Cabbage, Broccoli & Other Cole Crop Insect Pests

Introduction

Each year numerous insect pests damage crops in home gardens and commercial fruit and vegetable fields. Caterpillars, the immature larval stage of butterflies and moths, are the most significant pests of brassica crops (collards, kale, cabbage, broccoli, cauliflower, mustard, turnips, and others). Other pests that cause occasional damage include aphids, whiteflies, harlequin bugs, and flea beetles. Before making treatment decisions, use the information in this fact sheet to help correctly identify pests found in the garden. Extension agents can provide identification assistance as needed.

Diamondback Moth Caterpillars

Diamondback moth (Plutella xylostella) (DBM) caterpillars are the most numerous and problematic caterpillar in home gardens and commercial fields in South Carolina. DBM caterpillars are small, reaching just 0.5 inches prior to pupation. They have a short life cycle and reproduce prolifically, allowing populations to build and rapidly cause damage. When handled, DBM often drop and hang from a silk thread or thrash about violently. In addition to their small size, this behavior distinguishes them from other brassica caterpillars. DBM pupate in loosely woven cocoons on the undersides of leaves. These pupae are frequently observed but no longer threaten the plant.

Diamondback moth caterpillars are small (up to 0.5 inches) but are the most serious insect pest of brassica crops in South Carolina.
Justin Ballew, ©2018, Clemson Extension

This adult diamondback moth has just emerged from its cocoon and has not yet dispersed.
Justin Ballew, ©2021, Clemson Extension

DBM feed by chewing holes in the leaves of their host plant. Because they are so small, they often do not chew all the way through the leaves, leaving a “window-pane” appearance where the upper cuticle intact. DBM can be found anywhere on the host plants, though adult moths typically lay eggs on the younger foliage. Scout for DBM by carefully examining the undersides of the leaves, paying close attention along the sides of the leaf veins.

Diamondback moth feeding damage often does not go all the way through the leaf, creating a “window-pane” appearance where the upper cuticle is left intact.
Justin Ballew, ©2018, Clemson Extension

Severe DBM damage can occur quickly if the garden is not scouted frequently and regularly.
Justin Ballew, ©2021, Clemson Extension

Cabbage Looper

The cabbage looper (Trichoplusia ni) is one of the largest caterpillars that affects brassica crops. It reaches 1.25 to 1.5 inches in length and is fatter on the tail end than the head. Similar to an inch worm’s movement, loopers walk using a characteristic “looping” motion. When disturbed, cabbage loopers frequently rear up like a cobra. Cabbage loopers have only two pairs of abdominal prolegs, making it easy to distinguish them from other brassica caterpillars. Holes made in the leaves by cabbage looper feeding are typically much larger than those of DBM caterpillars. One cabbage loop creates roughly the same amount of damage as 5 DBM. Like DBMs, cabbage loopers pupate in a loosely woven cocoon on the underside of the leaves.

Cabbage loopers are large caterpillars that are fatter on the tail end than the head.
Justin Ballew, ©2021, Clemson Extension

Cabbage loopers have only two pairs of abdominal prolegs, making it easy to distinguish them from other brassica caterpillars. All others have four pairs.
Monica Farfan, ©2019, Clemson University

Imported Cabbageworm

The imported cabbageworm (Pieris rapae) (ICW) is unique among the other caterpillars listed as it is the only caterpillar of a butterfly, the cabbage white. ICWs reach a length of around 1 inch and are distinguishable by their fuzzy appearance. Feeding damage is similar to that of the cabbage looper, though ICWs cause only about 2/3 the damage of a looper. ICW pupate in a chrysalis on the host plant.

Imported cabbageworm larvae (Pieris rapae) reach a length of around 1 inch and are distinguishable by their fuzzy appearance.
Zachary Boone Snipes, ©2015, Clemson Extension

The cabbage white butterfly is the adult form of the imported cabbageworm. They are commonly observed foraging wildflowers.
Barbara Smith, ©2021 HGIC, Clemson Extension

Imported cabbageworms pupate in a chrysalis attached to the host plant.
Justin Ballew, ©2016, Clemson Extension

Cross-Striped Cabbageworm

Female cross-striped cabbageworm (Evergestis rimosalis) moths lay eggs in masses of up to 25. Once the eggs hatch, the caterpillars may rapidly skeletonize their host plant. Cross-striped cabbageworms are medium-sized caterpillars, reaching about 0.75 inches before pupation. They have alternating black and white stripes across their back and a yellow stripe that travels the length of their body on either side. When ready to pupate, cross-striped cabbageworms drop to the ground and pupate just under the surface of the soil, where they are rarely observed.

Crossed-striped cabbageworm larva (Evergestis rimosalis) have alternating black and white stripes across their back and a yellow stripe that travels the length of their body on either side.
Zachary Boone Snipes, ©2015, Clemson Extension

These cross-striped cabbageworm larvae just recently hatched and have not yet developed their easily recognizable stripes.
Justin Ballew, ©2015, Clemson Extension

The Southern armyworm (Spodoptera eridania) has a reddish-brown head and a dark spot on either side just behind its last pair of true legs.
Justin Ballew, ©2021, Clemson Extension

Armyworms

Beet armyworms (Spodoptera exigua) (BAW) and Southern armyworms (Spodoptera eridania) (SAW) look similar to each other. The SAW can be distinguished by a large, dark-colored spot on its sides just behind the last pair of true legs. and is also usually darker-colored with a brown to reddish-colored head. Armyworms are occasional pests that sometimes show up suddenly and heavily, complete their life cycle, and then disappear for the rest of the season.

Cabbage webworm (Hellula rogatalis) showing lengthwise stripes and a dark-colored head.
Alton N. Sparks, Jr., University of Georgia, www.insectimages.org

Cabbage Webworm

Cabbage webworms (Hellula rogatalis) (CWW) create webs in the tender new growth of their host plant to protect themselves from predators. CWW reach a length of only 0.5 inches prior to pupation, have tan and brown stripes traveling the length of their bodies, and a dark-colored head. They may cause severe damage to buds and growing points, resulting in lateral budding. The resulting lateral shoots are much slower to mature than undamaged main shoots.

Aphids

Cabbage aphids (Brevicoryne brassicae) and turnip aphids (Lipaphis erysimi) are true bugs with piercing/sucking mouthparts used to suck the sap out of their host plant. Feeding damage from large populations may cause yellowing, stunted growth, wrinkling or curling of the leaves, and sooty mold may grow on the “honeydew” they excrete as they feed. Aphid infestations may occur at any time, though in South Carolina, they tend to be more common in the fall when the weather is cool.

Cabbage aphids shown under 25x magnification. The light-colored, swollen aphid has been parasitized by a parasitic wasp.
Justin Ballew, ©2020, Clemson Extension

Aphid colonies may appear at any time, though they tend to be most common in fall crops.
Justin Ballew, ©2020, Clemson Extension

Whiteflies are small, piercing/sucking insects. They tend to be more problematic in the Coastal Plain region of South Carolina.Justin Ballew, ©2020, Clemson Extension

Whiteflies

The silverleaf whitefly (Bemisia argentifolii), also called the sweetpotato whitefly, is the most problematic species of whiteflies in brassica crops. Whiteflies are small and yellow-bodied with white wings that cover the abdomen when at rest. Like aphids, whiteflies are piercing/sucking insects that feed on the sap of their host plants. In South Carolina, whiteflies tend to be more problematic in the Coastal Plain region, especially in the fall.

Harlequin Bug

Harlequin bugs (Murgantia histrionica), members of the stink bug family, have a unique reddish-orange and black pattern on their backs. Harlequin bugs create distinct damage to the foliage of brassica plants as they feed with their piercing/sucking mouthparts. Eggs are laid in clusters and are also unique. They resemble small black- and white-striped barrels.

A harlequin bug adult (Murgantia histrionica) has a unique reddish-orange and black pattern on its back.
Zachary Boone Snipes, ©2015, Clemson Extension

Harlequin bugs create distinct feeding damage on the leaves of brassica crops.
Justin Ballew, ©2016, Clemson Extension

Harlequin bug eggs are laid in clusters and look like tiny black and white-striped barrels.
Justin Ballew, ©2020, Clemson Extension

Flea Beetles

Flea beetles are small, chewing insects with powerful hind legs that allow them to leap away when disturbed. The crucifer flea beetle (Phyllotreta cruciferae) and the striped flea beetle (Phyllotreta striolata) are the predominant species affecting brassica crops. Flea beetles are most problematic on mustard and turnips, as they lack the protective waxy leaf coating that other brassicas, such as collards, kale, cabbage, and broccoli, have.

Management Strategies for Brassica Crop Insects

Cultural Management: Manage weeds in and around the garden to minimize protection and overwintering sites for insect pests. Remove and destroy crop residue from the garden as soon as harvest is complete, so any pests that are present are not allowed to complete their life cycle.

Mechanical Management: Hand-picking caterpillars from plants can be an effective means of managing small plantings. Plants should be scouted every few days to make sure caterpillars are being removed shortly after hatching. Screens or fine mesh netting can also be effective in small plantings by preventing moths from laying eggs on the plants.

Biological Management: Numerous predatory and parasitic insects and spiders prey on brassica insect pests. A good way to promote biological management is to plant a variety of flowers around the garden, especially small flowers such as sweet alyssum, parsley, dill, cilantro, buckwheat, and fennel. These small flowers are particularly attractive to parasitic flies and wasps. In addition, avoid applying broad-spectrum insecticides, as these materials kill beneficial insects and spiders as well as pest species.

Chemical Management: Chemical management should be used only as a last resort. Scout plantings carefully and regularly to monitor pest populations and help determine when applications are necessary. Only active larvae should be targeted when treating caterpillar pests. Once pupation begins, feeding has ceased, and neither the pupa nor adult causes direct damage to the plant. Therefore, applications targeting pupae and adults are not effective at reducing plant damage.

Table 1. Insecticides Labeled for Use on Brassica Crops.

Table 2. Insecticide Products Labeled to Manage Brassica Insect Pests.

Pesticides are updated annually. Last updates were done on 1/22 by Justin Ballew.

Originally published 00/00