The roots are in top of soil. Do I need to cover them?
It may have lost some of its surface potting soil in transport. Check to see if the roots are growing out of the bottom of the pot. If you see roots poking out of the drainage holes, I would go ahead and repot and move up 1 size.
Other wise just add a few inches of good quality potting soil to the top of the pot. You may need to add a bit move after a few waterings.
https://www.gardeningknowhow.com/ornamental/vines/mandevilla/mandevilla-plant.htm
It appeared last Spring and again this year. Is it harmful to the tree?
This is a large Mealy Bug infestation.
Began treating with Neem Oil.
These links will help you.
https://www.gardeningknowhow.com/ornamental/vines/mandevilla/mandevilla-pest-problems.htm
https://www.gardeningknowhow.com/plant-problems/pests/pesticides/neem-oil-uses.htm
to help it climb? I fertilized it about two weeks ago.
It is likely that the form that you have is a shorter variety. If this is the case, then it may not vine as vigorously as you want it to.
If it is not flowering, there could be a few likely causes. This article will help: https://www.gardeningknowhow.com/ornamental/vines/mandevilla/getting-mandevilla-to-bloom.htm
It was bought a few weeks ago. It was doing great. It was outside on the porch. It got sheetrock dust on it. I washed it off best I could but it's not helping. What do I do? Oh, I did bring it in, but that didn't help . I don't want to lose my plant!!
Your plant may need to be watered more often. A container plant outdoors will need daily water, even twice a day during hot weather.
This article will help you.
https://www.gardeningknowhow.com/ornamental/vines/mandevilla/mandevilla-plant.htm
It is only a month old, but it is dying. It was outside on the porch. It got sheetrock dust on it. I washed it off, but didn't help. Brought it inside, didn't help either. What do I do?
Your plant may need to be watered more often. A container plant outdoors will need daily water, even twice a day during hot weather.
This article will help you.
https://www.gardeningknowhow.com/ornamental/vines/mandevilla/mandevilla-plant.htm
I wintered them over inside in front of window facing the East, lots of green leaves, no buds on either one.
This article will help you assess the plant.
https://www.gardeningknowhow.com/ornamental/vines/mandevilla/getting-mandevilla-to-bloom.htm
My mom has a mandevilla that has developed this yellow substance that she said looks like little tiny balls or might be some sort of powder. If you touch it, it stains your fingers. We've had mandevillas for many years & have never seen this before nor do we know how to treat it. We live in Wisconsin where this spring & summer has been extremely wet & cool so I don't know if it's some sort of mold/mildew?? Does anyone know what this is? If anyone can help answer this it would be greatly appreciated!!
Those are aphids. An article on home made remedies follows. There are many commercial brands of aphid control sprays. https://www.gardeningknowhow.com/plant-problems/pests/insects/homemade-aphid-control.htm