A dimensional lumber model was designed to test the sensitivity of the particle capture immunoassay (PCI) compared to traditional methods of culturing and microscopic examination for detection of brown-rot fungi. Southern yellow pine 2 x 4's (5.1x10.2 cm²), and 86.4 cm in length, were inoculated on one end with the brown-rot fungus, Postia placenta, and tested over the full length of the board for evidence of brown-rot decay after 21 days incubation. Hyphal growth was visible 12.7-15.2 cm from the site of inoculation, but fungal antigens were detected over the entire length of the test unit. The particle capture immunoassay uses antibody coated latex particles to capture extracellular hemicellulases which are secreted from brown-rot fungi. Movement of these fungal enzymes ahead of the visible hyphal growth may account for the ability of the PCI to detect the presence of brown-rot fungi at zero percent wood weight loss, although additional tests with isolated extracellular enzymes did not support a simple diffusion theory. Positive PCI results for brown-rot were detected 53.3 cm ahead of the visible hyphal growth. Culturing detected fungi only in the region of visible hyphae (17.8 cm from the site of inoculation), and microscopic examination subjectively gave positive results in the same region. The PCI is superior to culturing and microscopic examination for the early detection of brown-rot decay.

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