Concerns, Impacts, and Solutions to the Brown Marmorated Stink Bug Invasion

Kyle Runion

Enst233 Dr. Lance Yonkos

October 17, 2012

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The Brown Marmorated Stink Bug (BMSB) has become a serious agricultural and

economic problem in the United States. Native to Asia, it is an invasive pest that feeds on over

300 different crops like corn, soybeans, apples, and peppers. It has caused serious crop loss,

sometimes even resulting in total crop failure. The monetary figures lost due to this pest in just

the last few years are astounding and could grow even larger. While only the east coast is

currently seeing major losses, the BMSB has spread to the Midwest and is starting to be seen on

the west coast. There is no current environmentally and economically sustainable control for the

BMSB, but many are being tested. Pesticides, trap cropping, introduced predators and row

covering are all being researched to determine effectiveness. A solution needs to be found

quickly, as the agricultural losses due to these bugs are growing every year and many farmers

cannot take these hits for much longer. These losses would have a global impact, hurting

economies and the environment. It is important to find a solution before the U.S.’s major

agricultural centers in the Midwest are hit with the waves of BMSB and even more losses are

seen.

The BMSB is an invasive pest that has caused considerable crop damage in the Mid-

Atlantic and Southern eastern shore of the U.S. Native to Asia, the BMSB was introduced to

eastern Pennsylvania in the mid-1990s and has spread throughout multiple states since. New

Jersey, Maryland, Delaware, West Virginia, and Virginia all have significant populations of the

BMSB, and smaller populations can be found in Mississippi, Ohio, Oregon, and California

(Roberson 2010). Overall, the BMSB has been spotted in 35 different states (Nielson et al 2012).

Their adult form can fly, giving and easy mode of migration. Clearly this bug is thriving on U.S.

soil, and is starting to become a real problem for farmers in these states. It has been reported that

these bugs have over 300 possible host plants, allowing them to almost always have an available

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food source (Nielson et al. 2012). The stink bugs appear to be moving northwest, having been

spotted in Illinios for the first time in 2010 (McMahon 2011). This could be a major problem if

these pests realize their damaging potential in the Midwest, America’s major farming region.

The BMSB life cycle consists of five immature stages and adulthood (See Figure 1).

Adults emerge in early spring from overwintering sites and can survive until mid to late summer.

They reproduce during this period, with about 28 eggs per mass. They undergo five immature

nymph stages to become an adult and feed throughout the summer. In early fall, they find an

overwintering site to live in during the cold months. BMSB are different than other species of

stink bug in that they often use a man-made shelter as their overwintering site. They can survive

in wooded area shelter or cliff outcroppings, but homes, sheds, and barns become a very

attractive and easy place for them to live out the winter. Humans become annoyed with the stink

bugs invading their home over the winter, adding on to their list of difficulties (Nielson et al.

2012).

The BMSB damage is dangerously high for some farmers. They damage fruit by

puncturing the skin and sucking out juices. This causes deformed fruit, “corked” tissue, and

possible introduction of pathogens, which can downgrade the fruit or even make it completely

unsellable. Only ten years after the initial invasion, commercial pear and apple farms lost 25-

90% of their crop to BMSB damage. Years later, some farmers reported total crop loss.

Monetary losses have been seen in the past few years due to the BMSB, including an estimated

$37 million in the U.S. apple industry in 2010 (See Figure 2) and a 70% total feeding injury in

organic peppers in the state of New Jersey (Nielson et al. 2010).. A single farm in West Virginia,

the Redbud Farm, lost $20,000 from BMSB damage (Nielson et al. 2012). This amount can

change a fiscal year from profits to loss, a devastating change for many small scale farmers. The

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reason the damage they do costs so much deals with the grade of the product. Perfectly grown

fruit and vegetable with no damage will rank as the highest grade (different for each

fruit/vegetable), which will sell for a higher price. More damage on the fruit pushes it down the

grades, being used in lower quality foods for a less expensive price. An example of the grading

system with non-sweet peppers is Fancy, No.1, and No. 2. The peppers are separated into these

three groups based on maturity, shape, size, color, firmness, and damage. The first five of those

characteristics deal with growing quality, but the last, damage, mostly deals with pests. A

damaged fruit will quickly fall down the grades and be worth a fraction of a non-damaged one.

This is how the BMSB is affecting our crops: by lowering the quality and value, costing farmers

millions of dollars ("United States Standards for Grades of Peppers (Other Than Sweet Peppers)

2007).

Corn and soybeans, two of the BMSB’s main host plants, are also the United States’ most

grown crops. These two plants account for $27.6 billion of sales in the United States agriculture

industry (Major Crops Grown in the United States 2012). Significant losses here could do

substantial damage on the U.S. and global economy. Clearly the U.S. would be losing money by

producing a significant amount less than they are now. If the U.S. produces less corn and

soybean, prices all over the world increase, and imports to the U.S. will rise as there will be less

supply and more demand. Developing countries like Brazil are likely to pick up some of the

slack. Their economy would be helped by this, but agriculture in developing nations is extremely

unsustainable. They often burn entire forests to gain land to grow on, which in turn increases

global warming by reducing carbon pools and photosynthesis. The BMSB is causing a major loss

in crops and likely will continue to if unmonitored and untreated as it has few predators in its

new feeding ground, the United States.

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Invasive pests often thrive because, in their new habitat, they have few, or no natural

predators, and a large food supply. This is exactly the case with the BMSB. It has minimal

pressure from natural enemies and is able to exploit crops. Money is being spent to develop

defenses against these bugs. A $5.7 million grant was given to Penn State University for a three-

year project to find an economically and environmentally sustainable solution to the BMSB.

Many of the pesticides that are currently effective in killing the stink bug are very broad-

spectrum pesticides, meaning they kill many kinds of insects. This is a problem because many

insects killed with these pesticides are beneficial to the plants and ecosystem. Using these

pesticides to eliminate the BMSBs can be just as harmful as the BMSB themselves (Multi-state

project aimed at brown marmorated stink bug 2011). For this reason, researchers must study the

stink bug chemical ecology to try and develop a pesticide that can effectively control the BMSB

population without harming that plants and surrounding ecosystem.

Recent research has some reasons for optimism and pessimism. A soybean study in

Virginia has noted that while it has become fairly easy to kill BMSB with several common

pesticides, they are infesting deeper into fields this year compared to last, and that they are

beginning to re-infest areas that were previously sprayed when last year a single application kept

the stink bugs off for the entire season (Herbert 2012). It is good to see that they have been able

to control the population, but a bit scary to see that they are re-infesting. This could just be that

the pesticide wore off and that its residual effects are weak or that populations of BMSB are

higher this year and the pesticides didn’t work too well to start, but it could also be that the

BMSB are overcoming the simple pesticides used. They have multiple generation each year, so

they could be evolving to become resistant to these pesticides. Rutgers University has said that

they have seen resistance development already (“How to Control the Brown Marmorated Stink

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Bug”). They also say that insecticides and pesticides are sometimes ineffective with the BMSB

because they often live in trees and then repopulate crops through migration from non-treated

areas. The only known way to stop these bugs chemically is a short-term fix, as they can develop

resistances to nearly any applied pesticide.

Another strategy farmers have used to lure BMSB away from their cash crops is trap

cropping. Trap crops are a plant that a pest is attracted to rather than the cash crop that the farmer

actually wants. They are planted in a certain lifecycle of the pest, and the pest feeds on that crop.

The trap crop is then destroyed before that lifecycle is completed, in hopes that the pest will not

be able to advance to the next lifecycle without its main source of food. This has worked for

other types of stink bugs, but is not effective with the BMSB based on its resourcefulness. As

mentioned, the BMSB has over 300 possible host plants and generally hasn’t seemed to pick any

few as a main preference. Some researchers though think they have started to work on a solution,

like Thomas Kuhar, a Virginia Tech entomologist. "We collected some data last year and found

that the brown marmorated stink bug has a strong preference for sweet corn and sunflowers, so

we hope to use these two crops as trap crops to draw them in, and then evaluate ways to get rid

of them," Kuhar said earlier this spring (Pollock 2012). Another reason the trap cropping does

not work is that these insects are quick, being able to move quickly in their immature stages, and

being able to fly in the adult stage. Once the trap crops are removed they are able to move over

to the cash crop and feed there. The final reason trap crops are ineffective is the lack of a natural

predator. Often, trap crops are selected based on the preference of the pest and its enemies, in

hopes that natural predators will also flock to the trap crops and control the pest population. With

an invasive species like the BMSB though, this is not possible.

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Finding a natural predator would be a great way to control the BMSB population.

Predators are nature’s way of keeping each species population in check. One could be introduced

(although this procedure must be done very carefully, as the introduced species could have the

same effect as the prey it is introduced for) or an existing one could be amplified. The BMSB’s

primary predator in Asia is a parasitory wasp named Trissolcus halyomorphae. It lays its eggs

inside BMSB eggs, killing the stink bugs for its own offspring (See Figure 4). They are very

effective in Asia, killing on average about 2/3 of the BMSB eggs. Tests are being done to see if

these wasps can be introduced safely in the United States. A main concern is that once released,

they could parasitize other types of stink bug eggs which may be vital to the ecosystem. Some

stink bugs are predators to other pests, so removing these could be even worse than the BMSB

problem. A lab in Delaware is doing research in hopes of finding that the wasp would be safe to

introduce by mid-2013 (Marder 2011) and Virginia Tech has some bright findings. Doctoral

Student Amanda Koppel and Integrated Pest Manager Ames Herbert have been testing multiple

types of wasps with BMSB eggs. They found that about half of the BMSB eggs were parasitized

and killed after introducing the wasps in a test. Surprisingly, only 16% of Spined-Soldier Stink

Bug, a beneficial species, was parasitized and that other beneficial species saw lower parasitism

rate (Roberson 2009). Similar wasps exist locally, such as the Telenomus podisi and the

Trissolcus basalis. These wasps have been known to parasitize the eggs of other types of stink

bugs and usually kill about half of the eggs. These could also be a viable option, but clearly some

work would need to be done, such as growing the populations of these wasps, because they

aren’t naturally killing the BMSB (Neilson et al. 2012). These wasps could be a great solution, as

they fix the problem where it begins: in the eggs. Insecticides have been found to kill less than

30% of BMSB eggs it is applied to, where the wasps can continually and safely kill over half the

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eggs (Roberson 2009). Praying mantises and spiders have also been seen eating the BMSB, but

using these for control is not ideal either, because they don’t seem to prefer the BMSB and

therefore aren’t naturally controlling the population.

Kuhar is also looking at row covers as a BMSB control option. Row covers are like mesh

bags that go over an entire row or crops to protect the crops during critical growing stages. Many

types of row covers need to be removed after a certain plant growth stage to allow growth and

fruiting. They are stapled to the ground as to not let any insects that cannot go through the soil

onto the plants. Row covers have been used to effectively control against other pests like

cucumber beetles (Pollock 2012). These could work, but the plant growing stages would have to

line up with the BMSB growing stages. Any stage of BMSB can eat from fruit or vegetables

(save the first instar, which just eats its egg shell), so the row covers would have to protect the

crop at the same time that the BMSB are maturing. Before their adult stage, they need extra food

to support growth, so this is the most critical feeding time. Once they reach adult stage, they can

then fly and then wouldn’t be hurt as much by the row covers as they could find food in other

sources while the covers were on, then fly back over and feed on the previously covered crops.

Some row covers use wiring to hold the mesh up and shade fairly low as to create a sort of clear

tent to put around the plants (See Figure 3) (Dickerson 2004). This could work for small scale

farming, like organic farmers, but not for large scale industrial farming; it would not be

economically viable.

The BMSB is a proven pest and will continue to be in the United States if not dealt with.

Pesticides seem not to be the answer due to resistance development, but there may be a solution

in introduced predators, trap cropping, or row covers. Introduced predators seem to be the best

option, and much research is being done with this. Parasitory pests can kill a large proportion of

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the eggs, leading to reduced populations and less damage. Some studies show that they seem not

to parasitize beneficial species of stink bugs as much as harmful species, which is a key to

maintaining a healthy ecosystem. The damage being done is causing farmers millions of dollars,

which will in turn increase food prices here in America and increase necessary imports with a

lower supply. To combat this growing catastrophe, I would advise putting more money into

research of natural and introduced predators. The research done so far is promising, and if done

correctly, it can be the most environmentally and economically sustainable solution of all.

Figure 1 BMSB Life Cycle (Simplified, there are 5 nymph stages) (“Corn Insect and Disease Guide.”)

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Figure 2. BMSB damage on an apple (Marder 2011).

Figure 3. Wired Row Covers ("Broccoli: Row Cover Results & Recipe.")

Figure 4. Healthy vs. Parasitized BMSB eggs (“Brown Marmorated Stink Bug.”)

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Figure 5 BMSB damage on a bell pepper and tomato (Brust 2012)

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