Category Archives: Aquatic Environments

Too Late To Treat Pond Weeds?

Duckweed&Watermeal 001

Today I asked about duckweed taking over a pond around Meigs. On the way up, I passed another pond that was nearly 100% infested with duckweed. When we look at weeds like duckweed, we need to make sure another weed called watermeal is not also present. If that is the case, our treatment options change. To see more on these two weeds, click on my blog post titled Pond Weeds – Duckweed & Watermeal.

This pond is almost 100% full of both duckweed and watermeal. Some large bass have died as result of low oxygen. This pond needs to be treated, but we are very late in the season to do it.  I’m getting this question more this year since temperatures are so warm. There are few general rules we can follow, but every situation is different depending on weed present, water temperature, who treats, chemical availability, etc.

When is too late?

UGA Extension Aquatic Scientist Dr. Gary Burtle says our water is borderline for treatment right now. 70 degrees F is when we are generally safe to treat ponds. We still need to consider, however,  that some compounds work better at 80 degrees F though 70 is our cutoff. Right now, plants are not growing as fast, and chemical reaction is slower.

What does this mean? Some of our compounds are systemic and others contact. Diquat, cutrine and clipper are contact herbicides. Sonar, which is good on watermeal and duckweed, is systemic. Systemic chemicals needs 3 – 4 weeks of actively growing plants to be effective. We are certainly too late in the season for this kind of treatment. Clipper also works good on duckweed when watermeal is mixed. But the issue with contact herbicides is though they may provide a kill with borderline temperatures, timeliness is key. If we do not already have a plan, water temperature could drop to 60s in a short time.

We must to also consider pond converge. Dr. Burtle reminds us that if the pond is 80-100% covered, two treatments of a contact herbicide would be needed. Considering the cost, one application of a systemic herbicide (for a small pond < one acre) would be less expensive – which we are too late to apply.

Conditions now are essentially the same as conditions will be in late Febrary. At this time in the season oxygen in a pond is actually higher. This will keep us from losing too many fish and should also be considered. Cooler weather will also slow weed growth. Dr. Burtle says it is not totally bad to treat during these conditions; however, once all factors are considered, waiting until spring would be more beneficial.

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Duckweed & Watermeal

 

 

 

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Pond Weeds – Water Hyacinth

CherokeeLake 006

This is at Lake Cherokee in Thomasville where my wife and I and a friend were walking this past weekend. They have a nice track that is 1 mile long I used to walk when I lived at the apartments next door. We sometimes look at weeds they have working to control. Here is one I have not seen at the lake before but can become an issue.

Water Hyacinth

Water Hyacinth

Flower

Flower

Identification

Water hyacinth is a floating pond weed that can get about 3 feet tall. It is also perennial. It has a purple/violet flower that comes up on a terminal spike. The roots are very fibrous underneath and develop into a thick mat resulting in oxygen depletions.

Treatment

Many aquatic compounds have been successful at treating hyacinth like 2,4-D, diquat, and glyphosate. However, it is late in the season to think about treating. UGA Extension Aquaculture Specialist Dr. Gary Burtle says the only treatment option this late is diquat. It would be okay to apply a spot treatment with a 2% solution of diquat to the foliage to burn back plants. Then come back in March with another treatment to kill new growth.

CherokeeLake 004

Foliage

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Pond Weeds – Maidencane & Southern Watergrass

Smartweed & Maidencane 010

Here are a few pond weeds we looked at last week. Maidencane is standing in the back, southern watergrass and algae are in front of it. Maidenane and southern watergrass are both emergent plants. These are rooted plants that usually grow on the shoreline and stand above the surface of the water. These ponds are very shallow, and the plants can grow in the middle. The stems of emergent plants are somewhat stiff or firm.

Identification

Smartweed 011

Southern Watergrass

Southern watergrass is a perennial that growers in shallow water. It’s leaves can be underwater (to 3 feet), floating or in dense colonies that can rise to 12 inches in height on stems to 3 feet long. Leaves are more long and narrow.

Maidencane is hard to tell apart from other grass weeds. It’s leaves are long, narrow and tapered (up to 12 inches long and 1 inch wide). They have a rough upper surfaces and margins. Flowers form along a narrow spike. Maidencane forms extensive rhizomes.

Control

There is also algae between these two emergent weeds and copper sulfate was used. The copper worked on one pond and not another. UGA Extension Aquatic Scientist Dr. Gary Burtle says the copper spreads out in an open pond but may be prevented from spreading when heavy weeds mats are present.

Glyphosate works good on grassy weeds. It is good to use around pond edges, and certain formulations are used in the pond. However, much of the efficacy of glyphosate is lost when it touches water. The more leaves out of the water, the better it works. Glyphosate will work better on these maidencane than the watergrass, since most of these watergrass are underwater. Since most watergrass is submerged, imazamox would be a better control option here.

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Fish Kills

FishKill (6)

Last week, I was called to look at the first fish kill this season. This is a small 1/2 acre pond surrounded by trees. It is spring fed and no agriculture around. Different species of bass and bream were found dead the next morning. The fish kill happened overnight and is a result of low oxygen levels in the water. We know this is the case when larger fish die first, and lack of oxygen would affect larger fish before small fish. When temperatures are this high and we see cloudy days/nights, the lack of oxygen in the water from photosynthesis causes these kills.

FishKill (3)

We had a pond management program yesterday where UGA Extension Aquaculture Specialist Dr. Gary Burtle addressed this issue. He said historically, he would not necessarily recommend an aerator in every pond. However, he now recommends most ponds have some type of aerator. They can be expensive, but by the time you put the money into production of fish, losing them is more costly. The pond I visited was surrounded by trees were air could not get to it. It has been very hot and this is a factor in fish kills. We can also see fish kills after rain. Here is what Dr. Burtle has to say:

“The usual reason for fish death after rains is a partial oxygen depletion caused by the influx of water which has no algae in it or a high concentration of bacteria in it.  When algae are replaced by bacteria, the water turns brown in color and oxygen concentration drops. Bass are larger than bream, so may be affected first. The oxygen stress may cause the fish to become susceptible to disease, so fish deaths may occur for several days after the partial oxygen depletion.

When the pond begins to ‘green up’ again, oxygen concentrations will increase and fish deaths stop. Until oxygen concentration returns to normal levels, low oxygen each morning or during cloudy weather may cause more fish stress and death. The solution is to install an aerator and operate during cloudy weather, which seems to be more prevalent in Georgia in the late summer and fall.”

We had a great turn out at our pond meeting yesterday. Below is a photo of Dr. Burtle going over common weed species in ponds:

Thomas County Pond Management Program

Thomas County Pond Management Program

Dr. Gary Burtle passes around common weeds in ponds

Dr. Gary Burtle passes around common weeds in ponds

 

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2015 Pond Management Program

PondMgmtUpdate

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July 20, 2015 · 9:32 PM

Blue-Green Algae

Blue-GreenAlgae

Here is a spring fed pond where blue-green algae is showing up. There are many different types of pond scums and blue-green algaes. Based upon samples  microscope samples, this genera of blue-green algae that are capable of producing toxins. This can be harful to livestock and wildlife and is something we need to be careful about if you see this in the pond.

Blue-Green Algae

Blue-Green Algae

There must be a source of phosphorus and nitrogen that is allowing the growth of this algae. UGA Extension Aquaculture Specialist Dr. Gary Burtle says this is probably from water runoff in the winter and early spring brought nutrients into the pond. Without a volume of rainfall adequate to flush the pond, the algae continues to accumulate until scums form. Watershed ponds are more likely to flush, due to rainfall, than levee ponds used for aquaculture. We have long seen algal scum development as we feed catfish in ponds where water outflow is minimized and pumped water is used only to maintain water level. Some treatments Dr. Burtle has suggested can reduce the blue-green algae and destroy the scum.

I have information on pond scums I can send to anyone who would like to read about it. E-mail me at agsawyer@uga.edu. UGA also has a website called CyanoTracker dedicated to tracking toxic algal blooms anyone can report. If anyone wants to test water, The Warnell School of Forestry and Natural Resources and Dr. Burtle have also teamed developing a new test protocol that includes toxic algal identification.

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Pond Weeds – Fragrant Water Lilly

WaterLilly

This is a familiar weed seen in ponds. When folks see water lilly, they know what it is. Fragrant water lilly a perennial plant with leaves that come off stalks from rhizomes. The leaves of water lilly are more round than heart-shaped and 6 to 12 inches in diameter. Leaves usually float on the water’s surface. The flowers are very fragrant and have white petals with yellow centers. The flowers may float or stick above the water and each opens in the morning and closes in the afternoon. White water lily can spread from seeds or the rhizomes.

Water Lilly Flower

Water Lilly Flower

Products containing 2,4-D, glyphosate, fluridone, triclopy, and imazamox work well in controlling this weed. White water lily can be cut and the rhizomes be dug up; however physical control is difficult since it can reestablish from seeds or remaining rhizomes. Click this link for more information on Fragrant Water Lilly.

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Pond Weeds – Fanwort

Fanwort (3)

FanwortHere is a pond I looked at yesterday infested with fanwort, also called cabomba. Fanwort is a submerged, perennial weed.  The submerged leaves are opposite, and attached by a single petiole. Above the petiole they form a “fan-shaped” leaf. Fanwort also has a small white to pink flower which forms on the tip of the stem and stands just above the surface. One of my photos shows the flowers across the surface of the water.

UGA Extension Aquatic Scientist Dr. Gary Burtle says diquat has been used successfully on fanwort.  Fluridone can also be used if water flow through the pond is minimal. This pond has dense weed growth, so repeat treatment will be advisable.

Stock grass carp at 10 per infested acre following chemical application in order to obtain long term control.

Here is a link to more information on biology of Fanwort.

Flower of fanwort

Flower of fanwort

Fanwort (5)

Fanwort flowers

 

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Pond Weeds – Soft Rush

I’ve been looking at quite a few ponds for weed issues the past few weeks. Algae is showing up as well as water lilies and alligator weed. For pond weed management, it is generally best to begin with a chemical approach followed by the stocking of grass carp. Once weed growth has covered more than 10% of a pond, weed control expenses may exceed the desire or ability to pay. If fish are present in the pond, treat no more than 1/3 of the weed infestation as oxygen depletion from dying weeds may kill fish.

SoftRush

Here is some soft rush (Juncus effuses) growing on the edges of a pond. Rushes are perennial plants that are easily confused with grasses and sedges. They can grow in shallow water or moist soils. Soft rush grows in dense clusters from rhizomes, up to 3 1/2 feet in height. This rush can be controlled with a chemical treatment, but UGA Extension Aquaculture Specialist Dr. Gary Burtle says soft rush is good for shoreline stability and wildlife, so it is not usually considered for treatment.

Soft Rush

Soft Rush – Flower

More about Soft Rush can be found on the Texas A & M Aquaplant Website – Soft Rush.

 

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Pond Weeds – Watermilfoil

Watermilfoil 008We are getting closer to think about treating ponds for weeds as we approach spring. If a pond is infested with a particular weed, it is generally recommended to clean out the weeds with a herbicide application. Sometimes it may take more than one application. Then we will follow with stocking the pond with grass carp. Grass carp can help with many weeds, but may not help with all weeds. Grass carp help maintain smaller weeds, but will not eliminate a weed infestation.

Watermilfoil

Watermilfoil

I was asked to look at a common pond weed last week which turned out to be watermilfoil. Watermilfoil is a submergent, perennial weed that has reddish stems that can be branched and two leaf forms. All leaves are in whorls of four to six. The submerged leaves are feather-like and flaccid. This is what we observed. UGA Extension Aquaculture Specialist Dr. Gary Burtle says both liquid and granular herbicide formulations can be used to control water milfoil. Diquat, 2,4-D, and triclopyr all have acitivity. However, with granular applications, 70 degrees water tempuerature is needed for good results.

Here is some more information on Variable-Leaf Watermilfoil.

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