07-01-04

Question and Answer

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Q. In the June column, Beverly Shaw's response to "Thicket thinning" really piqued my interest. "Gardening Q&A" has probably at some time in the past dealt with the problem; nevertheless, I was disappointed that she did not elaborate on how one "selectively" or otherwise "removes" such things as honeysuckle and multiflora rose. Perhaps a future column can revisit ways of doing (or trying to do) this. (Also briars; poison ivy; I probably give up on.)

Late in January this year, we had a severe freeze, -14 F. Honeysuckle seemed to take it hard, so I hoped its growth might be retarded. It, with the help of the birds, had been threatening to take over my entire acre. Unhappily, it has rebounded with a vengeance this spring and will soon suffocate us all, plants, trees and maybe humans, if severe counter-measures are not taken. Help! -- Richard L. Lippke, Floyds Knobs, Ind.

A. Indeed, four species of honeysuckle and the multiflora rose are considered invasive plants of Indiana. An invasive plant is one that grows quickly and aggressively, displacing other plants as it spreads. Usually, those plants labeled as invasive by the Indiana Department of Natural Resources are not native to North America. Invasive plants hurt wildlife by eliminating the plants our native animals need for food and cover, and destroy habitat for rare wildflowers and animals.

The Nature Conservancy Web site gives the following control recommendations for exotic bush honeysuckle species: "Mechanical controls include grubbing or pulling seedlings and mature shrubs, and repeated clipping of shrubs. Effective mechanical management requires a commitment to repeated treatments for a period of three to five years. Winter clipping should be avoided as it encourages vigorous re-sprouting. Repeated annual prescribed burns during the growing season will top-kill shrubs and inhibit new shoot production. Because exotic bush honeysuckles readily resprout, it may be necessary to re-burn every year or every other year for several years. Most managers report that treatment with herbicides is necessary to control the exotic bush honeysuckles. Water-soluble formulations of glyphosate (brand names Roundup, and for use near waterbodies, Rodeo), a non-selective herbicide, and formulations of triclopyr (brand names Garlon, Pathfinder, and others), a selective herbicide for broad-leaved plants, have been used as foliar sprays or cut stump sprays and paints with varying degrees of success. Both glyphosate and triclopyr should be applied to the foliage late in the growing season, and to cut-stumps from late summer through the dormant season. The flush of seedlings that sometimes follows herbicide treatments must also be controlled. For more information, go to http://tncweeds.ucdavis.edu/esadocs.html. There you will find recommended controls for many weeds.

Personally, I physically remove some shrubs and spray others with glyphosate, but it does take repeated applications to truly kill the plant.

Multiflora rose can be controlled by removing the plant (and the use of a bulldozer is recommended in some studies), repeated mowing if the rose is in a grassy area or cutting followed by a 1 percent glyphosate application on the cut stems. Glyphosate sprayed on the leaves and stems will need to be repeated throughout a growing season to kill the plant.

Q.  The very first Japanese beetles have shown up and they drive me crazy. I found them burrowed in the blossoms of my shrub roses, but I know they'll be everywhere soon. I know not to use traps, but what's the best way to control them? -- Ruby Miller, Muncie, Ind.

A.  Japanese beetle larvae develop underground and emerge in late June or early July as adult beetles. They feed upon many plants.

Control a mild infestation by picking them off and dropping them in a bucket of soapy water. Severe infestations require the application of an appropriate insecticide, including cyfluthin (sold as Tempo or Bayer Lawn and Garden), malathion, carbaryl (Sevin) or permethrin (Spectracide), among others. To protect ornamentals against the feeding of adult Japanese beetle, leaves should be coated with insecticide during the adult flight period. Typically, this may entail two treatments during the peak beetle flight. Homeowners should make their first application when damage is becoming intolerable and beetles are still abundant. The need for repeated applications can be curtailed by inspecting plants for additional beetle damage prior to applying a second treatment.

For more information, ask the Purdue Extension office in your county for "Japanese Beetles in the Urban Landscape" (E-75-W) or find it online at http://www.entm.purdue.edu/Entomology/ext/targets/e-series/EseriesPDF/E-75.pdf.