Provided herein is a method of quantitating a fungus in a plant, plant product or agricultural product. Total nucleic acids are isolated from a sample of the plant or plant product, and an asymmetric PCR amplification reaction is performed using fluorescent labeled primer pairs to obtain fluorescent labeled fungal amplicons. These amplicons are hybridized to fungus specific nucleic acid probes that are attached on a microarray support. The microarray is imaged to detect fluorescent signals from the fluorescent labeled fungal amplicons. The fluorescent signal intensity is correlated to the quantity of fungus.