The Christmas tree industry in Michigan ranked third nationally in 2003, with 1.9 million trees sold [U.S. Department of Agriculture (USDA), 2007]. In 2005, there were 16,800 ha in commercial production, with cut-tree sales of $41.5 million at the producer level (Klewano and Matthews, 2005). Conifer seedlings typically are grown in nurseries for 3 to 5 years before transplanting in production fields. After transplanting, trees take an additional 8 to 12 years to reach harvestable size. Due to the length of rotation and sensitivity of some species (especially young transplants) to weed competition, adequate weed control continues to be an important issue facing the industry.
Chemical weed control provides numerous benefits over no weed control for intensive silviculture, such as greater than 25% increased biomass production for tree crops with rotations of less than 15 years (Mead, 2005). Seedling height, stem volume, and basal diameter of several conifers increased at four of five research sites when the weed-free area around the trees increased (Rose and Ketchum, 2002). In research trials with monterey pine (Pinus radiata), removing weed competition increased volumetric soil moisture 5% to 9%. The increase in available moisture increased midday needle water potential by up to 1.5 MPa (Sands and Nambiar, 1984). Foliar nutrition also has been shown to improve with better weed control. Woods et al. (1992) found that foliar nitrogen (N) levels increased consistently with increasing width of weed free area around monterey pine trees.
Despite the importance of weed control for intensive silviculture, few herbicides are developed and registered for these applications (Woeste et al., 2005). Flumioxazin is an N-phenylphthalimide herbicide and inhibits the protoporphyrinogen oxidase [PPO (EC 126.96.36.199)] enzyme (Yoshida et al., 1991). Michigan registration of this herbicide was approved before the 2004 growing season for nursery crops and Christmas trees at use rates of 0.25 to 0.38 lb/acre (Valent U.S.A. Corp., 2004). Flumioxazin has been evaluated for use in many other crops, including cotton (Gossypium hirsutum), peanut (Arachis hypogaea), potato (Solanum tuberosum), soybean (Glycine max), sugarcane (Saccharum spp.), and in orchards, vineyards, certain ornamentals, and noncropland (Askew et al., 2002; Burke et al., 2002; Cranmer et al., 2000; Dunst et al., 2004; Richardson and Zandstra, 2006; Taylor-Lovell et al., 2002; Valent U.S.A. Corp., 2005; Wilson et al., 2002; Zandstra and Particka, 2004). In previous research, preemergence (PRE) applications of flumioxazin at 0.031 to 0.094 lb/acre controlled common chickweed (Stellaria media), common lambsquarters (Chenopodium album), common ragweed, hairy nightshade (Solanum sarrachoides), entireleaf morningglory (Ipomoea hederacea var. integriuscula), ivyleaf morningglory (I. hederacea), pitted morningglory (I. lacunosa), tall morningglory (I. purpurea), palmer amaranth (Amaranthus palmeri), redroot pigweed (A. retroflexus), smooth pigweed (A. hybridus), sicklepod (Senna obtusifolia), common mallow (Malva neglecta), prickly sida (Sida spinosa), and velvetleaf (Abutilon theophrast) (Askew et al., 2002; Price et al., 2002; Taylor-Lovell et al., 2002; Wilson et al., 2002).
The three most widely used PRE herbicides in Michigan Christmas trees in 2003 were simazine, atrazine, and hexazinone (USDA, 2004). The effectiveness of these products is decreasing because of the emergence of resistant weed biotypes (Gower et al., 2004; Kuhns and Harpster, 2003). Therefore, additional PRE broadleaf herbicides are needed to maintain economical production systems and increase options for resistance management. Research studies were conducted to evaluate flumioxazin and other PRE herbicides for residual weed control in Christmas trees.
Askew, S.D., Wilcut, J.W. & Cranmer, J.R. 2002 Cotton (Gossypium hirsutum) and weed response to flumioxazin applied preplant and postemergence directed Weed Technol. 16 184 190
Burke, I.C., Askew, S.D. & Wilcut, J.W. 2002 Flumioxazin systems for weed management in North Carolina peanut (Arachis hypogaea) Weed Technol. 16 184 190
Cranmer, J.R., Altom, J.V., Braun, J.C. & Pawlak, J.A. 2000 Valor herbicide: A new herbicide for weed control in cotton, peanuts, soybeans, and sugarcane Proc. Southern Weed Sci. Soc. 53 158 (Abstr.).
Cristy, E.J. 1986 Effect of root competition and shading on growth of suppressed western hemlock (Tsuga heterophylla) Plant Ecol. 65 21 28
Dunst, R.M., Bates, T.R. & Kirfman, G.W. 2004 Effectiveness of flumioxazin for weed control in vineyards Proc. Northeastern Weed Sci. Soc. 58 142 (Abstr.).
Gower, S.A., Richardson, R.J. & Zandstra, B.H. 2004 Survey of herbicide resistant weeds in Michigan Christmas tree plantations Proc. North Central Weed Sci. Soc. 59 106 (Abstr.).
Klewano, D. & Matthews, V. 2005 Nursery and Christmas trees 2004–2005 1 June 2008 <http://www.nass.usda.gov/Statistics_by_State/Michigan/Publications/Michigan_Rotational_Surveys/mi_nurs05/christmas.PDF>.
Kuhns, L.J. & Harpster, T.L. 2003 Weed control provided by fall or spring applications of flumioxazin in Christmas trees Proc. Northeastern Weed Sci. Soc. 57 50 55
Lyytikäinen-Saarenmaa, P. 1999 The responses of scots pine, Pinus sylvestris, to natural and artificial defoliation stress Ecol. Appl. 9 469 474
Niekamp, J.W., Johnson, W.G. & Smeda, R.J. 1999 Broadleaf weed control with sulfentrazone and flumioxazin in no-tillage soybean (Glycine max) Weed Technol. 13 233 238
Price, A.J., Wilcut, J.W. & Cranmer, J.R. 2002 Flumioxazin preplant burndown weed management in strip-tillage cotton (Gossypium hirsutum) planted into wheat (Triticum aestivum) Weed Technol. 16 762 767
Richardson, R.J. & Zandstra, B.H. 2005 Hoary alyssum (Berteroa incana) control in fraser fir (Abies fraseri) Christmas trees Weed Sci. Soc. Amer. 45 33 (Abstr.).
Richardson, R.J. & Zandstra, B.H. 2006 Evaluation of flumioxazin and other herbicides for weed control in gladiolus Weed Technol. 20 394 398
Rose, R. & Ketchum, J.S. 2002 Interaction of vegetation control and fertilization on conifer species across the Pacific Northwest Can. J. For. Res. 32 136 152
Scott, G.H., Askew, S.D. & Wilcut, J.W. 2001 Economic evaluation of diclosulam and flumioxazin systems in peanut (Arachis hypogaea) Weed Technol. 15 360 364
Straw, N.A. & Green, G. 2001 Interactions between green spruce aphid (Elatobium abietinum (Walker)) and norway and sitka spruce under high and low nutrient conditions Agr. For. Entomol. 3 263 274
Taylor-Lovell, S., Wax, L.M. & Bollero, G. 2002 Preemergence flumioxazin and pendimethalin and postemergence herbicide systems for soybean (Glycine max) Weed Technol. 16 502 511
U.S. Department of Agriculture 2004 Agricultural chemical usage: 2003 Nursery and floriculture survey 30 Apr. 2008 <http://usda.mannlib.cornell.edu/reports/nassr/other/pcu-bb/agcn0904.pdf>.
U.S. Department of Agriculture 2007 Nursery crops: 2006 Summary 1 June 2008 <http://usda.mannlib.cornell.edu/usda/current/NursProd/NursProd-09-26-2007.pdf>.
Will, R.E. 2005 The effects of annual fertilization and complete competition control on fascicle morphology of different aged loblolly pine stands Trees (Berl.) 19 129 136
Wilson, D.E., Nissen, S.J. & Thompson, A. 2002 Potato (Solanum tuberosum) variety and weed response to sulfentrazone and flumioxazin Weed Technol. 16 567 574
Woeste, K.E., Seifert, J.R. & Selig, M.F. 2005 Evaluation of four herbicides and tillage for weed control on third year growth of tree seedlings Weed Sci. 53 331 336
Woods, P.V., Nambiar, E.K.S. & Smethurst, P. 1992 Effect of annual weeds and water and nitrogen availability to Pinus radiata trees in a young plantation For. Ecol. Mgt. 48 145 163
Yoshida, R., Sakaki, M., Sato, R., Haga, T., Nagano, E., Oshio, H. & Kamoshita, K. 1991 S-53482: A new N-phenyl phthalimide herbicide. Proc. Brighton Crop Protection Conf Weeds 1 69 75
Zandstra, B.H. & Ott, E.J. 2007 New formulations of pendimethalin and oxyfluorfen improve onion crop safety in tank mixes with flumioxazin Weed Sci. Soc. Amer. 47 214 (Abstr.).
Zandstra, B.H. & Particka, M.G. 2004 New herbicides for weed control in fruit trees Proc. North Central Weed Sci. Soc. 59 161 (Abstr.).