It’s Ascochyta Time

Tony Koski, Extension Turf Specialist

Ascochyta in a Greeley lawn. The green spot
just next to the sidewalk is where a sprinkler
head is located; others are about 30 feet away
in both directions. Pressure problem?

The calls and emails are coming in about beautiful lawns turning ugly almost overnight. This seems to be pretty much an annual happening throughout Colorado in the late spring. When we have wet, cool springs and move into hot, dry summer conditions without much of a transition, massive outbreaks of brown, dead-looking turf can be seen everywhere.

More Ascochyta! The green spot next to the
sidewalk is where there is an irrigation head.
Another head is about 36 feet away, just left of
the tree at the top of this photo. What could
be causing such poor irrigation coverage?
See the next photo for the answer!

Ascochyta leaf blight, though rarely a fatal turf disease, is a darn ugly one. When this disease occurs, it can almost always be connected with an irrigation problem of some sort – not watering at all (“It just rained last week. You mean I have to begin watering already?”), not applying enough water, and – most often – poor coverage due to some sort of irrigation malfunction. Broken heads, heads that have sunken, heads that are blocked by overgrown plants on the borders of lawns, poor system design (which results in poor coverage), pressure problems that prevent head-to-head coverage - and the list goes on. Just because you see water coming out of your heads when you turn your system on in the spring doesn’t mean all is well with your irrigation system.

The large green spot next
to the tree and utility box
suggests a large system
leak - enough to cause a
severe pressure problem for
the rest of the heads on that
station - so green spots
around every head on that
station.

When you experience this disease in your lawn, believe me – IT’S BECAUSE OF WATER (shouting was intentional :) ). Overseeding, fertilizing, applying fungicides, etc. WON’T fix the problem. You won’t get turf recovery until the irrigation problem is solved – or unless you get a number of well-timed, soaking rains. But the problem will show up again when the rain stops.

Once you have corrected the cause of the Ascochyta outbreak (corrected the irrigation problem), avoid overcompensating with water in an attempt to hasten recovery. Irrigate to maintain a moist soil, but not soggy, saturated turf. Too much water will delay recovery and perhaps lead to other disease problems. Depending on severity and turf species, recovery can take 2-4 weeks.

One more thing: the fungus causing this disease isn’t spread by mowers or other turf care equipment – so your lawn care professional did not bring this disease to your lawn.

Read more about Ascochyta in some of our past blogs:

http://csuhort.blogspot.com/2015/07/what-pain-in-ascochyta.html

http://csuhort.blogspot.com/2013/06/is-that-your-ascochyta-or-mine.html