Weed Control

Control of invasive and noxious weeds is taken serious by the Wetland Management District.  Each Waterfowl Production Area is visited at least twice during the weed season.  Noxious weeds are sprayed and mapped.  Spot spraying is done on individual plants and small patches.  Spot spraying is the most cost effective, applies the least amount of chemical, and causes the least harm to native plants. Mapping helps us monitor our control efforts and marks those areas for closer attention in future years. 

Control of invasive trees is becoming more aggressive as well.  We have begun using the herbicide to kill small trees.  This is beneficial, especially in areas we are not able to apply a prescribed burn.  On areas where dense stands of trees were shredded, the soil is sprayed with a herbicide which translocates into root remnants, killing them. 

Our District is also testing the effectiveness of a new herbicide on controlling reed canarygrass.  That herbicide causes reed canarygrass to prematurely senesce and die without harming nearby sedges or forbs.   

The table below shows the number of acres of each species treated by our staff.  There was much more musk thistle in 2008 than in previous years. The table also shows the dramatic increase in efforts targeting tree removal during 2008. The number of acres treated for the remaining species is within the range of the preceding three years.

 

                                       2005       2006       2007       2008

Canada thistle                 586        379         202          344

Musk thistle                 1,724     1,115      1,004       2,306

Bull thistle                        36          57           12            30

Crown vetch                   217        124         129          152

Leafy spurge                    29           41          16            18

Reed canarygrass                            23         141         108

Phragmites                                                     47           22

Trees (all species)            25            7          154         533

 

Total                           2,617     1,758       1,705      3,525

 

MUSK THISTLE (Carduus nutans) (Top of page)

The total numbers of acres with musk thistle sprayed in 2008 was more than twice the number in 2007.  Part of the increase can be attributed to differences in data entry between ArcView and ArcMap, but there were considerably more thistles on some WPAs this year than last. The number of WPAs with less than ten acres sprayed decreased by nine (42 to 31), while 10-100 acres were sprayed on seven more WPAs than in 2007 (14 to 21). More than 200 acres were sprayed on Massey, McMurtrey, Hultine, and Moger; with over 300 acres sprayed on the latter two. Funk, Mallard Haven, Atlanta , and Quadhammer had the largest decreases in acres sprayed. Figure 1 shows the number of acres treated on each WPA over the past four years. These estimates are the number of acres sprayed, not necessarily the number of acres with musk thistle.  In many cases the same area was sprayed at least twice. (This caveat applies to the remaining species as well).

 

BULL AND TALL THISTLE (Cirsium vulgare & Cirsium altissimum)

Bull thistle is very bad in some small areas on several WPAs, but is not a large District-wide problem. It often grows in close proximity to musk or Canada thistle and is seldom in single-species stands. The heaviest infestations seem to be in heavily grazed areas. The biggest problem areas are in the Redhead, Ruddy, and Whitefront units of Funk WPA, Hultine North, and the north end of Tamora. The wetland edge of Cottonwood, Freeman Lakes , and Linder also had some heavy infestations last year.

 

CANADA THISTLE (Cirsium arvense)

We continue to make progress in reducing or eliminating Canada thistle from some WPAs but we lost ground on others. Nineteen WPAs had Canada thistle on them in 2008. This is down three from 2007. Canada thistle was not found on four WPAs (Glenvil, Massey, Hultine, Troester) that had small amounts of it in 2007. Lindau did not have any Canada thistle in the previous three years, but we found a small number of plants this year. Fewer than five acres of Canada thistle was sprayed on 14 of the 19 WPAs having it, and less than an acre was sprayed on seven of those sites. Eradication is within reach on some of these areas, especially if we continue fall spraying.

Fall spraying efforts were expanded in 2008.  We revisited all areas where we had sprayed Canada thistle with ATVs earlier in the year (we did not attempt to spray large areas that had previously been boom sprayed) and searched out basal rosettes. We found rosettes on about half of the WPAs revisited. Most efforts targeted small, isolated patches, but Funk was an exception; all known areas of Canada thistle along dikes and WPA boundaries were sprayed. 

 LEAFY SPURGE (Euphorbia esula) (Top of page)

The total number of acres of leafy spurge that were sprayed was almost identical to 2007, although there were annual differences for individual WPAs. Small amounts of spurge were found on Quadhamer and Prairie Dog in 2007, but not in 2008. We should be able to eradicate spurge on Bluestem, Cottonwood, Funk, Johnson, and Clark within the next year or two. The remaining WPAs will probably take longer.

Less spurge was found on Victor Lakes in 2008, but this may be because early water levels prevented it from growing. High water levels may also explain why fewer areas of spurge were found on Morphy. Improved mapping, along with tree removal on Wilkins should help us control spurge on Wilkins and Rausher. Controlling leafy spurge on Brauning is made more difficult because we are downhill from landowners who have it on their property. 

PURPLE LOOSESTRIFE (Lythrum salicaria) (Top of page

None was found in 2008. A few plants were found on Johnson in 2006 and 2007.  

TALL/INTERMEDIATE WHEATGRASS (Elytrigia intermedia)Intermediate_wheatgrass_treatment_on_Lindau_WPA_7-31-02

Intermediate wheatgrass in another species, sometimes used by conservation agencies as a cover crop, that has become a problem on some of our areas. The species is not desired in native plant communities, and since cattle do not find it palatable grazing does not provide control. Although exotic wheat grasses are on several WPAs we have not targeted it recently. We last sprayed it on Hannon in 2006.

REED CANARYGRASS (Phalaris arundinacea) & RIVER BULLRUSH (Scirpus fluviatillis) 

Both species are considered weeds on our properties. While Reed canary grass may have a native strain we consider clones on the WPAs as the exotic and aggressive Eurasian cultivar. River bullrush is a native wetland emergent, but can dominate a wetland excluding other plant species, and filling in open water to the detriment of migratory birds.   

 

We sprayed reed canarygrass in autumn at Lange, Meadowlark, Moger, Harms, and Johnson WPAs. Weather conditions and water levels prevented us from spraying on other units.

 

KENTUCKY BLUEGRASS & SMOOTH BROMEGRASS (Poa pratensis & Bromus inermis) (Top of page)

Both species are common throughout many properties, but have not yet become a priority to spray, although we did treat one small patch on the southeast corner of Cottonwood this fall. Prescribed burning and grazing are the only treatments used to control these species.

TREES: Plains cottonwood (Populus deltoides), eastern redcedar (Juniperis viginiana), Siberian elm (Ulmus pumila), willow (Salix spp.), green ash (Fraxinus pennsylvanica), honeylocust (Gleditsia triacanthos), Russian olive (Elaeagnus angustifolia)

 

See the section on tree removal for an explanation of why trees are being removed from wildlife habitat areas.

 

Many of the WPAs have large stands of mature trees that have been allowed to become established through lack of management.  Fewer management tools are available/effective as the trees continue to spread and mature.  Haying is no longer an option, grazing does little to rejuvenate grass stands as the trees continue to shade them, burning becomes a risky option as fuel loads increase and the possibility of spotting and restarts increases, and worst of all the wetlands become unattractive to migratory birds and grassland nesting species are replaced with less undesirable species such as bluejays and fox squirrels.

 

Tree removal was a high priority in 2008, and we used both chemical and mechanical methods to kill or remove them. Trees removed mechanically had their stumps (except cedars) treated with herbicide to prevent regrowth whenever possible.  This was not always possible if trees were removed with skidsteers and cutting attachments because the stumps are time consuming to find. Cooperators removed trees from parts of Hannon and Haseman, while contractors spent most of the fall removing trees from a number of WPAs.   See Macon Lakes for details about the extensive tree removal work done by Ducks Unlimited.

 

YELLOW AND WHITE SWEETCLOVER (Melilotus officianalis, Melilotus alba) (Top of page)

Both clovers are found throughout the WMD and both are considered as one for this report. Although some conservation agencies (including FWS in some areas) and conservation groups still plant sweet clover for bird habitat, but we do not, because of its aggressive nature and because it is not in keeping with the concept of managing our lands for native species. Sweet clover is a highly prolific biennial. Its height and its monotypic nature shade out desired vegetation.

Since reproduction is from seeds only the best chance to eliminate sweet clover may be by controlling seed production. Tractor spraying, mowing, or haying are all control options for all but the smallest infestations. These can be sprayed from an ATV or hand-pulled. Encouraging cooperators to hay infestations prior to flowering is one approach, but apparently cattle can be poisoned by a straight sweet clover diet. If we cannot find willing cooperators, mowing is feasible, although time-consuming option. Spraying may be the most efficient control, but the cost of additional chemical may not be within the station’s budget and desirable species will be damaged along with the sweet clover.   

Sweet clover was rank on some areas, but none was sprayed, hayed, or shredded in 2008.

PHRAGMITES/NORTHERN REEDGRASS (Phragmites australis) 

Phragmites is an extremely aggressive plant which is established in the nearby Platte River.  Almost all Phragmites is on Funk, but there is one small patch (< 1 acre) on the west side of Johnson and a few plants growing alongside the center road at Hannon. Johnson was sprayed in early autumn, but the plants on Hannon were not discovered until too late in the year to spray them. We sprayed 22 acres at Funk, with the vast majority of Phragmites growing in the northeastern Peterson unit and in the Mallard unit. Bittern and Pintail also had small amounts.  

 

CROWN VETCH (Coronilla varia) and HAIRY VETCH (Vicia villosa) (Top of page)

There were four WPAs that had crown vetch in 2007, but where none was found in 2008. Unfortunately, we also found it on four WPAs that did not have any in 2007. Both the number of WPAs with crown vetch and the total number of acres sprayed was similar to 2007. There was an increase in the number of WPAs having less than one acre of crown vetch, and a decrease in the number of WPAs with one to five acres vetch since last year.  This suggests that we are making progress on some units. Nine WPAs however, have extensive amounts of crown vetch. Peterson is the worst of these with 44 acres. Although several WPAs had large patches of crown vetch in past years, grazing prevented us from finding many patches this year. Grazing probably stressed the plants, but unless heavy grazing continues vetch will most likely recover unless chemically treated. Crown vetch has not been found on Hansen, Rauscher, Tamora, or Youngson in three years.

BUTTER-AND-EGGS or TOADFLAX (Linnaria vulgaris) 

None was found in 2008.  

 

SALT CEDAR (Tamarix ramosissima)

It became a noxious weed in Nebraska on January 1, 2005. Purportedly it was found on Funk several years ago, but we have not found it on our properties until September 2005 when a single tree was found on Johnson. When found, salt cedar should be dug up, bagged, and burned if possible. Nebraska recommends spraying with Garlon 3, Habitat, or Habitat + Glyphosphate. Since salt cedar frequently has its “feet” in water we must ensure that the chemical chosen can be used near water.  In 2008, no salt cedar was found on WPAs.

 

MULTIFLORA ROSE (Rosa mutiflora)

We found multi-flora rose on a few WPAs during the past three years, but we found it on ten WPAs this year (Hansen, Harvard, Lange, Mallard Haven, Massie, Sinninger, Smith, Weseman, and Wilkins). So far, we have only found isolated plants or very small clusters. Multi-flora rose is highly invasive and should be chemically treated whenever found. 

Other Species

Others species on the watch list include: Korean lespedeza (sericea lespideza), spotted knapweed (Centaurea maculosa), Russian knapweed (Centaurea repens), and St. Johnswort (Hypericum perforatum). None of these were found in 2008.  What was found were several plants of multi-flora rose on several WPAs.  Each plant was sprayed with a basal bark treatment of Remedy and mapped.

 

WEED COMPLAINTS (Top of page)

We received one weed complaint from Phelps County for musk thistle around the prairie dog town on Atlanta . We had just sprayed the area days before, but made a special trip back to Atlanta immediately after receiving the letter.  

Last updated: August 24, 2009

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