Question
Two of our holly bushes that are close together have white spot(looks like a mold) and the lower branches are turhing very dark green to black.  Please advise what we can do.  

Thankyou,  Michael

Answer
It sounds like either an aphid or a scale type insect. Check and see if the leaves where the black is is sticky? If so try touching the white spot and if it moves it is an aphid if it does not move it is a scale insect. These insect suck the plant juices form the plant and secrete a substance called honeydew which is high in sugar content and sticky. The black is a sooty mold that will grow on the honeydew. Control the insect sand the back will go away.

You can control the aphids with an insecticide called Orthene--this is sprayed on the foliage on both sides of the leaf and the stems and this will kill the insect. For scales the spray does not work as well so I would use  an insecticide called Bayer Advanced Tree and Shrub Insect Control. This is applied to the soil around the plant and the roots will carry it to the leaves and stems and when the insects suck the juices they are killed. It will take a couple of weeks to get the insecticide to all parts of the bush but the effect will last all season. The Bayer product can also be used on the aphids if you do not want to spray. Here is a web link to this product--check with your local garden type store for this.

http://www.bayeradvanced.com/tree-shrub-care/products/12-month-tree-shrub-insect...