Find the pond weeds before they find you! That's the advice of Mike Hogan, Ohio State University Extension educator for Carroll and Harrison counties.
One of the biggest problems in aquatic-weed control is that pond owners do not start control programs early enough in the season. This is particularly true when pond owners use aquatic herbicides to control weeds.
"Too often pond owners begin aquatic-herbicide treatments in the middle of the summer, when the weeds reach the surface of the pond. Ideally, as soon as pond weeds are present and the water temperature in the pond reaches 65 degrees Fahrenheit, most aquatic herbicides should be applied," says Hogan.
Pond owners who have had submerged weeds in their ponds in previous years should begin looking for them now, instead of waiting for them to grow to the surface of the water. Hogan suggests using a rope to pull a garden rake, weighted with a brick, along the pond's bottom to look for vegetation. If you pull up a rake full of weeds, herbicide treatments should start as soon as the water temperature reaches 65 degrees.
The problem with waiting until the weeds reach the surface is more than just aesthetic. Large masses of decomposing vegetation that result from herbicide applications made later in the summer, coupled with higher temperatures and low dissolved oxygen in the pond, can be deadly to fish. The decomposition of vegetation is an oxygen-consuming process, which robs fish of what little dissolved oxygen there is in a pond with a summer temperature of 70 to 80 degrees. The result, says Hogan, is a mid-summer fish-kill due to suffocation.
To avoid the potential of a fish kill caused by decomposing vegetation, Hogan urges pond owners who use herbicides to begin treatments as early in the season as possible so that the vegetation is completely destroyed before the end of June.
Hogan also suggests that pond owners attempt to control pond weeds by non-chemical methods when possible. "Reducing the amount of sediment and phosphorus entering the pond will cut down on weed growth. Sediment from soil erosion or construction, livestock waste runoff, tree leaves, and other organic matter are all sources of phosphorus," says Hogan.
The Carroll County Office of OSU Extension has a videotape on the topic of pond-weed control that is available for loan, free of charge. Several pond-related publications are also available at the Extension office, including the following: Ohio Pond Management (Bull. 374) $3.75, Controlling Filamentous Algae in Ponds (A3) free, Chemical Control of Aquatic Weeds (A4) free, Cattail Management (A11) free, Planktonic Algae in Ponds (A9) free, Fish Species Selection for Pond Stocking (A10) free, Pond Construction (AEX 303) free, Pond Measurements (A2) free, When to Apply Aquatic Herbicides (A15) free, Placing Artificial Fish Attractors in Ponds and Reservoirs (A1).