Tuberose is a hardy crop and is not much affected by attacks of insect pests and diseases.
Pests of Tuberose
The important insects are thrips, aphids, bud borer, grass hoppers, weevils, nematodes, red spider mites, rodents, etc.
These are tiny insects, soft bodied, green, deep purple or black. These usually occur in clusters. They are found to feed on flower buds and young leaves
They can be controlled by a 0.1 % spray (1 ml/litre) of Malathion or Rogor at an interval of 15 days
Thrips feed on leaves, flower stalk, and flowers. The flowers get deformed by thrips attack. These suck the sap and damage the whole plant. Sometimes, these are associated with a contagious disease known as ‘bunchy top,’ where the inflorescence is malformed.
Thrips are controlled by the spray of Rogor or Metasystox @ 1.75 to 2.0 ml / litre or 0.1% (1 ml / litre) Malathion. Also, it is suggested to spray Nuvacron (0.1 %) or the application of Thimet to the soil.
These feed on young leaves and flower buds. Affected plants with damaged foliage and flowers lose their elegance, especially during rainy season.
Dusting the plants with 5% Cythione / Folidol dust may prevent the damage. Scraping of buds exposes
egg masses to natural enemies. Netting prevents damage from hoppers to nurseries. Spraying of Quinalphos @ 0.05% (0.5 ml / litre) or Malathion 0.1% or Carbaryl @ 0.2% protects foliage of newly planted crop.
4.Weevils (Myllocerus sp)
The weevils are nocturnal in habit, and they cause damage on shoots and leaves. Usually, they feed the edge of the leaves, producing a characteristic notched effect. Larvae feed on roots and tunnel into the bulbs.
Applying BHC dust (10%) in the soil before planting controls larvae. The weevils can be controlled by the spray of Thiodon @ 2.0 mg/litre
5.Red Spider Mites
Mites thrive well under hot and dry conditions, usually on the undersides of the leaves, where these make webs if allowed to continue. These are usually red or brown and multiply fast. Mites suck sap, which results in the formation of yellow stripes and streaks on the foliage. In due course of time, leaves become yellow, silvery or bronze and distorted.
Spraying with Kelthane @ 1.2% concentration is effective to control the mites.
6.Bud borer (Helicoverpa armigera)
This pest mainly damages flowers. Eggs are deposited singly on growing spikes. Larvae bore into buds and flowers and feed on them making holes.
Collection and destruction of damaged buds reduce the damage. Setting up of light traps helps to
control the population by attracting them. Spraying of monocrotophos (0.2%) or Thiodan (0.5-0.8%) or Methyl Parathion (0.05%) taken up at the appearance of eggs on buds and tender foliage controls borer damage. The spray of Neem oil (1%) also gives considerable protection by repelling various stages of the pest.
Two root-knot nematodes (Meloidogyne incognita and Meloidogyne javanica), reniform nematode (Rotylenchulus renioformis) and greasy streak nematode (Aphelencoides besseyi) are reported to cause damage to the crop, which is characterized by the stunted growth of the plants and resulting in extensive yield losses. The leaf size is reduced, and the flowers look sickly and, ultimately, the roots rot.
Application of Thimet or Furadan (20 kg/ha) , Furadon @ 2 g/plant or carbofuran @ 2-5 kg/ha, neem
@ 1 tonne/ha controls nematode infestation.
Rodents do considerable damage to tuberose plants in the field by making burrows.
Poison bait is helpful in checking rodent menace in the field. Commercial bait by the name, ‘Roban’ is available in the market and the same may be used effectively.
Diseases of Tuberose
The diseases reported are stem rot, flower bud rot, leaf blight or Botrytis blight, Sclerotial wilt, Alternaria leaf spot, rust, powdery mildew, etc
The infection is caused by the fungi Sclerotium rolfsii. The disease symptom is preceded by the appearance of prominent, coarse, mycelial masses on the leaf surface or near the soil level. Later, the infested spots exhibit a light-green colour due to rotting which extends and cover the whole leaf. The infected leaves get detached from the plant. More or less round sclerotic, brown spots are formed on and around the infected leaf. As a result, the infected plant becomes weak and unproductive
The disease can be controlled by drenching the soil around the stem with brassicol @ 1 % or Zineb (20%) at the rate of 30 kg per hectare. Also, the incidence can be minimized by reducing soil moisture or planting at wider spacing (45 cm X 30 cm).
2.Flower bud rot
It is caused by Erwinia sp. It results in dry rotting of the buds with brown necrotic discolouration of peduncles.
The diseased plants should be uprooted and destroyed. The disease can be controlled by the spray of
3.Leaf blight or Botrytis blight
This fungal disease is caused by Botrytis elliptica. The disease appears during the rainy season. Infected flowers show dark brown spots and ultimately the entire inflorescence dries up. The infection also occurs on the leaves and stalks.
Spraying the plants with Carbendazim @ 2g/ litre of water effectively controls the disease. The treatment should be repeated at 15 days interval. The disease can also be controlled by spraying the plant with ammoniacal copper (2%) or Greeno (0.5%). The treatment should b repeated at 15 days interval.
This fungal disease is caused by Sclerotium rolfsii, mostly affecting the roots. The initial symptom of this disease is flaccidity and drooping of leaves. The leaves become yellow and dry up. The fungus mainly affects the roots, and the infection gradually spreads upward through the tuber and collar portion of the stem. Both tubers and roots show rotting symptoms. The thick cottony growth of the fungus is visible on the rotten stem and petioles at the soil level.
Drenching the soil with 0.3% Zineb is effective in controlling the disease.
5.Alternaria leaf spot
This fungal leaf spot disease is caused by Alternaria polyantha. The disease is characterized by the
appearance of brown spots with faint concentric rings on the midrib.
The disease can be controlled by the spray of Bordeaux mixture (0.4%), Zineb (0.5%) or Mancozeb (0.2%) or Iprodione (0.2%) at 10 days interval. The other diseases reported are rust and powdery mildew, which are not serious. Suitable fungicides may be administered to control them when the damage is noticed.
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- Central Coastal Agricultural Research Institute, Ela, Old Goa, Goa