Detecting Heterobasidion irregulare in Minnesota and Assessment of Indigenous Fungi on Pines

Heterobasidion irregulare is one of the most problematic forest pathogens in northern hemisphere, but has only been found relatively recently north central United States. Discovered Wisconsin 1993, probably established sometime before that, it quickly spread throughout state. In November 2014, was southeastern Minnesota. Field surveys were then conducted Minnesota with focus southeast near initial discovery. To find additional infection sites, accompanying aerial imagery red pine (Pinus resinosa Aiton) stands that previously thinned. Samples collected from selected sites dead and dying trees as well samples stumps thinned stands. These processed first a nested polymerase chain reaction (PCR) protocol, which replaced by real-time PCR assay after its development. No tested positive for H. using these methods no cultures isolations obtained outside original area. Other indigenous fungi also identified. The majority wood decay Basidiomycota. A spore collection study field surveys. Automated rotary arm collectors used assayed an ITS TaqMan assay. Collectors placed strategically different areas control infected plantation this location had highest number spores trapped, 63,776 over week period. Spores detected at several Minnesota, total observed traps 413 All other locations sampled some except Itasca State Park located northwestern weekly deposition ranged 0 to 1.26 m−2 h−1. Low levels occurring indicate are present, they currently being amounts may not be sufficient colonization successful.