Cabbage white butterfly

Overview:

Pieris rapae, the Small White Butterfly or Cabbage White Butterfly, is a common pest that targets cruciferous crops, including cabbage, broccoli, and kale. Belonging to the Pieridae family, this butterfly is recognized for its widespread distribution and feeding habits that can lead to significant damage to host plants.

Detailed Appearance:

The adult Small White Butterfly has a wingspan ranging from 4 to 5.7 centimeters (1.6 to 2.2 inches). The wings are predominantly white, with a slight yellowish tint, and feature distinctive black markings near the tips. The larvae, commonly known as cabbage worms, are velvety green caterpillars with a yellow stripe along each side and reach lengths of approximately 2.5 centimeters (1 inch).

Life Cycle:

The life cycle of Pieris rapae involves four stages: egg, larva, pupa, and adult. Adult butterflies lay eggs on the undersides of host plant leaves. Upon hatching, the larvae feed voraciously on the foliage, causing damage. Larvae then pupate in silken cocoons attached to plant surfaces, and adult butterflies emerge to continue the cycle.

Identifying Infected Crops:

1. Leaf Damage: Look for irregularly shaped holes in leaves caused by the feeding activity of cabbage worm larvae. Severe infestations can result in skeletonized leaves.

2. Frass Presence: The presence of small greenish-black droppings, known as frass, on leaves is an indicator of cabbage worm activity.

3. Caterpillar Identification: Identify the velvety green caterpillars with a yellow stripe along each side actively feeding on plant foliage.

4. Adult Butterfly Observation: Monitor for the presence of adult butterflies, especially during the growing season, using visual inspections or yellow sticky traps.

Additional Identification Features:

1. Chewing Mouthparts: Cabbage worm larvae have chewing mouthparts, contributing to the characteristic feeding damage on leaves.

2. Silken Cocoons: Larvae create silken cocoons on plant surfaces for pupation, which can be observed during the later stages of their development.

Management:

1. Handpicking: Actively inspect plants and manually remove cabbage worm larvae when their numbers are manageable. This is particularly effective in smaller gardens.
2. Biological Control: Introduce natural predators such as parasitic wasps and predatory insects like ladybugs and lacewings to help control cabbage worm populations.
3. Bt (Bacillus thuringiensis) Sprays: Apply Bt-based insecticides, which are specific to caterpillars and are environmentally friendly. Dilute 15 to 30 milliliters (1 to 2 tablespoons) of Bt per liter (1 quart) of water.
4. Floating Row Covers: Use floating row covers to physically exclude adult butterflies from laying eggs on the plants.