Caterpillars Eating a Broccoli Plant

Healthy, pest-free broccoli

A member of the cabbage family, broccoli plants are cool-season crops that add deep green color to the home garden along with edibility. Though these plants are hardy, they function poorly in freezing temperatures, thriving instead within a range of 65 to 75 degrees Fahrenheit. Protect your edible crops by examining them often as broccoli plants attract a variety of chewing caterpillars that can lead to severe damage.

Preventive Care

Maintain appropriate care of broccoli crops for healthy growth as vigorous plants have an increased ability to avoid and overcome pest problems in comparison to neglected plants. Plant broccoli in parts of the landscape that provide full sun to partial sun with some shade. Broccoli is tolerant to a wide variety of soils; simply maintain moist, well-drained soil for best growth. Broccoli prefers a soil pH of 5.8 to 6.5. Extremes in pH, like excessively acidic soil, can result in health issues like hollow stem formation. Irrigate broccoli during the morning for consistently moist soil as water is highly significant to successful development. Apply water to a depth of about 6 inches.

Types

Imported cabbageworms (Pieris rapae) target broccoli plants in their larval form as caterpillars. These caterpillars display hair-covered green, yellow and orange striped bodies measuring up to 1 inch in length. As mature butterflies, they exhibit black spotted white bodies. Cabbage loopers (Trichoplusia ni) are the larval caterpillars of moths that display gray-brown bodies. Cabbage looper caterpillars display light green bodies with white stripes that run front to back. As their name suggests, these larvae move forward by bunching their backs into the air in the shape of a loop.

Damage

Imported cabbageworm and cabbage loopers create similar damage through chewing on broccoli plants. Both feed on leaves, eating abnormally shaped holes. Younger loopers typically target the tissue beneath leaves with a preference for more mature leaves while imported cabbageworms chew any part of the leaf available. Cabbage loopers, considered "very destructive and difficult to control," according to the Clemson University Extension, sometimes bore into the plant but often remain chewing on leaves. Imported cabbageworms tunnel into broccoli, as well, focusing primarily on the center of plants.

Solutions

To control caterpillars eating broccoli plants, first attempt to pick them from your plants by hand to avoid causing further damage. If the population is too numerous, apply the bacterial insecticide Bacillus thuringiensis (Bt), which inhibits chewing, slowly killing the caterpillar. For extremely severe problems, spray your broccoli plants with a chemical insecticide containing the active ingredient spinosad or permethrin for effective control.

References

• Clemson University Extension; Cabbage, Broccoli & Other Cole Crop Insect Pests; Randall P. Griffin; February 1999
• University of California IPM Online: Imported Cabbageworm -- Pieris Rapae
• University of California IPM Online: Loopers
• Clemson University Extension; Broccoli; Powell Smith, et al.; June 1999
• University of Illinois Extension: HortAnswers -- Broccoli

Resources

• University of California IPM Online