Question

Holly Disease   My china girl hollies have several white insect, which look like a grain of rice, on the underside of their leaves. Some of the leaves have turned black. I don't believe they are leaf miners since there are no visisble trails on the underside. If you know what they may be you ca you recommend a treatment.  Thank you

Answer
Hi Timothy,

The problem that you have is due to an insect, the cottony camellia scale.  This little insect is sucking the contents out of the holly leaves.  As they feed, they release a sticky substance called honeydew.  The black you see is actually a fungus called sooty mold that is growing on the honeydew.

The black color should mostly wash off with a strong host.  It will also go away as soon as the scales are taken care of.  The best thing to use to control the scales is an insecticide called horticultural oil.  Different types of oils are available in your local garden center such as neem oil.  Follow the label direction to mix up the product or purchase a ready mix in a spray bottle.  Be sure to coat the scales with the product.  The oil covers the insect and suffocates it.  Your plant should quickly improve once the scales are treated.  It is likely that you will have to make repeated applications about 7-10 days apart.  Once the insects are under control, periodically examine the leaves and determine if follow-up treatments are necessary.

Good luck!