Certified GKH Gardening Expert
Neem oil is generally quite effective in treating both the aphids and the sooty mold problem. In order to rid the plant of sooty mold, you must first take care of the aphids. Take care to wash off the sticky residue from foliage prior to applying the neem oil, and also coat both sides of the leaves--paying special attention to the backside, as this is most commonly where the aphids congregate. More than one application is often necessary but after some patience and vigilence, this should take care of the problem.