An Evaluation of Air Sampling Methods and Multiplexed Molecular Detection of Plasmopara viticola , Botrytis cinerea , and Erysiphe necator in Michigan

Airborne inoculum monitoring is becoming increasingly common as a disease monitoring and management tool. Approaches typically focus on monitoring a single pathogen rather than all pathogens of importance in a system. To increase efficiency, actively managed pathogens should be monitored simultaneously. It is also critical to examine the utility and positioning of different samplers for pathogens being monitored. The study objectives were to: optimize three qPCR assays into a single multiplex assay to detect Botrytis cinerea, Erysiphe necator, and Plasmopara viticola; evaluate the effect of sampler height on detection efficiency; and compare sampler performance among the rotating-arm, the SporeCam™ and Burkard. The qPCR multiplex assay was found to be sensitive to 10 fg of DNA for each of the three pathogens. During the sampling period of berry development to late veraison, the rotating-arm samplers successfully captured the pathogens at all heights (0.6, 1.4, and 1.8 m) and in- versus out-of-vineyard positions, with significant differences in collection only for B. cinerea. Detection of P. viticola was negatively correlated between the SporeCam™ and rotating-arm samplers (ρ = -0.48) but positively correlated between rotating-arms and Burkard (ρ = 0.53). Detection of B. cinerea was positively correlated between the SporeCam™ and rotating-arm samplers (ρ = 0.39). E. necator was never detected by the Burkard but was detected by rotating-arm samplers each season, which were positively correlated with the SporeCam™ (ρ = 0.38). These findings advance integrated airborne multi-pathogen inoculum detection in vineyards and highlight the need for refinement of sampling technologies for real-time disease management.