Tree of Heaven, paulownia are two tree species that provide refuge for brown marmorated stink bug after hibernation, study finds

Since its discovery in the United States in 1996, the brown marmorated stink bug has been testing the patience of farmers and homeowners alike. From spring to fall it decimates crops such as tree fruits, vegetables, cotton, corn and soybeans. After harvest it retreats to residential areas, covering buildings and vehicles, and often entering people’s homes.

The brown marmorated stink bug, or BMSB as it’s often called, was detected for the first time in Allentown, Pennsylvania in 1996. Over the next ten years, it spread to several states in the Northeast and began migrating south. By 2010 the pest was in North Carolina, and has since become a serious pest of fruit trees and vegetables. In some areas BMSB populations are so numerous that they are very difficult to control and inflict high levels of damage.

BMSB also presents problems for the non-agricultural sector. “We were recently asked to aid a shipping company that ships vehicles from a port in Charleston,” says Jim Walgenbach, Extension Entomologist at NC State University. “The company (in North Carolina) ships new vehicles to Australia and New Zealand where BMSB is not established. Many of the new vehicles produced in areas with high BMSB populations were infested with the pest before they reached loading docks, resulting in the need to fumigate them before loading onto ships. In addition to the cost of fumigation, ships needed to increase their speed on the ocean to make up for time lost to fumigation, resulting in higher fuel costs as well. So the pest was costing the company millions of dollars.”

“The shipping company wanted to know if the stink bug problem could be mitigated at the source. Unfortunately the plant that makes and stores the tractor trailers is in the middle of a hotspot of stink bugs, so there wasn’t much that could be done in the short term.”

After years of study, scientists discovered that the pest came out of hibernation in April and May and sought shelter in the forest while crops were still maturing. However, much was still unknown about their habits in the forest and whether they preferred some trees over others. In a recent peer-reviewed article in Environmental Entomology, North Carolina State University Extension entomologist Jim Walgenbach and other entomologists from North Carolina and Virginia reveal that the invasive tree of heaven and paulownia are two of several tree species that harbor brown marmorated stink bug in spring before it moves back into the field.

Because BMSB is such a serious pest for both homeowners and farmers, scientists have been trying to figure out the pest’s migration habits—when it leaves crops in the fall to go to neighborhoods and when it leaves the neighborhoods to go back to the crops in the spring. Monitoring efforts show that the pest leaves crops in September and then spends the winter hibernating in human-made structures, a process called “overwintering.” As the pest leaves its hibernation areas in May, crops are still in very early stages of development, so the bugs initially feed and reproduce in the forest until farm crops start forming fruit. Once crops start producing, BMSB disperse from forested areas to agricultural crops, usually gathered along the edge of fields that are adjacent to forests.

“We know there’s a strong edge effect in the fields,” says Walgenbach. “In the fields that don’t have a wooded border, BMSB has been less of an issue. So there’s the potential for edge treatments.”

In Japan BMSB uses cedar and cypress as forest hosts. Researchers from North Carolina and Virginia wanted to know what trees BMSB preferred in the U.S. They embarked on a 3-year survey of stink bug species on plants in nonmanaged areas along with a 1 and 5-year survey of stink bugs in commercial soybean fields in the mountain, piedmont and coastal regions of North Carolina and Virginia.

Tree species varied slightly depending on geographic area and life stage. For instance, in the mountain region of North Carolina, BMSB laid their eggs on paulownia and tree of heaven. Nymphs developed on catalpa, grape, yellowwood, paulownia and cherry; and adults were on catalpa, yellowwood, paulownia, sycamore and redbud.

In both North Carolina and Virginia, BMSB preferred tree of heaven, paulownia, catalpa, cherry, grape and yellowwood. Both tree of heaven and paulownia are exotic invasive trees and often are the target of invasive removal efforts in managed forests. However, both species, especially tree of heaven, are widespread and persistent in growth, sometimes even after removal. In addition, tree of heaven has invaded nearly every state in the U.S.

If growers begin monitoring for BMSB in woodlands adjacent to their land, they can better prepare for it with more timely and accurate insecticide treatments. The problem is more challenging for organic growers, who cannot use those insecticides effective against BMSB. Ongoing research is investigating the use of the use of trap crops and row covers to protect organic crops from BMSB populations.

Other entomologists involved in this research include Ames Herbert and Tom Kuhar from Virginia Tech, Dominic Reisig from NC State University and Mark Abney from the University of Georgia. Walgenbach and some of the researchers are part of a national working group on BMSB, led by Tracey Leskey of USDA Agricultural Research Service.

The working group is continuing to monitor BMSB distribution throughout the U.S. to prepare growers in newly invaded areas for the pest. Although BMSB is present in 40 states, it is a major problem only in some of the northeastern and upper southeastern states. In the South, North Carolina and east Tennessee are the southernmost areas where BMSB is currently a major agricultural problem. Walgenbach says the primary reason may have to do with the number of daylight hours.

“It is not yet clear if BMSB will be an issue further south,” he says. “The population in the U.S. originated from north of Beijing, where reproduction in that population only occurs at photoperiods of greater than 14 hours of daylight. The farther south you go, the shorter that time period is during the summer months.”

Also see: Bakken, A.J., S.C. Schoof, M. Bickerton, K.L. Kamminga. J.C. Jenrette, S. Malone, M.A. Abney, D.A. Herbert, D. Reisig, T.P. Kuhar, and J.F. Walgenbach. (2015) Occurrence of brown marmorated stink bug (Hemiptera: Pentatomidae) on wild hosts in nonmanaged woodlands and soybean fields in North Carolina and Virginia. Environmental Entomology 44(4), DOI: 10.1093/ee/nvv092

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