Knowledge: Pheromone traps to deter plant-killing beetles...

The tubular structures made of many cones are pheromone traps...they are smeared with chemicals that mimic insect hormones and kill them...a biological control strategy for the beetles ravaging the Torrey pines, a rare variety of pine growing only in two regions of California...

In Olympic National park..

This method of bug control is also used to deter bugs from crops...

Such traps might be helpful in killing the noxious Aedes mosquito spreading dengue, zika, Japanese encephalitis, among others....

Also, I spotted this hornet trap in a local park...........