The brown marmorated stink bug, or Halyomorpha halys, is an invasive insect native to East Asia that was first found in Pennsylvania in the mid- to late-1990s. Researchers at the U.S. Department of Agriculture believe the bug probably stowed away on shipping containers. While the stink bug is not harmful to pets or humans, it caused significant crop damage in Mid-Atlantic states in 2005 and has spread throughout the U.S. ever since. The stink bug earned its name for the scent glands it uses as a defense mechanism.
Karen Coluzzi, an entomologist and state pest survey coordinator with the Maine Department of Agriculture, Conservation and Forestry, said Maine has been aware of the bug’s presence for about 10 years. A 2007 state report found that the first evidence of the bug in Maine was November 2006 in Bangor on a trailer that was shipped from Maryland. The bugs mate and lay eggs in spring and then seek shelter indoors to overwinter.
“We knew that it could hitchhike,” Coluzzi said. “What it does is it gets into people’s vehicles or luggage. If anyone visited states that had this bug they could easily transport it to Maine. We never had any real evidence it was overwintering here and becoming established. I knew it became a home nuisance pest before it became a crop pest. I figured one way to find out if it’s here is ask the public if they’re seeing these bugs coming into their homes. We sort of got an overwhelming response.”
Coluzzi said the stink bug is often confused with other noninvasive insects that seek shelter during the winter, so she asked survey respondents to submit a photograph of the bug as well. Between Oct. 16, 2017 and Jan. 18, 2018 she said there were about 500 verified reports of the bug in Maine. The highest concentration in the state was Portland, followed by Westbrook, Biddeford and Saco, the latter three having between 31 and 50 cases each. She said some of the most vulnerable crops include apples, eggplant, corn, swiss chard and tomato.
Glen Koehler, an associate scientist for the University of Maine Orono studying integrated pest management, is waiting to hear back from the USDA about funding for survey work this summer. Koehler and his team hope to lay traps in crop fields and orchards that release pheromones, or specific odors, that attract the bugs. Koehler said the bugs’ appearance in Maine is not a serious concern right now, but it’s difficult to know for sure how much damage they could cause.
“This is not a crisis situation,” he said. “It hasn’t created biblical havoc in the new states they’ve moved into, though it certainly can be a significant pest. We’ll have to wait and see. We’re on the cutting edge of this thing extending its range. As it extends its range, its behavior and population dynamics are changing also. It’s really too early to know how significant it is. Its move into Maine is not a surprise. We knew they were going to get here. They’ve been here. Now we’re able to detect them. Our approach is, if we get funding, we’ll monitor and keep tabs on what they’re up to and how many are around. We’re always checking farms for pests anyways.”
Koehler said that if the stink bugs start to cause economic damage to crops in the state, farmers can use an insecticide spray. However, a less harmful and potentially more effective method is introducing a biological control to counteract the stink bug population growth. An example is a parasitoid wasp that lays its own eggs in the stink bugs’ eggs and kills the stink bug larvae before it hatches.
Helene Lewand, owner of Blackrock Farm in Kennebunk, employs this same method in her greenhouses when dealing with a pest known as the white fly.
“That pest will become immune to all pesticides and things being used on it,” she said. “They change and are able to fight off the pesticide. If you use a beneficial insect, it does not get immune to that. For the white fly we use Encarsia, little tiny wasps that are so small you really wouldn’t see it. It comes on a little card, a little egg sac, and you put it in the greenhouse. It hatches and the wasp flies around and finds the white fly eggs, parasitizes them, hatches its own eggs in there and eats the white fly eggs.
“That’s an example of one. There are millions. Lady bugs and dragonflies eat mosquitos. There are so many different relationships going on that are good. The stink bug probably had something in its own native place that kept it in check but something like that comes over here and doesn’t have an enemy anymore. It flourishes and becomes a problem.”
Koehler said the current administration has pushed back USDA funding decisions from January until March, so he’s not sure yet if he’ll have the funding available to study the bugs this summer. However, given the consequences of ignoring the bugs, Koehler said the state can’t afford not to monitor them.
“Relative to the damage potential, it’s a small, very wise and efficient investment,” he said. “We don’t want to find out there’s a problem after we already have the damage. We want to keep an eye on these things and see it coming.”