Q. My pond is covered in duckweed. What can I do to treat this stuff? – Tony in Indiana
Friend or Fowl
A: For the lucky pond guys and gals out there who have never experienced duckweed in their pond, or those of you who think you may have it but are unsure; duckweed is a very small floating plant with kidney shaped leaves and a small hair-like root hanging below. It is approximately the size of a pencil eraser and is frequently misidentified as algae. It can cut off sunlight to submersed plants and cut off oxygen to fish and other wildlife. Duckweed is an extremely prolific grower and can quickly cover an entire pond making it frustrating to treat and maintain. More often than not, duckweed is introduced into your pond by hitching a ride on the feet of waterfowl.
Don’t Go Daffy Over Duckweed
There are two great options available to you in your fight against duckweed. Choosing the product that is right for you depends on the time frame you have to treat your pond. For fast acting, short term results, you can use a contact herbicide like PondWeed Defense®. Treatments with these types of herbicides work best on mature aquatic plants that are in a contained environment. Multiple treatments are typically required for effective short term control. It is important to remember that whenever you are treating large amounts of weed growth, only treat one third of the pond at a time and implement aeration whenever possible to ensure safe oxygen levels. When treating with PondWeed Defense®, we suggest that you use a tank sprayer to apply the herbicide directly onto the weeds. PondWeed Defense® has no water use restrictions, but if you have koi or trout, make sure you test to make sure the carbonate hardness of your water is above 50 ppm (parts per million).
For long term treatment of duckweed, we suggest using WhiteCap™. By adding WhiteCap™ to your pond in early Spring, you will inhibit the weed’s ability to produce carotene, a pigment that protects the plant’s chlorophyll. Without carotene, the sun quickly degrades the green chlorophyll and the weed dies. WhiteCap™ must stay in your pond for up to 90 days for maximum results, so if your pond has a constant overflow or you are experiencing heavy rains, you may need to include additional treatments. WhiteCap™ is degraded by sunlight, so when applying, make sure you spray the product directly into the water and not onto the plant foliage itself. Also, adding Nature’s Blue™ Pond Dye after treatment will help prevent sun degradation as well as track water dilution from heavy rains. WhiteCap™ has a 30 day irrigation restriction.
POND TALK: Have you ever experienced duckweed in your pond? What did you use to treat it?