Biological control of Old World climbing fern by Neomusotima conspurcatalis in Florida: post-release impact assessment and agent monitoring

Authors: Boughton, Anthony; KULA, ROBERT - US Department Of Agriculture (USDA); Center, Ted

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 8/22/2011
Publication Date: 9/13/2011
Citation: Boughton, A.J., Kula, R.R., Center, T.D. 2011. Biological control of Old World climbing fern by Neomusotima conspurcatalis in Florida: post-release impact assessment and agent monitoring. Meeting Abstract. http://isbcw2011.uhhconferencecenter.com/. XIII International Symposium on Biological Control of Weeds.

Interpretive Summary: Old World climbing fern, Lygodium microphyllum, is one of the most problematic invasive weeds impacting natural areas in southern Florida. The brown lygodium moth, Neomusotima conspurcatalis (Lepidoptera: Crambidae), was introduced in early 2008 and rapidly developed large populations. Large larval populations caused substantial defoliation of lygodium that reduced ground cover by about 50 percent. As populations of the moth have fluctuated over recent years, some re-growth of lygodium has occurred, although recent data indicate that ground cover of lygodium is still lower than before the agent was released. Neomusotima conspurcatalis is a tropical insect and populations decline substantially during Florida’s cool winter season. This affords a period in spring and early summer when lygodium can grow in the absence of larval feeding pressure. Populations of the moth increase during late spring. By late summer, larval densities on lygodium foliage in areas experiencing moth population outbreaks may reach 2,000 larvae per square meter of ground area and may sometimes exceed 16,000 larvae per square meter. At these densities larvae cause complete defoliation and significant suppression of lygodium. Parasitic wasps were first recovered from field-collected N. conspurcatalis larvae in autumn 2008 and since that time parasitism rates have fluctuated from peaks of 20 to 34 percent to levels near zero. Six species of parasitoid have been reared from N. conspurcatalis, although the majority of individuals belong to a single, native braconid species, Rhygoplitis sp. Despite parasitism, densities of N. conspurcatalis larvae observed on foliage during autumn 2010 averaged 229 caterpillars per square meter, which was comparable to densities recorded at the same sites during autumn 2008. Results suggest that N. conspurcatalis is capable of contributing to suppression of lygodium in south Florida, although long term impacts on the population dynamics of the weed are not yet known.

Technical Abstract: Old World climbing fern, Lygodium microphyllum, is one of the most problematic invasive weeds impacting natural areas in southern Florida. The brown lygodium moth, Neomusotima conspurcatalis (Lepidoptera: Crambidae), was introduced in early 2008 and rapidly developed large populations. Large larval populations caused substantial defoliation of lygodium that reduced ground cover by about 50 percent. As populations of the moth have fluctuated over recent years, some re-growth of lygodium has occurred, although recent data indicate that ground cover of lygodium is still lower than before the agent was released. Neomusotima conspurcatalis is a tropical insect and populations decline substantially during Florida’s cool winter season. This affords a period in spring and early summer when lygodium can grow in the absence of larval feeding pressure. Populations of the moth increase during late spring. By late summer, larval densities on lygodium foliage in areas experiencing moth population outbreaks may reach 2,000 larvae per square meter of ground area and may sometimes exceed 16,000 larvae per square meter. At these densities larvae cause complete defoliation and significant suppression of lygodium. Parasitic wasps were first recovered from field-collected N. conspurcatalis larvae in autumn 2008 and since that time parasitism rates have fluctuated from peaks of 20 to 34 percent to levels near zero. Six species of parasitoid have been reared from N. conspurcatalis, although the majority of individuals belong to a single, native braconid species, Rhygoplitis sp. Despite parasitism, densities of N. conspurcatalis larvae observed on foliage during autumn 2010 averaged 229 caterpillars per square meter, which was comparable to densities recorded at the same sites during autumn 2008. Results suggest that N. conspurcatalis is capable of contributing to suppression of lygodium in south Florida, although long term impacts on the population dynamics of the weed are not yet known.