Are you actively monitoring for brown marmorated stink bug (BMSB) or other injurious stink bugs in your orchard? As we head into mid-August and onwards towards harvest, the risk from BMSB injury to apples and pears increases in areas where the pest is established. Our survey work* indicates BMSB is widespread in the Niagara region, and it is most likely present in much of southern Ontario from Windsor to Ottawa. Populations and pest pressure may vary by region and by year.

It's easy to miss both the presence of the bug and early signs of injury (Figure 1), which can take up to two weeks before it is obvious enough to detect without intensive monitoring in apple (Figure 2a and 2b) and pear (Figure 3a and 3b). What this means is that the pest may be gone by the time you see the injury. Adults are strong flyers that readily move between hosts, including landscape plants and crops. Brown marmorated stink bug is a perimeter driven pest, and most injury occurs around areas bordered by woods.

Figure 1. Early stink bug injury (external and internal). Photo credit to Matt Peters

Figure 2a. Initial injury develops into obvious depressions over time.

Figure 2b. Brown corky tissue under the skin of apple.

Figure 3a. External injury to pear.

Figure 3b. Internal injury in pear.

Commercially available pheromones and traps can provide information on pest presence and movement into crops. These trapping systems are designed to catch both adults and nymphs. There are several styles of traps, manufacturers and lures to choose from. Unlike the pheromones used to track codling moth, oriental fruit moth, or clearwing moths, the lures for BMSB are not very efficient and do not attract the pest over a long distance. Some of the most recent recommendations for orchards (Michigan State University) suggest using 6 traps per 4 hectares, with 4 traps around borders and 2 in the interior. Thresholds for numbers of adults in traps are still under development and will most certainly need adjustments depending on the trap and lure used. However, detection of nymphs in traps means it's time to actively manage this pest in apples. It's too late to set up traps this year, but something to consider in 2018.

In addition to traps, make sure to conduct visual inspections in the crop. Nymphs may be resident in the orchard, but they can be difficult to find because their brown colour pattern acts like a camouflage on bark, and they have a tendency to stay higher up in the tree canopy. However, it is possible to use tapping trays to jar bugs from their hiding spots. If nymphs are found in the crop, it's time to take action.

The pheromone trap-based monitoring program being conducted by OMAFRA and the University of Guelph has been scaled back in 2017. Most of our sites are in Niagara, with a few in Norfolk. We have traps set up in tree fruit and grapes. Almost all of our Niagara sites have come up positive for BMSB adults. A few grape sites and one mixed-production site have consistently caught large numbers of nymphs over the last month, and counts are ramping up. We only have a single trap at each site and we monitor these weekly. Last week (ending August 18th), one of our agricultural sites had over 60 BMSB nymphs in the trap! Given the pheromone probably doesn't attract bugs from far away, we were either "lucky" in our trap placement or the population at that site is very high.

There are very few options for managing BMSB in Ontario, and this presents a considerable challenge for a pest that poses a risk over such a long time period (BMSB can be active until early October). Products registered in apple include Lannate Toss-N-Go (1 application, 8 days PHI) for control, and for apple and pear Clutch (1 application if at high rate, 7 days PHI) for suppression. Actara is also registered for suppression, but has a PHI of 60 days. Malathion 85E was a conditional registration and is no longer labeled for BMSB. Products registered for other pests may either control or suppress BMSB. For more information on managing BMSB visit www.stopbmsb.org.

* Funding for this project through the OMAFRA / University of Guelph Partnership - Emergency Management and Production Systems - Plants. Study lead Dr. Cynthia Scott-Dupree