JOBNAME: horts 41#5 2006 PAGE: 1 OUTPUT: July 12 03:13:56 2006 tsp/horts/118440/01501 HORTSCIENCE 41(5):1347–1350. 2006. (usually February), trees are coppiced nearly to soil level. Multiple adventitious buds emerge from the remaining stub in early Foliar Chlorosis in Field-Grown spring, from which one is selected and trained up a stake to develop a single leader whip Red Maples with light branching. Trees are dug and sold both at the end of year 1 and some are kept James Altland and grown for a third year (year 2) into larger Department of Horticulture, Oregon State University, North Willamette trees with more branching. These trees are Research and Extension Center, 15210 NE Miley Rd., Aurora, OR 97002 generally grown in rows that are 1.2 to 1.5 m apart and spaced 0.3 m within the row. Additional index words. Acer rubrum, ÔFranksredÕ, manganese, soil pH The objective of this research was to Abstract. Franksred red maple (Acer rubrum ÔFranksredÕ) trees were sampled from identify the cause of chlorosis in franksred nursery fields in 2003 and 2004 to determine the cause of a common foliar chlorosis. Plots red maple trees throughout year 1 and 2 of in 21 and 39 different nurseries were identified in 2003 and 2004, respectively. A single production, and to develop minimum and plot from each nursery was sampled in June of each year, whereas two to four plots per maximum values for soil and tissue nutrient nursery were sampled in September. Each plot consisted of 20 consecutive trees in parameters that would lead to high-quality a single row. From each plot, a foliar tissue sample was analyzed for the complete range red maple trees. of essential nutrients. Plant height, stem diameter, leaf chlorophyll content, and a sub- jective plant quality rating were also recorded. From each plot, a soil sample was Materials and Methods collected and analyzed for pH, EC, organic matter, and a range of essential nutrients. The foliar chlorosis was determined to be incited by manganese (Mn) deficiency. Tissue Mn 2003. On 12 June 2003, plots were de- was highly correlated with soil pH. Chlorotic plants were smaller with less stem diameter lineated in fields with franksred red maple than nonchlorotic plants. Sufficiency ranges for tissue and soil tests were determined and (Acer rubrum) in 21 nurseries throughout the are provided for red maple nursery production. north Willamette Valley in Oregon. Soil types for each field varied but could be generalized as silt loam soils with little or no slope. Nurseries were selected based on Field-grown red maple (Acer rubrum L.) Oregon are often ineffective (personal obser- their willingness to participate. All fields often develops foliar chlorosis during mid to vation). Smiley et al. (1985) documented Mn contained trees that were planted in 2002 late summer. Although this problem is par- and nitrogen (N) deficiency in urban red and were in year 1 of production at the time of ticularly common in the Pacific Northwest, it maples throughout the Great Lakes region. sampling. Each plot consisted of 20 consec- has also been observed in nursery production He attributed low Mn levels in urban red utive trees within a single row (Ellis, 1975). in other parts of the country (personal obser- maples to high soil pH and high organic A single plot was randomly selected in each vation). The condition can be characterized matter levels. Later, a related study by the field, avoiding only the borders of the field. initially as mild interveinal chlorosis in ex- same primary author reported that of all soil From each plot, two to three recently matured panding foliage. As symptoms intensify, factors measured, Mn deficiency in red maple leaves from each tree were pooled for a single entire leaves turn chlorotic accompanied with foliage was most highly correlated to soil pH. foliar tissue sample (Mills and Jones, 1996). interveinal necrosis. The problem has most Furthermore, among trees observed, most A soil sample was taken by collecting 12 often been associated with manganese (Mn) chlorotic maples were planted in soil with soil cores to a depth of 15 cm within the root deficiency. Manganese deficiency has been pH greater than 6.6 (Smiley et al., 1986). This zone (30 cm on either side of the tree row) documented in Mn-sensitive plants growing same study reported that foliar Mn could best of the 20 trees. Tissue and soil samples were in mildly acid to alkaline soils. Oregon soils be described as a function of soil pH and analyzed for nutrients listed in Tables 1 and in the nursery producing region (North Will- organic matter (n = 118, r2 = 0.49). Green- 2, respectively. Trees were individually mea- amette Valley) typically have low soil pH house research in sand culture by Boyce and sured for height, stem diameter, chlorophyll (<5.5). Nonetheless, many nursery growers Sydnor (1983) seems to contradict the land- content using a SPAD 502 Chlorophyll Meter and crop consultants have diagnosed Mn scape research by Smiley et al. (1986), (Minolta Camera Co., Ramsey, N.J.), and deficiency with foliar tissue tests. This con- because they showed franksred red maple plant quality on a scale from 1 to 10 where 1 dition in nursery production has never been new stem growth increased with increasing is a chlorotic tree of poor quality and 10 is thoroughly studied. pH from 5.5 to 7.5. However, oxidation of a vigorous tree with dark green foliar color. Chlorosis in red maples incited by Mn plant available Mn2+ to unavailable forms of Plant quality ratings were assigned solely by deficiency has been documented in urban Mn (III) and Mn (IV) is regulated primarily the author. landscapes. Teuscher (1956) first described by pH-dependent soil microorganisms (Rus- On 6 Sept., the same data were collected maple chlorosis in a trade publication. He sell, 1988). It is unlikely that Mn availability from the same plots. In addition, two or three indicated the chlorosis was incited by plant- is affected in sterile sand culture with no additional plots per nursery were surveyed so ing in heavy alkaline soils and generically organic matter the same way it is in bi- that a total of 71 plots were sampled. Many suggested that the condition could be reme- ologically active landscape soils. Overall, fields contained regions with chlorotic plants died by amending the soil with a conditioner the literature suggests that chlorosis symp- and other regions with nonchlorotic plants. and fertilizing with NH4SO4. Smith (1976) toms in red maples is primarily a pH-induced When possible, separate plots were estab- later stated that the problem in nursery and Mn deficiency, as observed by local nurser- lished in chlorotic and nonchlorotic regions landscape situations is likely Mn deficiency ies. However, the literature does not offer of the same field. and offered that foliar sprays of Mn(SO4)2 are specific guidelines for growing red maples in 2004. Similar methods were used effective for alleviating symptoms. Foliar a production environment, specifically pro- throughout 2004 with the following excep- sprays of Mn(SO4)2 and Mn chelate in duction of bare-root red maple whips (lightly tions. Thirty-nine plots were delineated on 22 branched trees 2 to 2.5 m tall). June 2004. Among those, 16 plots contained Production of bare-root red maple whips trees in year 1 of production, whereas the Received for publication 13 Mar. 2006. Accepted is uniform across the majority of nurseries in remaining 23 plots contained trees in year 2. for publication 21 Apr. 2006. I thank the Oregon Oregon. Small plants from either tissue cul- On 9 Sept., additional plots were again Association of Nurseries and the Oregon Depart- ture or rooted cuttings are planted and al- identified in each field so that a total of ment of Agriculture for funding this research. lowed to grow freely in year 0 (no pruning or 90 were sampled (32 year 1 and 58 year 2 E-mail [email protected]. training). In late winter just before year 1 trees). HORTSCIENCE VOL. 41(5) AUGUST 2006 1347 JOBNAME: horts 41#5 2006 PAGE: 2 OUTPUT: July 12 03:13:57 2006 tsp/horts/118440/01501 Table 1. Soil variables that explain foliar Mn in field-grown franksred red maple (Acer rubrum) tissue as relationship between plant quality ratings and determined by the stepwise selection process. foliar Mn (Fig. 1). Plant quality increased as Samples collected, June 2003 Samples collected, Sept. 2003 foliar Mn increased up to 110 ppm Mn and Parameter Partial r2 P value Parameter Partial r2 P value then decreased. More interesting was the pH 0.702 <.0001 pH 0.5181 <0.0001 relationship between plant quality ratings in Soil Mg 0.068 0.0284 Soil K 0.0804 0.0006 September and foliar Mn levels the preceding Soil B 0.043 0.0575 Bases 0.0464 0.0193 June (Fig. 2). September plant quality ratings Soil K 0.036 0.0597 Organic matter 0.0385 0.0403 increased as June foliar Mn levels increased Soil NH4 0.019 0.1494 Soil Zn 0.0303 0.0499 up to 200 ppm. Above 300 ppm foliar Mn, 2 Cumulative r 0.868 Soil Mg 0.0189 0.0692 plant quality began to decrease, indicating Soil Fe 0.0161 0.1012 a toxic relationship from excessive Mn. Soil S 0.0128 0.1267 Cumulative r2 0.7573 There was no relationship between June plant quality and June foliar Mn, primarily because Samples collected, June 2004 Samples collected, Sept. 2004 all trees appeared healthy with dark green pH 0.5643 <.0001 pH 0.2685 <0.0001 foliage despite variation in foliar Mn.