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Careful gardening helps keep invasive species out
STARKVILLE, Miss. -- Mississippi’s climate has proven to be ideally suited to hosting a variety of introduced, invasive plants and insects, but vigilant residents can prevent these pests from becoming overwhelming problems.
One of the latest invaders is the box tree moth. North Mississippi residents are confronting this new challenge, which is a serious pest of boxwood shrubs that began showing up on boxwoods bought in Tennessee this spring.
Blake Layton, an entomologist with the Mississippi State University Extension Service, said the moth is of particular concern to residents of north Mississippi, but it could appear anywhere in the state.
“This is a caterpillar pest that can cause serious defoliation and webbing -- and even death -- of boxwoods in home and commercial landscapes,” Layton said.
The U.S. Department of Agriculture determined that this spring, potentially infested boxwoods were shipped from Canada to a number of U.S. nurseries in seven states. One of these nurseries was in the Memphis area, which serves part of Mississippi.
This latest threat serves as a reminder that new pests keep arriving, and it can happen very quickly.
“We already have a lot of invasive pests in the state,” Layton said. “About half of our important insect pests are nonnative, with fire ants and Formosan termites being just two examples of introduced pests that have very large economic impacts.”
The problem with nonnative species, whether plant or insect, is they tend to have no natural predators or control systems. This advantage allows them to thrive and sometimes overtake native populations.
“Quarantine and exclusion are the primary defense against these pests,” Layton said.
USDA, through the Animal and Plant Health Inspection Service, is responsible for attempting to keep invasive species out of the country. In-state, the Mississippi Department of Agriculture and Commerce, through the Bureau of Plant Industry, is the next line of defense.
The MSU Extension Service also plays a role in this battle.
“The Extension role is twofold: proactive education for the pests we don’t have, and developing and promoting control methods for the ones that get in,” Layton said.
Kacey Colquitt, the state plant regulatory official with the Bureau of Plant Industry, said some nonnative plants are initially welcomed, but they later become nuisances. The Bradford pear and the popcorn tree are on this list, but the crape myrtle, a nonnative from Asia, is appreciated.
“When they become a problem to agriculture or overpopulate and become a nuisance, that’s when they are no longer welcome,” Colquitt said. “For most plants, it takes a very long time for them to cause enough problems that they become a nuisance and are called a pest of significance and put on our noxious weed list.”
Much of the day-to-day efforts of the Bureau of Plant Industry involve stopping the spread of existing invasive species that have become well established in the state over the years. The fight against kudzu is a perennial battle, and cogongrass has also become a significant pest.
Colquitt said Mississippians who are interested in helping can start by educating themselves on where the problems are, and then being careful of what they introduce to their own landscape.
“Be careful what you purchase at a nursery,” Colquitt said. “Make sure it is a certified business that takes precautions to sell only clean and healthy plants. Be careful what you plant in your yard that you buy online.”
She also encouraged gardeners to be cautious when bringing in plants from other areas, especially those from long distances away. Many invasive plants and insects have made big geographic jumps in this way.
Information on nonnative, invasive plants is available online from the Mississippi Department of Agriculture and Commerce and the MSU Extension Service through such publications as M1194, “Mississippi’s 10 Worst Invasive Weeds,” https://extension.msstate.edu/publications/mississippi%E2%80%99s-10-worst-invasive-weeds.