Category Archives: Aquatic Environments

Pond Scum

PondScum-J.Surles

Some pond scums are showing up after heavy rain from the tropical storm.. There was some in the pond behind our house as well. These blooms usually appear during the summer and fall. We do have to beware of blue-green algal blooms (cyanobacteria). These produce toxins that can be lethal to most fish and livestock. Other aquatic weeds called pond scum are duckweeds and watermeal, Euglena, diatom blooms, filamentous algae, bacterial, protozoan, and zooplankton scums.  This photo is likely blue green algae scum which was sent to me last week.

UGA Extension Aquatic Scientist Dr. Gary Burtle says, “The hot temperatures make most algaecide applications dangerous to the fish due to possible oxygen depletion. However, low dose applications of copper may thin this bloom. Try one quart to one half gallon of cutrine plus per surface acre. Then repeat each week to thin the bloom. That would be about 0.2 lb to 0.4 pounds of copper per surface acre.  Dilute 1:10 in water for application to the scum.

An alternative is to use sodium percarbonate (many different label names) at 25 lbs per surface acre and repeat weekly. Spread evenly over the pond surface with a granular spreader and boat.”

Pond Scum

Pond Scum – Photo by John Surles

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Pond Weeds – Yellow Iris

PondWeed (2)

Yellow Iris Flower

Yellow Iris Flower

Here is a yellow flower thing growing by the pond I’ve never seen. It turns out to be Yellow Iris (Iris pseudacorus). It’s an herbaceous perennial with stuff leaves. It reproduces by floating seed and rhizomes. Up North, it is listed as a noxious weed, but UGA Extension Aquaculture Scientist Dr. Gary Burtle recommends leaving a margin of these plants along the shoreline to prevent erosion. The only thing we need to do is mow to leave a 3 to 5 ft strip.

Yellow Iris

Yellow Iris

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Pond Weeds – Common Salvinia

Common Salvinia (2)

With temperatures in the 70s and above, we need to think about treating pond weeds now. It is recommended to begin with chemical treatment and follow by biological control – stocking grass carp.

There are two salvinia’s we have. One is called Giant Salvinia. With giant salvinia, the leaf hairs are joined together (in fresh samples). The salvinia pictured here is Common Salvinia (Salvinia minima).

Common salvinia

Common salvinia

This is more of a recent invader, also called floating fern. It spreads very fast.

The leaves smaller than a man’s thumbnail indicate Common Salvinia. In salvinia species, the leaves are more round with a distinct midbrib. They will have a cupped appearance.

UGA Extension Aquatic Specialist Dr. Gary Burtle says Common Salvinia responds to contact herbicides like diquat and Cutrine-Plus. However, areas up stream and downstream from the pond usually reseed the pond so that a maintenance plan should be developed. Grass carp will help control salvinia once it has been burned back.

For more information, visit this link on Common Salvinia.

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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.

Duckweed&Watermeal 002.JPG

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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