Brown Marmorated Stink Bug showed up in Santa Barbara and Ventura Counties about 12 years ago. It had been roaming around LA and Orange Counties before that.  There was a small outbreak on avocados at the time, but it was mainly seen on a lot of other plant species, like tomatoes.  We have not seen much of the bug since the first introduction, but this summer, it has popped up on avocado in the Santa Paula area.  It’s probably present in other parts of the county, but unless you are going out to harvest, you may not notice it.  Once the fruit is off the tree, the bug seems to be less interested in the crop.  It can go to small fruit, as well as large, though.

Brown marmorated stink bug affects many different crops and is a serious residential problem. It moves around easily, so can be expected to spread. It can fly up to a half mile at a time and also travels long distances by hitching rides in vehicles or inside furniture or other articles when they are moved, often during winter months. As a result, most new infestations are found in urban areas.

Brown marmorated stink bugs are native to China, Japan and Korea. They were first documented in the in the United States in Pennsylvania in 2001, but was likely established there several years earlier. The pest has spread throughout Pennsylvania, is believed to be established in at least 15 states, and has been found occasionally in more than a dozen additional states. In 2004, BMSB made its way to Oregon and is now established in northwest Oregon and a portion of Southern Washington. The National Agricultural Pest Information System maintains a map showing current infestations, but it does not yet show California finds. The pest has been present in Los Angeles County for 15 years.

BMSB feeds on dozens of California crops, including apples, pears, cherries, peaches, melons, corn, tomatoes, berries and grapes. Feeding on fruit creates pock marks and distortions that make the fruit unmarketable. In grapes, berries collapse and rot increases. Wine tasters have been able to detect stink bug odor in wines made from grapes that had 10 bugs in a 35-pound lug. It is also a pest of many ornamentals, especially fruit-bearing trees, princess tree (Paulownia tomentosa), common Catalpa (Catalpa bignonioides) and tree-of–heaven (Ailanthus altissima).

In addition to the damage caused by the BMSB feeding, the "true bug" can cause disturbing problems for homeowners in the winter. When the weather cools down, bugs migrate in droves to sheltered areas, including inside homes and buildings.

When it showed up in Sacramento several years ago, the bugs aggregated in such numbers that there were reports of people using manure shovels and five-gallon buckets to dispose of them. They emit a strong, unpleasant odor  when disturbed making cleanup daunting.

 BSMB is a pest in its homeland, but is mostly controlled by parasitic wasps. USDA researchers have collected parasitic wasps in Asia, but they must be tested extensively before they can be released in California.  An egg parasitic wasp (Trissolcus japonicus) was found in LA County in 2018 and is spreading, but its not clear how it effective it will be in controlling the spread of the bug.

The pest can be distinguished from ordinary brown stink bugs by its larger size, marble-like coloring on its shield and white markings on the extended edge of the abdomen. BSMB also has distinctive white bands on the antennae and legs. The UC Integrated Pest Management Program has posted a video https://www.youtube.com/watch?v=Gu_ZIbcOIjo  to aid in identifying the pest.

Check out the biology and control procedures discussed at the IPM website: https://ipm.ucanr.edu/PMG/r3303211.html