Overwintering stinkbugs will soon begin to emerge

Researchers say the spread of brown marmorated stinkbugs has been slow but steady. Infestations of the pest were first discovered in Sacramento in 2014.

Known by the shorthand name BMSB, the stinkbugs represent a nuisance in urban environments and pose a threat to several California commodities.

In 2015, one male BMSB was found in a trap in Freeport in late October—the closest find to Sacramento County farmland so far. The pest is now established in one or more urban areas in eight other counties in California, but so far no crop damage has been reported.

A number of fruit, nut and vegetable crops are likely to be highly susceptible to damage from BMSB feeding, according to Chuck Ingels, a University of California Cooperative Extension farm advisor for Sacramento County. Among the susceptible tree fruit crops are peaches and apples. These fruit-bearing trees have been hardest hit in the Mid-Atlantic states where infestations have occurred.

Pears are also a major host crop, but there may be differences in crop susceptibility—a 2014 Oregon State University study showed Bosc pears caged with BMSB adults were damaged far more than D'Anjou pears, Ingels noted.

"Bartlett pears in the Sacramento Delta are harvested well before the BMSB second generation emerges," Ingels said. "However, Bartletts could provide food and shelter through much of the season, due to presence of late rattail fruit and the large numbers of cracks on the old trees that could become overwintering sites."

Most stone fruits will likely be highly susceptible, he said. Apricot, cherry and peach are currently on the host list, though plums are not.

Persimmons were extensively damaged in urban Sacramento in September, Ingels said. Citrus trees in the city's midtown, however, were not, he said, "most likely because citrus fruit does not ripen until winter, when BMSB are overwintering."

"It remains to be seen how BMSB will affect certain vegetable and field crops," Ingels said.

The bugs begin to emerge from overwintering as daylight lengthens and temperatures warm.

Monitoring for the presence of BMSB involves scanning foliage of host species, beating branches, and trapping from late spring through summer. Suspected BMSB should be taken to farm advisors or county agricultural commissioners.

Information about the brown marmorated stinkbug may be found online at a national BMSB website: www.StopBMSB.org.