Symptoms : Thrips are the most important insect pests on onions. Adults are yellowish to yellowish brown with narrow wings. Eggs are laid in clusters in leaf tissues. Numerous nymphs and adults are observed etween leaf sheaths and stems lacerating the epidermis of leaves and sucking the exuding cell sap. The affected leaves show silvery blotches which later turn into brownish colour. The leaves get distorted from tips downwards and plant ultimately wilt and dry away. Seedlings are killed due to heavy infestation and the plant growth is retarded. The shape and size of bulbs as well as yield is affected by thrips.
Apply neemc ake 250 kg/ha at 20-30 DAP
Spray NSPE 4% or neem soap 1% or acepate ( 1 g/l) or pipronil ( 1 ml/l) or lamda cyahlothrin ( 1 ml/l).
Regular irrigation also helps in minimizing losses due to thrips.
Collection and destruction of egg masses and gregarious caterpillar of the cut worm is the best method. For this regular scouting has to be done for the egg clumps and gregarious damage symptoms For controlling the grown up caterpillars, baiting with jaggery mixed rice bran has to be done.
Onion Head borer
Symptoms :The head borer is a serious pest of onion seed crop in Northern India. The larva of this insect cuts the pedicel of the flower and feeds on the stalk. Single larva damages many flower stalks. The fully-grown larva is greenish with dark brown grey lines along the side of body and measures about 35-45 mm in length.
Control: Spraying Endosulfan (2-3 ml/litre of water) along with sticker (Triton/ Sandovit) is recommended to control the insect.
Symptoms : The larvae of this insect are seen in nursery beds and newly transplanted onion fields. The tender plants are found damped at ground level during the night Young larvae feed gregariously on foliage but later segregate and enter into soil. Young larvae are yellowish grey and later on become brown, greasy to touch and coil when disturbed. They cut the seedlings at ground level during night and hide during day.
Control: Soil application of Carbofuran (1kg a.i./ha) at the time of planting is recommended. Chlorpyriphos (5ml/litre of water) also gives good control of this pest.
Symptoms : The adults of die insect appear like housefly. The flies lay their eggs on old leaves or on soil and larva enters into soil and damage disc portion of onion bulb. Infested plants turn yellowish brown and finally dry up. The affected bulbs rot in storage.
Control: Regular crop rotation should be followed and Thimet should be applied in the soil before transplanting.
Nematodes in Onion
Root knot Infected root of onion
The root-knot nematode Meloidogyne incognita is one of the major nematode pests in onion. Severe infestation causes reduction in onion bulb weight of 70%. Stunting and galling of roots or thickening of roots are the symptoms of onions heavily infected with nematodes. Delayed maturity of bulbs with thicker necks and smaller bulbs are some of the other symptoms. The nematode is particularly devastating in the seedling stage and amounts to huge loss at the seedling stage alone. Various incidences of the root-knot nematode in onion have been reported all over the world.
Pre-coat seeds with biopesticide before sowing.
• Add biopesticide Pseudomonas fluorescens at 20 ml/kg or 20 g/kg seed.
Preparation for raising seedlings.
• For substrate (propagating mixture) used in portrays/polybags mix biopesticide Pseudomonas fluorescens at 2 g/kg of substrate (cocopeat/ potting mixture) and fill in portrays/polybags.
• For nursery beds drench with 3 lit of Pseudomonas fluorescens suspension / m2 (add 5ml or 5g of formulation / lit of water) before sowing seeds.
Preparation of main field before planting/ transplanting
• Enrichment of FYM with bio-pesticides: Mix two kg each of Paecilomyces lilacinus, Pseudomonas fluorescens and Trichoderma harzianum / T. viride in one ton of FYM and leave it in shade for 15 days at 25 – 30% moisture for multiplication of beneficial microbes.
• Soil has to be incorporated with 20 – 30 tons of FYM enriched with bio-pesticides before planting/ transplanting seedlings.
• Enrich neem cake with bio-pesticides: Mix two kg of each of Paecilomyces lilacinus, Pseudomonas fluorescens and Trichoderma harzianum / T. viride in one ton of neem cake and leave it in shade for 15 days at 25 – 30% moisture for multiplication of beneficial microbes.
• Apply neem cake enriched with biopesticides in standing crop at 50 g/ m2 once in a month.
• Mix 20 kg of enriched neem cake mixture in 200 lit water, leave it for two days and this can be used for drenching beds @ 2 lit/ m2 or filter it thoroughly and use it for spraying the foliage or sending along the drip, once in a month.
• Spray Arka Plant Growth Promoter and Yield Enhancer (Pseudomonas fluorescens + Trichoderma harzianum) at 5 ml or 5g/lit, once in a month.
Or send along the drip, Arka Plant Growth Promoter and Yield Enhancer (Pseudomonas fluorescens + Trichoderma harzianum) at 5 ml or 5g/lit, once in a month.