In my experience people leave treating this problem until it is too late.
It is already too late in the life cycle of the chenille processionnaire to treat with [biological/bacteria] Bacillus thuringiensis as the caterpillars are in their 4th stage (setae). they don’t eat as they are getting ready for their mass migration from their cocoons to the earth where they continue their life cycle of pupa to moth. Below is a link to an article with graphic photos of damage these critters can do to your dogs (cats allegedly have more sense and avoid them).
I hate the thought of these things. My neighbour has loads in her cèder trees they had them removed from the pine trees but put pièges on the cedars. I hope they work as I really don’t want these critters near my kids!!
May be a funny story but I discovered a nest of them at the top of my scotch pine, thought about it for a while and pondered using a shotgun to blast it, I decided the grumpy neighbour ( whoes house is around 200m away) might moan so that wasn’t going to be an option. However, I bought one of those gas weed burners from Lidl and I also fly ‘drones’. yes you guessed it. Adapted the flame thrower to fit my 450 size FPV drone. Success! Unfortunately top of the tree caught alight, fortunately I had a hose nearby and was able to douse the flames which also doused the caterpillar nest…Oh well sod the neighbour, out with the shotgun. Jasper Carrots mole sketch runs through my mind at the moment.
They will have all left the nest by now, so you now have to kill the moths which will come back to start the process all over again so you need to read Robert Moon’s post, he is the expert on these critters.
Hello, tsk I go away for a few days and all hell breaks out! Jasper Carrott’s moling with a shotgun always amuses me. Hornet nests less so but I certainly wouldn’t advocate blasting cocoons out of trees. The caterpillars have toxic hairs which they shed, so a cocoon bazookering thousands of hairs into the environment perhaps wasn’t the best treatment. The flame thrower was a better move but pine trees have a reputation of being volatile if ignited.
So, if there’s anything alive, install an écopiège around the tree. If there is nothing left but a smoldering tree top then a pheromone trap will trap the moths thus reducing the population for next year.