Compost tea against disease on golf greens: what our field trial shows

Compost tea kept up well with the fungicides in our field trial on golf greens. On the most affected green it even had less disease in August. And the bentgrass became denser.

The trial

Lorenz Rieger ran the trial in 2020 for his master’s thesis at ZHAW Wädenswil, using our brewing system and our compost. The site was Golfclub Heidiland in Bad Ragaz at 511 m above sea level. Three greens, 22 weeks, from May to early November. The greenkeepers managed the greens as usual, only the treatments differed.

Rieger brewed the compost tea in the EdaLife V60: 1.8 litres of EdaBiom compost and 153 g of nutrients in 60 litres of water, aerated for 24 hours. The tea was applied every two weeks from 5 June, with the normal sprayer. Beforehand he tested several recipes on bentgrass in the ZHAW greenhouse. The photo above shows this preliminary trial.

Three times, in May, August and November, he estimated how much area was affected by disease and how many infection spots there were. According to the greenkeepers, anthracnose was the main disease of the season.

What came out

Over the whole season, the diseased area share with fungicides was 1.7 %. With compost tea it was 2.4 % at full and 3.6 % at half fertilisation. Untreated it was 4.4 %, with half fertilisation alone 4.6 %. Compost tea is thus close to the fungicides, and the difference is not statistically confirmed. For infection spots it is the same picture: 1.4 with fungicides, 1.6 and 1.7 with compost tea, but 2.3 and 2.4 untreated.

It gets interesting where the pressure was highest. On green 2 in August, a tenth of the fungicide area was affected. On the compost tea areas it was 5.8 % and 9.2 %. So fungicides are no absolute protection. This shows up precisely when disease pressure is high. On top of that, pathogens are increasingly developing resistance to active ingredients.

At moderate pressure on greens 5 and 8, the fungicides were better. They can do that. The compost tea was still not far behind.

The visible effect

In the greenhouse, the bentgrass emerged better with living compost tea than with sterilised. Leaf mass was lowest with fungicide. With compost tea, the grass therefore formed more leaf mass.

In the field, the bentgrass on the compost tea areas increased all season. On the fungicide areas it was the only one to decrease. You can see it on the green: the sward becomes denser, and the denser the bentgrass, the fewer infection spots. Bentgrass is less susceptible to anthracnose than annual meadow-grass, which made up about 20 % of the area.

On top of that comes what we see on the areas: diseased spots close up faster again with compost tea. We did not measure this individually. But it fits the numbers. In November the disease was almost gone everywhere, on average only 0.3 % still, and the bentgrass kept gaining on the compost tea areas.

The leaf sap also showed a difference. In a sample from green 2 in early November, phosphorus, silicon and iron were higher on the compost tea area than on the fungicide area.

Why this works

Compost tea brings living microorganisms onto the sward. They occupy space and food that pathogens would otherwise get, and some act directly against them. Rieger also suspects signalling substances that strengthen the plant itself. Then there are the roots: he points to studies showing that compost tea promotes root length on golf greens. Deeper roots reduce drought stress, and less stressed grass gets less sick.

The mycorrhiza benefits too. In his greenhouse trial the roots were colonised much more strongly with compost tea, and least with fungicide. More in the post Compost tea and mycorrhiza.

In my opinion this is the core difference: fungicides hit the pathogen. Compost tea strengthens the sward that has to withstand it.

What it costs

Rieger calculated the material costs for fertiliser and plant protection, using 2020 prices and 15 applications per season. Compost tea instead of fungicides, with full fertilisation: 14.2 % lower costs. Compost tea with half fertilisation: a good half lower than the conventional variant. Labour and equipment are not included. The sprayer needed no modification.

What you take from this

Test it on a partial area, with an untreated control next to it, and record the disease over the season. This was one season on one golf course, and your green may react differently. You do not have to stop using fungicides for this. Rieger considers it conceivable to run both side by side during the changeover when pressure is acute. In dry spells he recommends mowing less often and raising the cutting height.

How to make and test the tea is explained in the post How to check the quality of your compost tea. You will find our brewing systems in the shop. If you plan a trial on your green, we help you set it up in the advisory service.

You can read the full thesis at ZHAW.

Frequently asked questions about compost tea against disease on golf greens

Does compost tea work against disease on golf greens?

In the field trial, compost tea kept up well with the fungicides. Over the whole season, the diseased area share was 1.7 % with fungicides, 2.4 % with compost tea (full fertilisation) and 3.6 % (half fertilisation). Untreated it was 4.4 %. The difference to the fungicides is not statistically confirmed.

How did compost tea perform under high disease pressure?

On green 2 in August, a tenth of the fungicide area was affected. On the compost tea areas it was 5.8 % and 9.2 %. So fungicides are no absolute protection, especially when pressure is high.

How did the field trial work?

Lorenz Rieger ran it in 2020 for his master’s thesis at ZHAW Wädenswil, at Golfclub Heidiland in Bad Ragaz at 511 m above sea level. Three greens, 22 weeks, from May to early November. The compost tea was applied every two weeks from 5 June, with the normal sprayer.

How much cheaper is compost tea than fungicides?

Rieger calculated the material costs for fertiliser and plant protection, using 2020 prices and 15 applications per season. Compost tea instead of fungicides with full fertilisation: 14.2 % lower costs. With half fertilisation, a good half lower. Labour and equipment are not included.

What happens to the bentgrass?

On the compost tea areas the bentgrass increased all season, on the fungicide areas it was the only one to decrease. The denser the bentgrass, the fewer infection spots. Bentgrass is less susceptible to anthracnose than annual meadow-grass, which made up about 20 % of the area.

Last updated: November 2026. Author: EDAPRO GmbH, Ruswil, Switzerland. Sources: master’s thesis Rieger 2021 (ZHAW Wädenswil), EDAPRO trials, leaf sap analyses and field experience.