White spots indicate powdery mildew in phlox
Q We are being invaded by the bug [in this photo] on our hydrangeas, azaleas and zinnias. They have gotten worse the last couple of weeks. Do you have any suggestions?
A Unfortunately, you have Japanese beetles, which are horrific pests. The adult beetle will feed on a whole host of plants, up to 300 or more different species. Their larval stage is grubs, which feed on the roots of lawns. For now, Japanese beetles are limited to the northern tier of Arkansas, and I hope they stay there. If you just have a few (which doesn’t sound like the case) you can physically remove them by taking a bucket of soapy water around the yard, holding the bucket under the plant, and knocking them into it. There are several chemicals labeled for use to control the adults, but you manage them, you don’t eradicate them. Malathion, Pyrethrin, Sevin and products containing cyfluthrin or acephate will help. Here is a link to the University of Arkansas Cooperative Extension Service factsheet on common questions about Japanese beetles: arkansasonline. com/76beetle.
Q
We think this is a privet that has grown too tall and is now bending over quite a bit [the reader sent a photo]. The butterflies and bees love the white flowers, so we don’t want to destroy it. When and how should we trim the poor thing? Thank you for your time and knowledge.
A
You are probably not going to like my answer. Privet is one of the most invasive plants in Arkansas. It does have pretty white flowers in the spring that the bees love, and the seeds that follow are favored by birds, but then they drop the seeds everywhere they fly, and it just exacerbates the problem. I would recommend removing it from your yard. If you truly want it for bees, then prune it hard every year after bloom, to prevent seed set. Privet was one of the most common hedge plants in the early to mid-1900s, but it was kept sheared into hedge rows. Today you will find it overtaking many natural areas and parks.
Q What is this bush? It was growing outside a restaurant in Gentry.
A The plant in question is an oakleaf hydrangea. Most varieties have white flowers that can turn pinkish and then tan with age. A few new varieties have pink flowers. If you are considering buying one, make sure you look at mature size, which can vary from dwarf forms no taller than 3 feet up to standards which can be 6 feet or more in height. In Arkansas, they are best grown in morning sun or dappled sunlight, with some protection from full afternoon sun. Q For the past three springs, my phlox has been getting these spots, beginning low and rising. It doesn’t seem to affect the plants — the flowers always do well as summer progresses. But they’re unattractive, and I’d like to prevent it.
A Tall garden phlox are beautiful plants but highly susceptible to a fungal disease known as powdery mildew. Some varieties are more susceptible than others. The first indication is white spots on the leaves. In time, the spots enlarge and it can look like the whole leaf is covered in a white coating. Powdery mildew thrives in moist conditions — including humid weather and areas where plants are crowded. Make sure you have ample spacing between plants to aid in air circulation. Rarely will the disease kill the plant, but the fungus does rob your plant of nutrients and can result in stunting of leaves and flowers. It is also not the most attractive thing in the garden. There are fungicides that can control the disease but will not remove the symptoms you have now. Daconil or other products containing chlorothalonil work well.
Retired after 38 years with the University of Arkansas Cooperative Extension Service, Janet Carson ranks among Arkansas’ best known horticulture experts. Her blog is at arkansasonline.com/planitjanet . Write to her at P.O. Box 2221, Little Rock, AR 72203 or email jcarson@arkansasonline.com.