I have tiny yellow bugs on mandevilla. How do I treat?
It sounds like you have aphids. They come in several colors. This article will help:
https://www.gardeningknowhow.com/plant-problems/pests/homemade-aphid-control-a-natural-way-to-kill-aphids.htm
My mandevilla has brown spots on leaves. . . either a blight or fungus I assume. How do you treat it? Also, what is the best fertilizer for it?
If this is a fungus, neem oil will help. For fertilizer and general care of this plant, here is more information: https://www.gardeningknowhow.com/ornamental/vines/mandevilla/mandevilla-plant.htm
I have read that cinnamon will rid my mandevilla of ants, but do I put this directly on the soil in the pot or in a small container at the base of the plant? Thank you.
Place it directly on the soil. That will be the most effective for this.
I planted a mandevilla vine and planted it in a large container with a mixture of Miracle Gro and moisture control soil. The plant has some dead, black colored ends to some of the vines and has not grown much more since purchase and transplanting a few months ago. How can I help improve the growth?
How often are you watering it? It sounds like it needs more water. Water at least once a day and 2 times a day in temps over 85 F. Once it starting getting enough water, it should start growing quickly.
this will help you perk up your plant:
https://www.gardeningknowhow.com/ornamental/vines/mandevilla/mandevilla-plant.htm
Can I leave a Mandevilla plant outside for the winter if I cut it back instead of bringing it inside?
No, it willl not survive, I move mine into a unheated basement and it drops all of its leaved==no water and the move it outside and start Miracle Grow on it, however mine has not bloomed so far
I live in Zone 6 southern lower Michigan. Can I leave a mandevilla outside in the winter? Don't want to take in. Thanks.
Have had plant for three years. I winter it over in basement, halogen lights on timer. Plant grows wild, no flowers. In late May, cut back and placed on deck. Facing east/south, strong and then dappled sun. Plant begins to kick in early August, yet still no buds or flowers. Have fertilized with liquid from QVC (where we got plant). Any suggestions?
The fertilizer might be causing more leaf growth and less flower formation if it has a higher nitrogen content. You might want to try a fertilizer made for flowering plants (more phosphorus) and see if that helps. You could also try giving it a teaspoon of Epsom salts dissolved in a quart of water.