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Cactus Moth (Cactoblastis cactorum) |
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Cooperative Research on Control Strategies
Currently, the best hope for control of C. cactorum lies with mechanical removal of host plant material supplemented with the use of the sterile insect technique (SIT). There are effective insecticides if applied at the time when egg sticks or neonate larvae are present. Insecticides would only be appropriate in urban or agricultural situations, not in the vast natural environment where prickly pear cactus is widespread and negative impacts from chemicals to non target insects and animals would be unacceptable. The candidate biological control agents that are known are not specific enough in their host preferences to be considered at this time. However, additional studies on natural enemies are being conducted by the ARS South American Biological Control Laboratory in Argentina (Guillermo Logarzo and Laura Varone).
A trapping system was developed by researchers with the USDA Agriculture Research Service (ARS) and APHIS to monitor the presence and spread of C. cactorum. A wing trap (see photo below) is baited with a synthetic female sex pheromone that draws male C. cactorum into the trap where they are captured in the sticky trap bottom. The synthetic pheromone was identified by researchers with the ARS in Florida (Robert Heath, Nancy Epsky, Barbara Duben, and Peter Teal). Additional work is planned with ARS and a Mexican scientist (Juan Cibrian) to improve the pheromone.
Cactus removal has been the key control tactic throughout the program area with massive amount of the host being removed from areas that served as breeding grounds and colonization sites for the cactus moth pest. Dauphin Island and Fort Morgan in Alabama have been cleaned of cactus host plants with only a few stands left where property owners wanted to maintain the plants and some regrowth occurring. Pensacola Beach was cleaned of most host cactus at the end of the 2009 summer. The goal is to create an area with low amounts of host cactus between Dauphin Island, Alabama and Pensacola Beach, Florida. In this manner a barrier program can be maintained that should stop the natural westward spread of cactus moth into the western US and Mexico.
USDA, ARS and APHIS researchers in Florida (Stephen Hight), Georgia (Jim Carpenter), and North Carolina (Ken and Stephanie Bloem) have made great strides in research since 2000 and the resulting technical developments make SIT a viable alternative for suppressing C. cactorum populations. The artificial diet developed is effective to make large scale artificial rearing possible and the irradiation biology testing indicates that reared sterilized insects are as competitive as native moths in field cage studies. The concept of control using the SIT is to first reduce the pest population in an area by destroying infested plants and killing the insect, and then to overwhelm the remaining native population with sterile individuals; thereby drastically reducing the probability of native females mating with fertile, native males. The SIT program has been effectively used in Mexico and the United States to eradicate outbreak populations. Research by ARS and on-the-ground operational efforts by APHIS are continuing with the expectation that the SIT will be used to not only eradicate outbreaks of C. cactorum, but to create a barrier that prevents the expansion of this pest into the western United States and Mexico.
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The Pherocon® 1C wing trap has been tested by ARS and shown to be the most effective design at attracting males moths, with an optimum 3 to 4 foot trap height. Image: Stephen Hight, ARS. |
| Rearing C. cactorum on an artificial diet and irradiator used to sterilize pupae | |
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C. cactorum rearing trays |
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C. Cactorum larvae |
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Irradiator |
