Transcript Presentation File

Diseases and Insect-pests
of cole crops
Diseases
Black leg (Phoma lingam)
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Occurs in areas with rainfall during the growing
period
Seed borne and hence occurs from the early
stage
Stem of affected plant when split vertically
shows severe black discolouration of sap
stream.
Whole root system decays from bottom
upwards. Often, the affected plants fall over in
the field
Control
 Hot water treatment
 Seed infection can be prevented by spraying the
seed crop with copper oxychloride or with an
organomercuric compound
 Pusa drum head- tolerant under field condition.
Downy mildew (Pernospora parasitica)
 Causes serious damage at all stages of
plant growth
 Discolouration occurs in the young
seedlings and in severe cases whole plant
perishes.
 In adult plants, purplish leaf spots or
yellow brown spots on the upper surface
of the leaf appear, while fluffy downy
fungus growth is found on the lower
surface.
 During bolting stage the seed stalk show
blackish patches and in severe cases
whole curd is spoiled.
Control
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Spray of redomil MZ 72 @ 0.5 g/lt of water at 1015 days interval or with Dithane M 45 @ 1.5-2.0
g/lt of water.
Chinese cabbage and kale are resistant to
downy mildew while others are susceptible.
Rhizocotonia (R. solani)
 Causes damping off, wire
stem, bottom rot, head rot
or crown rot
Control
 Use of resistant variety and
application of Brassicol @ 20-30
kg/ha
 2-4 foliar sprays of Dithane-M-45,
Difolatan 80 or Daconil (Kavach)
@ 1.5 – 2.0 g / lt at an interval of
15 days.
Black spot (Alternaria brassicicola & Alternaria brassicae)
 The seed crop is affected mostly.
 Young plants show soft , water soaked
spots on the skin just above the ground,
the cotyledons wither and plants
eventually fall over and perishes
(resembles Rhizoctonia solani)
 In older plants, small, brown to black,
circular to slightly elongated spots
appear on leaves, petioles and stems.
Sometimes, the spots join together.
 It causes damage to cabbage heads and
cauliflower curds after maturity and
during seed production.
 Mainly caused by A. brassicicola and
known as curd and inflorescence blight
or brown rot.
 Resistance was initially found in MGS-23, Puakea 246-4 etc.
Yellows (Fusarium oxysporum f. conglutinans)
 Foliage of affected plants turn yellow,
dies and eventually drops off, the
lowest being the first to show the
symptoms.
 Vascular tissues become yellow to dark
brown.
 Young seedlings may occasionally
show signs of damping off.
 Use of resistant cultivar which are of
two types
1. Type A: resistance control by single
dominant gene. All Head Early,
Copenhagen Market, Glory of
Enkhuizen.
2. Type B: inherited as a quantitative
character and is controlled by a
number of genes. Cabbage cv.
Wisconson Hollander.
3. Both A & B are found in Wisconson
All Season.
Club root (Plasmodiophora brassicae)
 A typical root parasite.
 Irregular galls on the roots
and lateral roots take the
shape of spindle.
 Leaves become yellowish
and wilt on hot days
 Prevalent in soils with a pH
below 7
 DD (1, 2 Dichloropropane
with 1,3-dichloropropene)
@ 5 l/ha followed by soil
covering with plastic film or
10 l/ha with or without
covering.
 Liming of soil at the
earliest.
Watery soft rot (Sclerotinia sclerotiorum)
 Causes considerable damage in the seed
crops of snowball in Himachal Pradesh.
 It is not yet a problem in plains.
 In seedling crop, the infection starts on
leaves, particularly on the base of petioles
and passes into the adjoining part of the
stem.
 Large grayish white, elliptical spots arise
sometimes involving the whole surface of
stem.
 At the point of attack, the seed stalks can
break, wither and eventually die.
 In seed crop, most commonly known as
Sclerotinia stalk rot.
 Damp weather favour the occurrence of this
disease.
Control
Spray of bavistin
Powdery mildew (Erysiphe polygoni)
Occurs occasionally and known to cause limited damage.
Control
Karathane spray
Damping off (Pythium debaryanum)
 Causes damping off of young
seedlings
 Fungus hibernates in the soil
 Affected seedling fall over and perish.
 The disease is promoted by high
humidity and high temperature
Control
Soil sterilization and seed treatment are effective in reducing the attack.
BACTERIAL DISEASES:
Black rot (Xanthomonas campestris)
 Destructive in warm and wet climate.
 Infection of foliage results in yellow V- shaped spots
arising along the margin which extend in the
direction of mid rib.
 These spots are associated with the typical black
discolouration of the veins.
 Infection extends through the xylem to the stalk and
the vascular bundles turn black.
 In severe infection, the whole leaf show
discolouration and eventually falls off.
 Plants raised from infected seed may die
prematurely.
Control
 Hot water treatment of seeds at 50 ± 2 0C for 30
minutes followed by 20 minute dip in 100 ppm
streptocycline.
 Antibiotics
like
Agrimycin
100
(0.01%),
streptocycline (0.01%) and Aureomycin etc are
also found to be effective.
Bacterial soft rot (Erwinia carotovora)
 A weak parasite which penetrates the plants
through damaged tissue e.g. lesions caused
by other pathogen.
 In the field, it occurs only following black rot
or after mechanical injury of nearly mature
cabbage head.
 Infection favours by high humidity
 Affected plants show a soft, slimy, bad
smelling rot which under favourable
conditions rapidly spreads throughout the
plant.
Control
 The disease can be kept down by
controlling other diseases and preventing
damages
 Spraying 100-200 ppm streptocycline or
plantomycin
combined
with
copperoxychloride (0.3%) at 15 days
interval.
Insect-pests of cole crops
CUTWORMS
Damages seedlings in the newly planted crop
Stems are chewed near the soil level during night.
Some cutworms climb the host and feed on
unopened buds. Many cutworms prefer wilted plant
material and sever the plants sometime prior to
feeding.
Control
• Use of well decomposed manure helps in
reducing the incidence.
• Collection and destruction of larvae after
flooding of fields/ beds.
• Soil drenching with chlorpyriphos (0.04%)
or spraying of cypermethrin (0.0075%) on
foliage and soil surface reduces the incidence.
CABBAGE APHID
Initially, damaged leaves show yellowing.
Aphids attack plants during the cool dry season.
Control
• Encourage the biological control agents like
parasitoid Diaeretiella rapae, coccinellid and
syrphid predators.
• Selective use of insecticides on head and
seed crops.
Head Crop:
Foliar application of malathion (0.05%) with
the appearance of the pest and repeating
every 15 days. But stop spraying atleast 7
days before harvesting.
Seed Crop:
Apply phorate granules @ 1.5 kg a.i./ha as
side dressing during mid February to early
March or spray methyl demeton (0.025%) or
dimethoate (0.03%) as soon as aphid
population is above 50 aphids per plant.
CABBAGE BUTTERFLY (Pieris brassicae)
 Damage is caused by caterpillars which when
young are pale-yellow but later change to
greenish-yellow and measures 30 mm in
length.
 The white winged butterflies deposits yellow
coloured eggs in clusters on the undersurface
of leaves.
 The caterpillars in the early stages scrap the
leaf surface and feed gregariously whereas
later instars eat up leaves from the margin
inward leaving the main vein intact.
 Mechanical
control: Collection and destruction of
yellow egg masses and early stage larvae of cabbage
butterfly.
 Biological Control:Cotesia glomeratus parasitizes the
larvae.
 Malathion
(0.05%)/
deltamethrin
(0.0028%)/
cypermethrin (0.0075%) and fenvalerate (0.01%) can
be used for effective suppression of caterpillar complex
of cabbage and cauliflower.
 Since, these crops may be infested at or near harvesting;
it will be wise to spray malathion (0.05%) to minimize the
danger of toxic residues in marketable produce.
DIAMONDBACK MOTH
It infests all types of Brassica crops.
Spindle shaped pale yellowish green caterpillars (8
mm when full-fed) in the earlier instars feed on the
lower side of leaves but later feed on the exposed
leaves and enter the head/ curd affecting the
produce as well as quality.
Control
 Trap
crop: Indian mustard is effective in suppressing the
incidence of diamondback moth and cabbage aphid. Growing
paired rows of mustard after every 25 rows of cabbage and
cauliflower each at 15 days prior and 25 days after cabbage
transplanting. This will ensure adequate mustard foliage
throughout the cropping period.
 Release of Trichogrammatoidea bectrae @ 0.5-0.75 lakh eggs
per ha at weekly intervals.
 Pheromone traps installation @5-6 traps/ha for monitoring of
population of DBM.
 Use of 2 to 5 % NSKE at head initiation stage.
 Malathion (0.05%), deltamethrin (0.028%), cypermethrin
(0.0075%) and fenvalerate (0.01%) can be used for effective
suppression of caterpillar complex.
Snails and slugs
 Damage the growing tips of plant and also
the surface of curd in cauliflower.
 They are problematic when crop is irrigated
with sewerage water.
Control
 Baiting with metaldehyde and bran (1: 25 in
12 l of water)
 As a repellant, alum may be sprayed @ 2%
solution.
DISORDERS
Disorder
Symptoms
Management
Riceyness
A premature initiation of floral buds
It can be controlled by
is characterised by riceyness in
cultivation of genetically
cauliflower and is considered to be of pure seed and appropriate
poor quality for marketing.
varietieswith
recommended
cultural
practices. Harvest while
the curd is still firm,
compact
Fuzziness
It appears as the flower pedicels of
Sowing good quality seed
velvety curds elongate. The anomaly in right season under
is both hereditary and non-hereditary. proper cultural practices
minimizes fuzziness
Leafiness
formation of small thin leaves from
the curds which reduce quality of
curd. Prevalence of high temperature
during curding phase aggravates
leafiness.
Controlled by selection of
varieties according to
their adaptability and
seasons
Disorder
Browning
Buttoning
Symptoms
Management
Water soaked areas in the stem and centre
Due to Boron deficiency
of the branches of the curds. Hollow stem
Spray of 20kg/ha of
is a typical features.
common Borax
Development of small button shape curds.
Optimum use of N
fertilizer
Blindness
Plants without terminal bud and large, dark
Avoid over wintering
green, thick leathery foliage
Whip tail
Severe reduction of lamina and leaf blade
Spray 1Kg of MO as a
leaving the large bare mid rib in acute
Sodium or Ammonium
condition.
Molybdate
Name of
Disorder
Chlorosis
Symptoms
Management
Chlorosis shows on intervenial and yellow Use
of
mottling of lower leaves. The affected containing
leaves turn bronze in colour and become magnesium,
stiff.
fertilizers
soluble
keeps
the
disorder under control.
Premature
Before the formation of heads or failure of Use resistant cultivars,
Seeding/Bolting
leaves to form a solid head. The possible avoid setting plants two
causes of bolting include- Early sowing of early into field and prevent
seeds, warm winter, extreme change in the stimulation of early
temperature, poor growth of seedlings and plant growth are some of
varietal characters.
the control measures.
Thanks…