Stump the County Agent: Pesticide License & Algae

By Keith Hawkins, LSU AgCenter Extension Agent

This is the time of year when county agents across Louisiana are preparing to recertify the citizens who hold licenses to be private pesticide applicators. These applicators can purchase “restricted-use pesticide” for their own private use. One gentleman whose license will expire at the end of March asked about dates for recertifying. He also asked about licenses for his teenage children.

Well, he won “Stump the County Agent” because I had no answer at that time. However, the answer is now available. A person who is at least 16 years of age can obtain a license to be a private pesticide applicator. The process entails self-study of materials and then testing at an office of the Louisiana Department of Agriculture and Forestry (LDAF). The nearest office for Beauregard and Vernon Parishes is in Woodworth, LA. Here is the number for scheduling a test: 318/487-5090.

Dr. Greg Lutz recently sent out an email about filamentous algae because of questions he is receiving. Here is what Dr. Greg shared: “[Filamentous, slimy algae] gets started on the pond bottom during the winter months when the water is clear, then grows into big clumps as the water warms up.  The unusually cold weather we have been having has caused many ponds to get very clear, and this creates ideal conditions for the filamentous algae as the winter progresses.  


The best approach in terms of cost, labor and effectiveness is to use copper sulfate crystals to limit the growth of the filamentous algae.  This product is available at most big feed and seed stores or farm co-ops.  Tell your clientele to observe a limit of no more than 5 pounds of crystals per acre, per treatment.  The crystals should be sprinkled or broadcast directly onto the clumps of filamentous algae - a little goes a long way.  When roughly 5 pounds per acre (that would be 2.5 pounds in a half-acre pond, 10 pounds in a 2-acre pond, etc. etc. etc.) have been applied - even if only 1/4 or 1/3 of the algae in the pond has been treated, no more copper sulfate should be applied.  

After 8 days another treatment with the same amount of crystals can be applied.  
There is usually little or no fish mortality when people stick to this strategy, but clientele should be made aware that there is always some risk of killing fish when treating aquatic vegetation.  Are there more efficient ways of dealing with filamentous algae?  In some cases there probably are, but I have found over the years that it’s better to have folks knock this stuff back gradually rather than hit it hard and then blame us when they kill some fish. 

Check out all [AgCenter] recreational pond recommendations at “
If you want to play “Stump the County Agent”, please send your question and pictures to Keith Hawkins, County Agent, 337-463-7006 or