What can I do to rid my lawn of red thread fungus? Ask an expert

The gardening season is over, but you may still have questions. For answers, contact Ask an Expert, an online question-and-answer tool from Oregon State University’s Extension Service. OSU Extension faculty and master gardeners respond to inquiries within two business days, usually less. To ask a question, just go to the OSU Extension website, enter it and include the county where you live. Here are some questions asked by other gardeners. which one is yours

Q: Spots on my lawn are turning brown. Within these areas, individual leaves turn reddish and shrink. This situation has set in over the last few winters. This area is on the north side of our home and receives much less sun in the winter.

The lawn itself is well drained as we installed an artificial floor plus drainage tiles a few years ago. I would appreciate your input on what you think is causing this and how best to treat this condition. —Washington County

A: Your ryegrass lawn has a fungal disease aptly called “red thread.” It is a very common lawn disease in western Oregon and Washington. It is worse in humid, shaded conditions with low fertility (i.e. nitrogen), although it can still occur as late as June. Red thread is one of four very common wet weather fungal diseases, the others being Microdochium patch and two leaf spot diseases (brown rot and smelting).

In most cases (other than expulsion), these winter diseases do not kill the plants, but only affect the foliage. Lawns are recovering well as the weather gets drier and warmer.

The best way to treat these diseases judiciously without spraying fungicides (more on that later) is to apply fertilizer. Generally, two fertilizer applications in the fall (September and October) at 1 pound of nitrogen per 1,000 square feet per application will go a long way in minimizing these diseases. The only challenge is that two of these diseases get worse with higher fertility: Microdochium Patch and Fusing. So if you apply too much fertilizer (greater than 4 pounds of nitrogen per 1,000 square feet over four months in the sun) you can end up with melt damage (which can kill the lawn) or microdochium stains, which is generally the case don’t kill the lawn. You should also distinguish between the areas in the shade and the areas in the sun. Shaded areas should receive less fertilizer (1 less application).

Looking at your picture of the large lawn, it clearly looks like it has been under-fertilized. I can see nice patches of green where I suspect. Your dog or other animal has urinated on the lawn. I would apply ammonium sulfate or urea at 1 pound of nitrogen per 1,000 square feet. To apply 1 pound of nitrogen per 1,000 square feet, divide 1 by the decimal equivalent of the percentage of nitrogen on the bag (the first number). For example, ammonium sulfate is usually sold as 21-0-0 (sometimes as 20-0-0). So take 1/0.21 and you get 4.76. Therefore, to get 1 pound of nitrogen per 1,000 square feet, you need to apply 4.76 pounds of ammonium sulfate per 1,000 square feet.

With the cold weather we are having now, it may take some time for your lawn to start growing and turning green. It grows out of the red thread (i.e. the new leaves are not infected). Next, apply in May (Memorial Day), early July (4th of July), early September (Labor Day), and mid to late October (Halloween). Skip the last application in the shaded areas.

There are fungicides that can be applied to lawns to treat these fungal diseases, but I generally never recommend them because they need to be applied repeatedly (e.g. every two weeks). The time and expense is not worth it for most people. And in most cases, you can reduce disease by 95 percent with the right amount of nitrogen fertilizer.

In addition, fungicides must be sprayed to be effective. That means you need to be able to mix concentrated fungicides in a tank with agitation, calibrate a sprayer with a boom mounted with multiple nozzles of the right type, and go at a constant speed while maintaining a constant pressure maintained to apply the fungicide evenly at the correct rate. With a backpack sprayer this is almost impossible.

Remember this is a good place to start. You may need to adjust the schedule and/or prices based on what you see on the turf. If you stick to this schedule you will see a big improvement in quality and you should see a lot less disease. However, there will always be disease in the winter unless you choose to spray fungicide every two weeks.

Also, you don’t have to submit an application in January next year if you submit the two fall applications. Going forward, choose a fertilizer and stick with it for the sake of simplicity. Don’t get confused by “fall” vs. “spring” or a descriptive word like “Wintergarde” as this is all marketing and has no meaning whatsoever. – Brian McDonald, OSU Extension Turf Specialist

Fall is the time to plant garlic cloves to produce crops like these by next early summer. Archive photo.

Q: I received a pack of garlic and it is sprouting. can i plant it now I’m in Dundee. If so, should I plant them in the ground or in the greenhouse. — County Yamhill

A: Yes, you can plant garlic in the ground now. The heads will most likely be small, but it will still be garlic. To get big heads, garlic is usually planted in September/October. Here is some information from OSU Growing/cultivating/harvesting garlic in Oregon.

onion planting season

October is the best month of the year to plant spring flowering bulbs like these tulips. Archive photo.

Q: Can we still plant tulip, daffodil and crocus bulbs here in Springfield? – Lane County

A: You can, but you may get disappointing results. The ideal planting time is autumn to very early winter. They will grow well but may bloom sparsely. In any case, they will be ready to play in a year. — Pat Patterson, OSU Extension’s retired gardener

Q: I am an experienced home grower of northern highbush blueberries and I think I have pruning on these downpats. However, the different growth habit of my ‘Pink Lemonade’ blueberries surprised me a bit. Aside from general shaping and a bit of thinning, are there any tips I need to know about pruning this strain? Mine are about eight years old and productive, but I rarely get new canes popping up (unfortunately same with my northern Highbush canes). —Washington County

ONE: Here are instructions for growing blueberries. ‘Pink Lemonade’ is a rabbit eye cultivar and grows smaller than northern highbush blueberries. To encourage new growth, follow the pruning and fertilizing instructions in the publication. When pruning, remove some of the oldest (largest, gray) canes at the base to let in more light and encourage new cane development. Add fertilizer according to directions to get about 1 foot of new growth at the tops of established canes. These steps will also help your northern highbush strains. – Weston Miller, OSU Extension gardener

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