Similar to invasive plants that can take over your garden (looking at you, kudzu), there are also invasive insects to watch out for. Why? Because slowing or stopping their spread helps both your immediate landscape as well as the larger environment. According to the U.S. Department of Agriculture (USDA), the damage done by invasive pests and diseases costs the United States an estimated $40 billion a year in losses of plants, trees, and agricultural crops. Here’s what you should know about invasive insects and how to control them.

What Are Invasive Insects?

Insects often hitchhike on products, people, and plant material, usually without our being aware of it, says Kathryn Bronsky, national policy manager with the USDA’s Animal and Plant Health Inspection Service. They can come in on plants and seeds shipped by travelers or stow away in product shipments. Once in the country they can be moved about on plants and produce, soil, logs, firewood, and mulch.

A non-native bug, plant, or microbe is considered invasive once it displays certain harmful characteristics. “Invasive species are non-native organisms that could be plants, insects, or diseases and these harm our economy, food security, and the environment,” Bronsky says. “These are usually from other countries and when they come into a new area, they have no natural predators and can quickly spread, which disrupts the natural ecosystem and pushes out native species and impacts diversity.”

If unchecked, invasive insects “can harm our gardens and plant health in the U.S. and across the globe,” Bronsky says. Worldwide, she says, “The United Nations estimates that each year invasive pests destroy up to 40 percent of food crops and cost $220 billion in trade losses worldwide. That’s why it’s important everyone does everything they can to slow the spread by following import requirements and domestic requirements.”

Which Pests to Watch For

From giant snails to fire ants, there are numerous invaders to watch for in your yard. Here are the biggest threats, according to the USDA, and what to do if you spot them.

1. Spotted Lanternfly

Spotted lanternfly (Lycorma delicatula) is a moth-like “planthopper” that affects numerous food crops, including grapes, stone fruit, and hops as well as hardwood trees. Its preferred host is the aggressively spreading tree-of-heaven (Ailanthus altissima). The egg masses can be laid on almost any outside item, even metal, and are easily missed because they look like a dried daub of mud. First seen in 2014 in Pennsylvania, spotted lanternflies are now reported in 17 states.

Recommendation: If you see SLF adults or egg masses in a new area, Bronsky says, “we encourage you to report it. If already established in your region, just smash them. And in winter and spring, scrape egg masses with a credit card into a plastic bag and squish or place in soapy water.”

2. Emerald Ash Borer

Already found in 36 states, emerald ash borer (Agrilus planipennis) is a wood-boring flying Asian beetle which has killed tens of millions of ash trees. It lays eggs just under the bark, and when larvae hatch, they feed on the tissue, slowly killing the tree. Adaptable to varied climates, it also spreads easily through infested firewood, logs, or nursery stock. Signs of infestation include D-shaped exit holes in the bark, dead branches at the top of the ash tree or increased woodpecker activity hunting down the larvae.

Recommendation: Buy local firewood or certified heat-treated firewood to prevent spreading EAB.

3. Spongy Moth

Spongy moth (Lymantria dispar dispar) is a wide-ranging pest that feeds on over 300 species of trees and shrubs, endangering our forests. The eggs may be transported on firewood, lawn furniture, or outdoor toys and accessories.

Recommendation: Before moving homes or traveling out of an affected area, check for egg masses; some states require this by law.

4. Invasive Fruit Flies

The USDA lists four types of fruit flies on its “most threatening” list. The Mediterranean fruit fly, “one of the most damaging agricultural pests in the world” infests apples, avocados, bell peppers, melons and tomatoes making them inedible. Affected trees can be completely defoliated, giving a wintry appearance in summer.

Recommendation: Don’t ship into or move fruit to another state without clearing it first with the State Agriculture Department.

Tips for Stopping Invasive Pests

Awareness is a big part of keeping invasive pests at bay. Use these tips to further avoid spreading harmful pests.

• When traveling abroad, always declare any food, plant material including seeds, soil, and handicrafts including fresh wood at customs when traveling internationally to make sure it’s pest-free.
• At home, when buying plants online, source your plants responsibly. The USDA says, “When ordering online, ensure the plant is coming from a domestic source or follow import regulations. If you don’t know where an agricultural product is coming from, don’t buy it online.” Check with your local agricultural office about regulations on that plant.
• Don’t move untreated firewood to new areas.
• Be aware of state or federal quarantines for plants and insects so you can take appropriate action if you spot them in your yard.
• To avoid inadvertently sending hidden pests, don’t mail plants or produce to out-of-state friends or family without clearing it first with your local agricultural office.
• If you discover signs that a new pest has moved in, report it to state and local authorities.