Appendix 2 Eradicated Arundo/Native Riparian Tree Impact Zones along the Upper Napa River A-1
The Problem Arundo donax, or giant reed, is a non-native invasive grass. It grows up to 30 ft. tall and invades riparian ecosystems where it competes with native trees. Arundo provides little wildlife habitat or shade to the stream. It also does not provide stability to the stream bank. In 2010 the California Land Stewardship Institute (CLSI) mapped the extent of invasive non-native Arundo donax in the downstream portion of the Upper Napa River plan area (Reaches 10 and 11) extending down to Lodi Lane (Larkmead to Lodi Arundo eradication Project)(Figure 1). We contracted with the Napa County Flood Control and Water Conservation District (Flood District) to implement the eradication of the mapped Arundo. CLSI had worked with the Flood District on two other small projects. We understood that the methods and chemicals used would be the same as the earlier projects that used glyphosate (Round-up) only. The glyphosate had been applied as a foliar spray to the Arundo in the fall. This is the period when the plant translocates sugars to its roots and glyphosate has its greatest effect. The Flood District held a 1600 permit from the Ca Dept. of Fish and Wildlife (#R3-2001-0610) which was extended from 2/15/2007 to 12/31/11 and authorized the removal of Arundo under certain conditions. The Flood District contracted with the Mosquito Abatement District to apply the herbicide in October 2011. It appears from our vegetation mapping of the Upper Napa River that the Flood District carried out a similar Arundo eradication effort extending from Reach 2 to 9 of the project area (Figure 2). In 2012 staff from the Flood District informed CLSI that trees near the treated Arundo were dead or dying. We also learned that Imazapyr as well as glyphosate had been applied in the Arundo treatments. The Flood District did not inform CLSI that the chemicals used in the treatments had been changed. The Imazapyr was applied in the fall rather than spring as the herbicide label recommends. Imazapyr is a systemic herbicide not a contact herbicide and is supposed to be applied to living tissue. The following precaution is on the Imazapyr label: Precautions for avoiding injury to non-target plants Untreated desirable plants can be affected by root uptake of this product from treated soil. Injury or loss of desirable plants may result if this product is applied on or near desirable plants, on areas where their roots extend, or in locations where the treated soil may be washed or moved into contact with their roots. When making applications where desirable plants may be present, caution should be exercised to avoid spray contact with the foliage or spray application to the soil in which they are rooted As part of the Upper Napa River plan we mapped the damage that resulted from the 2011 Arundo treatment with Imazapyr. Approximately 2.0 acres of native riparian trees were killed as part of the Arundo eradication carried out by the Flood District in 2011 in Reaches 2-11 in the Upper Napa River plan area. We do not know the size of the impact zone along the river stretching from the end of Reach 11 to Lodi Lane. However the same problem is apparent on these properties. The total impact on the riparian habitat of the Upper Napa River is greater than the 2.01 acres mapped. We call the impacted areas Eradicated Arundo/ Native Riparian Tree Impact Zones as they appear as areas with dead Arundo and either no trees or dead trees. Some of these zones are large. These zones are one of the most significant environmental issues in the Upper Napa River plan area. The treatment of Arundo donax by the Flood Control District in 2011 created these significant environmental impacts due to the use of Imazapyr in the fall. Label directions for this herbicide recommend use on Arundo donax in the spring. Imazapyr moves through the soil rather than binding to A-2
clay particles. This feature allows the herbicide to affect vegetation distant from the application (Mangels 1991a and b, EPA 1987). In the fall, the native riparian trees as well as the Arundo are senescing for the winter and often take up water and nutrients from the soil. The Imazapyr was likely taken up by trees next to the Arundo and as far as 50 feet away. The particular characteristics of Imazapyr and its use in the wrong season likely increased the environmental damage. In the Upper Napa River Plan reach (Figure 2), the Arundo Eradication/Native Riparian Tree Impact Zones total 87,555.6 square feet or 2.01 acres. There are additional impact zones from Big Tree Lane to Lodi Lane that we did not map (Figure 1). Once we learned of the significant effect the District s use of Imazapyr had on native riparian trees we requested that the District write a letter to all the landowners to explain what they had done. We made this request on 1/31/13, 2/13/13, 1/23/14 and 3/17/14. We kept records of the dates of these communications at the request of our lawyer. We were always told no the District would not inform the landowners of this issue. Suggested Solution The eradication occurred in 2011 and the Arundo was largely killed. Still the Flood District has completed little to no successful revegetation or erosion control in Reaches 2-11. CLSI completed revegetation in Reaches 10 and 11 and found that many of the replanted tree seedlings were also affected by the Imazapyr in the soil. There are numerous locations with bank erosion where the Arundo was treated. Additionally we have learned that none of the landowners in the project reach have been informed of the District s mistake. This response calls for a greater level of oversight on the District s work in the Upper Napa River. As part of this plan we are proposing to form an oversight committee to make sure the Arundo Eradication/Native Riparian Tree Death Zones are revegetated and soil sampling or other tests are done if needed. Additionally there are landowners who will not work with the Flood District. These landowners should receive the needed funds to hire a different contractor to revegetate their damaged lands. We suggest the following organizations participate in the oversight committee: Ca. Dept of Fish and Wildlife Regional Water Quality Control Board Napa County Agricultural Commissioner Landowners Several environmental groups including Friends of the Napa River and ICARE Ca. Land Stewardship Institute Napa County Flood Control District The following figures document in detail the 2011 Arundo treatment and its aftermath in killing the riparian trees on 2.01 acres of riverside land. A-3
Figure 1. Arundo present in 2010 between Larkmead Lane and Lodi Lane, Upper Napa River. We do not have a map of the Arundo that was treated between Lincoln Ave and Larkmead Lane. Blue lines mark the portion of the Larkmead to Lodi project area included in the Upper Napa River plan area. A-4
Figure 2. Upper Napa River Plan Area A-5
Napa River low flow channel Figure 3. Licensed applicator from Mosquito Abatement District applying herbicide Oct. 19, 2011 to Arundo. Herbicide is dyed blue. Flood district staff is overseeing the operation and CLSI staff took photos. CLSI field notes with the photos state that CLSI staff voiced concerns about overspray and effects on native trees. Field notes also state that concerns were shrugged off by both agencies. A-6
Figure 4. Overspray of herbicides on Arundo and native trees. A-7
Figure 5. Photos shows ground saturated with herbicide. One of the chemicals used was Imazapyr which is well known to move through soil and affect nearby native vegetation. A-8
Figure 6. The owner of the adjacent vineyard reported damage to the vineyard from the herbicide treatments to the Arundo. A-9
Figure 7. Dead Arundo and dead native trees. Trees 0-50 feet away from the treated Arundo clumps were killed. A-10
Figure 8. Inset shows strange growth along branches in walnut tree next to treated Arundo. Walnut tree died. A-11
Figure 9. Strange growth along branches and trunk from Imazapyr being taken up by native tree roots. This tree did not recover and died. A-12
Dead Arundo and dead native trees Figure 10. Mapping in Reaches 2-11 focused on sites where dead Arundo and dead trees were present. Sites with no trees or dead trees but without dead Arundo were not mapped. This approach has likely underestimated the acreage of impact zones. A-13
Figure 11. Eradicated Arundo/Native Riparian Tree Impact Zones in Reach 5. The square of black weed mat indicates failed revegetation. A-14
Figure 12. Eradicated Arundo/Native Riparian Tree Impact Zones in Reaches 2 and 4. Site in bottom photo has only Arundo left growing. The tree behind the Arundo shows the effects of Imazapyr. A-15
Figure 13. Eradicated Arundo/Native Riparian Tree Impact Zones in Reaches 4 and 5. Top photo shows black weed mat from failed revegetation. A-16
Tree of heaven seedlings Arundo roots Figure 14. Eradicated Arundo/Native Riparian Tree Impact Zones with secondary infestations of invasive non-native tree of heaven. A-17
Dead native riparian trees Arundo remaining after trees died Figure 15. Eradicated Arundo/Native Riparian Tree Impact Zones in Reaches 10 and 11. A-18
Figure 16. Dead trees were removed from some sites by the Flood District. Some properties lost nearly all their riverside native trees. A-19
Impact Zone Figure 17a. Location and size of live patches of invasive non-native Arundo donax and those areas treated by the Napa Flood District in 2011 which had numerous native trees die from the herbicides and are called Eradicated Arundo/Native Riparian Tree Impact Zones. Trees within 0-50 feet of the sprayed Arundo clumps died. A total of 2.0 acres of native trees were killed. A-20
Impact Zone No Arundo treatments were done in Reach 9 Figure 17b. Location and size of live patches of invasive non-native Arundo donax and those areas treated by the Napa Flood District in 2011 which had numerous native trees die from the herbicides and are called Eradicated Arundo/Native Riparian Tree Imapct Zones. Trees within 0-50 feet of the sprayed Arundo clumps died. A total of 2.0 acres of native trees were killed. A-21
References Alligare. Imazapyr 4SL Specimen Label. BASF. Habitat herbicide Specimen Label. Mangels, G. 1991a. Behavior of the imidazolinone herbicides in the aquatic environment. Chpt 15 in The Imidazolinone Herbicides, D. L. Shaner and S. L. O Connor, eds. CRC Press. Boca Raton, FL. 290 pgs. Mangels, G. 1991b. Behavior of the imidazolinone herbicides in soil a review of the literature. Chpt 16 in The Imidazolinone Herbicides, D.L. Shaner and S. L. O Connor, eds. CRC Press. Boca Raton, FL. 290 pgs. The Nature Conservancy. 2004. Weed Control Methods Handbook: Imazapyr. United States Environmental Protection Agency. Office of Pesticide Programs. 1987. EEB Review of 241- EEO. Washington, DC. A-22