Manage An Invasion

You may not be able to address the root cause of the invasion on your own, but these root causes are worth keeping in mind for potential long-term, collaborative change. 

Many aquatic invasive species proliferate– on Long Island and elsewhere– due to excess nutrients in the water. This can come from fertilizer runoff, septic and sewage systems, as well as animal waste. Aquatic invasive species and harmful algal blooms can eventually make a waterbody anoxic, meaning they deplete the oxygen in the waterbody that other aquatic organisms need to survive. Reducing these inputs through updated septic systems and reduced or eliminated fertilizer inputs can improve the system.

Terrestrial invasive species thrive on Long Island for many reasons: they might have been planted for horticultural purposes, introduced along highways for erosion control, or accidentally introduced through trade, animal migration, or hitchhiking on recreational equipment like hiking boots or ATV tires. While not all non-native species introductions result in an invasion, understanding the pathways of introductions can help us all prevent future invasions. Avoiding soil disturbance, maintaining forested shade, mitigating erosion during construction projects, and finding native ruderals to fill open niches are all active ways to prevent invasive species from taking hold on your property.

In our forests, highly abundant white-tailed deer are helping invasive plants thrive, because the deer selectively eat the more-palatable native species over invasive ones. The high population density of white-tailed deer not only alters the biodiversity of our forests, but also contributes to the excessive tick issues and proliferation of Lyme disease on Long Island.

Preventing new infestations is the most cost-effective method of invasive plant management.

If you have invasive species on your site, do your best to prevent this species from spreading to neighboring properties. A simple way to do this can be clipping the flowering heads of invasive plants; this prevents them from going to seed and spreading to neighboring areas. 

Invasive plants can spread from other places on a single site, to and from neighboring properties, and between adjacent roads and trails. While some invasive species rely on wind or wild animals to move them around — they rely on us humans too! Keep your vehicles and equipment clean and free of invasive plant parts. Clean mowers and brush cutters, especially when moving between invaded areas and uninvaded areas. Avoid dumping fish tanks and unused bait into natural areas, and opt to throw them away in the trash instead.

Do your best to prevent new invasions. If you know how the species arrived on your property, you might be able to prevent future invasions of other species. For example, make sure mulch that arrives on your property has been properly heat-treated to kill any invasive plant seeds or invasive jumping worms. Disturbed soil is particularly vulnerable to invasion. 

See more ways you can prevent invasive species >>

Cultural management involves the establishment of competitive native vegetation that can resist invasion. Invasive plants will re-invade disturbed areas where native vegetation is not established and maintained. In wooded areas, maintaining shade can help prevent invasion. This includes cutting invasive vines at their base from trees, to preserve tree health and the shade it provides.

Manual and mechanical control consists of methods that kill or suppress weeds through physical disruption. This includes pulling, digging, cutting, and mowing. 

The success of mechanical control is dependent on the life cycle of the target species. For example, cutting plants while most of their energy is aboveground can deplete root or rhizome  energy storage more efficiently: this occurs when plants have begun to flower. Do not mechanically control plants once they have gone to seed, however, as this can inadvertently spread seeds.

Hand pulling and digging can be most effective on annual and biennial species. Repeated pulling and digging may be required to wear out the seed bank. 

For perennial species, hand pulling and digging can be somewhat effective if repeated over several seasons, depending on the species. 

Properly timed mowing can be used to suppress invasive plants by preventing or decreasing seed production, and can help native plants gain a modest competitive advantage. It is important to not cut native grasses lower than 6 inches, as it can damage the plants. 

When mowed, invasive plants may resprout and mowing will need to be repeated. Some invasive plants will set seed at a reduced height so that combining mowing with herbicide application may be effective. This can be accomplished by spot treating the lower resprouts. 

Clean all mowing and management equipment before entering and leaving invaded areas.

Check legal requirements and possible permits you may need before applying any herbicide. Always follow the label– it’s the law!

Herbicide application can provide an effective and efficient method of managing invasive plants. The careful use of appropriate herbicides via spot spraying, wicking, wiping, or painting not only manages invasive plants, but also minimizes soil disturbance in the process. 

In order to minimize potential adverse impacts to non-target organisms, it is important to try to use herbicide in selective spot treatments. Spot spraying and wicking (wiping) can be used to target individual plants. Cut stumps and stems can be treated with herbicide immediately after cutting so that the plant does not grow back (cut-stump method). Resprouts can be treated later with spot spraying or wicking. Whenever using herbicide, be careful to limit herbicide drift. Consider covering nearby native plants with plastic to protect them.

Biological control is the suppression of invasive species populations by natural predators, including the introduction of insects that feed on seeds, flowers, leaves, stems, or roots, or by transmitting plant pathogens that will infect plants. It takes many years of research and safety testing before biocontrol agents are available for use in the United States, but once available they provide a safe, cost-effective, and long-term solution for managing invasive species. For more information on biological control and current research, visit: http://www.nyisri.org/research/biological-control/