Selection of Large Surviving Sassafras from Throughout the SE with Potential Resistance to Laurel Wilt Disease

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Description

Laurel wilt disease is caused by the introduced insect vector, Xyleborus glabratus, and its fungal symbiont, Raffaelea lauricola, and is a threat to species in the Lauraceae plant family. The disease has killed over 300 million redbay, Persea borbonia, is moving north, and is presently having a significant impact on sassafras, Sassafras albidum, in areas without redbay. As with other diseases, natural resistance to this disease was identified by surveying severely diseased stands, identifying large surviving redbay trees, and screening them for resistance. We propose to take a similar approach to Hughes (2013) and Koch et al. (2015) for identifying glingeringh or putatively resistant sassafras and propagate them for future screening to identify resistant individuals. Semi-permanent plots have been established and locations have been identified where laurel wilt has occurred in areas with sassafras over the last 15 years. (Cameron et al. 2015; Fraedrich et al. 2015; personal communications, state and federal forest health personnel and researchers). While the majority of the previous research has focused on redbay, some studies in AL, GA, SC, NC, LA, TX, and AR have included monitoring of sassafras mortality (Cameron et al. 2015, Mayfield et al. 2018). Plots will be established at locations where laurel wilt has previous occurred in sassafras to document the current level of host mortality along with vector abundance. Redbay ambrosia beetles will be monitored using funnel traps baited with alpha-copaene lures during an 8-week period in summer or fall. Recently, the known range of the disease made a large jump to the north to include several counties along the KY/TN border, Figure 1, and initial sassafras monitoring plots have been established in this region as of August 2019 (Mayfield et al 2018). This region is in the upper 75th percentile for the number of live sassafras trees . 12.7cm DBH (Randolph 2017) and represents an opportunity to identify potential resistance because of the high density of large sassafras. Additional plots will be established in the new KY/TN infestation following guidelines from previous studies (Hughes 2013, Cameron et al. 2015, Fraedrich et al. 2008, Mayfield et al. 2018). Sassafras trees . 10 cm DBH will be considered putatively resistant to laurel wilt disease when mortality of all stems . 10 cm DBH in the monitoring plots is determined to be high and the RAB vector is present. This determination will be made after year 1 data collection and in consultation with FHP and managers. We believe that there is a high probability for large surviving trees in such areas to have some resistance to the wilt. The high mortality stands will be surveyed, and large surviving putatively resistant trees will be identified, and propagated for future disease resistance evaluations.
StatusFinished
Effective start/end date7/22/209/30/22

Funding

  • Forest Service: $13,864.00

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