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fusarium Patch (Microdochium nivale)

This month we are looking at one of the diseases that is a major nationwide winter disease of lawns, sports pitches and greens.

Fusarium Patch/Snow Mould is a fungus that loves cold and wet conditions.

It develops best at temperatures between 0 and 10 ºC and especially when there is a film of water on the leaves.

It starts to infect by living and breeding on the thatch layer in your lawn, only infecting the leaves and then crowns of the grass later as it grow in strength.

It prefers certain grass species including the important Browntop bent (Agrostis Castellana), Smooth stalked meadow grass (Poa Pratensis) and Perrenial ryegrass (Lolium Perenne). It also devastates the problem grass weed, Annual meadow grass (Poa Annua). This is a real problem because old swards are absolutely full of Annual meadow grass and can therefore get very serious attacks of Fusarium Patch.

The first visible sign of infection is a slight lightening of the grass in patches. This is followed by the appearance of small brown patches which grow to develop the larger patches as shown in the picture. The centre of these patches is distinctly pink in colour. If you look closely at the dead leaves, you would describe them as “wet” looking or “slimy”. The fungus mycelium (strands) can be clearly seen. The outside of the patch is generally darker than the inside.

If you have identified that you have an infection of Fusarium Patch then there is little you can do now to control it for this season. The best cure apart from resorting to fungicides is to remove dew and dampness from your lawn using a tool called a “Switch”. As the photo shows it is a long rod which breaks the surface tension of moisture drops so letting them fall to the base of the sward. The leaves are then able to dry better. This process however requires to be done regularly and is only for the keen lawn keepers out there.

There is no effective fungicide available for you to use as an amateur so if you have a severe infection you will need to call out a lawn treatment company.

If the patches are left to develop the lawn will take months to recover and so you will be into late spring before things start to improve.

Control of Fusarium Patch is best done preventatively, as are most of the problems we talk about. Healthy, not too lush grass, very low thatch levels and a well aerated and drained rootzone is the key.

As we keep saying, the autumn or spring renovation treatment is the core of your disease control strategy:

Deep scarification, hollow tining and applications of high quality top dressing containing compost as opposed to loam or peat.

Why do we keep advising the use of compost based topdressing?

Well the composting process produces a material rich in nutrients and beneficial fungi and bacteria. When this is laid on the lawn it allows the grass to grow healthier and is able to fight off infections much better.

For those of you who are interested, there has been a very good experiment carried out to prove this, you can find it if you follow this link. Be warned it is heavy reading, but go to the results and discussion pages for the key information.

The use of compost to control foliar diseases of lawn grass

In summary, this is the key control strategy that you should follow:

1. Avoid applying high nitrogen fertilisers to your lawn in late summer/autumn
2. Improve the overall drainage of your lawn
3. Aerate regularly, especially if the lawn is used heavily
4. Box off the grass clippings
5. Improve the air circulation over and around your lawn. Thin out shrubs and bushes and remove any overhanging branches. Although large trees are beautiful, if you remove them it is like doubling the size of your garden.
6. Carry out the renovation procedures mentioned above, scarification, hollow coring and top dressing
7. Mow regularly and with a mower with sharp blades
8. Switch off dew and moisture
9. Reduce the pH of your soil (applications of Iron sulphate will help)
10. Use compost based top dressing
11. Use Seaweed based growth promoters as the cytokynins have been seen to help fight off this disease

Here are some other tasks you should be doing this month:

• Keep mowing your lawn, the unusually warm autumn has meant the grass has kept growing. Choose a dry but not frosty day to do it
• Get your mower blades sharpened and set. Never skimp on this, if it is required, get reels and bottom blades ground or replaced
• Always protect your grass if you are carrying out heavy barrow work across your lawn. Use boards or anything you can find (even old carpet will help!!)
• Keep up the spiking of any particularly wet or shady patches

Above all at this time of year, have very merry Christmas and a happy new year. Put your feet up, drink mulled wine and re-charge your batteries for the next growing season.