Photo by Kristie Graham
Brown Marmorated Stink Bug
Brown Marmorated Stink Bug
Stink bugs, strawberry weevils and good news pest-predators top BC’s entomologist’s watch list
Pest pressures vary from year to year as climate change alters the environment and growers change control strategies. BC’s Ministry of Agriculture and Food entomologist Tracy Hueppelsheuser spoke to Orchard and Vine Magazine about her watch list for pests in 2023. Together with other experts in the industry, she is sharing that not all the bug news is bad.
Stink Bug
Seen in a wide range of crops such as pome fruits like apples as well as grapes, nuts, berries, vegetables and ornamentals, the brown marmorated stink bug (BMSB) which originated in Asia, has been a problem in North America since 2001. It was first seen in BC in 2015 and Hueppelsheuser says the hot weather of 2022 likely allowed more nymphs to complete their life cycle and become adults.
“We have been seeing damage mostly only in backyards,” she says. “The Okanagan did not see this huge appearance of the BMSB in the fall, so they didn’t see an increase in public reports or anything like that.”
Many people around the province have seen more of the pest this year, but she says that may not necessarily mean increased populations.
“I think it was a response to the hot dry fall where we could see lots of activity during their regular aggregation period,” she says. “We don’t know if that means it’s going to be a higher population that are going to be available to impact the various crops in 2023 or not. They are in backyard berry patches, but not known to cause damage to commercial berries as of yet.”
Like many pests, the BMSB is more active in warmer weather when they are more mobile and will fly. This increased appearance may have given the false impression of higher volumes of the pest. They overwinter as adults, so if more were able to complete their life cycle, the numbers may be higher in the 2023 monitoring.
While damage to berries and grapes is possible, the key concern in these crops is that the bugs may be harvested with fruit and the chemicals that produce their infamous stink when frightened could easily taint juices or other processed products. Direct fruit damage seen in backyard berry growing areas can be misshapen fruit and dead spots.
Damage has been seen commercially in greenhouses and fields in peppers and tomatoes.
The good news is that a parasitoid of BMSB eggs called Trissolcus japonicus, or the Samurai wasp, has been found established in both the Fraser Valley and Kelowna.
“This is great news,” Hueppelsheuser says. “We hope that this beneficial insect will help decrease the populations of BMSB over the next few years.”
Growers can sign up to assist with research on the Samuri wasp through the stink bug pest alert on the government of BC website.
Strawberry Blossom Weevil
Strawberry Blossom Weevil
A fan of cane berries, strawberries and ornamentals, the strawberry blossom weevil has not yet been seen in the Okanagan or on Vancouver Island but is widespread in the Fraser Valley. It was detected and confirmed in BC in 2019 and has been watched since to determine the biology and hosts of the pest.
“This year we have found that it can complete its lifecycle on… a common landscape plant. This is bad news,” she says. “It’s also been found in Europe and that’s bad news because it impacts the nursery industry and of course, the Americans don’t want nursery plants to come into the US – strawberries, raspberries, ornamentals, whatever – that might have this insect. It’s a trade issue.”
Therefore, the concern around the pest is for those producing and selling plant stock rather than those producing fruit.
“We’re still on the lookout for this. Its current distribution is just in the Fraser Valley, but keep an eye out for it in other regions,” she says. “If you think you might have it, you can certainly submit samples to me at the plant lab at the ministry or send pictures.”
A national survey of the strawberry blossom weevil was launched by Agriculture and Agri-Food Canada
“We’re trying to collectively learn if it’s in other places besides the Fraser Valley,” says Hueppelsheuser.
SWD parasitoids
Photo by Warren Wong
Parasitoid wasp
Parasitoid wasp Leptopilina japonica (left), which is one of the species from Asia that is now established in British Columbia. The parasitoid finds fruit infested by larvae of spotted wing Drosophila (right), and inserts eggs into the larvae beneath the surface of the fruit using a syringe-like “ovipositor”! (sort of like a stinger). The parasitoid’s offspring eats the spotted wing drosophila larva from the inside out and develops into an adult parasitoid (rather than a fly).
Another point of good news is the discovery of two larval parasitoids of spotted wing drosophila (SWD) established in the Fraser Valley and on Vancouver Island: Leptopilina japonica, the Ronin wasp, and Ganaspis brasiliensis, the Samba wasp.
“Both originated from Asia which is also where SWD is from,” she says. “Over the next few years, the parasitoids will hopefully contribute to a reduction in SWD.”
Natural enemies such as these parasitoids from the SWD’s originating region help control the pest’s population in its wild habitat which is expected to reduce populations over time. The two predator wasps are tiny at less than two millimeters long. They deposit eggs into the SWD larvae, then a new wasp will emerge from the pupae and no flies will hatch
