Controlling invasives with biology at CREW

By Allison Vincent

Lygodium Microphyllum

Have you ever been out on the trail, any trail, and that friend that knows a thing or two about invasive species points out a few for you? He or she discusses the threat they pose to the native ecosystem that they’re encroaching on and you wonder, what can we do about it?

One highly successful way of managing invasive species is to employ a biological control agent, using other living organisms to help control invasive and non-native species. It’s a way of reacquainting invasive pests – such as Old World Climbing Fern or Lygodium microphyllum – with their natural enemies to provide natural and sustained population reduction. In the case of Lygodium, the enemy is the brown Lygodium moth (Neomusotima conspurcatalis) which has been successfully used in Florida since 2008.

It’s time-consuming and difficult to get official approval to use biological control agents, but it’s worth the wait. Some agents have proven to be very successful and without unintended consequences. Biological treatment studies often extend for decades before hitting the ground, assuring that there are no negative impacts beyond their intended use.

You may have noticed technicians at the CREW Bird Rookery Swamp trails lately distributing state-approved biological control agents near pockets of a certain species. They hope to limit the expansion of Lygodium from the area – a tall order, as it is one of the worst invasive species, crowding out many native plants and habitats for wildlife. Management of this invasive plant using traditional strategies, such as mechanical and chemical treatments, has proved difficult and expensive, with limited long-term success. Enter biological control agents.

Without natural competition, invasive plants like Lygodium will inevitably wreak havoc on an area not ready for its intense growing cycle. Each fertile leaflet has 133 sori – or the frilly bits on the fern – and each sori has 215 spores! Multiply those numbers to find that each fertile-female leaflet may spread 28,500 spores into the surrounding area (Volin et. al, 2004). It doesn’t stretch the imagination to picture the fern-filled scene should the invasion go untreated. Every invasive plant spreads through different means and in the case of Lygodium, the female portion of the plant with her fertile spores does the work. Other common invasive plants, like Caesar weed, spread by other vectors, such as wildlife and humans. Caesar weed has a particularly sticky bur containing lots of seeds, so be sure to trash those burs that make it home with you after a hike.

Trail camera photo of Florida black bear covered in caesar weed “burs”

But how do the land managers, the South Florida Water Management District (SFWMD) in the case of CREW, go about treating such a powerful invasive plant? Well, they fight fire with fire, sometimes literally, as prescribed fires, after other biological and chemical treatments, have been known to increase the successful die-back – or sustained control of plant spread – both above and below the ground. Many times land management uses a combination of mechanical, chemical and biological control to yield the best results.

In the case of Lygodium, the biggest observable impact in the long-term comes primarily from biological control and, in particular, those brown Lygodium moths. While other species have been introduced and had some success in destroying Lygodium, the brown Lygodium moth has unleashed the biggest disaster for this invasive plant.

Neomusotima conspurcatalis, the brown lygodium moth

It all starts with little caterpillars, who feed on fern leaflets causing browning of leaves and breakdown of entire Lygodium plants. Female moths lay an average of 136 eggs during her short life span – the life cycle of the moth from egg, through caterpillar and pupa to adult, is only about 30 days. Researchers observing the impact of testing sites over 4-6 months found that moth populations increased, and noticeable caterpillar feeding damage in the form of browned-out patches of Lygodium became apparent. Good for us, bad for Lygodium.

Throughout the history of CREW, biological control agents have been used as one element of a three-part approach to treat the invasive Melaleuca quinquenervia tree on the CREW lands. You can still see the process in action in the “Melaleuca graveyard” on the Red trail of CREW Flint Pen Strand where large stands of trees were treated with a combination of mechanical and chemical treatment. Later, biological control agents were added for long-term success – if you look closely you can still see weevils and psyllids, the Melaleuca-loving biological control agent.

We all benefit from the long-term research studies on biological control agents. Through partnerships with leading wildlife agencies and the SFWMD, land managers for the CREW lands hope to see similar results, like the sustained success on throughout the state. There will always be a need for invasive treatment, but with each step we take toward restoring our natural Florida environment, everyone benefits.

CREW Flint Pen Strand lands under preservation for future generations to enjoy!

Horseback Riding on the CREW Trails

By Allison Vincent, CREW Trust Communications Director

Equestrians at CREW Cypress Dome trails

Have the equestrian trail rules changed? Not exactly, but there has been some need for clarification. The CREW lands, managed by the South Florida Water Management District in partnership with the Florida Fish and Wildlife Conservation Commision (FWC), have designated two trail systems available for riding. Two equestrian access points are available to riders, including one at CREW Flint Pen Strand main parking lot for the Yellow trail North and South, and the other at CREW Cypress Dome trails. Trails were designated for equestrian use based on several parameters, including the impact horses have on various ecosystems, including sensitive wetlands. 

To help make these rules easier to navigate for our equestrian riders, the language was updated on the special use license (SUL), the permit required to ride, including a map with more specific instructions for each trail location. Additionally, for the protection of the preservation lands, especially the wetlands, brown signs have been installed along the trails at CREW Flint Pen Strand aimed as a last effort to remind riders of the boundaries patrolled by FWC law enforcement. 

You might be wondering why aren’t all the trails accessible to equestrians? This is a complicated question, but ultimately it comes down to the long-term protection of the 60,000-acre watershed and the role preservation plays in the recharge of the local aquifer where our drinking water is extracted. Understandably, horses cause more disturbance to the land on which they tread than the average hiker, especially in sensitive areas throughout much of the CREW Flint Pen Strand trails. Which is why hikers won’t find equestrian riders in wetland and marsh areas such as the new Purple trail and lakes area of the CREW Flint Pen Strand trails, nor will they ever be seen on the CREW Bird Rookery Swamp tram. However, when you share the multi-use trails available to horseback riders, like the Yellow trails North and South, please be sure to yield to the horses.

Thank you to all our equestrians for pulling permits and staying on the designated trails. Your cooperation ensures the conservation of these CREW lands for future generations. We hope you enjoy the equestrian trails at CREW Flint Pen Strand and CREW Cypress Dome trails. 

Permit Required:

  • Learn pertinent information about equestrian riding trails by going to crewtrust.org/horseback-riding
  • Permits provide you with legal permission from the South Florida Water Management District with the Special Use License
  • Register yourself through the SUL page and pulling permits becomes quick and easy

National Trails Day

June 5th, 2021

A Day of Service and Advocacy for Hometown Trails

Join the CREW Trust and take the #NationalTrailsDay Pledge. Millions of people have found physical, mental, and emotional restoration on trails during the pandemic.

Let’s return the favor.

Together we can care for our hometown trails and advocate for equitable access to quality green space.

Taking place on the first Saturday in June, National Trails Day® is a day of public events aimed at advocacy and trail service. 

Thousands of hikers, bikers, rowers, horseback riders, trail clubs, federal and local agencies, land trusts (including the CREW Trust), and businesses come together in partnership to advocate for, maintain, and clean up public lands and trails. 

So no matter where you are, celebrate National Trails Day and join trail lovers everywhere on June 5th! Here’s how you can get involved: 

While the CREW Trust doesn’t have a group event scheduled this year, you can get together with friends and family and make a difference on any trail. The CREW trail system with the most need is at CREW Flint Pen Strand. Bring some trash bags and a few extra hands to help pack out some of that unnatural garbage! Remember, trash collects trash, so the more we can pack out together, the longer lasting impact your work will have.

Not in southwest Florida? Check out these resources for events and needs in your area

Discing, shredding, prescribed fire and other disruptive yet helpful things at CREW

By Allison Vincent

Pine trees and understory growth after a prescribed burn at CREW Flint Pen Strand

Some recent guests on the CREW trails have inquired why they’re torn up? The long-range plans and efforts of the South Florida Water Management District (the District hereafter) can be a challenge on initial view, as “discing” and “shredding” projects can resemble hog damage or really knobby ATV tires wrecking havoc, both of which land managers set out to prevent. So why are they seemingly adding to the destruction? 

These tracks of discing and shredding are in fact intentional and well-planned measures designed to prepare for upcoming prescribed burns or chemical treatment, ultimately preventing vegetation from getting out of control. Vegetation can include non-native plants, shrubby understory, or native plants and trees that have grown out of balance with historical norms. Forestry science is behind the land management plans in place and its driving force is the long-range preservation goals of the CREW project. 

Even though the trails look less than ideal when torn up and the rough patches can make hiking and biking more difficult, just remember why CREW is here in the first place. It’s all about the water. These efforts benefit the watershed where we get our drinking water. Also, it’s good to think of the hierarchy of needs throughout the CREW lands like this: it begins with water and land management, then comes preserving habitat and then recreational opportunities for everyone.

Let’s discuss the management process we’re looking at on the trails. In order to perform a prescribed burn the District team must get approval from the state of Florida. Often this overlaps with an annual shredding plan, replete with maps and intensity, to clear the ground of any obtrusive vegetation before burns are scheduled. The burn prescription is based on several environmental factors, such as wind speed and direction, humidity and the burn history in the area. 

Assuming the burn prescription was approved the team, formed from several agencies including the Florida Fish and Wildlife Conservation Commission (FWC hereafter), must then coordinate their efforts and communicate their plans with the surrounding community. Working from a burn map (or planning map), the lead manager will direct the team to burn the fire line. In constant communication, the team stays on the fire from start to finish, following up the next several days for safety and reporting. 

Ultimately, the goal is to decrease the amount of understory vegetation in the CREW project, to prevent wildfires from getting out of hand, and encourage healthy native species growth. Many native fire-dependent species exist in the CREW lands, including the Slash Pine trees and Saw Palmetto which have evolved to withstand heat and benefit from fire. Prescribed burns also benefit the wildlife native to CREW, including the gopher tortoise, which prefers some open scrub to the encroachment of the long-living Saw Palmetto.

Hopefully, the next time you see the process or after-effects of the land management efforts to preserve these lands you will have a better understanding of their long range intentions. If you would like to learn more about this process, there are a few great resources found here. Always feel free to reach out to our office or that of the District with your questions.

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