Location: Invasive Plant Research Laboratory2011 Annual Report
1a. Objectives (from AD-416)
To discover and identify natural enemies of Lygodium in its native range, conduct host specificity testing on promising enemies, petitioning for the release of suitable biocontrol agents with the potential for controlling Lygodium, colonizing the agents, and monitoring their effects on the target weed and on non-target vegetation.
1b. Approach (from AD-416)
Research will be conducted in the Australian Biological Control Laboratory in Brisbane and in the Austral-Southeast Asian Region and will focus on the discovery and identification and prelimary host range testing of promising biological control agents. Full host specificity testing will be conducted in domestic quarantine, after which appropriate agents will be petition for release, then after permission to release is obtained, mass reared, colonized and then monitored to determine their establishment and potential impact on Lygodium and non-target vegetation.
3. Progress Report
This research relates to in-house objective 5: Release, establish, evaluate efficacy, and corroborate environmental safety of approved biological control agents and develop and distribute the technology to customers in order to expedite their adoption and deployment. Exotic invasive weeds from overseas pose a severe threat to native plants and ecosystems within the United States. The mission of USDA-ARS Invasive Plant Research Laboratory is to find environmentally friendly, biologically based strategies for long-term sustainable management of invasive weeds within the United States. Old World climbing fern, Lygodium microphyllum, is recognized as one of the three most damaging invasive weeds currently impacting natural ecosystems in Florida. The research described below supports the mission of the national program by furthering progress towards sustainable management of L. microphyllum. Populations of the brown lygodium moth, Neomusotima conspurcatalis, have survived into their fourth year at release sites in southeast Florida. As moth populations have fluctuated over recent years, there have been corresponding reciprocal changes in ground cover of L. microphyllum. When populations of the moth decline, reductions in feeding by caterpillars allow re-growth of L. microphyllum. When large populations of the moth are present at sites, defoliation by caterpillars causes considerable reductions in ground cover of L. microphyllum. Data collected along 12 transects in March 2011, showed that less of the weed was present than before the agent was released in 2008. Surveys during fall of 2010 revealed average densities of 200-800 caterpillars per square meter of lygodium foliage, but on occasion peak densities as high as 16,000 caterpillars per square meter. At these densities caterpillars cause complete defoliation and significant suppression of lygodium. Six species of parasitic wasp have been reared from N. conspurcatalis caterpillars. Across, 22 collections of moth caterpillars made between 2008 and 2010, the overall rate of parasitism by wasps was 10 percent. A new colonization effort with the lygodium moth, Austromusotima camptozonale, was initiated in summer 2010. During fall 2010, 18,000 caterpillars were distributed in open releases, but there was no evidence of population establishment. During spring 2011, 24,000 caterpillars were released into large field cages in efforts to improve adult mating, prior to release of moths from cages. Although survival of lab-reared caterpillars was much improved inside the cages, there was no evidence that persistent moth populations had established or were increasing around the field cages, suggesting that predation remains a problem outside the rearing cages.