The diamondback moth is a pest of cole crops. This pest was introduced from Europe before the middle of the nineteenth century, and is now found everywhere its host crops are grown. The moth has trouble over-wintering in cooler regions, but when over-wintering populations are present, they increase significantly. Trade winds disperse the moth throughout the United States during the growing season.

The adult diamondback moth is small, grayish-brown, with fringed hind wings. The adult moth can be identified by the pattern of white diamonds present in a line down the insect's back when at rest. Both coloration and the manner in which the wings are held create this pattern. The eggs of the diamondback moth are round, white, and smaller than a pencil point. Eggs are found in groups of one, two, or in rare cases three, and will most often be located on the underside of leaves, adjacent to a large vein. The larvae are pale green, with a black head-capsule and sporadic black hairs. In contrast to some of the other cabbage worms, the larvae of the diamondback moth will wiggle furiously when picked up. The larvae are capable of producing silk, and may be observed hanging by a silken thread. The pupa is approximately one-quarter of an inch long, covered with a loose silken cocoon, and will frequently be found stuck to the plant.

Adult diamondback moths will feed in small amounts, and the damage is often so light that it will go unnoticed. It is the larvae of the diamondback moth that can cause significant economic damage.

Larvae have two distinct feeding styles. Shortly after emerging from the egg, larvae are extremely small and will feed by mining into the leaf (feeding on the leaf tissue between the upper and lower epidermis). The larvae themselves are not visible during this time (because they are inside the leaf). The only evidence is a long, tortuous white trail that is the result of underlying dead leaf tissue. As the larvae grow, they become too large to feed as leaf miners. It is at this point that larvae begin to burrow through the leaf tissue, resulting in many small holes in the leaf. This type of damage is most commonly called 'shotgun damage' due to the appearance of many small 'shotgun pellet' holes.

Economic damage is most severe after heading begins. Larvae will burrow into the developing head, destroying its marketability. The recommended treatment threshold for diamondback moth depends upon the plant's growth stage. From seeding to cupping, the recommended threshold is when 20 percent of the plants are infested. After heading begins, the recommended threshold decreases to 5 percent infestation.

The diamondback moth over-winters as a adult in the debris of the previous year's crop. In the spring, when temperatures increase, the moth will mate, and then begin a host search. Oviposition occurs on the underside of leaves, usually immediately adjacent to a vein. Eggs are usually oviposited in groups of singles, doubles, or triples, although more than one group may be oviposited per leaf. Larvae will feed for approximately ten days before beginning pupation. The pupal case of the diamondback moth is made of silk, and is used to adhere the pupa to the plant. An adult moth emerges from the pupal case in five to ten days, depending on the temperature.

The diamondback moth may be able to over-winter in most areas of Texas during mild winters. When populations successfully over-winter, it greatly increases both the amount and intensity of moth generation. Immigrating diamondback moths are the result of prevailing winds from the south.

The cornerstone of good pest management is monitoring. Optimal monitoring for the diamondback moth is the use of pheromone traps to monitor adults. When the adult population rises, begin scouting the plants for larvae and eggs.

When spraying, be sure to use a high-pressure blast sprayer (>200 psi) with three hollow-cone nozzles per row. One nozzle should point straight down into the row, while the other two spray from either side. Additionally, use a spreader-sticker to increase coverage. This procedure sprays the plants from three sides, and reduces the spray shadow that occurs as a result of the change in topography between the leaf and the vein. Keep in mind that it is this region — adjacent to the veins – where the diamondback moth oviposits its eggs. For proper control, it is critical to ensure that optimal spray coverage has been achieved.

In some cases, the intensity of summer infestations of the diamondback moth can be reduced by eliminating the over-wintering habitat. Because the diamondback moth over-winters in the debris of the previous year's field, all plant materials should be plowed under immediately after final harvest. Additionally, fields should be rotated between years as far as possible. This makes it more difficult for adults who have managed to over-winter to find the current year's crop.