Japanese Knotweed and Multiflora Rose: Is Herbicide the Answer?

In an effort to earn ‘extraordinary mitigation’ points and justify close encroachment to the wetlands off North Street, Kohl Construction proposes to apply herbicide in an effort to eradicate two invasive species on its property: Japanese knotweed and multiflora rose. Northampton Land Use and Conservation Planner Bruce Young says that if Kohl did this to all the wetlands on its property, planting native species in their place, this would qualify as extraordinary mitigation in his eyes.

Our questions include:

  1. Is lasting eradication with herbicides as proposed by Kohl likely in any reasonable period of time?
  2. Will the use of herbicides damage the ecology of the area?
  3. Will Kohl’s other actions on its property encourage the spread of invasive species?
  4. Are the invasive species providing benefits that might be missed if they’re gone?
  5. What is the forecast for the invasive species if no action is taken?

We have already discussed how the commonly used herbicide glyphosate (Rodeo and Roundup) has been shown to be highly toxic to amphibians. Two more scientific papers shed light on the other questions.

First up is this article on Japanese knotweed by R.H. Shaw and L.A. Seiger (2002):

…To be effective, Japanese knotweed control probably will need to be undertaken on a watershed-wide basis…

Once established, F. japonica is very difficult to eradicate and removal efforts may have further adverse impacts on the soil or other plants…

In areas where F. japonica has been introduced, it is found primarily in moist, unshaded habitats… Fallopia japonica requires high light environments and competes effectively for light in such situations. It is found primarily in open sites, and its growth and abundance are depressed in shady sites (Beerling, 1991b; Seiger, 1993). Consequently, it is unable to invade forest (Beerling, 1991b, Seiger, 1993)…

In contrast to the situation in the United Kingdom and United States, damage to F. japonica by foliage-feeding invertebrates and pathogens was high in some of the Japanese sites examined by Yano and co-workers in 1991 and 1992 (K. Yano, pers. comm.). At least 12 species of insect herbivores were commonly found on the plant at these sites and many more species of insect herbivores have been recorded on the plant. At least 39 of these are likely to be to be feeding on plant parts other than the flowers (Shaw, 1995)…

In Japan, F. japonica also is attacked by a suite of fungal pathogens in the field, including Puccinia polygoni-weyrichii Miyabe, whose erupting uredinia are shown in Fig. 4. It is apparent that a combination of insect and fungal agents severely damages the plant in its native range, reducing it to an innocuous member of the flora in competition with the other members of the “giant herb” community common in Japan…

…environmental and financial costs associated with ineffective chemical-based control measures… Japanese knotweed is certainly a plant for which classical biological control is the only long-term, sustainable solution.

Even if Kohl tries to eradicate knotweed from its entire parcel, this is far short of a “watershed-wide basis”. And while Bruce Young disputes the notion that removal of invasives can disturb the wetland and its buffer zone, just such a risk is mentioned by Shaw and Seiger. We also note that Kohl’s proposed condo development calls for extensive tree-cutting. The resulting increase in light penetration on the property may well facilitate the spread of Japanese knotweed.

Let’s now turn our attention to multiflora rose, and this paper by J.W. Amrine, Jr. (2002):

Where plants have become well established, a huge seed bank develops that can continue to produce seedlings for at least twenty years after removal of mature plants…

The abundant floral production of this plant may be the result of the plant’s evolution in the presence of its seed predator, the multiflora rose seed chalcid, Megastigmus aculeatus var. nigroflavus Hoffmeyer (Hymenoptera: Torymidae). In Asia, the chalcid may infest 95% of the achenes or seeds (Weiss, 1917)… Multiflora rose is moderately winter-hardy, tolerant to many North American insects and diseases, and grows rapidly into dense thorny thickets favorable for many species of wildlife. Its abundant fruits are food to deer and birds. The flowers produce large amounts of golden, sweet-tasting pollen that can be harvested by fitting bee hives with pollen traps (Amrine unpublished). The plant has a vigorous root system capable of checking erosion…

Of 31 states in the eastern United States sampled by the author, the chalcid was found in all except Florida, Louisiana, Mississippi, Texas, and northern New England…

It is virtually certain that RRD [Rose Rosette Disease] will greatly reduce the density of multiflora rose. No multifloras have been found that are resistant to the disease (Amrine et al., 1990, Amrine and Stasny,1993; Epstein and Hill, 1998). The reduced populations of multiflora rose remaining after the RRD epidemic are likely to be infested by the seed chalcid at the same rate (90 to 95%) as plants in Korea and Japan. Multiflora rose will then be another occasional plant in the environment, and not the noxious weed that it is today. We estimate that this scenario will transpire within the next three to five decades. Farmers and others wanting eradication of multiflora rose desire human intervention to increase the rate of spread of the disease, the mite and the torymid into uninfested areas. However, rosarians desire that all augmentation work with RRD and the mite cease…

Amrine et al. (1990) showed that RRD and P. fructiphilus have excellent potential to reduce multiflora rose… The rate of infestation of the rose seed chalcid is increasing in all areas surveyed. In some areas of West Virginia, rates of seed infestation now exceed 80% (Amrine, unpub.)…

Even if not deliberately spread, its [rose seed chalcid’s] range will increase by birds. Eventually, multiflora rose will be reduced to low levels, occurrence of RRD will become minimal, as in California, Wyoming and Utah, where it originated, and problems for farmers and rosarians alike should be greatly reduced.

During this time when multiflora rose is flourishing, it is providing several benefits to the ecology, including erosion control. Its thorns might even be considered an additional feature, discouraging humans from too much tramping around within Kohl’s wetlands and wetland buffer zone. Based on the longevity of the seed bank, eradication might be a 20-year project or more, far longer than the year or two (or even 10) contemplated in Kohl’s latest written proposal. It seems unreasonable and unrealistic to ask a developer and the Conservation Commission to implement and monitor such a lengthy program, especially when non-compliance with wetlands agreements has proven to be a widespread problem in Northampton.

In contrast to a relatively short program of toxic herbicides–extraordinary or not–the long-term, low-risk, environmentally gentle solution to these invasive species appears to be bringing the ecology back into balance, allowing and in some cases encouraging the natural predators of knotweed and multiflora rose to feast on their abundance. Additionally, preserving mature trees will help control knotweed.

See also:

Organic Weed Management: Japanese Knotweed
When control is limited to one problem area, re-infestation is likely from adjacent areas. It is necessary to deal with plants in the adjacent areas too and prevent the spread of plant fragments, especially near water or where loose soil is likely to become moved around.

Japanese knotweed would appear to be an appropriate candidate for biological control. However, few native insects or plant diseases are known to attack the weed in Britain. An extensive programme of research would be needed to evaluate and develop biological control measures introduced from elsewhere. A rust fungus Puccinia spp. from Japan, has shown some promise as a control agent. More recently, a pathogenic leafspot, Mycoshaerella spp. and a sap-sucking plant louse, Aphalara itadori have been found living on the weed in Japan. Both have given encouraging results and are under assessment as biocontrol agents for Japanese knotweed.

Invasive Plant Atlas of New England: Japanese Knotweed
Polygonum cuspidatum can be found in a variety of habitats. It thrives in riparian areas and wetlands, but can be found along roadsides and other disturbed areas. It prefers full sunlight, but can tolerate moderate shade. This plant is tolerant of high temperatures, dry soil and salt.

Conservation Commission Meeting of 1/22/09; Non-Compliance with
Wetlands Protection Agreements; Kohl Asked to Revise Condo Proposal

0:39:00-0:51:01… Bruce Young: “Honestly I have too much going
on [to closely monitor EBD’s planting plan], and part of that ‘too
much’ is enforcing encroachments on projects similar to this. So, to
add to this, I’d like to say that I would recommend that the commission
require large boulders two feet on center across the entire
encroachment zone…four feet in diameter boulders two feet apart… I
think two feet keeps people from mowing and creates a border….
Because I’ve spent a huge amount of time going to these projects now
that we had, we started a few years ago at 30 feet apart, then we went
to 25 feet apart, now we’re at 15. Actually, I’ve had enough. I’ve had
enough of sending enforcement orders to people and having them deny
them in the mail, and then have it come back to me, and then having to
send one certified mail, and then have them deny it three times before
I have to issue a…someone to deliver a subpeona, and then this is a
huge waste of time for someone who is mowing down a wetland that is
a…what begins in the process as a fair kind of negotiation but then
turns into…it gets sold to one person who gets sold to another and
people…no longer respect that line…”

Gazette Reports on January 22 Kohl Condo Hearings; Pictures of the Latest Proposal; Conservation Staff Report; HYLA Critique

[Dr. Bryan Windmiller:] …the applicant proposes to mitigate the impacts of buffer zone
disturbance by disturbing even more area of inner buffer zone and
forested wetland itself.  This mitigation effort will, in fact, only
worsen the impacts to the wetlands bordering Millyard Brook…

Increased Abundance of Invasive Exotic Plant Species:  One of
the most insidious edge effects that propagate into surrounding
wetlands and woodlands from residential edges is the increased
abundance of many invasive exotic species. I have already alluded to
how changes in wind patterns, soil disturbance following construction,
and the mortality of trees near newly-created forest edges facilitates
invasion by exotic plant species.  R. Watkins et al. (“Effects of forest roads on understory plants in a managed hardwood landscape”.  Conservation Biology 17(2): 411-419. 2003) report findings that: “Exotic species were most prevalent within 15 m (50 feet)
of roads, occurring infrequently in the interior forest.”  Allowing the
proponent to build within 15 feet of the edge of the Millyard Brook
wetlands will greatly encourage further invasion of this area by exotic
plant species.

…the intended removal of Norway spruce (Picea abies), a
non-native species occurring in a dense mature stand in the Millyard
Brook wetlands can, in no way be construed as an improvement.  Although
these trees are not native, they provide complex habitat structure for
wildlife, help bind the soil that enhances the erosion control and
pollution attenuation functions of the wetlands, and moderate climate
and humidity levels in the wetlands.  The removal of these trees will
cause major direct impacts to the wetlands and adjacent buffer zone and
will greatly facilitate the establishment of truly invasive exotic
species.  The tree removal will also greatly reduce and simplify
existing wildlife habitat.  The resident birds, mammals, and
invertebrates care not one whit that these mature trees are originally
native to Europe; they exist and provide excellent habitat structure.

The intended use of herbicides by the applicant to control Japanese knotweed (Polygonum cuspidatum)
will moreover result in the pollution of the wetland with herbicides
and their toxic surfactant agents.  The commonly used herbicide
glyphosate (Rodeo and Roundup) has been shown to be highly toxic to
amphibians, for example, in numerous papers by Rick Relyea and
colleagues (see summary at: http://www.medicalnewstoday.com/articles/22159.php).   Japanese knotweed and multiflora rose (Rosa multiflora)
are furthermore difficult to eradicate, even with herbicides.  To do so
will require significant doses of herbicide applied many times.

the end, such schemes are likely only to result in further degradation
of the wetland system.  How long will the applicant continue to remove
exotic species and replace dead shrubs and trees that are planted in
the mitigation areas?  Three years?  Five?  Ten?  A single generation
for native forest trees lasts decades.  In such a time scale, any such
heroic efforts will certainly have been abandoned and the seed bank of
invasive species in the soil will still be healthy.  The Millyard Brook
wetland will have been reduced and degraded physically, chemically, and
biologically by the construction of the proposed development.  Deed
restrictions and the exact location of no-build boundaries will have
been long forgotten and yard waste, trash, and additional clearings
will have extended into the wetlands and beyond the edge of the nearby
lawns.  This effect will be exacerbated by the minimal outdoor space
provided for residential development of such high density.

Boxborough Wetlands Regulations: Plans that Require Replication Discouraged
history of wetland replication is mixed. Scientific reviews [Brown,
S&P Veneman, 1998] conclude that for the most part replications
fail to reproduce the range of values–in quantity and quality–of the
wetlands they are intended to replace, in particular, difficulties in
replicating proper hydrological conditions in a consistent and enduring
fashion seem to be a major source of the problem.

The Commission shall strongly discourage any plan that requires wetland replication…

Carlon Drive: Compensatory Wetland Not Working

Our Ad in Today’s Gazette: A Review of Our Objections to the Kohl Condo Proposal

Topographical Map Shows How Kohl Condo Proposal Will Eat Into a Rare Stand of Mature Trees in Downtown