The Q&A Archives: lawn grubs

Question: I'm in the Chicago area and my lawn looks sickly. One of my first thoughts was grub infestation. I used a shovel and dug 5 widely distributed 6-8 inch diameter holes in my lawn to check for grubs. I found 2 grubs in 1 hole, 1 grub in each of 3 holes, and no grubs in 1 hole. Is that I high enough grub population to warrent using a grubicide on my lawn? If yes, should I apply it now or wait for spring? If no, what would you suggest? Thanks, Chuck

Answer: Sampling for grubs is a good first step in determining the cause of your lawn problem. Random holes throughout the lawn will give you a general idea of how large the grub population might be. What you've found indicates a very low population; less than six grubs per square foot can usually be masked by water and fertilizers. Populations between 10 and 15 per square foot can cause significant turf damage in September and October. Of course, populations occasionally reach 40 to 60 grubs per square foot and these levels can cause significant damage.

So, instead of treating for grubs, I'd suggest feeding your lawn now and then in spring putting it on a regular watering, mowing and feeding schedule. If you already do routine maintenance on your lawn and it's still looking bad, it may have a build up of thatch or the soil might be overly compacted. These can be remedied by de-thatching and/or aerating the lawn and then overseeding. I'd wait until spring to do these things. For right now, use a winterizing fertilizer (one that is low in nitrogen but high in phosphorus and potassium). These two elements will encourage strong, healthy root and stem growth over the winter months which will help your lawn green up faster in the spring.

Best wishes with your lawn!

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