This week, we fielded a call from our garden staff that there were large yellow jacket (Vespula maculifrons) nests in several arborvitae near where they were working. Knowing how aggressive and toxic the stings of these native vespid wasps can be for humans, they had requested help in getting the nests eliminated.
When Patrick arrived to check out the problem, he noticed that instead of finding nests, the yellow jackets were actually feeding on the arborvitae. Since this species of arborvitae was currently in the midst of pollen and cone production, there also appears to be some type of resin being exuded at the same time, which is a delicacy for the yellow jackets.
We estimate there were between 100 and 200 yellow jackets per plant. Because they were busy feeding, they had no interest in us, despite our close up study of their behavior. Our entomologist, Bill Reynolds, who had observed this phenomenon before with vespid wasps and arborvitae, showed us that we could actually touch the yellow jackets without drawing their ire. This is certainly not the case if you’ve ever been anywhere near a yellow jacket nesting site.
The other interesting phenomenon is that despite being Eastern US natives, the yellow jackets were only interested in the Asian arborvitae species, Platycladus (Thuja) orientalis. Growing adjacent was the East Coast and West Coast arborvitae, Thuja occidentalis and Thuja plicata, but neither attracted a single insect. This is another nail in the coffin of that oft repeated myth that only native plants feed native pollinators. One of many lessons here, but it’s especially important not to spray first and ask questions later.
A timely post! Here in Delaware, the yellow jackets are likewise feeding on exudates from Dwarf Alberta Spruce (Picea glauca).
We have the same thing happen every year on our Dwarf Alberta Spruce, in the mountains of western North Carolina.
I have seen this in the fall for years and wondered what it was on the arborvitae that the yellow jackets were attracted to. Also noticed that they paid no attention to me standing a foot away and then walking on with my dog.