Jessica

Irrigation ponds that are heavily used will be replenished from groundwater which cools the pond (mid 60-degree range) but also dilutes the amount of oxygen in the water. The cooler temperature will decrease algae growth. If you are not using the capacity of the pond at least once a week the water will begin to warm, and you'll have more algae growth. The major factors for algae growth are the presence of phosphorus in the water and temperature. Lowering the phosphorus content, short of pulling the capacity of the pond out on a weekly basis, is difficult. Avoiding leaves and any plant material degrading in the water can help minimize phosphorus and ultimately algae growth.

Adding oxygen to the water is a stopgap measure to avoid the immediate demise of the fish population. This can be done by bubblers that compressed and emit air at the bottom of the pond, pond pumps that agitate the surface - greatly increasing the amount of oxygen that diffuses to the water or by spraying a small quantity of irrigation water back over the surface. Common practice among irrigators is to use a small impact sprinkler positioned to cover as much of the pond as possible, agitating the water surface anytime irrigation applications are made. This will require 20lbs of pressure or more to be effective.

There are several pesticides available to treat ponds to reduce or kill off algae, some of these can be used in the presence of fish safely. Be aware that there are two issues: will the fish die and is the fish safe to eat. Link to the bulletin below will help provide background information and help you select a product.

Some irrigators utilizing ponds treat the pond with barley straw before warm up to control algae, I have seen moderate success with this process. The treatment must begin in spring before the algae growth, this allows time for the breakdown of the barley straw that increases the breakdown of the algae populations before they hit the rapid growth stage. Be aware that barley straw itself contains a fair amount of phosphorus; to avoid feeding the problem, pond owners have devised a method for removing the straw once the season is over. I see growers using a net bag tied in position near areas where algae have grown previous years. At the end of the season the bag is retrieved, and the decayed straw is dumped in the field away from the pond.

There are several excellent publications related to weed management. I recently pulled together a list of publications for a new employee to review before working on a fact sheet for MSU this winter, Our publication will not be ready in time help you. However, below is the reading list:

General pond management

https://content.ces.ncsu.edu/pond-management-guide

https://www.canr.msu.edu/resources/managing_michigan_ponds_for_sports_fishing_e1554

https://archive.lib.msu.edu/DMC/extension_publications/e1554/e1554-1994-print3.pdf

Irrigation Pond weed management

https://extension.okstate.edu/fact-sheets/aquatic-weed-mangement-control-methods.html

https://extension.okstate.edu/fact-sheets/aquatic-weed-management-herbicides.html

https://lgpress.clemson.edu/publication/pond-weeds-causes-prevention-and-treatment-options/

Algae control

https://extension.rwfm.tamu.edu/wp-content/uploads/sites/7/2023/06/Managing-and-controlling-algae-in-ponds.pdf

https://www.extension.purdue.edu/extmedia/Ho/Ho-247-W.pdf

Control of phragmites/reeds

https://dnr.wisconsin.gov/sites/default/files/topic/Invasives/phragmite_control_management.pdf

https://www.greatlakesphragmites.net/files/HerbicideQuickGuide.pdf

Lyndon Kelley

Irrigation Educator - MSU Extension/Purdue Extension

612 E  Main St,  Centreville, MI 49032

https://www.canr.msu.edu/irrigation/

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