The Brown Marmorated Stink Bug

Halomorpha halys, the brown marmorated stink bug, is native to Asia and was introduced on the East Coast of the U.S. in the late 1990s. It has spread to 43 states and as far north as two Canadian provinces. The brown marmorated stink bug has piercing-sucking mouthparts with a straw-like stylet that sucks plant juices. They feed on leaves and stems but prefer reproductive structures like fruits, pods and seeds. It is an agricultural pest to fruit, vegetable and grain crops.

The brown marmorated stink bug is also a homeowner nuisance pest because it has overwintering habits to seek shelter in residents’ homes, similar to boxelder bugs and lady beetles.

The brown marmorated stink bug first appeared in the Portland area in 2004 and has spread to most Oregon counties that lie along the Interstate 5 and Interstate 84 corridors. The spread of the brown marmorated stink bug is likely due to its ability to hitchhike on vehicles and cargo trains. Also contributing to the brown marmorated stink bug's spread is the adults’ great flying capabilities, which aid in dispersal.

The brown marmorated stink bug has white bands on its antennae, smooth shoulders, and mottled brown coloration. Adults look similar to native stink bugs, including predatory species like the rough stink bug. Brown marmorated stink bugs and rough stink bugs have similar coloration and fall behaviors of seeking refuge indoors to overwinter. However, rough stink bugs differ because of their rough shoulders and solid antennae color.

Adult female brown marmorated stink bugs lay eggs from spring until late summer. There are usually about 28 clear-blue eggs in a cluster, and the eggs are primarily laid on the underside leaves. The eggs hatch in four to six days and the first instar larvae, which are typically red and black or white and black, stay around the egg mass feeding on bacteria left by the mother. Once the nymphs reach the second instar stage, they begin feeding on plant tissues, including leaves, stems and fruit. As the nymphs continue to grow, they develop the same brown and black mottled coloration as the adults but lack fully developed wings.

The brown marmorated stink bug is a polyphagous feeder that attacks more than 170 different plant species, including agricultural crops like vegetables, legumes and tree fruits. The brown marmorated stink bug has piercing-sucking mouthparts which extract plant juices and sugars while leaving behind puncture holes. These puncture holes can then cause further damage like scarring and secondary infections. Brown marmorated stink bugs can further contaminate and taint produce by releasing their chemical defense compound as they cling to fruits or vegetables during transport.

Because of brown marmorated stink bugs' wide host range and high mobility, a whole-farm pest management approach is needed. Research is being conducted to investigate sustainable management strategies like biological control, habitat manipulation, trap crops and barriers.

Researchers are currently assessing natural enemy predation and parasitism. Results from an egg parasitism and predator study show that egg parasitism is low and predation is primarily from the big-eyed bug and spined soldier bug. However, in the last year a parasitoid native to Asia, Trissolcus japonicas, was discovered in the United States and was found to use brown marmorated stink bug eggs as a host. Scientists are now researching Trissolcus japonicas by studying the parasitoid’s rates of parasitism both on brown marmorated stink bug and native stink bug egg masses.

In addition to biological controls, researchers are studying habitat manipulation to further help organic farmers combat brown marmorated stink bug. They are looking at brown marmorated stink bug movement patterns in mixed environments, including wild and cultivated hosts, in order to discover potential aggregation hot spots throughout the season. Identifying movement patterns may help farmers target the location of trap crops or manipulate the habitat unfavorably for the insect. Further research is needed to understand the behavior and host plant selection of brown marmorated stink bug.

Cultural controls like barriers and trap crops can help small farmers protect their crops if the brown marmorated stink bug becomes a problem. First, consistent monitoring and correct identification are necessary to prevent big outbreaks. Once the brown marmorated stink bug has been detected and correctly identified, the best line of defense is to prevent the insect from feeding on host plants by using barriers such as row covers, sticky traps around tree trunks or bagging fruit in small orchards. In vegetable production, researchers are studying trap crops like sunflowers and sorghum. These types of trap crops can be used to attract brown marmorated stink bug populations, therefore keeping them away from cash crops. A preliminary trap crop study conducted in Sacramento found brown marmorated stink bug in high numbers on taller sunflowers. If trap crops are used, Anne Neilson from Rutgers University suggests planting them at least six feet away from the cash crop in order to minimize insect migration between crops and to allow air flow. Additional studies are underway to assess trap crops as a management tool.

Brown marmorated stink bugs are showing signs of resistance to pesticides. However, they are repelled by essential oils like spearmint, lemongrass, clove and ylang-ylang. Essential oils volatize quickly, reducing ongoing protection. Further investigations are needed into both conventional and organic chemicals, although the brown marmorated stink bug does not readily respond to chemical controls.

This pest has the potential to be devastating, and scientists are learning more about its behaviors in order to suggest the best pest management strategies. Monitoring and correct identification are valuable tools in assessing infestations. Excluding the pest from agricultural hosts provides the best pest management tool, so far. Biological control looks promising in the future, but more research is needed to evaluate its impact on brown marmorated stink bug populations.

Source: Oregon Small Farm News Vol. X No. 4 Page 7


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