Invasive Species and Where to Find Them

Finding invasive species very easy once you know what you’re looking for, because they’re everywhere.

But what make a species invasive? There are a few factors that make a species be considered invasive. 1. Prolific Seeding 2. Leafing Out Early and Staying Leafed Out Late 3. Reaction to Disturbance. These three factors often dictate whether a species is invasive. A species doesn’t have to be non-native to be invasive. Native wild grape vine (Vitis) can take over areas if given the opportunity along with the native spicebush (Lindera benzoin).

In Ohio, the most common woody invasives are bush honeysuckle (Lonicera tatarica L), autumn olive (Elaeagnus umbellata), tree of heaven (Ailanthus altisima), privet (Ligustrum), Japanese barberry (Berberis thunbergii), Japanese honeysuckle (Lonicera japonica), sawtooth oak (Quercus acutissiima), paulownia (Paulownia tomentosa). Some herbicous invasives that affect Ohio’s forests include: Japanese stiltgrass (Microstegium vimineum) and garlic mustard (Alliaria petiolata).

Control Methods:

It is likely that without control, the invasive species will out-compete native species. A combination of mechanical and chemical control will likely be necessary to control the issue.  Two primary herbicides are recommended for treating the majority of these woody and herbaceous invasive species.  Glyphosate (Brand name RoundUp) is great for honey suckle, stilt grass, and privet. Triclopyr (brand name Garlon 3a or 4) is great for tree of heaven and autumn olive.  There are 3 primary treatment methods – 1. Foliar, 2. Basal bark, 3. Stump cut.  First, foliar is spraying the leaves with a 2% concentration by volume (generally). It is practical if the plant is shorter than the applicator and assuming leaves are out but not yet wilted from autumn.  It’s best used mid summer to late September when the plant starts converting sugars and transporting them down to the roots.  If the plant is still pushing sugars up the leaves in the early season this can push pesticide away from the plant making treatment less effective.  Basal bark treatment is spraying the lower 18 inches of the stem with a 20% concentration by volume (generally).  This is not ideal if the plant is bushy and hard to spray.  When a plant is taller than the applicator and a foliar application is not practical, then stump cut is a great option. This involves using a chainsaw or handsaw to cut the plant down at the stump.  Spraying this stump with a 20% concentration by volume helps isolate the spray to a specific area (lowering non target spray) and is very effective at killing the plant, though cutting is an extra step and requires another tool. As long as you have a fresh cut, this method works year around assuming the treated plant is a wood plant The landowners should monitor the property as needed to keep track of populations of known invasive species.

I personally don’t use basal spray on shrubby invasives as the over spray potential is high. I prefer the stump cut method as it localizes the herbicide. But foliar doesn’t require a chainsaw. If the whole woods is invasives, I don’t feel bad using the foliar method. I just make sure I stay under my legal per-acre limits of active ingredient.

For more detailed treatment information, check out your state’s extension resources on the specific invasive.