Today discuss this article how to control onion pest and disease with there management method. The onion pest disease management is given below-
Onion pest disease management
Onion pest management
There thrips are minute insects with fringed wings. The adults are slender, yellow, active and pointed at both the ends. The insects lacerate the tissues and suck sap from tender leaves and stems. The infected plants produce spotted appearance on the leaves which turn into pale white blotches. In case of serious infection the tips of leaves become blasted and distorted and later on whole plants turn brown or yellow, wither and fall over the ground. Bulbs become distorted and remain undersized. The thrips also transmit the spotted wilt virus of tobacco and tomato.
Spray 625 ml of malathion 50EC in 200 litres of water/ha as soon as the pest appears. A waiting period of 7days should be observed before harvest.
Onion maggot( onion pest disease management)
The adults are slender, grayish bodied large winged flies with bristles. They measure about 6mm long. The maggots are small, white and devoid of legs. The maggots crawl down the plants, mostly behind the leaf sheaths and enter into the bulbs through roots and attack the tender portions. Infested plants turn brown and finally dry up. The infected bulbs rot in storage due to attack of other secondary infections.
i) Spray malathion 50EC @2ml/litre of water and repeat at 5-6 days interval
ii) Apply 10kg of carbaryl 4G or lindane 6G or phorate 10G granules to the soil followed by light irrigation per hectare.
Seedlings raised from the infected seeds fail to emerge and are killed. Those which escape, remain stunted, pale or abnormally white and twisted. The leaves may be thickened. The swollen areas often show splitting of the epidermis. When infested bulbs are planted, the new leaves show yellowish specks and remain stunted. The cracks appear in the bulbs which predispose the bulb for the secondary infection by the fungi and bacteria. On older onion bulbs the attack appears as a planting material through seeds and bulbs.
i) Follow long rotation
ii) Use certified seeds
iii) In case of areas of severe infection disinfect the soil with DD or Telone.
This article is onion pest disease management
Onion disease management
Large number of white specks are seen on the leaves. The fungi produce toxic substances which kill the cells of the leaves. The disease spreads very rapidly in presence of thrips infestation and the tops of entire crop may be killed.
Spray captan or ziram or Dithane M-45 @ 2g/litre of water with the appearance of the disease.
Downy mildew (onion pest disease management)
Oval to cylinder spots of paler than normal green colour are formed on the leaves. The sports may contain alternating green and carotid zones. White to purplish downy growth develops on these spots during humid weather. In case of infection and pale green. Downy growth of fungus develops over the entire leaf surface in humid weather. The fungus perpetuates through the disease bulbs.
i) Procure bulbs for propagation from healthy fields.
ii) Chemical control measure are same as in case of purple blotch.
Typical elongated dark, slightly thickened areas develop on the cotyledons of young seedlings. The black lesions appear near the base of the scales on planting. The affected leaves bend downward abnormally. On older plants readily visible streaks show within the tissues of the leaves, leaf sheaths and bulbs. These streaks crack open to expose black powdery masses of spores of the fungus. These streaks continue to develop throughout the life of the plant. The affected leaves bend downwards abnormally. The fungus overwinters in the form of chlamydospores.
i) Treat seeds with Thiram or Captan @ 2.5g/kg of seed.
ii) Seed bed soil can be treated with methyl bromide @ 1 kg/25 m2
The disease appears at the time of maturity of the crop. The roots turn pink. The pink colour then darkens to red, purple and finally brown or black. The pink roots rapidly turn brown, shrivel and die. New shoots that develop subsequently are also attacked and killed. In case of severe infection the tops turn white, yellow or brown and finally die. The fungus perennation in the soil on the crop refuse and spreads and spreads by means of bulbs and seedlings.
i) Do not grow seedlings in the infested soils.
ii) Do not cultivate onion garlic or leek in the infested soils.
iii) In small fields soil disinfection can be done.
Basal rot (onion pest disease management)
The characteristic symptom is the wilting and rapid die back of leaves from tip as the plants approach maturity. The roots turn pinkish and most of them rot off within certain period of lime. The bulbs become soft and when cut semi watery decay is found advantage from the base of the scales upwards. The fungus survives in the soil.
i) Grow resistant cultivars like while large, poona large, patna –Red, N-257-7-1, Udaipur 103, etc.
ii) Follow a long rotation for 4-5 years with non-related crops.
The onion disease appears as small yellow to pale orange sports or streaks in the middle of leaves and flower stalks on one side. The symptoms are observed on the radical leaves of transplanted seedlings at 3-4 leaf stage.
i) Spray Dithane M-45 @ 2g/litre of water mixed with Sandovit or Triton @ 1ml/2 litre of solution.
ii) Black mold of onion bulbs
White rot of onion disease
The infected plants are stunted with yellow leaves. The base of the plant is rotten and often covered with a white fungi growth in which black sclerotia may be embedded. The fungus is soil borne and it perennation by means of sclerotia.
i) Treat seeds with Bavistin or Benlate @ 1g/kg of seed which may check the seed infection
ii) Treat bulbs with PCNB or Agrosan GN @ 6g/kg bulb.
Bacterial soft rot (onion pest disease management)
The rot begins at the neck of the bulb and later on it gives foul sulphurous smell through the neck when squeezed . Sour skin rot affects only some of the outer scale and is characterized by slimy and yellow appearance of affected scale which give off a vinegar like odour. Theoutside scale slips off readly during handling.
i) Proper curing and drying at harvest time should be done.
ii) Discard all the infected bulbs before storing.