Question
We have had Mandevilla plants each year growing on a post/trellis for 15 years (Michigan). The last 2 years something has been eating the new buds and the new stems.  I have looked all over the plant and can find no culprits. The plant is very thick and healthy with no sign of any leaves being chewed on. The buds are chewed on until gone in a couple of days. The stems appear to have been chewed thru often with the portion chewed off hanging by a thread.
The squirrels use the post to go to trees and at first I suspected them but now I'm not sure. The time it takes for a bud to be eaten makes me think of an insect.
What do you suspect the culprit is? And. how to treat the plant to rid it of the culprit.
Thank you for your response and I do hope you had a nice vacation!  Ken  

Answer
Hi Ken, because you are unable to locate them during the day tells me your Mands are being attacked by either slugs or night feeding catepillas; Get yourself a container of Bayer Rose and Flower systemic, and treat it with this, also lay some slug bait down near your plant, finally, go out at night and with a flashlight you should see them. Nick