Restoration of a forest understory after the removal of an invasive shrub, Amur honeysuckle (Lonicera maackii)

  • Published source details Hartman K.M. & McCarthy B.C. (2004) Restoration of a forest understory after the removal of an invasive shrub, Amur honeysuckle (Lonicera maackii). Restoration Ecology, 12, 154-165.


Amur honeysuckle Lonicera maackii (native to eastern Asia) has become an invasive of forests in the eastern USA; it has spread also into Ontario, Canada. Where Amur honeysuckle is abundant, recruitment of native tree seedlings is reduced, therefore honeysuckle control is desirable. The effectiveness of two eradication methods using glyphosate herbicide were evaluated: cut and paint, and stem injection with an EZ-Ject lance.

Study site: This experiment was carried out at the Fernald Environmental Management Project Site (425 ha) located 29 km northwest of Cincinnati, Ohio. Within this area, the eradication trials were conducted in the 'North Woodlot' (65 ha), an area contains four general habitat types including old fields, previously mowed meadows, regenerating forest, and mature forest.

Experimental design: Eight 5.5 × 13.5 m blocks in two areas (A - five replicate blocks; and B - three replicate blocks ) roughly 150 m apart containing honeysuckle stands were established. Site A was dominated by shellbark hickory Carya laciniosa. Site B was dominated by a boxelder Acer negundo, flowering dogwood Cornus florida, green ash Fraxinus pennsylvanica, black cherry Prunus serotina and American elm Ulmus americana.

Within each block, three 4.5 × 5.5 m subplots were established and all honeysuckle stems within them were tagged and measured. Honeysuckle eradication treatments were applied on 24 March 1999. Each block consisted of:

i) a control subplot - no L.maackii was removed;

ii) a cut subplot - all L.maackii stems cut near ground level, cut material removed, and stumps painted with 50% glyphosate isopropylamine salt solution (Roundup);

iii) an injection subplot - L.maackii treated using an EZ-Ject lance but left standing; a glyphosate-filled 22-calibre capsule is injected through the bark. On large honeysuckles with two or more stems, each stem was injected separately.

Eradication treatment effectiveness: Honeysuckle mortality was assessed at the end of the 1999 and 2000 growing seasons.

Eradication treatment effectiveness: At the end of 1999, mortality was 99% for both treatments. It was found to be difficult to inject stems smaller than 1.5 cm, therefore, delayed resprouting occurred in some cases after the initial injection. In 2000, honeysuckle had 98% mortality where no operator error occurred in the injection plots (95% if operator error included), and 94% in the cut and paint plots.

Ease of a eradication treatment application: The cut and paint method required more time to apply (7 h to eradicate 66 m² or 1,060 person-hours/ha) than the injection treatment (3 h to eradicate 66 m² or 454 person-hours/ha).

Comparison of costs: The cost for the cut and paint method was $253 USD, including clippers ($30), loppers ($65) and glyphosate herbicide (2.5 gallons at $158). The injection costs were $599, including the EZ-Ject lance ($467) and glyphosate capsules (1,200 capsules at $132).

Conclusions: Both eradication treatments were effective in killing Amur honeysuckle (≥ 94%). The injection treatment was most effective on large honeysuckle plants (>1.5 cm stem diameter) and was 43% faster to apply than cutting and painting. This method was also less tiring for the operator, and had safety benefits in that it decreased operator exposure to herbicide, and minimized impact to non-target vegetation.

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