Early Detection and Spread of Tomato Powdery Mildew (TPM) in Commercial Greenhouses

Technologies are constantly evolving to detect plant pathogens before visible symptoms occur on the crop. The technology used in this project is spore trapping and it is the only technique that can detect the presence of airborne fungal pathogens before they infect the plant. It has been successfully used in the field to guide timing of fungicide application or to reduce the use of expensive fungicide during low disease pressures (Mahaffee, 2014). However, this technology isn’t widely used in commercial greenhouses because it relies heavily on air currents which are weaker in a greenhouse than a field. In this project we have explored the capabilities of this technology to perform in a commercial tomato greenhouse to detect Tomato Powdery Mildew (TPM)(Pseudoidium neolycopersici). We have used a combination of molecular tools (qPCR, LAMP), spore traps and spatial modelling to determine the efficacy of spore traps in commercial greenhouses and study the spread of P. neolycopersici. We found that: 1. TPM was more likely to spread along than between rows 2. It was more likely to be introduced through the main pathways used by personnel and machinery 3. Sampling height to position a spore trap was relatively unimportant (little difference between low, mid and above-canopy locations) compared to proximity to known hotspots of the disease.