September 1995 - Indiana Yard and Garden - Purdue Consumer Horticulture

September 1995

Q. We have six flowering dogwood trees in our yard that are approximately 3 years old. (They have not flowered, yet.) Our yard is adjacent to a cornfield. Our problem is Japanese beetles. They especially like our dogwoods.

According to publication E-75 from the Purdue University Cooperative Extension Service on Japanese beetles, flowering dogwoods are “relatively free of feeding by adult Japanese beetles.” Our dogwoods are not “relatively free.” Why are the Japanese beetles feeding on our dogwoods? What can I do about them? Are there any natural enemies to Japanese beetles, such as a type of bird we could attract to our yard?

I have applied Sevin to the trees by shaking the dust onto the leaves. I’ve tried to do this about twice a week. I have also sprayed the beetles with a fly and mosquito spray that lists Japanese beetles as one of the bugs it will kill. Both of these products seem to kill the beetles. The dust appears to discourage them for a day or two.

Also, when can we look forward to flowers on our dogwoods? – Marcia Motter, Warsaw, Ind.

A. Obviously, the beetles didn’t read the chart that says they aren’t supposed to like dogwoods! Almost nothing has been free of Japanese beetles this year. Our mild winter led to unprecedented populations in parts of the state. It’s probably too crowded on their preferred food sources, so they’re moving onto anything green. Carbaryl (Sevin) and malathion are effective for about 10 days and should be reapplied as new beetles migrate into the yard. I know of no birds able to control this year’s population. Some homeowners have had success controlling them through hand removal once a day!

Fortunately, the beetles will begin to disappear as the adults die off. Unfortunately, their young become one of several species of white grubs that feed on the roots of our lawns. Readers can obtain a copy of publication E-75 (Japanese Beetles) by contacting their county Extension office.

Your dogwoods should be blooming if they are fairly well established. They still may be settling in and concentrating on root and foliar growth. You probably just need to wait another year or two.

There is another possibility, though. Plants purchased in hardiness zone 5 should be grown from seed collected from trees indigenous to zone 5. Dogwoods in the Midwest may have minimal flower production because of a lack of flower bud hardiness. When purchasing a dogwood, always ask your nurseryman where the trees are grown to avoid disappointment.

Q. We have a beautiful birch tree next to our patio. We have not been able to use the patio this summer or last summer because of Japanese beetles. Last summer, we used traps. This summer we sprayed with Sevin. We are considering cutting the tree down and replacing it. We’d hate to do that. Any ideas? And if we cut it down, any suggestions as to what we could replace it with that would be ornamental, shady, preferably fast-growing, would not make a mess and not be subject to insects or worms? Also, it’s near our septic field. – Norma Guy, Lafayette, Ind.

A. Beetle traps actually attract beetles to the area from a great distance. While many are trapped, many more munch happily on plants in the area. The only good place for a trap is in a neighbor’s yard! In my recollection, the beetles have been worse in the last two years. Perhaps we’ll have a harsh winter and a few less beetles next year. You may want to wait for a more normal year to decide the fate of the birch.

You’re looking for a perfect plant to replace it with, and it’s a tough role to fill. The letter above illustrates how a year like this causes problems for usually trouble-free plants, and I could write a monthly column debating the pros and cons of different trees to fit your needs. Contact your county Extension office for a copy of E-75 (Japanese Beetles), which lists plants that are usually not bothered by beetles, and HO-123 (Trees for the Landscape) to help you choose a potential replacement tree.

Q. I was given a sack of wildflower seeds from my children. I tilled my garden and left a 2-foot section, 40 feet long. They took off, and what a beautiful sight, all colors of the rainbow and more. My question is: What do I do with them after they quit blooming? They are perennials. I don’t want them to take over the garden completely next year. – James R. Bement, DeMotte, Ind.

A. Regular deadheading (removing the spent blossoms) will keep the seed from spreading throughout the yard, but it goes against the definition of a “wild” flower planting. Most of the flowers will stay where you planted them and return next year. You could apply a pre-emergent herbicide this fall and again next spring in other areas of the garden, where you don’t want any wildflowers, to prevent their seed from germinating. Follow all label instructions carefully, and be sure the herbicide is labeled safe for the plants around which you’re applying it.


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