Here are some photos of open dish monitoring this year. No insect deaths recorded. The bait was 1/3 beer, 1/3 white wine, 1/3 *Ribena, plus glucose powder. As much as you think the hornets would like.
The dish has a piece of paper towel in it which is kept damp with the bait solution. It seems to work all summer
Several queen European hornets came regularly in the Spring. They came early in the morning. Later in the season, the worker hornets came frequently and jealously defended their valuable feeding site against bumble bees and wasps.
No insects were killed and it didn’t matter if the dishes were not inspected for a day or two. Watching the visitors was very interesting. More time spent than necessary. Great opportunities for photographs. Fortunately, no Asian hornets. Yet! Seeing them early and ensuring notification is more important than killing them. For now that’s the job for professionals.