2010 White pine (pinus strobus) needle cast event Brendan Fagan, Forestry, Natural Resources, Abstract White pines were losing needles at an alarming rate in 2010 for unknown reasons. This project compared three white pine trees (Pinus strobus) from Newmarket with three white pine trees from Durham. The project found no fungi, chlorotic mottling and only 1 incident of tip necrosis in first year needles. All six trees had scarce second year (2012) needles and no third-year needles (2011). Healthy white pines should retain to third year needles. Spectral analysis of current year needles did not reveal any evidence of stress; all indices describe the six trees as healthy. Further analysis of cores from each show possible false growth rings in the 2010 and 2011 wood, suggesting a past stress event. Method Tools included: pole pruner, tree corer, dissecting microscope, dissecting microscope with attached camera, the Visible Infrared Intelligent Spectrophotometer (VIRIS). A Forest Watch protocol for Needle Damage Assessment was used to measure needle length and to search for signs of tip necrosis or chlorotic mottling on 30 current year needles from each location. Tree core samples of each were taken at breast height, glued to wooden trays with the grain structure perpendicular to the bottom of the tray. The convex of each core was then sanded flat. Rings were examined and counted with microscopes. Segments of the 2010 and 2011 rings were marked and photographed with camera attachment. Durham needles were collected on November 7, Newmarket on November 10 and processed with the VIRIS on November 14. Needle samples from each tree were scanned three times and data was charted in Excel. Literature Cited Rock, B.N., and M. Carlson Forest Watch Data Book : Research with 2011 Needles. Forest Watch, University of New Hampshire, Durham, NH. Hypothesis White pines in the Seacoast area will show evidence of stress from the 2010 event. The pines in Newmarket and Durham are far enough apart to validate test results. Fig. 4 Needle lengths (mm) Durham Newmarket tree #1tree #2tree #3tree #1tree #2tree # Only 1 occurrence of needle tip necrosis; Newmarket tree #1, 85mm length Fig. 1 Location of white pine collection sites Image source: NR 782, 2013, Class materials, Fall 2013 All VIRIS indices describe good tree health of current year needles False growth rings might indicate water stress, atmospheric pollution, fungal pathogenic disease, or any stress related to photosynthesis. Some stress apparently occurred in 2010 and continued in Introduction Studies of needle cast have revealed links to atmospheric and pathogenic causes. Research has shown that atmospheric pollution is a disease factor causing chlorotic mottling, needle tip necrosis and water stress. Pathogenic fungi that historically had little effect on the foliage now impact needle retention (Rock & Carlson, 2013). Six trees in two neighboring towns were tested to examine for evidence of stress correlating to the year 2010 in the tree rings. Needle samples from each were collected for a damage assessment on the current year growth. Fungi present? Pines in the Seacoast area show evidence of stress from 2010? Pines in Newmarket and Durham validate test results by difference of results? Evidence of atmospheric pollution i.e.; mottling or tip necrosis? Chlorotic mottle and tip necrosis are key indicators of ozone damage. Discussion A drop in second and third year needles can result in a reduction of photosynthates, meaning the tree is not making as much sugar Image source: NR 782, 2013, Class materials, Fall Fig. 2 Reflectance data for first-year needles Fig. 3A Wood core sample from Newmarket, tree #2 Fig. 3B Wood core sample from Newmarket, tree #3 Fig. 3C Wood core sample from Durham, tree #2 for wood. Tip necrosis on one of the needles may indicate that the loss of 2011 and most 2012 needles might have been caused by ozone. Growth rings present evidence of past stress event but the six trees appear to have recovered from the 2010 – 2011 stressor. Without evidence of fungal presence it was ruled out as a potential cause. For future tests I would examine trees at further distances watching for fungi, symptoms of ozone damage, and chronograph rates of needle loss. Tools used were sufficient regarding hypothesis but I would utilize the scanning electronic microscope for views of pathogens and growth rings. Conclusion Neither hypothesis is rejected. The VIRIS scans indicate that the trees are not currently under stress. Possible false growth rings seen in 2010 and 2011 annual rings in the core samples may be evidence of stress. No fungal pathogens were discovered. Ozone is the likely stressor.