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Flowers, Fruits, and Frass

Local and statewide information on a variety of current topics for home gardeners and market growers.
imported cabbage worm and cross striped cabbage worm
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Worms on your Cabbage

Posted by Kelly Allsup - Bugs

Let the caterpillar picking commence


If squash bugs (Anasa tristis) decimated your zucchini (Cucurbia pepo) plants this year then you are going to detest imported cabbage worm and cross-striped cabbage worm on your cruciferous crops says Horticulture Educator, Kelly Allsup. Crucifer crops include cabbage, kale, broccoli, cauliflower, kale, collards and mustard. These pests are worst on fall grown crops because multiple generations started in the spring. These very hungry caterpillars come from eggs laid by pretty white and brown butterflies.

The white butterflies with black spots are the adults of the imported cabbage worm, a plush light green caterpillar with yellow lines running down the length of the body. The imported cabbage worm is a larva coming from yellow eggs attached to the undersides of the leaves. They feed on your plants for 1-2 weeks then turn into a chrysalis (cocoon) to overwinter in plant debris. The boundless feeding of this garden pest will eat leaves until only the veins remain intact and will prevent head formation of your precious cabbage.

The brown and yellow butterflies are the adults of the cross-striped cabbage worm, a black and white striped caterpillar with yellow racing stripes. The cross-striped cabbage worm is the larva coming from eggs laid on the undersides of the leaves that looks like small white round pearls. The caterpillars eat ragged holes until they turn into a chrysalis and drop into the soil.

University of Illinois suggests taking a combined approach.

  1. Inspect your plants for feeding damage, caterpillar frass (excrement), and worms on the bottom of the leaves or in the growing tips.
  2. Use row covers or frost cloth to prevent butterflies from laying eggs.
  1. Get your gloves out and let the handpicking commence.
  1. Use safer chemicals with lower impact on natural enemies like Bacillus thuringiensis, Neem oil, Pyrethrum or Spinosad to kill caterpillars. Add a spreader-sticker to pesticides for better coverage and spray at night to avoid killing pollinators.
  1. Late fall clean up; composting.
  1. Weed Control.
  1. Crop rotation (2 years). Keep a garden journal.
  1. Natural enemies include parasitic wasps, parasitic flies, soldier bugs, assassin bugs. Plant pollen and nectar producing plants to attract beneficial insects.

Upon my inspection of infested kale, cabbage and angel trumpet's (Brugmansia suaveolens) in the Solanaceae family, I found braconid wasp eggs, assassin bug eggs and spined soldier bug nymphs. All ready to aid in the battle against the caterpillar population.

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