Cactus Moth

If you live in an area with a lot of cacti, chances are you are familiar with cactus moths.

These pests are not dangerous to people but can cause quite a bit of damage to cacti, especially prickly pear. To help control the growth of prickly pear cacti, some areas have introduced this South American native moth to their ecosystem. Learn more about how to identify cactus moths, their habitat and habits, as well as how to keep their expansion to safe levels.

Cactus Moth Species, Types, and Scientific Name

Cactus moths, also known as Cactoblastis cactorum, are part of the Cactoblastis genus. There are five other species in the genus and they are all native to the same area of the world. There are no different types of cactus moths, only C. cactorum. Adult male and female cactus moths are not recognizable to most observers, although some may be more familiar with the larvae of cactus moths.

They belong to the Pyralidae family of moths and are part of the Lepidoptera order. Lepidoptera includes all moths and butterflies. Like all other moths, cactus moths are most active at night. They can be hard to spot due to their coloring and that they are most active after the sun has gone down. They have four wings, which they keep extended around their bodies while at rest. In contrast, butterflies fold their wings vertically when resting.

Appearance

Cactus moths aren’t all that exciting to look at, unfortunately for people trying to spot them in the wild. This helps the cactus moths blend into their surroundings, however. Adult cactus moths are brownish-gray. They have four wings: two forewings and two hindwings. Cactus moths do not have any distinctive markings on their wings or bodies. They do have two antennae and are similar in appearance to other moths in the Cactoblasis genus.

The wingspan of a cactus moth can be between 0.91 to 1.57 inches. Females tend to be a little bit larger than males, although it is not a very visible difference for the casual observer. These are smaller moths and don’t grow to be especially large or recognizable. Cactus moth larvae get up to 0.98 – 1.18 inches when fully grown and ready to pupate.

If you want to spot a cactus moth and recognize its species, your best chance is to find it when it is still a caterpillar larva. Cactus moth caterpillars are light pink and become a darker orange as they grow and mature. They have distinct black bands around their bodies. If you see a black-striped orange larva crawling around on a cactus leaf, chances are it is a cactus moth.

After they pupate and become moths, these more distinct colors are replaced by the drag brownish-gray that helps them blend into their habitat as adults. The larvae are exclusively located on cacti if they are going to survive. Female cactus moths lay their egg sticks on cacti so that when the larvae hatch, they can get right to eating.

Habitat

One of the best clues that you can find to tell you if you are looking at a cactus moth is to consider its habitat. Cactus moths lay their eggs in the flat leaves of cacti. The larvae then consume the cacti as a parasite. In their native South America, the cactus moth population is kept in check by their natural predators. Ants and New World Monkeys eat the larvae. This keeps them from reproducing and becoming invasive.

In other places where cactus moths have been introduced, these natural predators do not exist. Cactus moths larvae are free to infest and kill off cacti without any checks and balances. Female cactus moths lay their fertilized eggs directly onto cacti. When they turn into larvae, these little guys and gals consume the cactus leaves, fruit, and eventually enough of the plant to kill it.

Cactus moths were actually introduced to Australia and later the Caribbean and South Africa to help control the cacti population. They had quite a bit of success, especially in Australia. They soon became invasive in some areas, however.

How Cactus Moths Spread

Some cactus moth expansion was planned, such as that in Australia. The spread of cactus moths to other areas occurs when infested cacti are transported. The moths can also be moved by human dispersal and livestock dispersal. Areas where cactus moths pose a serious threat to the natural ecosystem, such as the Southwestern United States, track cactus moth infestations very closely. They encourage residents with infestations to get them treated right away.

Diet

Cactus moth larvae eat cacti plants. They are a parasite on these plants, consuming them to the point where the plant dies. Cactus moths are very destructive to cacti, especially prickly pear cactus. In areas where certain species of cacti became invasive, cactus moths provided a great natural way to keep the cactus population under control.

As they were brought out of their natural habitat to other areas, however, cactus moths continued to look for cacti. They are now found in Florida, South Carolina, Texas, and the Southwest. In these areas, their preferred food, the prickly pear cactus, is also a valuable part of the ecosystem for other animals. Food is scarce in some areas, especially deserts, and without the prickly pear cactus, other species are in significant danger. For this reason, the cactus moth is considered an invasive species in some areas. Pest treatments and controls help keep these moths from infesting cacti that are needed.

Adult cactus moths do not live long. Their main purpose is to reproduce and create the next generation of cactus moths. Once they find a plentiful food source to lay their eggs on and feed the larvae that will develop, it is unlikely that the adult cactus moth will travel much further.

Prevention: How To Get Rid Of Cactus Moths

The best way to keep the cactus moth population from growing too large is to remove the egg sticks that the female lays before they can develop into larvae. Cactus moth larvae burrow into cacti leaves to eat, resulting in an infestation that is very hard to get rid of. Once a cactus has been infested with cactus moths, it is unlikely to survive. Allowing the larvae to eat, grow, and reproduce will result in many more cactus moths. This endangers other cacti in the area and contributes to the overall invasiveness of the species.

Some pest control companies are able to eliminate cactus moths. They will remove the larvae or infested plants. They may also opt to release sterile adult cactus moths to prevent future fertilization and spread. This works for small infestations, although isn’t a feasible option for large infestations.

In their natural habitat of South America, natural predators and disease keep cactus moths from overtaking the wildlife. Ants and some monkeys eat cactus moth larvae. New World Monkeys can even dig into cactus leaves with a cactus moth infestation to get a tasty morsel. Other factors, such as moth parasites and disease, control the spread of cactus moths in these areas.

Where cactus moths have been introduced by people, including in Australia, the Caribbean, and parts of the United States, these natural predators are not present. This lets cactus moths spread faster. Pest control companies become the best way to prevent and treat cactus moths.

How to Tell if You Have a Cactus Moth Infestation

If you see the visible egg sticks laid by the female, you will know that you have a cactus moth infestation. Visible larvae are another clear indication. Because the larvae burrow and eat quickly, you may not be able to see them before they are already infesting your cactus. If you notice your cactus leaves turning yellow or drooping, it may be time to check for cactus moth larvae feeding inside. In some cases, you may even be able to see them wriggling around as they eat when you hold the leaf up to a light source.

1. Invasive Species Info, Available here: https://www.invasivespeciesinfo.gov/terrestrial/invertebrates/cactus-moth
2. Orkin, Available here: https://www.orkin.com/pests/moths/cactus-moths