Two species of honeysuckle shrubs — Morrow's (Lonicera morrowii) and Amur (L. maackii) — cause the most frequently observed invasive problems in Missouri. Here they will be referred to collectively as bush honeysuckles. Two other species, Bell’s (L. x bella) and Tartarian honeysuckle (L. tartarica), are also considered when referring to bush honeysuckles. Bell’s and Tartarian honeysuckle have similar impacts to natural communities and similar management implications.
Effects on Natural Communities
Bush honeysuckles will invade a wide variety of natural communities with or without previous disturbances. Affected natural communities can include: lake and stream banks, marsh, fens, sedge meadow, wet and dry prairies, savannas, floodplain and upland forests and woodlands.
Because bush honeysuckles form a thick understory, they limit how much sunlight reaches the seedlings of native plants and thus inhibit the growth of new plants. They also compete with native plants for moisture and nutrients in the soil. All bush honeysuckles spread from the roots, allowing them to further dominate an area.
Recommended Practices in Natural Communities of High Quality
Control measures may enlist one or more of the following techniques: prescribed burning, hand pulling of seedlings, cutting and herbicide treatments. A recently introduced pest, the European Honeysuckle aphid, somewhat controls flower and fruit production in some of the bush honeysuckles. Heavy infestations cause tips of branches to form "witches' brooms" or deformed twigs. This often greatly reduces fruit production. Native ladybug beetles, however, have been noted to control this aphid.
In fire-adapted communities, spring prescribed burning will kill seedlings and kill the tops of mature plants. Bush honeysuckles readily re-sprout and repeated fires are necessary for adequate control. It may be necessary to burn annually or biennially for five years or more for effective control.
Hand-pulling of Seedlings
Seedlings may be hand-pulled when soils are moist. All of the root should be removed or re-sprouting will occur. Physical removal by hand-pulling smaller plants or grubbing out large plants should not be used in sensitive habitats. Open soil and remaining root stocks will result in rapid re-invasion or re-sprouting of honeysuckles and other exotic species.
Cutting Followed by Herbicide Application
Bush honeysuckle stems can be cut at the base with brush-cutters, chainsaws or hand tools. After cutting, a 20-percent solution of glyphosate should be applied to the cut stump either by spraying the stump with a low pressure hand-held sprayer or wiping the herbicide on the stump with a sponge applicator to prevent re-sprouting.
Glyphosate is available under the trade names Roundup and Rodeo, products manufactured by Monsanto. While the Roundup and Rodeo labels recommend a 50- to 100-percent concentration of herbicide for stump treatment, a 20-percent concentration of Roundup has proven effective (Note: some products containing glyphosate or another herbicide may be pre-diluted, so be sure to read product labels to understand herbicide concentration levels). It is not known if this lesser concentration is effective for Rodeo also. Rodeo can be used in wetlands and over open water, but Roundup is labeled only for use in non-wetlands.
Herbicides should be applied to the cut stump immediately after cutting for best results. Application in late summer, early fall, or the dormant season has proven effective. Some re-sprouting may occur, making a follow-up treatment necessary. Glyphosate is nonselective, so care should be taken to avoid contacting non-target plants. The wood of bush honeysuckles is very tough and easily dulls power tool blades. Underplanting of native species following honeysuckle removal may be necessary to reestablish a desirable composition of ground cover, shrubs, and understory trees. This may also minimize the risk of reinvasion by bush honeysuckles and other exotic species.
Recommended Practices on Lands Other Than High-Quality Natural Areas
Methods given above for high-quality natural communities are also effective and preferred on buffer and disturbed sites. When an area with bush honeysuckle lacks sufficient fuel to carry a fire, herbicides may be necessary to obtain control.
In dry, upland areas, a foliar spray of 1-percent glyphosate will control seedlings. A 1.5-percent foliar spray of glyphosate just after plant blooming in June will control mature shrubs. Application should occur from late June to just prior to leaf color changes in fall. The herbicide should be applied while backing away from treated areas so as not to walk through the wet herbicide.
In areas near water, a foliar spray of 1-percent Rodeo (glyphosate) with Ortho-X27 spreader, will control seedlings. Application should occur from late June to just prior to changes in leaf color in the fall. Foliar application of a 1.5-percent solution of Rodeo (2 oz. Rodeo/gallon clean water) will kill mature plants if all foliage is sprayed. This control method usually requires less labor but more herbicide.
In addition, Krenite controls bush honeysuckle when applied according to label instructions. Any treatment should be rechecked in following years for reinvasion. Glyphosate is a nonselective herbicide and care should be taken to avoid contacting non-target plants with herbicide. Do not spray so heavily that herbicide drips off the target species. By law, herbicides may only be applied according to label instructions.
Failed or Ineffective Practices
The herbicide Garlon does not control bush honeysuckle.