Don’t pick up that hitchhiker: Invasive species interfere with native landscape

Don’t pick up that hitchhiker: Invasive species interfere with native landscape
                        
This summer has proven to be quite drastic from monsoon rains to a sweltering drought. My oldest granddaughter and I were walking in the woods recently, and we noticed most of the perennial woodland plants have died back for the season; however, we spotted some garlic mustard looking green and robust next to dying Christmas ferns. If you are unaware of the garlic mustard, it has become one of the most wanted (dead not alive) invasive species in northeastern United States. An invasive species is one not considered to be native to a region. In order to be “native” the species must have originated in the area. For Ohio, that means it was here pre-1700s when our ancestors first reached the Americas. Garlic mustard made its appearance in our area about a decade or so ago and has thrived in the woods and along roadsides. Like other invasive plants such as multifloral rose, garlic mustard readily outcompetes the native plants. You may notice in early spring that multiflora rose plants are green long before other plants sprout. This year I spotted garlic mustard the last part of February, and it was still partially covered in snow. When an invasive moves into a region it usually has no predator and in the case of plants no insect species that readily feeds on it. Without any way to cull the population, it takes off. In the case of garlic mustard, it produces millions of seeds. With an early emergence, it gets the jump on other woodland plants, growing fast enough to literally “shade them out.” Some recent studies suggest it can even change the chemistry of the soil as it robs natives of nutrients and water. Several years ago one of my students selected this plant for a science project. She wanted to see what might kill the seeds. She cooked them, she microwaved them, and she soaked them in vinegar. All three treatments failed and the seeds germinated. Herbicides might work for awhile, but we cannot realistically spray entire forests and risk the effects of herbicides on other species of herbaceous plants. Garlic mustard hand pulls have become one of the alternative techniques. We use this method on our four acres. Each spring my husband, armed with his garbage bag, spends hours hoping to extricate all the villains from our woods. The most important lesson to learn from this example is how quickly an invasive species can spread and how destructive it can become. This is especially true when considering the billions of trees devastated by being accidentally introduced Asian fungi. The Elm bark beetle spread a fungus (Dutch elm disease) to most of the American elm trees. American chestnut tree blight, another fungal disease, wiped out most of our chestnut trees. More recently the woolly adelgid, a small Asian insect, is eating its way through our hemlock trees. The Emerald Ash Borer, a metallic green beetle, eats the inner bark of ash trees. It hitchhiked its way to the U.S. on shipping crates from Asia. With international travel and imports it is hard to keep exotic species in their places. Invasive seeds can hitchhike on our clothes while dirt on shoes can harbor molds, spores and bacteria. Several years ago while traveling to New Hampshire I encountered another destructive invasive, the Gypsy moth. I had pulled onto a roadside rest area in Massachusetts to call my husband. While I was talking I heard what I thought were raindrops on the tree leaves overhead. When I looked up the sky was blue. That sound was not raindrops but was instead thousands of Gypsy moth caterpillars pooping on the leaves of the oak trees they were feasting on around me.


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