What is the yellow powdery-type substance on these vines?
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