Worms In Broccoli - Caterpillars In The Broccoli Head

Caterpillars In Broccoli Head
broccoli worms
(Image credit: Gardening Know How, via Nikki Tilley)

Although broccoli is one of the few plants least affected by pests, especially during fall, it is not uncommon to occasionally find worms on broccoli heads. If left unprotected, these broccoli worms can wreak havoc on your plants.

Types of Broccoli Worms

Broccoli worms feed on cabbage, kale, cauliflower, and brussels sprouts, in addition to broccoli. They usually prefer the undersides of plants, chewing holes and eating their way into the heads from the bottom. There are generally three types of worms in broccoli:

  • Cabbage worms, which are velvety green caterpillars (larvae of white butterflies)
  • Cabbage loopers, which are smooth and light green (larvae of brown moths)
  • Diamondback worms, which are smaller in size and pale green in color (larvae of gray moths with diamond shape on back)

All broccoli worms are difficult to see, as they blend in easily with the green plants. However, the presence of white butterflies in the afternoon or moths in the evening can signal the beginning of an infestation, as they will lay their eggs on the undersides of leaves. Once present, worms on broccoli can completely defoliate plants.

Remove Worms from Broccoli

Worms in broccoli don't have to be a problem. Nearly all broccoli worms can be controlled by using products containing Bacillus thuringiensis (Bt). This bacterium makes worms sick, eventually killing them; however, it is perfectly safe for plants, humans and other beneficial insects. Bt is available at most garden centers and is best used in the afternoon. To effectively remove worms from broccoli, spray broccoli plants thoroughly using about 1 to 2 teaspoons (5-10 mL.) of liquid detergent per gallon (3.8 L.) of Bt.

Preventing Broccoli Pests

One of the best ways to prevent broccoli pests from attacking your crop is through the use of row covers. Row covers provide adequate protection from most types of broccoli pests, especially during spring and summer when they are most prevalent. To prevent broccoli worms from burrowing into the heads, try placing the entire head in pantyhose or other suitable nylon stocking until ready for harvesting. In addition to worms on broccoli, other broccoli pests may be found. These include:

Many of these can be easily controlled through hand picking or spraying with insecticidal soaps. The best defense against broccoli worms and other pests is to continually inspect plants for signs of infestation.

Nikki Tilley
Senior Editor

Nikki Tilley has been gardening for nearly three decades. The former Senior Editor and Archivist of Gardening Know How, Nikki has also authored six gardening books.