Spore Reproduction of Japanese Climbing Fern in Florida as a Function of Management Timing Candice M. Prince1, Dr. Gregory E. MacDonald1, Dr. Kimberly Bohn2, Ashlynn Smith1, and Dr. Mack Thetford1 1University of Florida, 2Pennsylvania State University Photo Credit: Chris Evans, University of Illinois, Bugwood.org Exotic climbing ferns in Florida Old world climbing fern Japanese climbing fern (Lygodium microphyllum) (Lygodium japonicum) Keith Bradley, Atlas of Florida Vascular Plants Chris Evans, University of Illinois, Bugwood.org Japanese climbing fern (Lygodium japonicum) • Native to temperate and tropical Asia • Climbing habit • Early 1900s: introduced as an ornamental1 • Long-distance dispersal via wind, pine straw bales2,3 Chris Evans, University of Illinois, Bugwood.org Dennis Teague, U.S. Air Force, Bugwood.org Distribution • Established in 9 southeastern states • In FL: present throughout the state, USDA NRCS National Plant Data Team, 2016 but most invasive in northern areas • Winter dieback, re-sprouts from rhizomes1 • Occurs in mesic and temporally hydric areas1 Atlas of Florida Vascular Plants, Institute of Systemic Botany, 2016 Impacts Chris Evans, University of Illinois, Bugwood.org • Smothers and displaces vegetation, fire ladders • Florida Exotic Pest Plant Council: Category I species Chuck Bargeron, University of Georgia, Bugwood.org • Florida Noxious Weed List • Alabama Noxious Weed List (Class B) Japanese climbing fern: life cycle John Tiftickjian, Sigel Lab, University of Delta State University Louisiana at Lafayette Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Spore Gametophyte Sporophyte Development of Spores disperse bank stage Stage fertile fronds Management • Preventative: • Constant monitoring of areas • Remove plants prior to spore formation in the fall • Spores are easily transported by wind, water, equipment, and humans • Avoid intensive management during spore formation to limit spread Management • Biological: • Naturalized rust fungi (Puccinia lygodii) from South America will infect plants, but limited in effect • Insects currently being evaluated for old world climbing fern R. Pemberton, USDA-ARS Management • Mechanical: • Hand-pull young plants • Mowing generally not an option, take care to avoid spread • Cutting fronds - regrowth occurs. Pair with chemical control. • Fire: limited due to off-target impacts (fire ladders) Chuck Bargeron, University of Georgia, Bugwood.org Management • Chemical: • Most effective on new fronds • Glyphosate • Metsulfuron • Best results in fall prior to spores Chris Evans, University of Illinois, Bugwood.org Previous research • Herbicide studies to control mature plants: • Glyphosate, imazapyr, and metsulfuron methyl • Applications: mid-September in the western Panhandle • Glyphosate (2% v:v): best control over 2 years • Observed increased spore production following herbicide application Previous research • Timing of herbicide applications: • Objective: limit spore development • Glyphosate and metsulfuron at 4 intervals from July – Sept • Applications on individual plants • Metsulfuron: better at limiting gametophyte development Current research: • Two main objectives: 1. Determine if reduced gametophyte development is similar when applications are made at a broad, plot-level scale 2. Assess the effect of timing of herbicide treatments on sites across Florida • Two year project began in 2015 Western Panhandle sites: 1. Blackwater River State Forest (BRSF): upland longleaf pine forest 2. Neal site in Blountstown: hardwood forest • Treatments applied to 10 ft. x 20 ft. plots Central Florida sites: 1. Ocala National Forest: upland longleaf pine/sand pine 2. Lake County: hardwood forest • Treatments applied to fern patches Herbicide application: Herbicide treatments: 1. Glyphosate – 2% (v/v) 2. Metsulfuron methyl – 0.5 g per liter 3. Glyphosate + metsulfuron methyl 4. Untreated Control • Herbicide applications via backpack sprayer with a handgun. Plants sprayed to wet. Spore collection: • Fertile fronds collected 4 weeks after herbicide treatment • Spores were separated from fronds and weighed Total Spore Yield Spore yield = • Total Frond Weight Spore germination and gametophyte development: • Only BRSF and Ocala • Spores mixed in water (0.015 g spores to 20 mL water) • 4 mL spread over pot surface • Measured % cover after 5 weeks in growth chambers: • 25ºC • 75% humidity • 12 hour day Results: Results: spore yield BRSF Neal 0.16 0.16 Gly 0.14 0.14 Met 0.12 0.12 Gly+Met 0.1 0.1 Control 0.08 0.08 0.06 0.06 Spore Yield (g/g) Spore Spore Yield (g/g) Spore 0.04 0.04 0.02 0.02 0 0 July Aug Sept July Aug Sept Ocala Lake County 0.16 0.16 0.14 0.14 0.12 0.12 0.1 0.1 0.08 0.08 0.06 0.06 Spore Yield (g/g) Spore 0.04 Yield (g/g) Spore 0.04 0.02 0.02 0 0 July Aug Sept July Aug Sept Results: spore yield • No significant relationship between herbicide treatment and spore yield, in contrast to previous studies. • Inconsistencies between sites may be due to: • Site differences – hardwood sites had relatively greater shade • Reproductive biology – reproductive sporangia only develop on current year’s growth • Confounding weather events Results: spore germination and gametophyte development Blackwater River State Forest Ocala National Forest Management Implications • Although previous research suggested metsulfuron was more effective than glyphosate at limiting spore production, broadscale applications showed no differences between herbicides. • The effect of application timing was location dependent, although there were significant effects in mid-September for both sites. Current work: • Due to confounding weather events, replication of field experiments is needed to re-assess results • Three sites: 1. Jay, FL (western panhandle) 2. Ocala National Forest (central Florida) 3. Chito Branch Reserve (south- central Florida) Current work: • Test spore viability directly • % cover is somewhat subjective Current work: • Test spore viability directly • Developed methodology for spore germination on microscope slides • Measure % germination instead of % cover References: 1. Van Loan, A. 2006. Japanese climbing fern: the insidious “other” Lygodium. Wildland Weeds, Spring 2006: 25-27 2. Lott, M.S., Volin, J.C., Pemberton, R.W., and Austin, D.F. 2003. The reproductive biology of the invasive ferns Lygodium microphyllum and L. japonicum (Schizaeaceae): implications for invasive potential. American Journal of Botany, 90:1144-1152 3. Zeller, M. and Leslie, D. 2004. Japanese climbing fern control trials in planted pine. Wildland Weeds, Summer 2004: 6-9 Acknowledgements: • Funding for all studies provided by the Florida Fish and Wildlife Conservation Commission, Bureau of Invasive Species Management • USFS assistance at Ocala National Forest provided by Liz Ramirez • Site access at Blounstown provided by Neal Land and Timber Co. • Field and technical support provided by: Justin McKeithen, Nathan Mooers, and Heather Van Heuvlen Thank you! Questions? Chris Evans, University of Illinois, Bugwood.org.