Cactus moth (Cactoblastis cactorum)

Historic, Archive Document

Do not assume content reflects current
scientific knowledge, policies, or practices.

aSB945
• P95C33

Pest Alert

Plant Protection and Quarantine

August 2009

■ Cactus Moth

(Cactoblastis cactorum)

Cactus moth larvae.

Adult cactus moths (male on the left;
female on the right).

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

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 egg stick.

Damage to prickly-pear cactus pad
caused by larvae of the cactus moth.

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 land-
grant 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.

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