Organic pest management of cabbage butterflies

Cabbage butterfly adults are pretty, but their caterpillars are small creatures with big appetites

Description

The following tools are meant to guide decisions for managing cabbage butterflies (Pieris rapae).

Target

Target 1. Cabbage butterfly adults.

Target 2. Cabbage butterfly eggs.

Target 3. Cabbage butterfly young larvae.

Target 4. Cabbage butterlfy mature larvae.

Target 5. 2nd generation cabbage butterfly adults.

Timing

General calendar time: Outdoors. The winged forms of adult cabbage butterflies typically emerge mid to early May.

Degree days: Adults emerge 150-240 DD

Biofix: Jan. 1

Tool(s)

Tool #1: Trapping (Type: Monitoring)

Cabbage butterflies are attracted to yellow sticky cards, and their large wings make them particularly susceptible to being caught.

Techniques

  1. Spread yellow sticky cards around the perimeter of your growing area.

Tool #2: Spray kaolin clay on leaves to prevent egg lay (Type: Mineral/Physical)

A mineral layer can interfere with cabbage butterfly females’ ability to lay eggs on the surface of cabbage leaves.

Techniques

  1. Cover clay on the top of leaves to confuse butterflies.
  2. Cover clay unnder leaves to prevent butterflies from laying eggs.
Cabbage butterfly eggs are not always laid in a single egg mass, but dropped in a kind of Morse code-like pattern with individual eggs laid next to larger clusters.

Tool #3: Spray insecticidal soap (Type: Chemical)

Insecticidal soap works well against young cabbage butterfly larvae because their bodies are soft.

Note: Insecticidal soap is not a poison or a nerve toxin…it is a formulation of soap that is designed to be gentle enough to use on most plants.

The “insecticidal” part of insecticidal soap comes from its mode of action. The active ingredient of insecticidal soap – the potassium salts of fatty acids – work to dissolve young caterpillar’s bodies that causes them to dry out from loss of moisture.

Cabbage damaged by insects pests close-up. Head and leaves of cabbage in hole, eaten by larvae butterflies and caterpillars. Consequences of the butterfly Pieris brassicae.
Tool #4: Release beneficial insects that consume eggs and/or young larvae (Type: Biological)

You do not want to use just any beneficial insect. You want an insect that will actually consume aphids on the plants in your growing area.

  1. Eggs/young caterpillars. Release Orius insidiosus, Green lacewing eggs and/or larvae or spray horticultural oil or insecticidal soap with neem oil.
  2. Larger caterpillars. Release soldier bugs (Podisus maculiventris) or spray biopesticide with Beavaria bassiana

List of suppliers of beneficial organisms (University of Kentucky)


Resources

University of Minnesota Extension

Gertens

BFG Suppliers – Crop protection section

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