It may reduce the absorption of sunlight that creates photosynthesis in the leaf. The soap will need to be shredded and dissolved in water before it is applied to the plants. It is more advisable to use the soap on tender plants but the oil can be used on citrus, camellias and other plants with a glossy leaf. Both of these materials will remove the sooty mold as well as kill the aphids, scale and even worms. One of the best controls for chewing worms like Io caterpillar, horn worm, saddle back or orange dog on citrus is Dipel.
Scale insects have many forms.
The Florida red scale looks like a dark red bump on the upper or lower surface of the leaf. Cottony cushion scale looks like a small bump of cotton with an orange ring around the head end of the insect. Snow scale is pure white and usually feeds on the trunk of citrus but can migrate to the limbs high up in the tree. There are two types of wax scale, Florida and Japanese. Florida wax scale is small and Japanese wax is twice as large.