Larva of Cactoblastis cactorum.
The cactus moth (Cactoblastis cactorum) is a moth native to South America, but an invasive species here in the US. It attacks Opuntia stricta and Opuntia engelmanii, keystone species in ecosystems of south Texas and northern Mexico, but will also attack other North American species. The female moth lays “egg sticks” on the cladode (pad) of the cactus. Each “stick” has 30-50 eggs that hatch into larvae and begin to bore into the cactus pad. The damage reveals itself via hollowed-out, yellow pads that drip with insect frass (waste.) A single caterpillar can consume an entire pad in one day. Over time, the larvae leave nothing behind but the surface cuticle and some thin fibrous tissue. With the loss of enough pads, the whole cactus dies.
The moth was first found in Brazoria County in 2017. In 2018 and 2019, the moth began colonizing and dispersing south along a narrow corridor of Texas’ coastal dunes and grasslands. Loss of these iconic cacti affect food webs and overall biodiversity.
Potential biological control might be found through a parasitoid that is host-specific and sustainable. Current research is focusing on a small Argentinian wasp.