to suddenly
tact. Black rot is spread on seed        drainage and free air movement.          fall over due to the deterioration of
and seedlings, by movement of            Provide a balanced soil fertility pro-   the stem (Figure 19).
contaminated plant material, in irri-    gram based on recent soil test in-
gation water or splashing rain, by       formation. Control all cruciferous       Transmission and Persistence
insects, by cultivation equipment,       weeds in and around the produc-               The fungus can survive in
and by field workers. The organism        tion field. To avoid spreading the        plant residue for 2 to 3 years. It
can also survive on numerous             disease, do not work in fields when       can also be carried on seed. Plants
weed hosts in the mustard family,        plants are wet. Control cabbage          are often infected in the seedbed,
including black mustard, field            root maggots, cutworms, cabbage-         where splashing water spreads the
mustard, wild turnip, wild radish,       worms, and other insects, using          spores of the fungus from one
shepherdspurse, and Virginia pep-        recommended control practices.           plant to another. Secondary
perweed.                                 When possible, clean up and burn         spread of the disease may occur
     In the spring when seedlings        or cleanly plow down all crop de-        during the transplanting/pulling
emerge, bacteria are typically car-      bris immediately after harvest.          operation. The fungus can also be
ried from diseased plant refuse to       Removing plant residue from the          spread by splashing rain, by work-
leaf edges by splashing rain.            field surface will greatly reduce the     ers, and on equipment in the
Bacteria invade young leaves             bacterium’s ability to survive the       field. The disease is more severe
                                                                                  under wet conditions.

                                                                           Guide to Commercial Cabbage Production    9
Control                                  Control                                 Downy Mildew
    Purchase only transplants certi-          Never grow cabbage in a field           Downy mildew is caused by
fied to be free of black leg. Never       where a cole crop was grown in          the fungus Peronospora parasitica.
grow cabbage in a field where a           the past 3 years. Remove plant de-      The disease can enter a field on in-
cole crop was grown in the past 3        bris following a season when the        fected transplants or wind-blown
years. Remove plant debris follow-       disease was present. Plant disease-     spores. Plants can be infected any-
ing a season when the disease was        free transplants. Begin a fungicide     time during the growing season.
present. Fungicide seed treatments       spray program at the first sign of
and soil fumigation or solarization      the disease, and continue at 7- to      Symptoms
have been shown to be effective in       10-day intervals with a protective-         In moist weather, a white,
controlling black leg.                   type fungicide (fungicides with the     fluffy, fungal growth develops
                                         active ingredient chlorothalonil        mostly on the undersides of infect-
Alternaria Leaf Spot                     [Bravo] or maneb [Manex, Maneb          ed leaves. With time, yellow to tan
    Alternaria leaf spot is caused by    80]).                                   spots develop on the correspond-
the fungus Alternaria brassicae.                                                 ing upper leaf surface. Infected
The disease can cause severe dam-        Wirestem                                leaves on young plants may drop,
age to cabbage if left uncontrolled.          Wirestem, caused by the fun-       and plants may die. Infected leaves
                                         gus Rhizoctonia solani, can be a        on older plants usually remain at-
Symptoms                                 problem in transplant beds as well      tached. On older leaves, the infect-
    The initial symptoms are small,      as in the field. Early, fall-planted     ed areas turn tan in color and pa-
circular, dark spots on the surfaces     cabbage is more vulnerable to the       pery in texture. A mass of gray
of older leaves. As the spots en-        disease.                                spores can be seen on the under-
large, concentric rings develop                                                  sides of infected leaves. Downy
within the lesions (Figure 20). A le-    Symptoms                                mildew can predispose infected
sion is often surrounded by a yel-            Plants infected with wirestem      plants to bacterial soft rot.
low halo. The tan-colored centers        often have a reddish-brown discol-
of spots may eventually drop out,        oration to their stem near the soil     Transmission and Persistence
producing a shot-hole appearance,        line; the discolored area often ap-          The fungus overwinters on
or under wet conditions may be-          pears severely constricted. Plants      seed, in cruciferous weeds, and
come covered with a black mass of        may be bent or twisted at this point    possibly in the soil. Heavy fogs,
fungal spores (Figure 21). If left un-   but do not break, hence the name        light rains, prolonged dews, and
controlled, the disease can defoliate    “wirestem.” Affected plants that sur-   night temperatures between 46°F
a plant. In storage, spots enlarge       vive are weak and produce small         and 61°F with day temperatures
and soft-rotting bacteria may enter      heads.                                  below 75°F greatly favor this path-
through these lesions.                                                           ogen. Spores of the fungus float
                                         Transmission and Persistence            long distances in cool, moist air.
Transmission and Persistence                  The fungus is present in all
    The disease can overwinter on        soils but is more common in soil        Control
crop debris. Cruciferous weeds may       with infected plant debris that has          Eradicate cruciferous weeds to
also harbor the fungus. Spores of        not decomposed. Prolonged, overly       eliminate potential overwintering
Alternaria can be spread by wind         moist soil favors development of        disease inoculum. Do not use over-
and in water. The disease is most        the disease. The amount of wire-        head irrigation. The fungicides
damaging under wet, warm condi-          stem is greatly influenced by the        Alliette, Aliette/Maneb 2+2, and
tions (68°F to 81°F).                    recent cropping history.                Ridomil/Bravo 81 are labeled for
                                                                                 use on cabbage for control of
                                         Control                                 downy mildew.
                                              Never grow cabbage in a field
                                         where a cole crop was grown in
                                         the past 3 years. Remove plant de-
                                         bris following a season when the
                                         disease was present. Soil fumiga-
                                         tion and careful watering may re-
                                         duce damage from this disease.
                                         The fungicide Terraclor can be
                                         used in the transplant water for
                                         control of wirestem.

10 Alabama Cooperative Extension System
Figure 15. Close-up of lesions on
cabbage leaves caused by black rot.
Note the V- or U-shaped areas ex-       Figure 17. Close-up of cabbage leaf      Figure 20. Lesion caused by
tending inward from the leaf margins.   with characteristic symptoms of black    Alternaria leaf spot. Note the en-
                                        rot. Lesions have turned brown, and      larged, concentric rings that develop
                                        tissue has begun to die.                 within the lesions.

                                        Figure 18. Area of cabbage field in-      Figure 21. Black mass of fungal
                                        fected with black rot where soft-rot-    spores on lesion produced by
                                        ting bacteria have invaded the heads     Alternaria leaf spot

Figure 16. Production field with cab-
bage infected by black rot

                                        Figure 19. Root and stem tissue dam-
                                        age and deterioration caused by black
                                        leg infection

                                                                         Guide to Commercial Cabbage Production      11
Harvesting and                                     When harvesting, cut stems                                   Acknowledgement: Some of
                                              close to the ground near the base                             the information on insect pest biol-
Storing Cabbage                               of the head. Be sure that heads are                           ogy and treatment thresholds was
     Yields will vary with the season         well formed and firm (see Figure                               developed by the New York State
of production, variety, and produc-           1). Typically, outer wrapper leaves                           IPM Program and the Georgia
tion system used. With proper man-            are removed. Once cut, remove                                 Cooperative Extension Service and
agement, cabbage can produce 10               cabbage from direct sunlight be-                              used with permission. We sincerely
to 12 tons per acre (400 to 500 50-           cause cabbage wilts quickly when                              thank Dr. David Adams, Georgia
pound crates or bags). Growers in             exposed to sunlight. Wilting results                          Cooperative Extension Service, for
Alabama have produced upwards                 from a loss of water from the head.                           permission to use some insect im-
of 16 to 20 tons per acre. Generally,         Cool cabbage to 40°F before ship-                             ages originally published in
most markets prefer heads that av-            ping it. This will increase shelf life                        Georgia Cooperative Extension
erage 2 to 21⁄2 pounds. Some vari-            and reduce the development of rot                             Service Bulletin 1067, Leafy Greens
eties of cabbage mature uniformly,            diseases. In cold storage, cabbage                            and Cabbage Production.
requiring one to two harvests.                can be stored at 32°F with 98 to
Others can require three or more              100 percent relative humidity for 5
pickings to complete harvesting.              to 6 months.

                                J.M. Kemble, Extension Horticulturist, Assistant Professor, Horticulture, G.W. Zehnder, Extension
                                Entomologist, Professor, Entomology, E.J. Sikora, Extension Plant Pathologist, Associate Professor,
                                Plant Pathology, and M.G. Patterson, Extension Weed Specialist, Professor, Agronomy and Soils, all
                                at Auburn University
                                Use pesticides only according to the directions on the label. Follow all directions, precautions, and restrictions that are list-
                                ed. Do not use pesticides on plants that are not listed on the label.

                                The pesticide rates in this publication are recommended only if they are registered with the Environmental Protection
                                Agency and the Alabama Department of Agriculture and Industries. If a registration is changed or cancelled, the rate listed
                                here is no longer recommended. Before you apply any pesticide, check with your county Extension agent for the latest in-

                                Trade names are used only to give specific information. The Alabama Cooperative Extension System does not endorse or
                                guarantee any product and does not recommend one product instead of another that might be similar.

                                For more information, call your county Extension office. Look in your telephone directory under your county’s name to
                                find the number.

                                Issued in furtherance of Cooperative Extension work in agriculture and home economics, Acts of May 8 and June 30, 1914, and
                                other related acts, in cooperation with the U.S. Department of Agriculture. The Alabama Cooperative Extension System
                                (Alabama A&M University and Auburn University) offers educational programs, materials, and equal opportunity employment
                                to all people without regard to race, color, national origin, religion, sex, age, veteran status, or disability.
            ANR-1135                                                                                                        CP, 3M76, New July 1999, ANR-1135

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