Grass Browning

grass with brown spots
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Q:

I recently moved into a home with a sprinkler system, and have been watering since June; but now I have a large portion of the grass that has brown spots. Is this because of the soil? My watering? Or bugs? Or none of the above?

- Jackson County
A:

Oregon Lawns in the summer in general… The majority of lawns in Oregon are established with perennial ryegrass. However, due to the environmental conditions, moderate winters with continuous rainfall, annual bluegrass quickly invades. The problem with this is that annual bluegrass is very susceptible to heat and drought stress. You may be regularly irrigating these areas, but the annual bluegrass just cannot take the summer heat. Annual bluegrass is also very susceptible to a handful of fungal disease at this time. Fungicides may prevent the disease from progressing for 14-21 days after application, but because the annual bluegrass is in a weakened state the plant cannot recover from the initial injury, and therefore the symptoms will often persist throughout the remaining summer months.

Localized dry spot… These issues are only multiplied by adjacent driveways, roads and sidewalks, which are substantially hotter than the soil. We call this localized dry spot - the edges of the lawn are drying faster than the rest of the area. Variability is soil type across your lawn is also responsible for this effect. Unfortunately the only solution is hand watering the localized dry spots with a garden hose, potentially daily during the summer heat. This will provide the weakened turf with some much needed heat and localized dry spot relief. Learn more about localized dry spot and treatment option (PDF).

Watering practices… I agree that 14 minutes of irrigation applied every other day is adequate for perennial ryegrass or fescue, but this may not be enough for annual bluegrass. Therefore, if you want to nurse the annual bluegrass through the summer up your irrigation or consider hand watering, but if you would rather keep the annual bluegrass thin out the annual bluegrass keep the irrigation the way it is. Also consider hand watering the areas prone to localized dry spot, i.e. areas adjacent to sidewalks and driveways.

Greenbugs… The green bugs you are seeing are likely aphids (which are also known as greenbugs) or leafhoppers, both are weak turfgrass pests meaning that while they do feed on grass, they rarely reach populations capable of producing damage. View more control options for aphids and leafhoppers.

Alec Kowalewski
Turfgrass Specialist
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