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WSU Christmas Tree Research Newsletter |
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Fall 2001, Volume 2, Number 2
Stump removal and the treatment of stumps at harvest are the two methods that are commonly recommended to control this disease in forest situations. At this time, the only registered stump treatment that is available in Washington and Oregon is a borax product, 'Sporax', marketed by Wilbur Ellis. This product is applied to freshly cut stumps to prevent them from becoming infected by the fungus spores. Although test data are not yet available from Christmas tree plantations, treatment of stumps should help limit both the spread of disease within diseased fields and also its introduction into healthy fields that are adjacent to diseased fields or timber stands. Sporax should be applied to the stump as soon as possible after cutting the tree, preferably within a couple of hours. If applied later than this, the fungus may have already infected the stump. Sporax is a granular material and should be applied using a container with a shaker top, such as a jar with nail holes punched in the lid. In the case of choose and cut fields, it may also be helpful to spray the surface of the stump with some sort of dye so that it is possible to identify which stumps have already been treated. MAKE SURE TO FOLLOW THE LABEL WHEN USING ANY PESTICIDE. Swiss Needle Cast Swiss needle cast (SNC) is the most important disease on Douglas-fir Christmas trees in the Pacific Northwest. It is also causing extensive damage to Douglas-fir timber stands along the Oregon and Washington coast. During the past few years, the Swiss Needle Cast Cooperative (SNCC) has supported work at WSU Puyallup to examine the effectiveness of two reduced-risk fungicides, two formulations of chlorothalonil, and two sulfur products in protecting needles from SNC infection. Cooperative studies with Dr. Jeff Stone at Oregon State University were also done to compare the results from traditional, springtime fruiting body-based disease assessments from these trials to DNA-based, PCR molecular data from samples collected in February. Results indicate that:
Rhabdocline Needle Cast Using a planting of intermountain forms of Douglas-fir at WSU Puyallup, cooperative studies with Dr. Gerry Adams at Michigan State University have shown that it is possible to reliably detect, identify, and quantify levels of Rhabdocline infection in symptomless foliage of Douglas-fir using DNA-based PCR molecular probes. These studies have also shown that intermountain Douglas-fir from the Clearwater National Forest in Idaho have excellent resistance to Rhabdocline needle cast (see: http://www.plantmanagementnetwork.org/sub/php/research/rhabdocline/. You must be a subscriber to access this document.). Coastline June Beetle Some growers are experiencing the loss of seedlings due to the Coastline June Beetle that feeds on the roots of these trees. The large, cream-colored grub of this insect has a dark brown head. This insect has a 3-year overlapping life cycle and the grub can be found grasping onto roots of young trees that show signs of stress. Because of the damage being caused by this pest, a test is being established to find an effective control. Initial applications will be in the spring of 2002. Root Aphids and Cooley Spruce Gall Adelgids This past summer, plots were established to confirm the effectiveness of Aphistar treatments in controlling root aphids on various size noble fir trees. A plot has also been established to look at the effects of Aphistar treatments in preventing symptom development on newly planted trees. Studies were also conducted to determine the effectiveness of acetamiprid for control of Cooley spruce gall adelgid on Douglas-fir Christmas trees. Impact of Interior Needle Blight (INB) and Root Aphids on the Production of High Quality Noble Fir Christmas Trees The final data will be collected from a 4-year-long trial to examine the impact of INB and root aphids on the growth and quality of noble fir trees at two test sites in western Washington. After three years, the data indicated that applications of Aphistar have had no effect on tree growth and quality. Applications of Daconil Weather Stik significantly reduced the damage caused by INB and improved the quality of trees compared to the unsprayed checks or trees that were sprayed with only Aphistar. POSTHARVEST HIGHLIGHTS Danish Nordmann Fir Project - A 3-year-long project at the Danish Forest and Landscape Research Institute to identify sources of Nordmann fir with superior needle retention was completed during early 2001. The USDA and the Danish Christmas Tree Growers Association provided the support for this project. Working with geneticist Dr. Ulrik Nielsen, we have used a detached branch technique to identify clones and provenances of Nordmann fir having superior needle retention and have also shown that needle retention is a highly heritable trait. Seed from these Danish trees and other sources of Nordmann and Turkish fir from their natural range are being grown in British Columbia for a series of trials to examine the suitability of this material for the production of high quality trees in the PNW. Water-Holding Capacity of Christmas Tree Stands Because displaying trees in water is one of the most effective ways of maintaining tree quality and minimizing fire hazards associated with the use of cut Christmas trees, it is important that retailers who sell stands and the consumers who purchase them pay particular attention to their design and water-holding capacity. The water-holding capacity of 22 stands was recently evaluated at WSU Puyallup. Only two of the 22 stands tested provided an adequate volume of water (1 qt/inch of stem diameter) for all the sizes of trees they were capable of holding. Three of the stands did not provide an adequate amount of water for even a 2" diameter tree. All but one of the stands would hold a 3" diameter tree, but less than half of these stands provided the minimum 3 quarts of water to such a tree. As the size of the tree increased, fewer stands provided the volume of water that a tree would be expected to use on a daily basis. A major problem with many of the stands relates to the design of their water-holding reservoirs. When a large diameter tree is placed in a stand that has a cylindrically-shaped reservoir, very little water can be held in the stand because of its displacement by the base of the tree. Another problem noted during these evaluations is that with some stands it would be very difficult to check the water because it is not possible to see the base of the tree. A full report of this work can be found in the October issue of the American Christmas Tree Journal (See below). Preservatives This past year, we conducted a series of tests involving Vita Christmas Tree and Wreath Preservative and Season's Greenings Christmas Tree Preservative. Tests with the Vita preservative were conducted to determine the effect of spray or dip applications of this material on the moisture retention and quality of noble and Balsam fir wreaths. Tests also were conducted to determine what effects spraying or adding Vita to the water in the stand had on the keepability of Douglas-fir, noble fir, Fraser fir, and Balsam fir Christmas trees. Results of these tests indicated that there was no benefit associated with the use of Vita. The tests with Season's Greenings Christmas Tree Preservative on noble fir, Douglas-fir, Fraser fir, and grand fir Christmas trees indicated that the use of this product had a detrimental effect on the moisture levels of displayed trees. Studies to be Conducted This Fall Three studies will be conducted this fall in our continuing effort to identify sources of trees with superior postharvest characteristics. These include:
Project leaders: Gary A Chastagner, Plant Pathologist John Stark, Environmental Toxicologist and Entomologist Art Antonelli, Extension Entomologist Visiting Scientist: Iben Thomsen, Danish Forest and Landscape Research Institute Support Personnel: Joe Hudak, Agricultural Research Technologist II Kathy Riley, Agricultural Research Technologist II Paul Kaufmann, Agricultural Research Technologist II |
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