Insect Pests of Vegetable, Ornamental and Spice Crops (2+1)

Potato tuber moth

1. Potato tuber moth, Phthorimaea operculella (Gelechiidae: Lepidoptera)

• Distribution: Cosmopolitan in distribution.

• Native of South America and was introduced to India in 1906 with seed potatoes imported from Italy. It has
• Host range: It is a major pest of potato but has also been reported from crops like egg plant, tomato, tobacco, etc.

Damage:

• Larvae which mine the leaves, petiole and terminal shoots causing wilting.
• After tuberization, the larvae enter into the tubers and feed on them.
• Bore the tubers in stores also
• Larvae tunnel into the pulp which ultimately becomes unfit for use as seed or for human consumption.
• The infested tubers are further exposed to microbial infection which leads to rotting.
• The extent of damage to stored tubers varies from 20 - 85 per cent

Identification

• The eggs are oval and measure less than 1mm in diameter.
• Newly emerged larvae are gray yellowish white with brown head.
• Pupate in silken cocoons

Life cycle

• Each female can lay 150-200 eggs.
• Incubation period is 3-6 days,
• Larval period is 10-25 days
• Pupal period lasts for 5-9 days.
• Total life cycle is completed in 20-30 days at optimum conditions
• There are 8-9 overlapping generations in a year.

Salient features

• This pest breeds throughout the year under favorable conditions.
• The females lay eggs either on the under surface of leaves or on exposed tubers near eyes.
• Full grown caterpillars come out of the tubers/ foliage and pupate in silken cocoons either in dried leaves, soils, over the stored tubers or in cracks and crevices in the store.

Management:

• Plant tubers slightly deeper (10 cm) and follow proper earthing up
• Lift all the tubers from the field at harvest
• Destroy self grown potato plants
• Intercropping with chillies, onions or peas.
• Harvested potatoes should be lifted to cold stores immediately.
• If cold store facilities are not available, only healthy tubers should be stored.
• Cover the stored tubers with 2.5 cm layer of chopped dry leaves of Lantana or Eucalyptus or Eupatorium below and above the potato
• Mass trapping of adults with sex pheromones
• Under field conditions more than 20 traps/ha (some times up to 40 traps/ha) are required
• Spray of crop with chlorfenvinphos (0.4 Kg a.i./ha) or quinalphos (0.375 Kga.i./ha) or acephate (0.5Kg a.i./ha)
• In stores dusting the tubers with 5% malathion or 1.5 5 quinalphos dust @ 125g dust/100 Kg of potatoes.
• Alternatively, dipping of tubers before storage with 0.0028% deltamethrin
• Parasitoids like Chelonus curvimaculatus, Bracon gelechiae, Apanteles sp, Melanis sp and Diadegma molliplum are also found to reduce the population of PTM.
• Bacillus thuringiensis has also been reported to suppress this pest.