Treatments for the Control of Algae and Aquatic Weeds & Plants

By Patrick Simmsgeiger, Founder of DWI

In September of 2000 a call came from a local, Southern Orange County, CA water district regarding a ten-year-old, 450 surface acre lake that had seen a growth spurt in the water hyacinth in a lake called Dove Canyon. Water hyacinth is a beautiful, but rapid growing and troublesome aquatic plant. The aquatic plant has a pleasing appearance and adds to the aesthetics of a lake, stream, or pond because of the deep green color and appealing purple blooms. But, it is known to double in population in under twelve days. In addition to the obvious problems of preventing boat access, swimming and fishing, an overgrowth of water hyacinth doesn’t allow sunlight to penetrate the lakes surface to allow the growth of beneficial plants, it cuts off oxygen, which oftentimes will result in a fish kill, and adversely affects the lake’s aesthetics, fish habitats, biological balance, and odor.

The district requested consultation from the owner, who holds a qualified applicator’s license and is a certified lake manager through NALMS (North American Lake Mangement Society), of Diversified Waterscapes, Inc., a licensed pest control business, regarding treatments for, and maintenance of, the lake.

After first inspecting the lake, he then met with the County representative to discuss products, methods, and frequency of application to use to eliminate the problematic water hyacinth.

The lake had its challenges. There were huge areas of open water, small fingers, and areas so narrow a boat would never be able to navigate. They could use their boat and outboard motor to treat the larger portions of lake and the boat could still be used in the smaller sections but without the outboard. There were areas where a boat could not go at all, which meant a man would need to walk in with a backpack sprayer or treat from the top of the hillside with a high power hose using a large tank attached to the company truck or golf cart.

After careful evaluation, a solution was devised to treat the aquatic plant problem and work began in mid-December. Using one man in a small boat equipped with a custom made sprayer an algaecide was applied, formula F-30 Algae Control, along with a herbicide, Reward, to the water hyacinth.

There were no other options considered, as the company already knew the safest, most effective and rapid method to control this plant was to spray a tank mix of algaecide and and herbicide on the nuissance plant.

The herbicide and algaecide were the best and safest choices. They have years of proven effectiveness and had been repeatedly used whenever the company’s assistance was requested to control the growth of a problem plant. this combination was used because it is safe, known to improve the water quality and there are no adverse affects on aquatic life. At that time the hyacinth was not “out of control” but merely a nuisance due to the excessive growth. The treatment method and products used were successful but the customer declined the necessary follow-up additional as-needed treatment and twice monthly monitoring.

In May 2001 the company was again called and an estimate was requested for another spray treatment of the water hyacinth. Because five months had passed with no monitoring or maintenance treatments, it was necessary to go back to the lake to see if there were any changes in plant life or water conditions. The water hyacinth had returned to its former state. There were various portions of the lake that had experienced a re-growth of the nuisance plant. A course of spray treatments was suggested and accepted. With each aquatic environment this question of how often to treat is one that is always answered with a request to wait and see. EACH lake, pond, or stream is DIFFERENT. Once lake can experience a rapid growth of a weed or form of algae while another only a few feet away has beautiful clarity, no algae, or weeds and rarely requires attention. As with all things in nature, given the slightest chance, plants will grow again. Look at the weeds, or flowers, or trees, growing in the smallest of cracks in cement. Like earth’s plants, aquatlic plants will take whatever opportunity offered to grow again. You never want to introduce the quantity of water treatment products necessary to kill everything as the balance of the eco-system will be destroyed and the lake will have been killed.

After treating the water hyacinth was completed, the company called the water district two to three times, made site visits, and performed overhead observations. During this two year period the water district trained and certified some of their employees to treat and maintain control of the water hyacinth. It was unknown (they could not recall) what quantities, brands, or types of products they used during this period of time. The lake was surrounded by hillsides that were not dotted with million dollar homes where the main selling feature was the view. This view not only caputured the beauty of the surrounding hillsides and mountain areas, but also included, directly below, the lake. Being a lake and reservoir, the design and purpose is to catch rain and hillside runoff. However, the lake was now a catchall for residential runoff bringing in a load of nutrients from debris, tree droppings, car oils, soaps, etc. This runoff “feeds” the plants, unbalances the eco-systems and wreaks havoc with the clarity, appearance, odor, and plant growth in the lake, which had now become a source of numerous compaints.

In July 2003, the company received a call from the water district this time reqeusting a harvester (seperate contractor) for the water hyacinth. This call was what the company termed a “warning flag”. Requesting a harvester usually means there is a large body of water with a massive problem with weeds, algae, and/ or plants.

When diversified Waterscapes arrived, they discovered the water hyacinth had returned with a vengeance covering approximately 75% of a twenty-one surface acre portion of Dove Canyon Lake. The water hyacinth was growing at a rate of one foot per day and was killing the lake. A strong “attack” using the same approach to treatment was scheduled after the harvestor.

The goal of the treatment was to totally eradicate the water hyacinth, not to gain and maintain control of the plant’s growth. Most caretakers of aquatic environments keep certain areas of the water covered with the hyacinth because it is so attractive. In this case, the water district requested all of the invasive plant be removed.

The reason for a follow-up treatment after harvesting is once a harvestor is used, spores from the plants, algae, and weeds are released and spread. If these spores are hit with a treatment of herbicide and algaecide mix the re-growth will be minimal and slow.

Because the weather was extremely hot and the sun was beating down the water’s surface, (contributing factors to rapid growth) the water hyacinth was coming back faster than they could harvest. The district requested the company perform spray treatments while the harvesting was taking place. Some portions of the lake were still densely covered with hyacinth, which made it a challenge to treat.

The herbicide and algaecide spray treatment was started and is ordinarily performed in one day, followed by a wait period. On initial treatment it is important to allow time (three to seven days) for the products used in the treatment to “settle” and do their jobs. Then, the developing results are monitored. This enables the applicator to factor in the speed at which the products worked. how effective the “kill” was and decide if they need to make adjustments in their approach to the subsequent treatment. In this case, due to the incredibly rapid re-growth of hyacinth that the lake was experiencing, another crew was sent out the very next day and was followed by another treatment a few days later.

The combined treatments were so successful the district called the company a bit later for another different, but larger area, of the lake that was experiencing problems with water hyacinth, algae, and duckweed. The spray treatments were performed using the same herbicide and algaecide this time adding a surfactant, Activator 90, the the mix, (as more than just the water hyacinth was involved). This combination was quite successful.

After the company’s treatment program for total eradication of the water hyacinth, the problematic hyacinth has not returned. The problem was eradicated and the water district was happy. If any re-growth is observed, the water district personnel immediately remove the hyacinth. In this case the treatment avenue chosen was a long term solution as the district desired total eradication of the plant. However, one cannot consider this a “permanent” solution. To attain a “permanent” solution would involve the overuse of chemicals and the risk of killing the very body of water you are trying to save. This company does not ascribe to this ideology.


The odor and invasive plant was virtually eliminated. The lake was again aesthetically pleasing to the homeowners adn the complaints had stopped. The lake is alive and accessible.

This treatment process, from the very first treatment to the last had spanned a period of two and a half years. The cost of the one month treatments was close to $20,000.00, the harvesting took two and a half weeks at a cost nearing $45,000.00, all of this to eliminate growth of weeds, algae, and plants that had increased to the point of being out of control.

The lake maintenance company has been performing follow-up treatments of the same reservoir and lake to control the re-growth of the water hyacinth and manage the duckweed and algae. There have been regular treatments and the hyacinth has never come close to reaching the state it did in 2003 so everyone is happy.

The lesson learned? You can’t treat and walk away. You have to perform regular maintenance on a body of water. Maintenance means to keep in an existing state (as of repair, efficiency, or validity): preserve from failure or decline. And that’s what lake, stream, and pond maintenance is all about, restoring it to a more natural, appealing state and keeping it that way.

Posted on April 16, 2014 and filed under Algae Control.