1.Diamond back moth
The caterpillars are pale yellowish green while the adult is a small greyish moth. A patch of three diamond shaped yellowish white spots is visible by joining both the forewings, hence the name ‘diamond back’. Young larvae feed by scrapping leaf tissues causing typical whitish patches on under side of leaves. Grown up larvae bite holes in the leaves. Damage to the crop is more in the main and late winter season as compared to rainy season crop in the Northern region.
Causes maximum damage from July to November to rainy season crop. The adult moth is stout, brown coloured, with wavy white markings on the forewings. Eggs are laid on leaves in masses and are covered with brown hairs. Neonate larvae scrap the green matter in the leaf. Late instars feed voraciously on tender leaves and fresh growth. The larvae are blackish grey to dark green with dark longitudinal bands on the side of the body.
Moths are pale greyish-brown, suffused with reddish colour. The adult female lays eggs on the growing point or the older leaves. Pale whitish brown with longitudinal stripes caterpillars initially mine the leaves and make it a white papery structure filled with their excreta. Later these caterpillars bore into the stem, and multiple shoots are formed. As a result, infested plants are killed forming side shoots which don’t form heads. The entrance hole is covered with excreta.
Aphids are serious during February – March months. Aphids disappear due to good rain fall. As a result of sucking of vital sap from the tissues, plants remain stunted resulting in poor head formation. Aphids also produce honey dew which makes the plant sticky and favours the growth of sooty mold with black coating thus hindering the photosynthesis and plant growth.
1.Damping-off and wire stem
Damage results from the reduced plant stand and sometimes it is so serious that resowing becomes inevitable. Major symptoms are the failure of the seedlings to emerge as a result of seed or seedling decay or sudden death of the emerged seedlings. In wire stem, light to dark brown areas appears on the stem extending 1-2 cm below the soil line. Affected region is relatively thinner than the stems of the healthy plants.
Downy mildew is a serious problem in cauliflower, cabbage and broccoli during cool, moist weather which favour sporulation, dissemination and infection. In the nursery, the disease appears as irregular yellow patches on leaves with white fungal growth on the underside of the lesions. Severe infection leads to the death of seedlings. On mature cabbage, downy mildew appears as dark sunken spots on the head or wrapper leaves resulting in purplish tinge.
3.Alternaria leaf spot
They cause serious damage at all stages causing a heavy loss in yield and seed quality. On seedlings, minute dark spots appear on the cotyledons and seedling stem, causing severe damping off or stunting of young plants. In older plants, all above ground parts are attacked. The bottom leaves are infected first where circular brown spots with characteristic concentric rings (target spots) are seen. Infected leaves soon turn yellow and drop. Disease gets enhanced in a warm, humid weather with a temperature between 25 to 30oC.
4.Bacterial black rot
This disease is more severe in cauliflower than cabbage. Plants can be infected during any crop stage. Seedlings drop lower leaves and may die. In grown up plants, infection occurs at margins. Infected tissue turns yellow, and the chlorosis advances towards the centre of the leaf forming a wilted ‘V’ shape notch. Severely infected leaves may drop off. The head formation gets affected, and heads of infected plants remain small, and its quality is reduced. Head may rot if the disease occurs late.
Validated Integrated Pest Management strategies for Cabbage / Cauliflower
- Prepare raised nursery beds about 10 cm above ground level for good drainage to avoid damping off etc.
- Follow soil solarization for 2-3 weeks using 0.45 mm thick polythene sheet. Sufficient moisture should be present in the soil for solarisation.
- Treat the soil with neem cake at 50 g / m2 impregnated with 10-15 g effective strain of Trichoderma.
- Seed treatment with an effective strain of Trichoderma @ 4 g / kg seed to manage rots. Seedling dip for 30 min with Trichoderma viride 1 % WP @ 10 g / lit water to manage collar rot in cabbage can also be followed.
- Need based soil drenching with captan 75 WP @ 0.25 % or captan 75 WS @ 0.3 % to manage damping off.
- Seed treatment with imidacloprid 70 WS with 5 g / kg for management of painted bug in rainy season and aphids in late rabi season.
- Spray Bacillus thuringiensis kurstaki 5 WP (Bt) @ 3 g / litre if DBM is present @ 1 larva / leaf (South India).
- Spray NSKE 5% or carbaryl 50 WP @ 0.3 % for management of H. undallis which appears in rainy season nursery sometimes.
- Adopt wide spacing of 60 x 50 cm to reduce the spread of diseases.
- Growing of Indian mustard as trap crop after every 25 rows of cabbage. (One row of mustard is sown 15 days before cabbage planting and second 25 days after planting of cabbage). First and the last row should be of mustard.
- Mustard traps 80-90% of diamond back moth (DBM) population and other pests like aphids. Mustard is sprayed with dimethoate 30 EC @ 660 ml in 500-1000 lit or dichlorvos 76 EC / ha @ 627 ml water. Spray fenvalerate 5 % EC @ 300 ml / ha in 600 lit water to manage DBM in trap crop mustard.
- Spraying of B. thuringiensis var.kurstaki 5 WP @ @ 50 g a.i./ ha or 3 gm / litre at 10 DAP for DBM
- Installation of light traps / bulb @ 3 / acre for DBM. Adults are attracted to light trap and fall in the water bucket. Within 3-4 days most of the adults get killed.
- Release egg parasitoid Trichogrammatoidea bactrae at 1.0 lakh/ha 3-4 times at weekly interval (optional).
- Spray mancozeb 75 WP or zineb 75 WP @ 1.5-2 kg / ha in 750-1000 lit water to manage leaf spot.
- Removal of basal and infected leaves to reduce Alternaria leaf spot and bacterial black rot of early stage.
- Spray NSKE 5% or carbaryl 50 WP @ 1600 g or malathion 50 EC @ 1500 ml / ha in 1000 lit water for stem / head borer.
- Spray NSKE 5% at primordia formation (18-25 DAP-head initiation stage – most critical stage) for DBM control. Repeat, if DBM is >1 / plant at 10-15 days interval. Maximum of 3-4 NSKE sprays in one crop season is required. When NSKE are sprayed, thorough coverage of the entire plant surface is a must. Use sticker with spray. This will control aphids as well as tobacco caterpillar. 40 kg/ha of NSKE powder is required.
- Need based spray of cypermethrin 10 EC @ 650 -760 ml in 100-400 lit water, or spinosad 2.5 SC @ 600 ml or emmamectin benzoate 5 SG @ 150-200 g or chlorantraniliprole 18.5 SC @ 50 ml / ha in 500 lit water or novaluron 10 EC @ 750 ml or indoxacarb 15.8 SC @ 266 ml / ha in 500-1000 lit water for DBM control.
- Spray acetamiprid 20 SP @ 75 g ha in 500-600 lit water or dimethoate 30 EC @ 660 ml ha in 500-1000 lit water for aphids in late cauliflower.
- Installation of yellow sticky traps for trapping winged aphids
- Collection of egg masses and larvae of tobacco caterpillar as they are gregarious. Scout for papery patches & apply baits.
- Set up sex pheromone traps @ 5 / ha for mass trapping and to monitor the activity of adult
- Spray SlNPV @ 250 LE / ha (2×109 POB) 2-3 times in evening with jiggery 2% when larvae are young.
- Need-based spray of cyantraniliprole 10.26 OD @ 600 g or trichlorfon 50 EC @ 1.5 kg / ha in appr. 500 lit water for tobacco caterpillar
- Need based spray of dimethoate 30 EC @ 660 ml/ha in 500-1000 lit water for the control of painted bug.
- National Research Centre for Integrated Pest Management.