Disease pressure is a great phrase that most experienced course managers can instantly identify with but is quite tricky to explain – but I’ll have a go using 2018 v 2019.
Without question disease pressure during last Autumn was significantly higher than this Autumn. But what are the drivers behind fuzz acceleration? What were the differences between Autumn 2018 and 2019?
In its simplest form the answer is Moisture. Although it’s a little more complex than that, where did that moisture come from?
Dew Formation or Rainfall?
Although we traditionally associate Microdochium (Fuz) development with damper conditions, periods of high and prolonged rainfall tend to lead to lower disease pressure.
Microdochium really enjoys having stagnant moisture on the leaf that gives it time to move through it to find it’s next infection point where it can invade and attack the plant. Extended periods of heavy dew is a perfect environment for the pathogen to spread.
The above video is time lapsed over a 24 hour period in a very humid environment and you can see the fragile mycelium structures growing. Heavy periods of prolonged rainfall will physically distrupt this process and hinder the pathogen’s ability to move into other plants.
The above two charts show the difference between Autumn (yellow box) 2018 and 2019.
2019 is dominated by the Blue lines which represents rainfall – compared to a very red line dominant 2018. The red lines represent the days when Dew would have been in place for more than 10 hours (this is worked out by using dew points – check this blog out for more info).
Whilst both 2018 and 2019 both had high levels of leaf moisture – in 2018 that was mainly dew but 2019 rain.