Dear Angie: I've noticed some dead spots in my grass. How can I tell if the cause is some kind of pest, improper fertilizing or something else? In spring, I noticed a vole trail and what looked like a rodent hole. — Matthew V., St. Paul, Minn.
Answer: I wish I could offer a quick and easy answer, but there are many potential sources of your grass problem.
Lawn care pros who've earned top ratings from Angie's List members list these possible causes of dead spots in a lawn:
■ Insufficient or excess water
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■ Weather that's unusually hot or cool
■ Fungal disease
■ Over-fertilizing with a salt-based or all-chemical product
■ Ineffective mowing practices.
■ Acidic pet urine
They say voles are unlikely culprits because they tend to chew the tops of grass in spring but aren't likely to damage root systems.
My main advice is to have a few reputable lawn service providers examine your yard. Many will offer free inspections and assessments. Those that charge for a service call might deduct the fee from the total job cost if hired.
You could try to diagnose the problem yourself, if you're willing to research turf types, insects, weeds, fungus, pesticides and more. Be aware that if you treat for the wrong cause, you could further damage your lawn.
Here are additional expert details about some possible sources of lawn spots:
Fungal diseases: These generally leave lesions or blight on grass blades. Early in the morning you might be able to see fungus, which can look like small tufts of cotton on grass blades. Lawn disease is typically triggered by humidity and excessive moisture.
Insects: Bugs should be visible at close range. Experts note that most cool-season turf types — the kind you most likely have in Minnesota — face few insects that create noticeable damage.
Improper fertilizing: You'd probably notice granules in the areas where grass died. Generally, pros recommend avoiding cheaper store-bought, all-chemical fertilizer.
Poor mowing practices: Alternate mowing patterns by mowing in different directions each time. And follow the one-third rule: Never cut grass by more than one-third of its height at any one time. Also, set your mower's blade height so grass is at least 3 inches tall.
Acidic pet urine: If this is the cause, you'll probably notice round yellow spots in your yard. Your vet might have products you can give your pet to reduce the problem, or you can apply lime a few times a month to neutralize the acid.
Before you hire a lawn care company, make sure you've gotten several estimates from services that are appropriately licensed, including for use of chemicals, as well as insured and bonded. Focus on getting quotes from companies that have a good online reputation. Get all details in writing, and make sure you fully understand the diagnosis and treatment plan before signing a contract.
Angie Hicks compiles the best advice from the most highly rated service pros on Angieslist.com to answer your questions. Ask Angie your question at firstname.lastname@example.org.
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