Organic Farming :: Organic Farming Practices

PEST MANAGEMENT

Insects and diseases are a major threat to tomato cultivation and are responsible for a considerable loss in yields. A major part of the cultivation cost is in fact incurred for crop protection. A list of major pests and diseases affecting tomato cultivation are listed below, along with their organic management measures.

  • Fruit borer – Helicoverpa armigera
  • Tobacco caterpillar – Spodoptera litura
  • Serpentine leaf miner – Liriomyza trifolii
  • White fly – Bemisia tabacci
  • Root-knot nematode – Meloidogyne spp.
Fruit borer (Helicoverpa armigera)
 

This is a polyphagous pest infesting most cultivated crops. It is a major pest of tomato as well and is widely distributed throughout India.

Life cycle (4–6 weeks)

The adult moths are medium sized, stout and pale brown in colour with a reddish brown tinge. The forewings are olive green to pale brown in colour with a circular brown spot at the centre. The hind wings are smoky white in colour with a broad dull blackish outer border.

The eggs are ribbed, dome-shaped and yellowish white. The freshly hatched larvae are yellowish white and the fully grown caterpillars are in varied colours. They are mostly apple green with white and dark grey longitudinal lines. They have a white wavy line on the lower lateral part of the body. The eggs are laid on the leaves and flowers. At times, they are also found on young fruits. Pupation occurs in the soil.

Damage pattern

The young larvae feed on the tender leaves. At later stages, they attack the fruits and bore circular holes. Usually the larvae thrust only their heads inside the fruits. They move from one fruit to another, causing damage. Externally, the damage appears in the form of holes. They are found from flowering to harvest stage, especially during July to November.

Economic threshold level : 2 larvae / 2 m row length

Management

  • Monitor top three leaves for Helicoverpa eggs and hand pick larvae.
  • Intercropping tomato with marigold is an effective IPM practice. Planting of the trap crop should be adjusted in such a manner that tomato flowering coincides with the tight bud stage of the marigolds. Marigolds attract both fruit borer and leaf miner adults for egg laying.
  • Growing sorghum (8 rows) as a border crop around the field at 30 x 10 cm spacing promotes natural predators like Chrysoperla and Coccinellids.
  • Place 15–20 bird perches per hectare. This invites predatory birds.
  • Spray 5% neem seed kernel extract, Andrographis kashayam or five leaf extract to kill larvae at their early stages.
  • Soil application of the seed extracts of Strychnos nux-vomica @ 1.5 gm/plant at an interval of 20 days, twice, when there is severe borer attack.

Use of biocontrol agents like NPV (@ 250 LE/ha), Bacillus thuringiensis (@ 1 gm/litre of water), Trichogramma chilonis (@ 50,000 eggs/ha, six times at weekly intervals) and Bracon hibitor (larval parasite).

fruit borer
fruit borer
fruit borer
fruit borer
fruit borer
Tobacco caterpillar (Spodoptera litura)
 

This caterpillar is a major tomato pest and is widely distributed throughout the world. It is polyphagous in nature.

Life cycle (30–40 days)

  • The adult moths are stout and pale brown in colour.
  • The forewings are greyish brown with white markings.
  • The hind wings are palescent and semi-hyaline.
  • The caterpillars are also stout and cylindrical.
  • When fully grown, they are 40–50 mm in length and pale brown in colour with a greenish violet tinge.
  • They are smooth and velvety.
  • They possess a series of sub marginal narrow yellow spots with black lunules above them.
  • A black band is found around the body both on the anterior and posterior ends.
  • Eggs are laid in clusters on the ventral surface of young leaves.
  • The egg clusters are usually covered with brown hairs.

Damage pattern

Freshly hatched larvae feed gregariously, scraping the leaves from the ventral side. They feed voraciously on the leaves at night. They also feed on the fruits by making holes in them.

Management

  • Plant castor @ 125 per hectare as a trap crop. Castor attracts the egg laying moths. The egg masses and larvae can be collected and destroyed.
  • Pheromone traps can be installed @ 10 per hectare to monitor the pest.
  • 5% neem seed kernel extract can be sprayed to kill the young larvae.
tobacco caterpillar
tobacco caterpillar
tobacco caterpillar
 
Serpentine leaf miner (Liriomyza trifolii)
 

The leaf miner is a polyphagous pest introduced from the USA in the early nineties. It is widely distributed now in India. Life cycle (15 days) The adult fly is tiny with transparent wings. The female has a prominent retractile ovipositor. The maggots are legless and pale yellow in colour. Pupation occurs in the soil.

Damage pattern

The maggots damage the plant by mining into the leaf. They feed on the inner most subphyla tissues. The diameter of the serpentine mines increases as the larva grows.

Economic threshold level : Two miners per plant.

Management

  • Grow one row of field bean as an intercrop after every eight rows of tomato. Field beans should be sown 10–12 days before transplanting the tomato seedlings.
  • Spray 5% neem seed kernel extract or ginger, garlic, chili extract (@1 litre/tank).
leaf miner
 
White fly (Bemisia tabaci)
 

Life cycle

  • Both the nymphs and adults of the white fly are very sluggish and they are found clustered together on the under surface of the leaves.
  • Nymphs are oval, scale-like and pale yellow in colour.
  • Adults are yellow with a white waxy coating over the body. Their wings are whitish.

Damage pattern

  • The adults lay eggs on the under surface of the leaves.
  • Both nymphs and adults suck the sap from the underside of the leaves and flowers.
  • White flies are also responsible for transmitting leaf curl virus.

Economic threshold level

Two nymphs or adults per leaf

Management

  • Cover the nursery bed with a 40 mesh nylon net to prevent entry of the flies.
  • Sow pearl millet as a barrier crop around the main field. This should be done 15 days before transplanting the tomato.
  • Install 50 yellow sticky traps/ha. • Spray 5% neem kernel extract when the pest incidence is above ETL.
white fly
white fly
white fly
white fly

General management of insects

A decoction prepared by boiling the leaves of Aloe vera, neem, Ocimum tenuiflorum, Achyranthes aspera and Aristolochia bracteata in water can be used to prevent pest and disease attack. This is mixed with water (@100 ml decoction per litre of water) and sprayed on the plants.

Beneficial insects : Spiders, ladybird beetles and other coccinellids.

Source : Centre for Indian Knowledge Systems, Chennai

Updated on : Dec 2014

 
 

© 2009-16 TNAU. All Rights Reserved.