Graduation Year

2006

Document Type

Thesis

Degree

M.S.

Degree Granting Department

Biology

Major Professor

Peter Stiling , Ph.D.

Keywords

Plant-insect interactions, Invasive species, Native species, Insect ecology, Biological control, Prescribed fire

Abstract

Exotic species are a great concern because of the possibility of negative effects once they become established. The exotic cactus moth, Cactoblastis cactorum has a reputation for being detrimental to Opuntia populations throughout Florida and the southeastern United States. Multiple projects are currently underway to attempt to contain and eradicate this species before it can migrate to the Opuntia-rich desert southwest and the agricultural Opuntia fields in the Mexican highlands. These projects have been undertaken without previous studies to determine what negative effects, if any, the moth is having on the common native Opuntia species. This is understandable; since it was earlier suggested that C. cactorum was doing great harm to rare and endangered species in the Florida Keys (Stiling et al. 2004). This study looks at the effects of the native moth borer, Melitara prodenialis and the exotic invader, Cactoblastis cactorum on two common Opuntia spp. within central Flo

rida. Throughout the duration of this study, the coastal plants were subjected to damage solely by C. cactorum and the inland plants by M. prodenialis. The amount of moth damage was compared between three inland and three coastal sites, as well as between plants subjected to prescribed fire and those that were not within these sites. Plant mortality was determined for both the sites and burn treatments. The number of eggsticks was also compared between inland and coastal sites and burned and unburned treatments. The results of this study show that although there is a significant difference in plant mortality between inland and coastal sites (higher mortality was shown at inland locations), there is no difference in moth damage at these sites. This suggests that the exotic moth is doing similar or less damage to the cactus than is the native moth. The number of eggsticks was also greater at coastal sites. This indicates that although the exotic moth is more prolific than the native,

it is still unable to cause higher cactus mortality rates. None of the data was significant between burned and unburned treatments, indicating that prescribed fire does not have any effect, negative or positive on the Opuntia.

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