Several causes possible for aucuba problems Q:I have a cluster of aucuba about 28 feet in circumference and 3 feet tall. They are planted in full sun and are more than 15 years old. Last fall, many leaves and stems turned black and withered. This spring, leaves continue to turn yellow with black spots. Can they be salvaged? Or should they be replaced?

Answer: Several diseases cause aucuba to get spots on their leaves, including anthracnose and leaf spot. Aucuba is also known for sunscald, which causes leaves and twigs to turn black.

My initial reaction is that the problems may be related to being planted in full sun. Aucuba prefers shade or partial sun, thus the sunscald issue. However, if they have survived in full sun for 15 years, they must surely be acclimated to it in your yard. On the other hand, I wonder if something has happened to some of your trees in the last year or so, which is allowing more sun to reach these plants.

Without seeing a sample, I can only guess at the cause of your spots. I'd suggest you take a sample to your local Extension Service office or a good garden center. They should be able to help determine if the spots are weather related or the result of some pathogen. If it is one of the fungal leaf spots, they can be treated with a fungicide.

These are nice plants, and it would be a shame to replace them, if you can resolve the problem otherwise.

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Q:You so kindly advised me four or five years ago that the probable suspect in the demise of my helleri holly was voles. Since then, they have killed a few more bushes. I am about to till and recondition the soil so that I can plant three new hollies where the previous ones were located. I've looked for vole repellents, but they seem to be toxic, and I don't want my animals to be harmed in the process of vole-damage prevention. Do you have any suggestions?

Answer: You've picked the perfect time to work some hard, finely ground material into your beds. There are several on the market that are either shale-like or made of volcanic material that has sharp edges. Voles don't like it because it damages their feet and snouts. It does not decompose, so it will stay in your soil for a long time. Most good garden centers will have one or more products to meet this need.

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Q:In a recent column, you wrote about glyphosate as a treatment to kill wire grass. Will this chemical also kill existing good grasses?

Answer: Glyphosate will kill good grass as well as unwanted grass. It is a nonselective herbicide for grass control that works best when unwanted grasses are creeping into places where you don't want any grass at all.

However, there is a relatively new product that will control wire grass in fescue without killing the fescue. It is sold as Turflon. It has to be used on actively growing wire grass but can cause yellowing of fescue under hot, dry conditions.

However, you won't find the name wire grass on the label. Its real name is common Bermuda grass. So you'll find the directions for treating it under Bermuda grass. As with any pesticide, be sure to read the label before you buy it and before you use it.