A Gardeners Forum Forums General Discussion The Plants and Flowers Forum flies killing my plants

We had some extensive landscaping done earlier this summer. The plants that reside under a catalpa tree have recently been attacked by what appear to be house flies. They have latched themselves all over our young russian sage and many other bushes. We believe it is the catalpa sap that has fallen onto the plants that is attracting the flies. The flies are dead (not sure if they get stuck or if the sap is killing them) and so are the part of the plants they have latched onto. It is quite disgusting as the flies are layers thick.
Has anyone seen such a thing before?

No, never seen that, and I have a catalpa I keep certain house plants under in the summer. It truely does sound quite disgusting. Is the catalpa healthy?

That is a good question- it is a HUGE, old tree (over 100 years). The sap leaves a sticky coating on everything (fence, car, BBQ) but this is a unique occurence. I am going to have a tree expert come take a look. I would HATE to lose the tree- it is amazing.