Efforts to establish a foilage-feeding moth, Austromusotima camptozonale, against Lygodium microphyllum in Florida, considered in the light of a retrospective review of establishment success of weed biocontrol agents...

Authors: Boughton, Anthony; Pemberton, Robert

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/4/2008
Publication Date: 9/15/2008
Citation: Boughton, A.J., Pemberton, R.W. 2008. Efforts to establish a foilage-feeding moth, Austromusotima camptozonale, against Lygodium microphyllum in Florida, considered in the light of a retrospective review of establishment success of weed biocontrol agents.... Biological Control 47 (2008), pp. 28-36.

Interpretive Summary: Old World climbing fern, Lygodium microphyllum is a serious invasive weed in southern Florida. Biological control is an approach that uses insect and mite herbivores from the native range of an invasive weed, and introduces them into areas that have been colonized by the invasive weed. These herbivores feed upon the invasive weed and reduce its capacity for growth and reproduction. Unfortunately, relatively few insects and mites feed upon L. microphyllum, which makes developing biological control options more difficult. Austromusotima camptozonale is a species of moth whose caterpillars do feed on L. microphyllum. Austromusotima camptozonale was the first biological control agent to be approved for release against L. microphyllum in the United States. From 2004-2005, 10,555 adult moths of A. camptozonale were released at lygodium-infested sites but subsequent monitoring failed to recover surviving insects. From 2006-2007, 30,000 A. camptozonale caterpillars were released at sites in southern Florida, but survivors were never recovered from sites in pine flatwoods or on Everglades’s tree islands, and were only recoverable for three months at sites in cypress. Studies in which A. camptozonale eggs and caterpillars were set out at release sites and subsequently retrieved, indicated no evidence of predation or parasitization of eggs, although eggs in pine systems suffered 20% mortality, attributed to high temperatures. No evidence of parasitization of A. camptozonale larvae was detected, although significantly fewer caterpillars were recovered on plants to which predatory insects had access, relative to plants from which predatory insects were excluded. Ants were recovered trapped in the exclusion treatments and had previously being observed predating A. camptozonale in the field. Based on rates of establishment observed in past weed biocontrol programs, the attempted introduction of a moth as a biological control agent would not be a strategy predicted to offer the best likelihood of success. However given that the selection of insect herbivores that feed on L. microphyllum in its native range is limited, and that moth species make up a large proportion of these herbivores, we had few alternatives but to proceed with efforts to introduce A. camptozonale. We conclude that ant predation was a contributing factor in the failure of A. camptozonale to establish.

Technical Abstract: Old World climbing fern, Lygodium microphyllum, is a serious invasive weed in south Florida. Development of biological control is vital for sustainable management of L. microphyllum, although candidate control agents are limited. Austromusotima camptozonale was the first agent to be approved for release against L. microphyllum. From 2004-2005, 10,555 adults were released at lygodium-infested sites but subsequent monitoring failed to recover insects. From 2006-2007, 30,000 larvae were released, but survivors were never recovered from pine or tree island sites, and were only recoverable for three months at cypress sites. Studies in which A. camptozonale eggs and larvae were set out at release sites and subsequently retrieved, indicated no evidence of predation or parasitization of eggs, although eggs in pine systems suffered 20% mortality, attributed to high temperatures. No evidence of parasitization of A. camptozonale larvae was detected, although significantly fewer larvae were recovered in treatments to which walking predators had access, relative to Tangle-Trap exclusion treatments. Ants were recovered trapped in Tangle-Trap treatments and had previously being observed predating A. camptozonale in the field. Based on rates of establishment observed in past weed biocontrol programs, colonization of a lepidopteran agent within the Pyralidae sensu lato, would not be a strategy predicted to offer the best likelihood of success. However a limited herbivore fauna composed predominantly of Lepidoptera offered few alternatives. We conclude that ant predation was a contributing factor in the failure of A. camptozonale to establish.