2012 Annual Report
1a.Objectives (from AD-416):
Objective 1: Discover, identify, and initiate the characterization of new biological control agents for targets, including, but not limited to, the weeds Melaleuca quinquenervia, Lygodium microphyllum, Casuarina spp., Paederia foetida, Rhodomyrtus tomentosa, Triadica sebifera and Hydrilla verticillata, and the psyllid pest, Diaphorina citri. Other weeds and insect pests that are invasive in the U.S. and native to Australia and/or Southeast Asia can become priority targets as required.
Objective 2: Conduct preliminary field and laboratory research on natural enemies to assess efficacy and host-range to determine their potential for use as biological control agents. Assess results to prioritize potential agents for introduction into the United States. Expedite establishment of high-priority agents by collecting, rearing and shipping to U.S. collaborators for high priority target weeds, such as additional agents for M. quinquenervia.
Objective 3: Conduct ecological studies on targets that identify the key regulatory factors in its native habitat and use this understanding to direct selection of agents.
1b.Approach (from AD-416):
Objective 1: Foreign exploration will be conducted in Australia and Southeast Asia for potential biological control agents of Melaleuca quinquenervia, Lygodium microphyllum, Casuarina spp., Paederia foetida, Rhodomyrtus tomentosa, Triadica sebifera and Hydrilla verticillata and additional weed targets as determined by ARS and stakeholders. Selection of search areas will be guided by the center of origin of the weed species (classical and molecular diagnostics), habitat diversity, climate matching, specific phenology and ecology of the targets, and consultation with local and foreign contacts.
Objective 2: High priority agents identified in exploration will be further evaluated in laboratory and field studies. Studies will investigate the basic biology of the organism, seasonal phenology, impact on its host, and host range. Specific aspects of an agent’s biology such as critical temperature limits will be investigated.
Objective 3: Field and laboratory studies will be conducted on target weed species which measure factors such as stand regeneration, seed production, biomass accumulation, litter fall, etc. Data will also be used to identify biological attributes that can be manipulated with biological control agents to affect control.
Evaluation and colonisation of the gall midge Lophodiplosis indentata and the stem-galler L. trifida was the priority for research on the biological control of melaleuca, Melaleuca quinquenervia. A greenhouse-based experiment was designed to examine the interactions of L. trifida and L. indentata and the consequence plant-stage-specific impacts on seedlings and sapling of melaleuca. Preliminary results indicate little interference between the species with major impacts of melaleuca growth rates.
Overseas exploration continued to focus on the Lygodium stem-boring pyralid moths, Ambia sp., that are known to occur in Singapore, Hong Kong, mainland China, Malaysia and Thailand. Research continued to survey the abundance of these moths at several sites at different times of the year so that seasonal fluctuations and preferred habitat conditions could be modelled to assist with coordinating field surveys and to locate new collection sites. This year the priority for research was a similar stem-boring species attacking L. microphyllum near Bamaga on Cape York, Queensland, Australia. Large numbers were reared successfully. Colonisation and host-range testing could commence within the next year. Larvae of the defoliating sawfly Neostrombocerus albicomus were collected by ABCL staff in Thailand and shipped to IPRL in Florida for the completion of host-range testing.
Surveys of downy rose myrtle, Rhodomyrtus tomentosa, continued in mainland China, Hong Kong and Thailand. Thus far 29 moth species from 10 families and three Coleoptera species from three families have been discovered feeding on R. tomentosa. Some preliminary host range testing has been conducted at IPRL quarantine in Florida and these studies will be expanded to ABCL quarantine in Australia within the next year. Field collected immatures were reared for taxonomic purposes and new host records on R. tomentosa were determined for several Lepidoptera species including the Arna bipunctapex (Lymantriidae) and Metanastria gemella (Lasiocampidae). Surveys were conducted in November 2011 and again in June 2012. Demography research in China was conducted in collaboration with staff from the Chinese Academy of Sciences in Wuhan.
Exploratory research continued on Australian pine, Casuarina spp. and the Queensland Tree Fern, Cyathea cooperi, pests in Florida and Hawaii respectively. Several potential biological control agents are being evaluated at ABCL including a Selitrichodes sp. gall wasp on Casuarina glauca and a Tortricidae defoliating moth on C. Cooperi.
Lygodium microphyllum is a serious weed in south Florida and threatens natural wetland areas such as the Florida Everglades. Stem-boring moth larvae of Ambia spp. moths are being evaluated from Asia as biological control agents for this fern but rearing under quarantine conditions has been problematic. Incremental improvements were made this year in rearing techniques and several F1 generation adults were reared. Research has focused on a new stem-boring moth species recently discovered in Australia, attacking L. microphyllum near Bamaga on Cape York, Queensland. Evaluation of this species outside of the confines of quarantine has resulted in major improvements in rearing. Further progress could lead to colonisation and host-range testing of this and other Asian species.
Downy rose myrtle, Rhodomyrtus tomentosa is native to Asia and was introduced into the U.S. as an ornamental plant in the late 1800’s. It has become invasive in Florida and Hawaii, where it displaces native vegetation. Exploration for biological control agents has been undertaken by ABCL in South East Asia, particularly Hong Kong, mainland China and Thailand. Over 30 insect herbivores have been identified for further evaluation including defoliating and stem-boring Lepidoptera. This year multiple shipments were made from Hong Kong to IPRL in Florida where the insects were reared for identification and preliminary host-range testing was performed.
Evaluation of the gall midge, Lophodiplosis indentata, continued at the USDA ARS Australian Biological Control Laboratory in Australia (ABCL) in Brisbane for the biological control of the melaleuca paperbark tree, Melaleuca quinquenervia, a serious weed in south Florida where it invades wetland areas. A sister species, L. trifida, has already been released in Florida and spread rapidly causing extensive damage to saplings. Two other released agents, a foliage-feeding weevil and a sap-sucking psyllid, discovered by ABCL staff have had a significant impact on this tree. The melaleuca project has been a major success in biological control as a result of collaborative research between the ABCL in Brisbane and the USDA ARS Invasive Plant Research Laboratory (IPRL) in Fort Lauderdale and Gainesville, Florida. A greenhouse-based experiment was designed to examine the interactions between L. trifida and the yet to be released gall fly L. indentata. Preliminary results indicated little interference between the species with major impacts of melaleuca growth rates.