Impact of Cactoblastis cactorum on Opuntia stricta in a protected Florida inter-dune area

Cactoblastis cactorum is an important biological control agent of weedy prickly pear cactus (Opuntia spp.) in parts of the world, but an invasive species in Florida.  The moth has been established along Florida’s Atlantic Coast for over 12 years, has become widespread, and attacks all native/ornamental species of Opuntia.  A 2-year collaboration was begun in March 2012 to study the feasibility of protecting cactus from damage by C. cactorum in the inter-dune area of the Guana Tolomato Matanzas National Estuarine Research Reserve (GTM).  Using volunteers and staff, biweekly “clean sweeps” were conducted to remove all life stages of C. cactorum on plants among the dunes in a treatment area.  Plants in a similar area were monitored but C. cactorum was not removed.  Although captures of males in pheromone baited traps remained similar at both sites, eggstick numbers significantly decreased at the treated site while slightly increasing at the untreated site.  Significant decreases were identified at the untreated site in plant growth characteristics of height, pad number, and fruit/flower number.  Significant increases in all plant characteristics were found at the treated site.  GTM Opuntia spp. under attack by this moth were diminished in both plant population size and structure.