Garden Pests and Diseases: Black gunk covering leaves of my giant bird of paradise, 1 by valtal

valtal wrote:
Thanks for the comments and advice. Our four giant birds are more than 30 years old and have been magnificent until this year, with practically no attention. So, we do not want to lose them. Today, I spoke with the gardener and we investigated the plants further. He looked at the underside of the leaves and found what some online readings had revealed as the potential culprit. It appears to be whitefly. Along the central shaft of the leaves, there are a lot of white splotches which look like the online photos of whitefly. He says he can spray the leaves to kill the whitefly. So, I don't know whether I should try the various cleaning suggestions or just use a pesticide. I hope we are not too late to save our plants.