Cabbage looper

The cabbage looper (Trichoplusia ni) is a medium-sized moth in the family Noctuidae, often called owlet moths. It gets its name from the plants it likes to eat, such as cabbage, bok choy, and broccoli, and from the way its baby stage, or larva, moves. When the larva crawls, it makes a looping motion by arching its back, which looks like it's making a loop.

Even though it prefers plants like cabbage, the cabbage looper can eat more than 160 different plants. The adult moth travels long distances and can be found all over North America and Eurasia, from places as far south as Florida to as far north as British Columbia. Because it moves around a lot and can live on many plants, it is seen in many areas.

The cabbage looper larva can be a small problem for gardens, especially for plants like cabbage, broccoli, and other cruciferous vegetables. While it does not usually cause big damage, it is becoming harder to control because it can resist many common insect-killing sprays. Scientists are studying many ways to manage and reduce the number of cabbage loopers.

Taxonomy

The cabbage looper larva is a type of cabbage worm. Cabbage worms are pests that eat vegetables like cabbage and broccoli. The cabbage looper belongs to the family Noctuidae. This is a large family in Lepidoptera. It is related to other pests like the cutworm and armyworms.

Reproduction and life cycle

Cabbage loopers have interesting ways of growing. After they are ready, they mate at night a few days after they come out of their cocoons.

After mating, females lay eggs on big leaves higher up on plants. The eggs are small and yellow-white and hatch in about three days. The babies, called larvae, are green with a white stripe and move in a looping way. They eat many leaves.

Finally, the larvae make a silky cocoon under leaves. This stage lasts from four to thirteen days. When they emerge as adult moths, they have gray-brown front wings and light brown back wings and are active at night. The whole process from egg to adult takes about twenty-four to thirty-three days.

Distribution and migration

The cabbage looper lives in North America and Eurasia, from Florida to British Columbia.

In North America, cabbage loopers travel from Mexico to Canada when the weather changes. They spend winter in Mexico or southern California, where it is warm. When northern areas warm up, the cabbage looper moves north, but only if it is above 16 °C (61 °F). They are less common in very hot southern areas during summer. Like the monarch butterfly, they probably travel in groups.

In Europe, the cabbage looper can be found from England to southeastern Europe.

Temperature

The cabbage looper's movement and growth depend on temperature. If the temperature is around 10 °C (50 °F), the pupae might stop developing. Very hot temperatures above 35 °C (95 °F) can cause problems for adult moths, such as bad wing development. Mating and flying are harder when it is too hot or too cold, which is why these moths move north when it gets warmer. Even though the embryos can grow in both very cold and very hot temperatures, they might not be able to hatch.

Host plants

The cabbage looper is an insect that eats from over 160 different plants. It likes plants such as cabbage and broccoli because it grows faster on them. It can also eat from tobacco plants, but these are not as good because some plants have sticky substances or tiny hairs that can harm young caterpillars. Older caterpillars can handle these plant defenses better.

The number of caterpillars on a plant can change depending on how old the plant is. Young plants are more attractive to the caterpillars. The cabbage looper can find plants by smelling their odors. Female moths that have laid eggs are especially good at finding these smells because they need plants for both food and laying eggs. The cabbage looper likes several plant smells, and a mix of different odors is even more attractive than just one smell.

Pheromones

Cabbage loopers, like many moths, use special smells called pheromones to find mates. Females release these smells to attract males. Males look for these smells to find a mate.

Males also make smells from special parts on their bodies. These smells help them attract females and compete with other males. When males are near plants that cabbage loopers like, their smells become more attractive to females. This helps females find males close to food. The smells can also help both males and females find food when they are hungry.

Enemies

Spiders, ants, and lady beetles often eat cabbage looper eggs and young caterpillars. Lady beetles are especially good at finding and eating them.

The cabbage looper can also be affected by tiny flies called tachinid flies. These flies lay eggs on the caterpillars, and the baby flies eat the caterpillar.

The moth can also get sick from a natural virus. This virus is used to help control the moth population. Another natural enemy is a soil bacterium called Bacillus thuringiensis, which can slow down the growth of the caterpillars.

Genome

The cabbage looper's DNA, called its genome, is 368.2 million base pairs long. This is bigger than the genome of the common fruit fly but smaller than that of the silkworm. The genome has genes that help the moth break down harmful substances.

Scientists found a useful tool for changing genes called the PiggyBac Transposon in the cabbage looper, and it is now used in many different species.

Interactions with humans

The cabbage looper moth can harm crops, especially vegetables like cabbage, broccoli, and bok choy. Its babies, called larvae, chew holes in leaves and eat parts of the plants. They also leave sticky waste called frass, making the plants messy. Even though this moth can damage crops, young plants can usually survive. But when the plants grow bigger, the cabbage looper becomes harder to control. This moth is tricky because it can live on many different plants.

Scientists are finding new ways to catch and control cabbage loopers. They make special traps using a smell that the moths like, called a pheromone. These traps can catch some moths, but they are not enough to stop all the damage. Because these moths can become resistant to sprays, scientists also look at natural ways to control them, like using special viruses. One safe spray approved in the US works well on the moth’s eggs. Mixing different kinds of sprays helps slow down resistance. Researchers also use cabbage looper cells in labs to make important proteins for scientific studies.