Samples were collected and sent in for lab diagnostics (Madison Forest Health Lab) to confirm the presence of oak wilt, since two-lined chestnut borer can be a problem in the study areas. Only pockets with lab-confirmed oak wilt present were used in this study. At each site, a rough determination was made in the field to determine soil texture was appropriate for the study, but soil was also collected and subsequently analyzed for percent sand, silt, and clay. Information regarding understory species and regeneration was also collected at each site.
All symptomatic or infected trees were marked near the base to ensure trees could be identified if harvested. DBH and Lat/Long was recorded for each infected tree (IT). A basal area sweep was performed, with a 10-factor prism, at each IT. The number of “in” trees was recorded, specifying species. The root grafting model developed by Bruhn, Pickens, and Stanfield (1991) was used to determine which trees in the red oak group were likely grafted with infected trees (IT); these trees were considered treatment trees (TT). Root grafting distances were predicted using the sandy soils model for all sites independent of the actual soil texture starting in 2016 due to field and lab soil type discrepancies in 2015. Calculations were done using a 95% confidence interval. All ITs and TTs were stem-mapped and marked with paint in the field. White oaks were stem-mapped, but were not marked or treated.
Each tree (ITs and TTs) was doubled girdled, with the girdles being 6” apart and 3” deep. Girdles were done low on the trees, but forked trees received a double girdle on each stem that was below breast height. A second person followed with an herbicide treatment. The herbicide mix was approximately 12oz of solution (25% Element, 75% diesel) per tree. Herbicide was applied to both cuts with a backpack sprayer.
There were also two types of control sites. The first type (C1) included oak wilt pockets with no treatment, only measurement and observation. The second type (C2) required measuring and girdling only, followed by yearly observations.