Progress 01/01/06 to 12/31/06
Outputs
Field studies were conducted to evaluate herbicide alternatives to the triazines. Mesotrione, clopyralid, trifloxysulfuron, rimsulfuron and imazethapyr provided 80-100 percent control of hoary alyssum, common catsear, quackgrass and wild carrot. Flumioxazin alone provided marginal control of quackgrass. White clover and red fescue ground covers were inter-seeded among three-year-old Fraser fir. Organic mulches and seeded ground covers suppressed populations of hoary alyssum, quackgrass and horseweed. Flumioxazin plus glyphosate maintained almost bare ground throughout the growing season. Use of seeded ground covers such as hard fescue is a beneficial cultural control because it minimizes herbicide use while providing suppression of light-germinating weeds. Differential reactions of the varieties Shuswap Lake and San Isabel to Rhabdocline needlecast species as determined by real-time QPCR assays were consistent with their status as resistant and susceptible varieties
in previous studies. The variety Shuswap Lake was not infected and colonized by Rhabdocline needlecast pathogens since no fungal DNA was detected in any needle samples tested regardless of needle age or time. On the other hand, the variety San Isabel was infected right after bud break as significant levels of pathogen DNA were detected in newly emerged needles. In older needles of San Isabel, high levels of fungal colonization were observed. These results strongly suggest that Shuswap Lake is completely resistant or immune, whereas San Isabel is highly susceptible to Rhabdocline needlecast fungi. Observations suggest that trees from the Shuswap Lake seed source are not infected because the buds break two weeks later than San Isabel and therefore escape infection could not be supported, since Rhabdocline spores continue to release during and after Shuswap bud break.
Impacts
Low-risk herbicides and ground covers appear to provide sufficient weed control for Christmas trees. Their use will allow growers to reduce or eliminate triazines, which results in less negative environmental impact and improves the quality of Christmas trees. Douglas fir is susceptible to several needlecasting fungal pathogens, including three species of Rhabdocline in Michigan. Management generally involves sprays with fungicides. Trees from the Shuswap Lake seed source appeared to be resistant, but it was not known if infection occurs and symptoms did not appear or if infection does not occur. Our findings suggest that trees from Shuswap Lake are resistant to Rhabdocline needlecasting species, and their use should be strongly considered when planting in areas with high levels of Rhabdocline needlecast.
Publications
- Marshall, M.W., Zandstra, B.H., Uhlig, R.E. and Little, D.A. 2006. Hoary alyssum control in Fraser fir Christmas tree plantations. Northeastern Weed Sci. Soc. Proc. 60:71.
- Marshall, M.W., Zandstra, B.H., Uhlig, R.E. and Little, D.A. 2006. Horseweed control in conifer beds. Northeastern Weed Sci. Soc. Proc. 60:14.
- Marshall, M.W., Zandstra, B.H., Uhlig, R.E., Little, D.A. and Richardson, R.J. 2006. Response of Fraser fir to various formulations and application timings of glyphosate. Weed Sci. Soc. Amer. Abstracts 46:56.
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Progress 08/15/04 to 08/14/06
Outputs
Field weed control studies were conducted from 2004 to 2007 at cooperator sites near Manton, Michigan to evaluate herbicide alternatives to triazines and groundcovers as weed control methods in Christmas tree plantations. Flumioxazin, mesotrione, mesotrione plus simazine, trifloxysulfuron, rimsulfuron, and imazethapyr provided 80-100 percent control of horseweed, common ragweed, wild carrot, and hoary alyssum. Flumioxazin provided partial control of quackgrass and common milkweed. White clover and red fescue over-seeded plots suppressed hoary alyssum and common catsear, but not quackgrass, common milkweed, and vetch. Plots treated with flumioxazin plus glyphosate remained almost weed free throughout the growing season. There was virtually no conifer injury in any treatment except for some tip dieback from glyphosate applied during the growing season. No differences were observed in stem growth and diameter of Fraser fir and Douglas fir with the two ground covers. Some
chlorosis of the trees was noted in the hard fescue-seeded plots. Organic mulches and seeded ground covers suppressed hoary alyssum, quackgrass, and horseweed. Establishing ground covers, such as hard fescue or white clover, is an environmentally beneficial weed control practice because it minimizes herbicide use and reduces erosion while suppressing weeds. Differential reactions of the varieties Shuswap Lake, Deep Mountain, and San Isabel to Rhabdocline needlecast species as determined by real-time PCR assays were consistent with their status as resistant and susceptible varieties in previous studies. The varieties Shuswap Lake (2006 and 2007) and Deep Mountain (2007) were not infected and colonized by Rhabdocline needlecast pathogens, as indicated by lack of fungal DNA in any needle samples tested regardless of needle age or time. On the other hand, the variety San Isabel was infected soon after bud break as significant levels of pathogen DNA were detected in newly emerged needles.
In older needles of San Isabel, high levels of fungal colonization were observed. These results strongly suggest that Shuswap Lake seed source are not infected because the buds break two weeks later than San Isabel and therefore escape infection, could not be supported since Rhabdocline spores continue to be released during and after Shuswap bud break. Therefore, chlorothanonil treatments do not need to be used to manage Rhabdocline needlecast pathogens on Shuswap Lake and Deep Mountain Douglas fir seed sources.
Impacts
Low-risk herbicides and ground covers appear to provide sufficient weed control for Christmas trees. Their use will allow growers to reduce or eliminate triazine herbicides, which results in less negative environmental impact and improved Christmas tree quality. Douglas fir is susceptible to several needle casting fungal pathogens, including three species of Rhabdocline in Michigan. Management generally involves sprays with fungicides, primarily chlorothalonil. Trees from the Shuswap Lake and Deep Mountain seed sources have appeared to be resistant to infection, but it was not known if infection was genetic or due to buds breaking after spore populations had subsided. Our results suggest that trees from Shuswap Lake and Deep Mountain have genetic resistance to Rhabdocline needle casting species, and their use should be strongly considered when planting in areas with high levels of Rhabdocline needlecast.
Publications
- Marshall, M.W., Richardson, R.J. and Zandstra, B.H. 2007. Comparison of integrated weed management strategoes om Christmas tree plantations. 8th International Christmas Tree Research Extension Conference 8:28-29. Bogense, Denmark, August 28-29, 2007.
- Marshall, M.W., Richardson, R.J. and Zandstra, B.H. 2007. Herbicide alternatives for atrazine and simazine in Christmas tree plantations. Weed Science Society America Abstracts 47:51.
- Marshall, M.W., Richardson, R.J. and Zandstra, B.H. 2007. Comparison of integrated weed management strategies in Christmas tree plantations. Proc. Northeast Weed Science Society 61:7.
- Marshall, M.W., Wildeman, A., Zandstra, B.H., Dudek, T.A. and O'Donnell, J.L. 2007. Weed control research on ornamental crops and Christmas trees. Horticultural Report No. 71. Michigan State University.
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Progress 01/01/05 to 12/31/05
Outputs
Field studies were conducted to evaluate potential alternative herbicides to replace triazines in Christmas tree production. Flumioxazin, mesotrione, mesotrione plus simazine, trifloxysulfuron, rimsulfuron, and imazethapyr provided 70-100 percent control of horseweed, common ragweed, wild carrot, and hoary alyssum. Flumioxazin also provided suppression of common milkweed and quackgrass. In another study, groundcovers were interseeded in a three-year-old Fraser fir plantation to compare them to herbicides for weed suppression. White clover and red fescue suppressed populations of hoary alyssum and common catsear, but not quackgrass. Herbicide-treated plots had a higher percentage of soil covered with these weeds than did cover crop plots. The ground covers did not reduce Fraser fir stem diameter or height. Rhadocline needle cast is a serious disease of Douglas fir. The normal control method has been multiple applications of chlorothalonil. Seed from Shuswap Lake, B.C.
appears to be naturally resistant to Rhabdocline needle cast, which makes chlorothalonil sprays unnecessary. Visual surveys and PCR analysis of needle tissue indicate that the pathogen does not infect trees grown from Shuswap seed. Shuswap trees have been planted in an infected plantation to observe time of year of spore release using PCR analysis.
Impacts
Low-risk herbicides and ground covers appear to provide sufficient weed control for Christmas trees. Their use will allow growers to reduce or eliminate triazines, which should result in less negative environmental impact and production of higher quality and cleaner Christmas trees. The use of Rhodocline-resistant Douglas fir trees should reduce use of chlorothalonil and result in less negative environmental impact and better quality trees.
Publications
- Marshall, M.W., Richardson, R.J., Uhlig, R.E., Little, D.A., Particka, M.G., Dudek, T., O'Donnell, J., Myers, N. and Zandstra, B.H. 2005. Weed control research on ornamental crops and Christmas trees. Horticulture Report 67, Michigan State University.
- Marshall, M.W. and Zandstra, B.H. 2005. The response of seedling confers to flumioxazin. Proc. North Central Weed Science Society. 60:58.
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Progress 01/01/04 to 12/31/04
Outputs
A replicated experiment was established in fall 2004 for the evaluation of integrated weed management systems in Christmas trees. White clover and glyphosate-tolerant red fescue were seeded into appropriate plots. Other treatments will be applied in spring 2005. Site location for the reduced risk herbicide trial has been arranged with the cooperator and will be established in spring 2005. All necessary materials for both weed control trials have been obtained. For disease management objectives, arrangements have been made with cooperators, and trial work will begin in spring of 2005. No data are currently available for extension activities. However, advertising for the 2005 International Christmas Tree Research and Extension Conference is ongoing, and updated conference information will be available online (http://www.hrt.msu.edu/CTRE2005). Plots and research results will be demonstrated at this event in fall 2005.
Impacts
Research results will allow growers to develop weed management programs using additional integrated techniques and/or lower risk herbicide chemistry for improved economic and environmental sustainability. Extension personnel also will learn through the study results allowing them to provide better advice and planning to growers. Results will be made available in print, on the internet, and through presentations to reach a broad audience.
Publications
- Richardson, R.J., Zandstra, B.H., O'Donnell, J. and Myers, N. 2004. Fraser fir and weed responses to hexazinone and sulfometuron. Proc. North Central Weed Science Society 59:108.
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