ARS | Publication request: Pre-Release Evaluation and Host Range Testing of Floracarus Perrepae (Eriophyidae) Genotypes for Biological Control of Old World Climbing Fern

Submitted to: XI Symposium On Biological Control Of Weeds
Publication Acceptance Date: May 1, 2003
Publication Date: August 1, 2004
Citation: Goolsby, J., Wright, T., Makinson, J.R., Hartley, D.M., Zonneveld, R. 2004. Pre-Release Evaluation And Host Range Testing Of Floracarus Perrepae (Eriophyidae) Genotypes For Biological Control Of Old World Climbing Fern. XI Symposium On Biological Control Of Weeds. (Eds Cullen, J.M., Briese, D.T., Kriticos, D.J., Lonsdale, W.M., Morin, L. And Scott, J.K.) PP.113-116. Csiro Entomology, Canberra, AUSTRALIA.(EDS Cullen, J.M., Briese, D.T., Kriticos, D.J., Lonsdale, W.M., Morin, L. And Scott, J.K.) PP.113-116. Csiro Entomology, Canberra, Australia.

Interpretive Summary: Lygodium microphyllum, Old World climbing fern is the most serious terrestrial weed in Florida. It is spreading rapidly across southern Florida including the Everglades. It is now too widespread to be managed using chemical or mechanical controls. Biological control is the best option for minimizing the impact of this invasive species. Foreign exploration for biological control agents of Lygodium microphyllum was conducted throughout the fern's native range in Australia, Asia and Oceania and several herbivores were discovered including a mite, Floracarus perrepae. We discovered that the mite was actually a complex of many different genotypes or host races. Each mite genotype adapted to the local host race of L. microphyllum. We developed a mobile field laboratory to travel throughout Australia and Southeast Asia to test each of the major host races and determine which one had the best potential as a biological control agent. We also used the molecular methods to analyze the chloroplast DNA from plant to select the best match for Florida. The L. microphyllum from Cape York Queensland was found to be an exact match with Florida and the F. perrepae from this location performed well on the invasive Florida genotype of the fern. We concluded that finding the origin, or genetic match, of the invasive Florida genotype in its native range was critical to finding the right mite genotype or host race to use as a biological control agent. Host range testing of native North and South American Lygodium species and important horticultural ferns is now underway prior to export of the mite to Florida for release as a biological control agent.

Technical Abstract: A biological control program for Lygodium microphyllum, an invasive climbing fern in Florida, USA was initiated in 1997. Surveys for natural enemies were conducted in the fern's native range which includes Australia, Asia and Oceania. Twenty-two herbivores were documented including an eriophyid mite, Floracarus perrepae Knihinicki & Boczek. Molecular diagnostics was used to match the origin of the invasive Florida population with the native range. The population from Cape York Queensland was found to be an exact match with the invasive populations in Florida for the two chloroplast DNA sequences analyzed. Field studies of F. perrepae were conducted which found that the mite was active year round with populations peaking during periods of ample soil moisture. Predator mites and a pathogen had significant impacts on F. perrepae populations, but heavy plant damage was still observed. Pre-release field impact studies revealed that F. perrepae caused more than 50% impact on L. microphyllum biomass production over a two-year period. Several genotypes of F. perrepae were identified from southeast Queensland, New Caledonia, China, Thailand, India/Sri Lanka, and Cape York. Each of these populations were screened for their acceptance of the invasive Florida genotype of the climbing fern. The populations from Cape York and Thailand performed best and came from fern genotypes that were most closely related to the Florida genotype.