Article written by Madeline Wimmer, UMN Extension Fruit Production Educator.
Brown Marmorated Stink Bugs (BMSB) are an invasive insect species that many people are familiar with as a general issue for households as they seek shelter in cold conditions. BMSB tend to have a wide range of hosts, including apples, in which they directly feed on fruits. At the Minnesota Department of Agriculture (MDA) this year, Angie Ambourn (MDA Entomologist/Pest Detection) has received reports from orchards in Washington and Scott County, prompting this article and request for growers to report damage and detection of BMSB if you see it on site.
Images: Brown Marmorated Stink Bug (BMSB) damage usually occurs late in the season when apples are 4-8 weeks from harvest and is more likely to be seen on late-season ripening varieties. Images from Angie Ambourn.
BMSB in Minnesota and the U.S.
BMSB is considered a severe agricultural pest in states on the east coast, Michigan, and Oregon, but it’s been found in 48 states, including Minnesota where it is noted as a less severe, but still agricultural problem for various regions. The first county that identified it as an issue was Ramsey County in 2010. By 2019, a number of other counties (Washington, Dakota, Chisago, Scott, Goodhue, Nicollet, and Carver) had also detected BMSB through the MDA trapping program, which was found in 15 orchards throughout those counties. Detection in Minnesota orchards has continued since 2019, although the MDA has deployed fewer traps in recent years due to funding availability.
Image: A map (EDDMapS) showing counts of BMSB throughout Minnesota.
Identification
Image: Adult BMSB can look similar to other stink bugs, but are primarily distinguished by its dark colors and specific patterns. Photo credited to Michael Bush, WA State University Extension.
BMSB are not the only stink bugs that exist, so distinguishing them from other stink bugs is important. Other stink bug species that live in Minnesota include brown, green, one-spotted, dusky, rough, and spined soldier stink bugs. To help you identify BMSB specifically, refer to this MDA guide sheet.
Features that can be used to identify BMSB include light-colored banding on their antennae, metallic green punctures underneath their head and thorax (visible by hand lens), and light and dark banding that sticks out from underneath their wings and is visible.
Timing, symptoms, and damage
While BMSB mate and lay eggs earlier in the season, unlike other apple insect pests like codling moth and apple maggot, it is not the larva that causes damage to the fruits (although blossom damage is occasionally an issue). Rather, it is direct feeding from adults, using piercing sucking mouthparts, that causes damage to apples.
Literature indicates in Minnesota there is more likely to be an issue in apple orchards starting in late August and October (more research may be needed to verify this). Some research indicates that apples that are 4 to 8 weeks from harvest are more susceptible, but less so for varieties that ripen earlier.
This damage can lead to unmarketable fruits as it is visually noticeable and leads to superficial internal damage. On the outside, apples have some slight depressions that can be confused with bitterpit on Honeycrisp, for example; but the damage looks very different on the inside, where more severe, less uniform corking is associated with BMSB damage.
Tracking and management
Both black pyramid traps and clear sticky card traps are recommended for tracking and monitoring BMSB. Susceptibility in trees increases in the upper canopy of a tree, as well as for trees that are located closer to wooded edges; thus, it can be helpful to place some traps between an orchard row and nearby wood edge. Lures are available specifically for BMSB, which can increase a trap's effectiveness. The established economic threshold for BMSB is 10 adults per trap, which should take into account whether a lure was used and the trap location. Traps with lures and located next to the woods, for example, will likely have more trap counts.
Image: BMSB are caught using clear sticky traps in MN apple orchards by the MDA. Photo credited to Angie Ambourn.
The Midwest Fruit Pest Management Guide section on apples includes information on managing BMSB during the third and summer covers for apples, but this should be based on trap indicators and thresholds mentioned above. For more information on effective pesticides for control, refer to page 40 in the Midwest Fruit Pest Management Guide apple section. The guide notes that some products may pose risk to harming beneficial arthropods used to help control San Jose scale and mites, which should be considered when making pest management decisions.
Our UMN resources recommend applying pesticide products as two alternate-row-middle spray, and then waiting seven days before reapplying, remembering to rotate pesticides based on their classification.
For organic growers, based on research that has been done, it’s important to note that a combination of azadirachtin + potassium salts and pyrethrin can help control nymphs, but is relatively ineffective for managing adult populations and can incidentally cause phototoxicity. However, kaolin clay applications can be helpful when applied strategically. While more research is needed on the practice of managing BMSB using trap crops, this is one method that may be able to delay them from moving into the orchard.
Seeing BMSB? Share your findings with the MDA!
The more reports of BMSB that are shared, the easier it is for state experts to understand the degree of the problem and make a stronger case to pursue research that helps with detection and management.
If you see BMSB damage or detect adults through trapping at your orchard, reach out to myself (wimm0035@umn.edu), Angie Ambourn (angie.ambourn@state.mn.us), or go to the MDA’s Report a Pest page to submit your findings!
Resources:
Brown Marmorated Stink Bug Provisional Guidelines for Apple (UC IPM)
Brown Marmorated Stink Bug (BMSB) (New England Tree Fruit Management Guide)
BMSB in Minnesota Apple Orchards (UMN)
Comments
Post a Comment