September 11, 2007 in Home

Resistant turfs fend off necrotic ring

The Spokesman-Review
 
Joe Barrentine photo

A necrotic ring grows out from the middle, forming a ring as grass and weeds emerge from the center.
(Full-size photo)

Is there a way to control necrotic ring (not fairy ring) in my yard short of digging it out and starting over?

Kathy Arbuckle,

Nine Mile Falls

Necrotic ring spot is a fairly new disease to the Inland Northwest, but it has quickly become one of the most destructive. The disease is caused by the Leptospaeria korrae fungus. The disease first appears as small circular dead areas which enlarge and move outward as the disease progresses. Both roots and shoots are killed. The centers of these circles may be filled in by weeds and resistant grasses leaving a doughnut effect. Actively expanding patches have reddish-brown borders. The symptoms may appear at any time, but are most common in late spring and from mid-August through fall. The disease is very difficult to correctly identify without sending samples to a laboratory.

The disease appears most often in plantings of bluegrass or mixes of bluegrass and fine fescues, especially on lawns that were sodded in the last five to ten years. It seems to be worse in sandy soils that are low in organic matter. These soils generally have poor fertility and lack beneficial microorganisms that help keep the disease in check. Either too much or too little water can cause adverse conditions which make symptoms worse.

The best and most long lasting control method is to overplant or replant affected areas with perennial ryegrass and turf-type tall fescues that are quite resistant to the disease and have many of the same qualities of bluegrass. A special necrotic ring resistant seed mix is available at Northwest Seed. There are chemical controls available, but they are expensive and must be applied annually with mixed results.

Looking for a cover crop

What do I use for a cover crop for a small garden - barley?

Sherolyn Hurlbert,

 Suncrest

Cover crops are crops that are planted in the early fall in an empty garden and allowed to remain through the winter. In the spring, they are tilled under before spring crops are planted. Planting a cover crop on even a small garden has some definite benefits. First, the crop will add organic material – a lot of organic matter – to the soil without you doing anything more than planting it and tilling it under. Second, a cover crop can push out the weeds that pop up both this fall and next spring when it may be too wet to work the soil. Finally, cover crops protect the soil from erosion by winter rains and wind. Barley, oats and annual rye are good small grain choices for our colder climate while Austrian peas are a good nitrogen-fixing legume. If we get a cold winter with no snow cover, the crop will likely be killed but the dead stalks can still provide weed control and add their organic matter to the soil when they are turned under. Plant them as early as you can in the fall to give them a chance to get started. In the spring, it may be better to mow before you till.


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