Measures to Control Diamondback Moth pest in Cabbage Crop

The diamondback moth (Plutella xylostella) is a major pest of cabbage crops worldwide, including in India. They are small, grayish-brown moths with wingspans of about 13-16 millimeters. Their caterpillars are the main culprits, feeding on the leaves of cabbage plants and causing significant damage. The diamondback moth has a relatively short life cycle, which can be completed in as little as 2-3 weeks under warm conditions. Tiny, oval-shaped, pale yellow eggs laid on the undersides of leaves. Green caterpillars with dark heads, going through four instar stages. Light brown pupae formed in silken cocoons on the leaves or stems. Grayish-brown moths with diamond-shaped markings on their wings.

• Type of Infestation: Pest
• Common Name: Diamondback Moth
• Causal Organism: Plutella xylostella
• Affected Parts Of the plant: Leaves

Identification:

Adult Moth:

• Size: Tiny, with a wingspan of about 15 millimeters and a body length of 6 millimeters.
• Color: Greyish-brown with a distinct diamond-shaped, cream-colored marking on its back (hence the name).
• Activity: Most active at night, but can be seen flying during the day when disturbed.

Eggs:

• Size: Minute, only about 0.5 millimeters long.
• Color: Initially pale yellow, turning deep yellow closer to hatching.
• Location: Laid singly or in small groups on the upper or underside of leaves, often near veins.

Caterpillars (Larvae):

• Size: Start small and grow up to 12 millimeters in length through four instars.
• Color: Pale green, slightly tapered at both ends.
• Feeding: Initially mine within leaves, later feed externally on the underside, leaving irregular holes.
• Behavior: Wiggle when disturbed and may drop from the plant on a silken thread.

Pupae:

• Size: About 10 millimeters long.
• Color: Dark green or light brown.
• Location: Attached to the underside of leaves in a silken cocoon.

Environmental favorable factors for pests/Diseases:

Temperature: 

• DBM thrives in warm temperatures, with optimal development occurring between 20-30°C (68-86°F). Plutella xylostella]
• Cooler temperatures slow down development and may even lead to increased egg mortality.

Humidity: 

• Moderate humidity (50-70%) is ideal for DBM development.
• Very dry or wet conditions can reduce survival rates.
• High humidity can also promote the growth of fungal diseases that can infect DBM larvae.

Symptoms of Pest/Disease:

• Leaf feeding: Caterpillars feed on the undersides of leaves, creating irregular holes and "windowpane" damage, where the upper leaf surface remains intact but transparent.
• Stunted growth: Heavy feeding can slow down the growth of young plants and reduce yields.
• Unmarketable cabbages: Damage to the leaves and heads can make cabbages unmarketable.

Measures to control Pests/Diseases: