Cactus Moth

FACTS, IDENTIFICATION & CONTROL

LATIN NAME

Cactoblastis Cactorum

APPEARANCE

The cactus moth is grayish-brown in color with dark spots and wavy lines on its wings. The hindwings are whitish with long and thin antennae and legs. As larvae, cactus moths are a bright orange-red in color with bands of large spots that become more distinct over time. Once matured, larvae are typically 25 mm to 30 mm long. The adult’s wingspan can range from 22 mm to 35 mm. Their forewings are grayish-brown, but sometimes can appear closer to white. 

BEHAVIOR, DIET & HABITS

Cactus moths are native to South America. They were introduced to Australian, Hawaiian, south African and Caribbean ecosystems in the early 20th century to control Opuntia cacti species, which had become a major pest plant. In 1989, the cactus moth was discovered in the Florida Keys. It became a serious threat to a number of cactus species. Since then, the cactus moth population has spread up the peninsula to South Carolina and northwest along the coast of the Gulf of Mexico. The cactus moth can kill most cacti, particularly those with flat pads. In Florida, the moth has already seriously damaged the populations of six species of pear cacti.

The cactus moth is most threatening to the desert environments of the southwestern United States and northern Mexico. In this environment, the pear cacti are a reliable food source for many wildlife species, including deer, iguanas and pollen-feeding insects. These cacti also serve as a shelter for many other animals like packrats. 

REPRODUCTION

Female cactus moths lay their eggs in the form of a chain. The first egg is attached to the end of the spine and the succeeding eggs are stacked in a coin-like structure. Females usually lay an average of 75-90 eggs per stick. Larvae move from the egg stick to the cladode, a padded portion of cacti, consuming and eventually hollowing out the plant from the inside as they mature. Once developed, the larvae begin to spin white cocoons in the leaf litter between crevices in the bark of nearby trees or in other safe places. 

SIGNS OF A CACTUS MOTH INFESTATION

Egg sticks are the surest sign of an infestation, but they are difficult to find without close inspection. Another visible sign is the yellowing of the cactus’ pads and brown excrement. After a period of yellowing, the pads often hollow out and collapse. When an infested pad is under bright light, the pad appears translucent and larvae can be seen feeding inside. 

ADDITIONAL INFORMATION

Cactus moth control techniques include removal of infested host cacti or the release of sterile moths. Host plant removal entails the sanitation and elimination of all Opuntia plants from an area and should only be used in certain circumstances. The use of sterile moths has proven an effective management technique, but only for small populations, as scientists are not able to produce enough sterile insects to manage a large population.