Agriculture Reference
In-Depth Information
When flowers have been well pollinated, seedpods grow to be fairly long and the outlines of seeds are clearly visible.
DISEASES AND PESTS
Cole crops are subject to a large number of diseases and pests. There are two
phases of the reproductive cycle that are critical. First is overwintering, where numerous fungal infec-
tions can occur. The second is during flowering: in areas where oilseed rape (including canola) is
grown, rapeseed pests thrive. Rapeseed is often just finishing up with flowering when cole crops being
grown for seed are beginning to flower, which is a welcome treat for these pests. They include pollen
beetles (
Meligethes aeneus
), the rape stem weevil (
Ceutorhynchus quadridens
), the brassica pod midge
(
Dasineura brassicae
), and the green peach aphid (
Myzus persicae
), to name but the most prevalent.
Growing cabbage for seed in areas where oilseed rape is not grown is no problem at all; but at Arche
Noah, oilseed rape is grown in the surrounding areas, and it is no longer possible to grow cabbage for
seed without isolation cages to keep pests out. These sucking and biting insects also lay eggs in the
pods of brassicas and easily ruin an entire seed crop. Insect netting has been the only effective organic
measure, though this sort of mechanical isolation requires the introduction of pollinator insects. Leaf
beetles (
Phyllotreta
spp.) like to attack fresh seedlings or freshly planted plants and can cause great
damage. These beetles are capable of jumping like fleas. They overwinter in the soil and immediately
attack brassica plant-outs. Prevention: cover plants immediately after planting with leaf beetle-proof
netting. Weed and water frequently when leaf beetles appear.
Phoma lingam
is the cause of the seed-borne blackleg disease. This kills young plants but can also
affect older plants. A head of cabbage carrying this disease can cause all other plants to rot in storage.
This fungus causes black spots on stalks that quickly spread to other plants and can affect seed yield.
The disease can live on and inside seeds. The disease spreads quickly during propagation by seed,
meaning a small amount of infected seed can lead to a large amount of infected plants. Prevention:
crop rotation, wide planting distances of second-year plants, disinfecting root cellar, hot water treat-
ment (30 minutes at exactly 122°F [50°C]). With the same hot water treatment, the pathogen causing
brassica dark leaf spot (
Alternaria brassicicola
) can also be mitigated. Symptoms: spots on the leaves
of seedlings, black spots on shoots.
CULTIVATION HISTORY
Cole crops are among the few to have originated in Europe. Wild cabbage is
a relatively inconspicuous plant that grows on rocks and beaches; it is mainly found in the Mediter-
ranean region, but also on the Atlantic coasts of England, Spain, France, and northern Germany. It is
perennial and can live to be five to eight years old. Wild cabbage originally appeared in several differ-
ent isolated locations, which, through spontaneous mutations and selection by humans, led to varied
crop forms such as heading cabbage and the swollen-stemmed kohlrabi.
CABBAGE
Brassica oleracea
convar.
capitata
var.
capitata
