Yellow jackets, a wasp that gets very aggressive late in the season, eat many types of sugars and meats. Their predilection for sweets creates an interesting phenomenon in fall around trees that are plagued by aphids. Wasps swarm the tree, flying about in such numbers that homeowners are very afraid.
To understand the wasp, first you need to know the aphids – small, soft bodied, sap-sucking pests of many plants found on most shrubs and trees in our area. We have several hundred species of these insects, which come in a variety of sizes and colors, from green to black, purple, and red.
Aphids are greedy feeders, pulling out the sap of the tree so quickly their tiny bodies can’t process all of it. What isn’t used flows out their back end in a sticky, sugary liquid entomologists politely dub “honeydew.” Wasps love this yummy treat, lapping up the sugar snack without a thought to its origin.
If you have a problem with wasps flying around a tree, check it for large numbers of honeydew producing insects – most likely aphids but it could be scale. The honeydew is what the wasps are after.
A similar behavior occurred this summer, with wasps scavenging along tomato plants. On closer observation, I discovered that the wasps were gleaning lerps from the plants, which is excrement left by a different sap sucking insect called psyllids. Unlike honeydew, lerps is solid, resembling sugar crystals and apparently tasting like them too.
That’s a sweet tooth that’s out of control.
There’s little to be done about the tree at this time, since the leaves will fall soon and the aphids will go into dormancy. The time for action is next year, just before budbreak, when you could apply dormant oil to the tree to try and smother aphid eggs. The wasps will eventually die off, leaving only the queen to survive winter.