Pests and Diseases

Ponds are excellent wildlife habitats; however, they are often attacked by various invasive species. In this section, discover how to manage pests and diseases of aquatic plants and algae. Access educational resources on excessive plant growth, aquatic noxious weed, filamentous algae, and pest management training.

Pests and Diseases of Water Plants

Ponds and water gardens are vulnerable to various pests that – if not properly managed – can cause significant damage. To effectively control pest infestations, it’s important to first identify what is causing the problem.

Some of the more common issues affecting Pennsylvania ponds are caused by aquatic invasive species. These include animals, plants, and algae that are not native to the given ecosystem.

Invasive aquatic plants that may be found in PA include water chestnut, parrot feather, and hydrilla. These plants may lead to dense mat formation that prevents recreation, crowds out native plants, destroys habitat, and clogs water intakes.

Ponds may also be attacked by invasive animal species, such as crayfish and round goby. They out-compete native species for habitat, food sources, and spawning sites. In addition, invasive animals can destroy native water plants, as well as contract and spread diseases.

Discover how invasives appear – as well as how to prevent their spread – during Penn State Extension’s water gardening and aquatic invasive species presentation.

Controlling Excessive Growth of Aquatic Plants

When carried into ponds and water gardens, nutrients such as nitrogen and phosphorus can lead to excessive aquatic plant growth. In turn, this excess of nutrients can result in eutrophication and pond ecosystem damage.

The first step to controlling excessive growth is reducing the nutrients that are feeding the plants. Creating a buffer strip of unmowed grass around the pond edge is often a good way of capturing nutrients before they enter the pond. In addition, incorporating native vegetation and wildflowers into the buffer strip can help attract wildlife to the pond.

Managing Toxic Algae Bloom

Ranging from microscopic planktonic organisms to large seaweeds, pond algae are an important part of the pond and lake ecology. Algae blooms are overgrowths of algae that can produce toxins in fresh and marine water. They can have a dangerous impact on both aquatic ecosystems and human health. Harmful algal blooms include cyanobacteria, red tides, and blue-green algae.

Abundant growth of aquatic plants and toxic algae can be managed through various physical control tactics. As well as biological methods, such as grass carp and barley straw. Pond owners can implement chemical control options, as well.

Herbicide and Pesticide Use in Ponds

Aquatic herbicides and pesticides are a chemical treatment option that offers rapid control. If used incorrectly, however, chemical treatment products can have a serious environmental impact. It is recommended to consider implementing biological and physical alternatives first.

Before applying herbicides to the pond, it is critical to correctly identify the plants that need to be controlled. The type of nuisance plant will help you select an appropriate herbicide and apply it at the optimal time. Discover more about pond measurements and control methods with Penn State Extension’s Aquatic Pesticide Management course.

Note: To apply aquatic herbicides in Pennsylvania, a permit from the PA Department of Environmental Protection is required.

On this page, find further resources on aquatic pest control. Information on aquatic plants management and growth prevention, as well as pond agencies and permits in Pennsylvania is available.