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Gaining Ground on Lygodium microphyllum

E.M. Call1, S. Duke-Sylvester2, A.G. Snow1, L.A. Brandt3, D.L. DeAngelis4, and L.J. Gross2.

 1U.S. Geological Survey 2University of Tennessee 3U.S. Fish and Wildlife Service 4U.S. Geological Survey, Department of Biology, University of Miami

Poster presented at the 2004 A.R.M. Loxahatchee NWR Science Workshop on May 17, 18th, 2004.

Background:

photo of lygodium cover
Vegetation monitoring plots provide information about the affects of herbicide treatments on Lygodium and native plant species. [larger image]
The Everglades ecosystem is under threat from invading species. One species that is spreading at an alarming rate is Old World Climbing Fern (Lygodium microphyllum). This native to Africa, Australia, Asia, and Melanesia was discovered as a naturalized population in 1965 in South Florida. The rapidity of this exotic's invasion can be explained by its efficient reproductive strategies. Spores are released from fern fronds in the tree canopy and dispersed by wind. Each fertile leaf has the potential to produce 20,000 spores. To address L. microphyllum infestation within A.R.M Loxahatchee National Wildlife Refuge, an optimal control model is being developed. The model incorporates information relating to spore dispersal patterns, levels of infestation, treatment costs, and effectiveness. This model will serve as a tool to aid managers in identifying the most efficient way to treat L. microphyllum.

Study Objective:

  • Provide a method to collect all available data and suggest additional requirements.
  • Provide a means to assess the impacts of alternative possible control schemes.
  • Provide guidance to managers regarding the economics of control.

photo of lygodium leaves
Old World Climbing Fern (Lygodium microphyllum). [larger image]

systematic reconnasaince survey graph
(Above) Systematic Reconnaissance Surveys are flown by an aircraft every 2 years to document the levels of exotic plant infestations across the refuge. [larger image]
ikonos graph
(Above) IKONOS satellite imagery provided a detailed distribution map of Lygodium microphyllum in the refuge. [larger image]
spore disposal graph showing percentage of highly infected areas
(Above) Placement of spore traps within the refuge. [larger image]
exotics treatment graph for 2001-2004
(Above) Areas that exotic plant species have been or will be treated. [larger image]

Treatment Effectiveness Research

Ground: The cut and spray (glyphosphate) method is highly effective but costly and may not be logistically feasible at a large scale (Thomas and Brandt 2003).

Aerial: Glyphosphate and Escort showed different effectiveness 12 and 24 months post treatment.

12 months* 24 months*
Glyphosphate 97% 57%
Escort 66% 8%

*% decrease in live Lygodium from pretreatment values.

arrow pointing down towards "optimal control model"

Treatment Costs

Relative (est.) Cost Per Acre (cpa)
Per Tree Island Per Treatment Method/Type

Treatment Method Ground Aerial
Treatment Type cut 'n spray foliar Escort glypho-
sphate
Lightly infested $300 $45 $40 $85
Moderately infested $600 $90 $40 $85
Moderate-heavy $875 $125 $40 $85
Heavily infested $1,100 $150 $40 $85
arrow pointing towards "optimal control model" arrow pointing towards "optimal control model"

Optimal Control Model

arrow pointing towards user interface icon
user interface icon showing woman saying "lygodium microphyllum, you are done for!"


What are our management goals?

  • Stop the spread of L. microphyllum.
  • Keep infestation levels where plants are unable to reproduce.
  • No new infestations over X number of years.
  • Obtain maintenance control by 2017.

Significance of results:

close up photo of lygodium leaves
Lygodium microphyllum fertile frond. [larger image]
The Optimal Control Model will serve as a tool that will allow managers to answer important questions such as:
  • What is the most optimal control strategy, given treatment must occur in X amount of time?
  • What is the best treatment strategy to attain maintenance control by 2017?
  • How often do we have to treat to maintain maintenance control?
  • Given a number of different treatment scenarios, what is the level of infestation for each at 5, 10, 15, 20 years post treatment?
  • Which areas are best to treat to avoid spread?
  • Given X amount of funding, what is the best treatment strategy?

Acknowledgements:

  • The National Science Foundation funded model development and analysis through grant (DMS-0010920) to the University of Tennessee.
  • Ken Rutchey, IKONOS classification.
  • USGS/FWS Science Support Project funded field work.

Citations:

Brandt, L.A. and F.J. Mazotti. 2003. Effectiveness of different aerial spray for control of Lygodium microphyllum on tree islands - 12 month monitoring report.

Thomas, W.G. and L.A. Brandt. 2003. Monitoring ground treatments of Old World Climbing Fern (Lygodium microphyllum) on the Arthur R. Marshall Loxahatchee NWR. Wildland Weeds. Vol. 6, Number 2.

National Science Foundation logoUnited sStates Geological Survey logoUniversity of Tennessee at Knoxville logoU.S. Fish and Wildlife logo


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Related information:

SOFIA Project: Collection of Information on the Old World Climbing Fern for Use in a Model for Control of this Invading Vine




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