What Is It?

Adult cactus moths are 

inconspicuous, brownish-gray 

moths with two wavy transverse 

bands on their wing tips. 

Females are generally larger 

than males, and their wings are 

slightly darker.

Caterpillars of this moth are 

capable of destroying entire 

stands of cacti with their feeding. 

The moths feed exclusively 

on prickly pear cacti, thereby 

threatening native landscapes 

and agriculture in the Southern 

United States and Mexico.

Where Did It 

Come From?

The cactus moth occurs 

naturally in the northern parts 

of Argentina, in Uruguay and 

Paraguay, and in the southern 

parts of Brazil. The moth was 

Pest Alert Plant Protection and Quarantine

August 2009

Cactus Moth 

(Cactoblastis cactorum)

introduced into Australia and 

South Africa, and from there 

spread to the Caribbean islands 

and the United States. Cactus 

moths are now found in Alabama, 

Florida, Georgia, Louisiana, 

Mississippi, and South Carolina.

What To Look for and 

Where To Look

1. Check for Larvae. Adult 

moths are difficult to identify 

without dissection. So the best 

detection strategy is to look for 

the cactus moth’s distinctive 

larvae. Mature larvae are 

reddish-orange with blackish 

spots forming transverse bands. 

In larvae in their final (sixth) 

instar, these transverse bands 

are nearly always divided into 

spots.

2. Check for Egg Sticks. 

Between late February and 

November, adult cactus moths 

lay chains of eggs called egg 

sticks that resemble the naturally 

occurring spines on prickly 

pear pads. The egg sticks 

are initially cream colored but 

darken to brown, and later 

almost black, shortly before the 

larvae emerge. The egg sticks 

are distinguished from spines 

by their curved appearance. An 

egg stick with about 70 eggs is 

approximately 2.4 cm (nearly 1 

inch) long. Other native prickly 

pear-feeding moth species in the 

genus Melitara also lay their eggs 

in sticks. Their egg sticks cannot 

reliably be distinguished from 

those of the cactus moth.

Cactus moth larvae.

Adult cactus moths (male on the left; 

female on the right).
Damage to prickly-pear cactus pad 

caused by larvae of the cactus moth.

Cactus moth egg stick.

The U.S. Department of Agriculture is an 

equal opportunity provider and employer.

Photo credits: The photograph of the 

damaged prickly pear cactus was taken 

by Joel Floyd of APHIS Plant Protection 

and Quarantine. The remaining images 

were shot by Ignacio Baez, a biological 

science technician with USDA’s 

Agricultural Research Service. 

United States 

Department of Agriculture

Animal and Plant Health 

Inspection Service

Program Aid No. 1879

Issued August 2005

Slightly revised August 2009

3. Check for Hollowed 

Cactus Pads. Cactus moth 

larvae live and feed communally 

inside the pads of prickly pear 

cacti. Damaged pads will 

show characteristic oozing of 

internal plant juices and insect 

droppings. The cactus moth has 

been found to eat most prickly 

pear cactus with flat pads in the 

genus Opuntia. However, the 

members of the genus Opuntia

known as “cholla” cactus are 

not normally hosts of the cactus 

moth.

How Does it Spread?

Adult cactus moths have been 

known to disperse naturally a 

maximum of about 24 km (16 

miles). Commercial sales of 

infected cacti, as well as weather 

events, could spread the larvae 

and eggs greater distances.

Where Should I Report 

Cactus Moth Sightings?

There are other species of 

cactus-feeding larvae that are 

native to the United States. 

These native species may be 

confused for the exotic species, 

so proper identification is 

important. To have a specimen 

properly identified, please 

contact your State department 

of agriculture or the entomology 

department at your local landgrant university. 

For information about the cactus 

moth and its impact on prickly 

pear cacti, please visit

www.aphis.usda.gov/

plant_health/plant_pest_info/

cactoblastis/index.shtml.