Monitor your ponds closely throughout the spring and make any necessary herbicide applications before weed growth becomes too excessive.
Photo Credit: Mark Mauldin
Even though the calendar says we are only a few weeks into spring, recent weather has been more like summer. The early arrival of sustained warm weather has water temperatures in local ponds high enough that aquatic vegetation growth has really taken off. This early growth period is the ideal time to evaluate ponds and address any aquatic weed issues that may be present, since aquatic weed infestations tend to become worse through the summer. Getting an early start generally helps control efforts to be more successful and less expensive, so get started sooner rather than later.
As plants grow, they are able to build up energy reserves, making them more difficult to control. The longer they are allowed to grow, the stronger and more difficult they are to control. Controlling weeds earlier in the growing season reduces this problem.
Similarly, as the growing season progresses plants produce more and more biomass. If a herbicide is applied and the weeds are killed, large amounts of decomposing plant material in the water can cause problems. The decomposition process uses oxygen; dissolved oxygen in the pond can drop to levels that are hazardous to fish and other aquatic species. The more plant material that is present when herbicides are applied the bigger concern this becomes. Applying herbicides earlier in the growing season, before large amounts of biomass are produced, can help lessen this problem.
Further compounding the issue, warm water is physically able to hold less dissolved oxygen than cooler water. Late in the summer, pond water can be very warm with low concentrations of dissolved oxygen even before large amounts of decomposing plant material are added.
To help reduce the risk of oxygen depletion never treat more than ½ of a pond at one time, if weed growth is already substantial treat no more than 1/3 of a pond at one time and always allow 10 -14 days for oxygen recovery between treatments. Also, avoid treating on cloudy days, another factor that can lead to lowered dissolved oxygen. Photo Credit: Mark Mauldin
Evaluating the vegetation in a pond is always the first step in the management process. Figuring out what kind of weeds you have, and if the population warrants control might seem simple, but it can be somewhat challenging. This is particularly true for submerged weeds – those that grow beneath the surface of the water. Unfortunately, submerged weeds are often the most troublesome weeds for pond owners to deal with. All submerged vegetation is not necessarily a bad thing, but there are several aggressive and/or invasive species of submerged aquatic plants that grow very rapidly and can be quite problematic, making proper evaluation critical.
While emergent and floating plants are easier to evaluate than their submerged counterparts, proper identification of all aquatic plants can help determine their potential for spread and, if warranted, the most effective control measures. If you had problem weeds in your pond last summer, you probably still do; get them identified and under control before they have time to spread. If you did not have problem weeds last summer, be on the lookout for any new/different kinds of weeds to head-off any potential issues.
Due to the current situation with COVID-19, generally speaking, County Extension Agents are not permitted to make field visits, but we are still here to help identify and provide control recommendations for your aquatic weeds. Floating and emergent weeds can generally be effectively identified using pictures. Submerged weeds can be much harder to identify using only pictures. For the best results, special care should be taken when photographing aquatic weeds. Collect a small sample of the weed, place the sample in an opaque container (preferably white in color), cover the sample with clean/clear water just deep enough for the sample to completely spread out and be supported by the water. Take multiple, well focused pictures of the sample. Some pictures should be of the entire sample, while other need to focus on the leaves and the attachment of the leaves to the stem(s). The pictures need to be emailed (not sent via text message) so the image size/quality is not compressed.
A good image of a submerged weed sample. In addition to this image close-ups of the leaves and attachment points will likely be needed for identification. Photo Credit: Nikki West
Now is the time to start managing aquatic weeds. The current situation in the world will make the process a little different, but with some effort and patience your County Extension Agent can help you get your weeds identified and develop a plan for control. On a positive side-note, most of the commonly recommended herbicides used to control aquatic weeds are available to order online, so it is quite possible you can address your aquatic weed issues all while staying “safer at home“.
Common Salvinia Covering Farm pond in Gadsden County
Photo Credit – Shep Eubanks UF/IFAS Gadsden County Extension
Close up of common Salvinia
Photo Credit – Shep Eubanks UF/IFAS Gadsden County Extension
Aquatic weed problems are common in the panhandle of Florida. Common Salvinia (Salvinia minima) is a persistent invasive weed problem found in many ponds in Gadsden County. There are ten species of salvinia in the tropical Americas but none are native to Florida. They are actually floating ferns that measure about 3/4 inch in length. Typically it is found in still waters that contain high organic matter. It can be found free-floating or in the mud. The leaves are round to somewhat broadly elliptic, (0.4–1 in long), with the upper surface having 4-pronged hairs and the lower surface is hairy. It commonly occurs in freshwater ponds and swamps from the peninsula to the central panhandle of Florida.
Reproduction is by spores, or fragmentation of plants, and it can proliferate rapidly allowing it to be an aggressive invasive species. When these colonies cover the surface of a pond as pictured above they need to be controlled as the risk of oxygen depletion and fish kill is a possibility. If the pond is heavily infested with weeds, it may be possible (depending on the herbicide chosen) to treat the pond in sections and let each section decompose for about two weeks before treating another section. Aeration, particularly at night, for several days after treatment may help control the oxygen depletion.
Control measures include raking or seining, but remember that fragmentation propagates the plant. Grass carp will consume salvinia but are usually not effective for total control. Chemical control measures include :carfentrazone, diquat, fluridone, flumioxazin, glyphosate, imazamox, and penoxsulam.
For more information reference these IFAS publications:
Efficacy of Herbicide Active ingredients Against Aquatic Weeds
For help with controlling Common salvinia consult with your local Extension Agent for weed control recommendations, as needed.
Farm ponds are used in a number of different ways, including fishing, irrigation, water control, and wildlife viewing. UF/IFAS Photo by Tyler Jones.
Farm ponds of all shapes and sizes are common in rural Northwest Florida. They are built for a number of reasons such as irrigation, water management, boating, fishing, wildlife viewing, livestock watering, and food production. Each of these uses guides the way the pond is managed to maintain its function, as well as its ecological beauty, but a factor that is important to all uses is having enough oxygen!
As you have probably observed, your pond is a dynamic system, which is influenced literally from the ground up! Much of the water’s basic chemical and physical characteristics reflect those of underlying soils (sand, clay, organic, etc.) and major sources of water (ground water, rainfall, runoff, etc.). The pond’s characteristics also influence how much oxygen is available for use by the plants and animals that live in it.
Why is Dissolved Oxygen and Aeration so Important?
Fish kills are often the result of low dissolved oxygen levels and occur in both natural waters and man-made ponds. Photo by Vic Ramey.
The idea of oxygen being dissolved in water is a little counter-intuitive. Especially to us, as air-breathing humans! Think of your pond as a giant living, breathing organism. Its atmosphere is the water itself, and it contains dissolved oxygen gas for the fish, aquatic plants, insects, and zooplankton to “breathe.” Even bacteria need to breathe, and one of their fundamental roles in your pond is the decomposition of organic wastes like un-eaten fish food, and dead plant and animal materials.
Having enough dissolved oxygen in the water is one of the driving forces sustaining the health of your pond. Oxygen is dissolved into water directly from the atmosphere, wind and wave action, and by plant photosynthesis. Because warm water “holds” less dissolved oxygen than cold water, your pond’s dissolved oxygen levels can be lower in the summer than in the winter, especially in the early morning hours before plants begin to photosynthesize and produce oxygen. While longer days and warmer temperatures mean more sunlight for plants to photosynthesize and produce oxygen, the demand or need for oxygen by fish, bacteria, and other aquatic organisms is also increased. Periods of rainy, overcast days during the summer can greatly reduce oxygen production by plant photosynthesis. Combined that with the increased oxygen demand by other organisms, and dissolved oxygen levels can drop fast. These drops in dissolved oxygen levels often result in fish kills. Productive, nutrient-rich ponds with high levels of organic materials, and a high fish density are at a greater risk of the devastating effects of low dissolved oxygen levels.
What Can You Do to Insure Your Pond Has Enough Oxygen?
Do not be tempted to overfeed your fish. Feed them floating fish food so you can see how much they will consume in 10 to 15 minutes at each feeding. Consider feeding them every other day. In addition, as recommended in Managing Florida Ponds for Fishing “do not feed them when the water temperature is below 60° F, or, above 95° F. Fish do not actively feed at these times.” Use fish feeding behavior as your guide. Uneaten food will only add excess organic matter to the pond. The decomposition of this excess organic matter by bacteria increases the oxygen demand and likewise increases the chances of low oxygen levels and a fish kill.
Reduce nutrient inputs from runoff, livestock waste, excess fertilizer, and uneaten foods as described above, to help reduce the demand for oxygen in the system. Additionally, remove as much excess debris as possible that may have been blown into your pond as a result of October’s Hurricane Michael that affected much of Florida’s panhandle. Excess nutrients from these sources are freely available for use by hungry algae and other plants, which can then proliferate and, in turn, cause demand for more oxygen. This increased demand for oxygen can cause fish kills due to low oxygen levels as described above.
If you have an aerator, keep it operative especially during extended periods of cloudy and rainy weather. Watch your fish for signs of oxygen stress (not eating, remaining near and gulping at the surface) and aerate accordingly. Oxygen levels naturally fluctuate, and the lowest levels occur in the late evening through early morning hours when plants are not photosynthesizing and replenishing oxygen. Therefore, most important time to routinely operate the aerator is the late overnight hours into early morning.
If you don’t have an aerator, consider purchasing one, especially as your pond ages and grows more fish, plants, and algae. It is certainly less costly in the end to be proactive when it comes to maintaining adequate dissolved oxygen in your pond.
Recreation and fishing are important uses of many rural farm ponds. Photo by UF/IFAS Tyler Jones.
What kind of Aerator should I get?
There are a few basic aerator types. There are surface water agitators or fountains, and there are bottom air diffusers. They can be powered by electricity, wind, or solar power.
Diffuser aerators can help achieve a uniform oxygen distribution in your pond from top to bottom. This is especially important in deeper ponds (greater than 6-10 feet average depth) where temperature and oxygen stratification can occur. Diffuser aerators pump surface air through the base sitting on the bottom of the pond causing bubbles of air to rise to the surface. Diffusers also increase circulation and keep the deeper parts of your pond from becoming oxygen depleted. In a new pond, or one with flocculent sediments, a diffuser may cause turbidity due to the physical action of the diffuser base sitting on the pond bottom circulating oxygen from the bottom to the surface.
Other aerator options are the fountain sprays or surface agitators that aerate surface water. At a bare minimum, this can be a hose shooting water out over the water surface. Surface fountains and agitators work well in small shallow ponds, but are generally not recommended for larger more productive ponds that need more oxygen. In some commercial or farm ponds, paddle wheel agitators powered by a tractor’s pto are used during periods of low oxygen as an emergency measure when a fish kill is just beginning to occur.
Where Can I Purchase One?
The type or types of aerators you need for your pond will depend on the pond’s size, depth, level of productivity (nutrient level, number of fish), use, and water quality. There are a number of shopping options online for pond aerators. Try searching using the term “pond aerators Florida.” Also, some local Panhandle fingerling fish farms sell these products too. Here is a list of fish farms from the Florida Fish and Wildlife Conservation Commission: FWC Freshwater Fish Stocking List. Additionally, there are dissolved oxygen meters you can purchase which accurately read the amount of oxygen in your ponds. This is yet another tool to use in the overall management of your pond.
Simple surface agitators can be used to aerate small shallow ponds, but are generally not recommended for larger more productive ponds that need more oxygen. Photo by Judy Biss
More information about pond management can be found in the following references used for this article:
Overview of Florida Waters – Dissolved Oxygen
Clemson Cooperative Extension: Aeration, Circulation, and Fountains
Southern Regional Aquaculture Center: Pond Aeration
Managing Florida Ponds for Fishing
The Role of Aeration in Pond Management
Local estuaries are a beautiful place to explore with your family. Credit: Matthew Deitch, UF IFAS Extension
Florida’s rivers, springs, wetlands, and estuaries are central features to the identity of northwest Florida. They provide a wide range of services that benefit peoples’ health and well-being in our region. They create recreational opportunities for swimmers, canoers, and kayakers; support diverse wildlife for birders and plant enthusiasts; sustain a vibrant commercial and recreational fishery and shellfishery; serve as corridors for shipping and transportation; and support ecosystems that help to improve water quality. Maintaining these aquatic ecosystem services requires a low level of chemical inputs from the upstream areas that comprise their watersheds.
Aquatic ecosystems are especially sensitive to nitrogen and phosphorus, which are key nutrients for the growth of plants, algae, and bacteria that live in these waters. High levels of these nutrients combined with our sunny weather and warm summer temperatures create conditions that can lead to rapid growth of aquatic plants and algae, which can cover these water bodies and make them no longer enjoyable for people and wildlife. It can also cause dissolved oxygen levels to fall, as plants respire (especially at night, when they are not photosynthesizing) and as bacteria consume oxygen to break down dead plant material. Low dissolved oxygen can create conditions that are deadly for fish and shellfish.
The Florida Department of Environmental Protection (FDEP) lists more than 1,400 water bodies (including rivers, springs, wetlands, and estuaries) as impaired by pollutants. Many of these are impaired by excessive nitrogen or phosphorus. It is a daunting challenge to reduce pollutants in these water bodies because their inputs frequently come from all over the landscape, rather than a specific point—nutrients can come from agricultural fields, residential landscapes, septic tanks, atmospheric deposition, and livestock throughout the watershed.
In Florida, FDEP has begun a program to reduce nutrient concentrations in impaired watersheds by collaborating with landowners and other stakeholders to develop management programs to reduce pollutants entering the state’s waters. This pollutant reduction program is currently focused on Florida’s spring systems, including Jackson Blue Spring and Merritt’s Mill Pond in Jackson County. Merritt’s Mill Pond is a 4-mile long, 270-acre pond located near Marianna, and it is a popular regional destination for swimming, boating, kayaking, and fishing in the Panhandle. Its main source is Jackson Blue Spring, which produces, on average, more than 70 million gallons of water each day. Excessive growth of aquatic plants and algae in the pond during summer reduces the area available for swimming and boating. In 2014, FDEP began working with agricultural producers, residents, developers, local government officials, and other stakeholders to identify nutrient contributions in the Merritt’s Mill Pond watershed and develop an action plan to reduce nutrients entering the pond in the coming decades. Collaborations with stakeholders help to improve the accuracy of pollutant estimates, and to ensure the plan is designed appropriately to achieve desired ecological outcomes.
This Action Plan for reducing nutrients into Merritt’s Mill Pond provides an opportunity for land managers to implement their own plans to reduce nutrient contributions without FDEP imposing rigid regulations or mandating particular actions. People can choose from an array of Best Management Practices designed to reduce nutrient contributions, and the state has made funds available for people to help implement these plans. Implementing this Action Plan will restore the wonders of Merritt’s Mill through the 21st Century.
This article was written by: Matthew J Deitch, PhD, Assistant Professor, Watershed Management with the UF IFAS Soil and Water Sciences Department at the West Florida Research and Education Center. For more information, you can contact him at email@example.com or 850-377-2592.
Adult grass carp, Ctenopharyngodon idella Val. Credit: Jeffrey E. Hill, University of Florida
Spring is only days away. Everywhere you look, plants of all kinds are awakening to recent rains, longer days, and fertile soils; and this includes aquatic plants as well! Florida has hundreds of aquatic plant species, and they are an often-overlooked feature of Florida’s landscape. Overlooked that is, until the growth of non-native (or even some native) species interferes with use of our waters. Some aquatic plant species can become problematic in Florida waters as their growth interferes with fishing, flood control, navigation, recreation, livestock watering, or irrigation. For these reasons, being knowledgeable about properly managing aquatic plants is important to the many uses of Florida’s waters, whether it be a state managed public waterbody, or your own backyard farm pond.
Any pest, whether plant, animal, or insect, is best managed using “IPM” or Integrated Pest Management. IPM involves using a variety of available management “tools” to control pests in an economically and environmentally sound manner. As in any IPM effort, the first thing to do is identify what is causing the problem. Next, define what your management goals are. Then, research what tools are available for you to manage the problem. And finally, devise and implement your management plan.
In this article, we will look at one of the IPM “tools” used to manage aquatic plants – the grass carp (Ctenopharyngodon idella Val.). The use of grass carp to manage problematic levels of aquatic plants falls under the general management term of “biological control.” Biological control essentially uses one living organism to control another living organism. Grass carp have become one of the most widely recognized examples of biological control.
The Grass Carp
As the name implies, the grass carp is an herbivorous fish that eats plants. It is native to eastern Russia and China living in large muddy rivers and associated lakes, and is actually one of the largest members of the minnow family. According to the Florida Fish and Wildlife Conservation Commission the largest triploid grass carp taken in Florida was 15 years old, 56″ long and weighed 75 pounds! The grass carp has been introduced into more than 50 countries and is used as a food item in many places around the world. They are used in nearly all states of the USA to manage aquatic plants.
Introduction into the United States:
“The grass carp was considered for introduction into the U.S. primarily because of its plant-eating diet, which was thought to have great potential for the control of aquatic weeds. In 1963 the U.S. Bureau of Sport Fisheries and Wildlife Fish Farming Experiment Station, Stuttgart, Arkansas, in cooperation with Auburn University, imported grass carp for experimental purposes; in 1970, this fish was introduced into Florida primarily for researchers to study its ability to control hydrilla.” (Grass Carp: A Fish for Biological Management of Hydrilla and Other Aquatic Weeds in Florida). “Early release of diploid fish led to reproductive populations in several US drainage systems, including the Mississippi River and major tributaries” (Grass Carp, the White Amur: Ctenopharyngodon idella Cuvier and Valenciennes (Actinopterygii: Cyprinidae: Squaliobarbinae))
Development of the Sterile Triploid
According to the UF/IFAS publication, Grass Carp, the White Amur: Ctenopharyngodon idella Cuvier and Valenciennes (Actinopterygii: Cyprinidae: Squaliobarbinae), “Use of the fish was limited from 1970 until 1984 due to tight regulations surrounding concerns of escape and reproduction, and the potential impacts that colonization of the fish could have on native flora and fauna. These concerns led to research that developed a non-reproductive fish, which was equally effective in controlling hydrilla.” This non-reproductive fish is known as the triploid grass carp. Through a process of subjecting fertilized grass carp eggs to heat, cold, or pressure, the resulting fish have an extra set of chromosomes rendering the fish sterile. Triploid carp have the same herbivorous characteristics as the normal diploid carp, but they are unable to spawn and reproduce. Their inability to reproduce is what makes them a viable tool to manage aquatic plants, and that is because their numbers and feeding pressure can be controlled, they cannot overpopulate a waterbody, nor if they escape, will they overpopulate un-managed areas.
The growth of invasive non-native (or even some native) aquatic plant species can interfere with the many uses of Florida’s waters. This is invasive hydrilla mixed with water lilies in a Florida lake. Photo by Judy Biss
What kinds of aquatic plants do they eat?
The grass carp grazes on many types of aquatic plants, but it does have its preferences. Its most preferred aquatics plants are hydrilla, chara (musk grass), pondweed, southern naiad, and Brazilian elodea. Its least favorite aquatic plants are species such as water lily, sedges, cattails, and filamentous algae. It will, however, graze on many types of plants even shoreline or overhanging vegetation in the absence of its preferred foods. Another reason the grass carp is an effective plant management tool is because it eats many times its body weight in plant material. As stated in Grass Carp, the White Amur: Ctenopharyngodon idella Cuvier and Valenciennes (Actinopterygii: Cyprinidae: Squaliobarbinae), “every 1 lb. increase in fish weight requires 5–6 lbs. of dry hydrilla (Sutton et al. 2012), which—considering hydrilla is 95% water—is a great deal of live plant material.”
Use of Grass Carp as a Biological Control:
Integrating the use of grass carp in aquatic plant management plans is usually cost effective. In many cases involving the use of grass carp, overabundant aquatic weed infestations are first treated with an aquatic herbicide to reduce biomass. The carp are then stocked to control regrowth and to extend the time between herbicide treatments. This can be up to 5 or more years, depending on the situation. One factor in long term control is the survival of the stocked grass carp. They are not without predators as largemouth bass, otters, birds, etc. readily prey on small grass carp. Stocked fish should be at least 12 inches long to help avoid predation and provide plant control. Other considerations to factor into your management plans are the long term, yet non-specific, control that grass carp can provide. If not stocked in the correct manner, they may end up eating aquatic plants that you wish to maintain. Also, if they eat all the aquatic plants, your once clear water may become dominated by algae instead.
How can I get grass carp for my lake or pond?
The Florida Fish and Wildlife Conservation Commission (FWC) administers the Grass Carp program for Florida. A permit is required before you can purchase carp, and only the sterile triploid carp are permitted for use in Florida. The FWC can answer many questions about the use of grass carp and if this aquatic plant management “tool” is the right one for you to use in your particular situation. In north Florida, the regional FWC office is located at 3911 Highway 2321 Panama City, FL 32409, Phone: 850-767-3638.
What do I need to know about triploid grass carp?
Cost: Triploid grass carp cost between $5 and $15 each and are usually stocked at three to ten fish per acre, resulting in costs as low as $15 per acre. In comparison, herbicides cost between $100 and $500 per acre and mechanical control may cost more than twice that.
Time: Grass carp usually take six months to a year to be effective in reducing problem vegetation, although they provide much longer term control than other methods, often up to five years before restocking is necessary. When used in conjunction with an initial herbicide treatment, control of problem vegetation can be achieved quickly, and fewer carp are required to maintain the desired level of vegetation.
Overstocking: Once stocked in a lake or pond, carp are very difficult to remove. If overstocking occurs, it may be ten years or more before the vegetation community recovers. Even after carp are removed, other herbivores such as turtles may prevent the regrowth of vegetation.
Water Clarity: Aquatic plants remove nutrients in the water. When plants are removed, nutrients may then be utilized by phytoplankton, turning the water green. Clarity may be improved by reducing or eliminating sources of nutrients into the lake such as road runoff and lawn fertilizer.
Inflows/Outflows: It is in the best interest of people stocking carp to keep them in the desired lake or pond. It is also a required condition of the permit. Any inflows or outflows through which carp could escape into other waters require barriers to prevent fish from escaping into waters not permitted.
For more information on this topic, please see the following resources used for this article:
Aquatic and Wetland Plants in Florida
Plant Management in Florida Waters
Grass Carp, the White Amur: Ctenopharyngodon idella Cuvier and Valenciennes (Actinopterygii: Cyprinidae: Squaliobarbinae),
Grass Carp: A Fish for Biological Management of Hydrilla and Other Aquatic Weeds in Florida).
Chinese Grass Carp
FWC Triploid Grass Carp Permit
UF/IFAS Center for Aquatic and Invasive Plants – Aquatic Plant Control Methods
Bacopa caroliniana, also known as lemon bacopa, is a popular aquatic plant. It is mostly found in the southeastern United States in states such as Florida, Alabama, Georgia, South Carolina, Mississippi and even Texas. Lemon bacopa has a perennial life cycle that could make it a weed to some, or desired plant to others. Also, it can be found as a submergent plant or an emergent one.
It tends to grow near shorelines and sometimes in water that is less than 3 inches deep. Lemon bacopa has a single stem with opposite leaf growth. The leaves are thick and juicy. The reason some people enjoy and even encourage planting this plant is the pretty, attractive, purple-blue flower that sprouts. They are a popular plant used to add beauty to water gardens and to provide habitat in wetland enhancement as well as restoration projects. However, this plant can be easily propagated which could lead to it becoming weedy if not paid attention to carefully. Lemon bacopa roots easily from cuttings, so whether if it is purposely cut or by natural causes, it can easily spread and take over a water garden.
This species is very adapted and common throughout Florida. Although lemon bacopa can be weedy in some situations, it is most often considered a beneficial native plant that brings a number of desirable characteristics to almost any aquatic setting.
Source: UF IFAS EDIS publications