grub damage

[dlhein]

I'm starting to get some yellow spots in an area of my lawn that otherwise looks beautiful -- thick, green. I don't think it can be a lack of iron, because put down Millorganite two weeks ago. I put down Sevin at the same time because we had some Japanese beetles (not many), but I now know I didn't put down the right amount. I put 2.5 lbs. per 1000 sq. ft. instead of the prescribed 9 lbs. per 1000 sq. ft. My concern is it's the start of grub damage. But from what I've been reading, it's too early for it to be that. Can anybody tell me if it could be from grubs in the middle of July? We didn't have a noticeable grub problem last year. Thank you.

[rainbowgardener]

Seems likely... If you put down the Sevin (nasty stuff!) because you were seeing Japanese beetles, then you know you have grubs, because that's the larval stage of the Japanese beetle.

Here's a link to a nice little article on their life cycle (complete with gross pictures): http://www.nysipm.cornell.edu/publications/grubs/default.asp?metatags_Action=Find('PID','5')

Damage they did last fall can just be showing up now.

In the meantime, your problem is likely worse now BECAUSE you put down the Sevin, which kills everything, including the predators like beneficial insects and nematodes, which were keeping your grub population in check.

Here's an article about that process and ways to control grubs by working with nature: http://en.allexperts.com/q/Lawns-725/Grubs-Clay-Soil-1.htm

Anyway if you are going to insist on poisoning your environment, where did you get 9 lbs per 1000 sq ft? That sounds HUGE. Here's some info about that: http://www.aces.edu/pubs/docs/A/ANR-0500-B/VOL2-2008/home_lawns_insect.pdf

[dlhein]

Mod,

Thank you for your detailed response and for the great links! Since I first posted that on the 21st, I've still been researching like crazy (Internet and phone) and I'm convinced my problem isn't grubs. I'm pretty sure it's too much rain. The areas with the most yellow spots are where the new grass is. Cornell Cooperative Extension's thought.....that the grass isn't as well established, roots not as deep, as the old lawn (haven't needed to go deep with all the rain), and then when it gets hot at all, it turns yellow or brown, esp. near hardscape areas. Plus not much sun to green up.

I saw so few Japanese Beetles this year and have never had a grub problem. I think I was just being paranoid.

As far as the 9 lbs. per square inch, it says it on the bag under the section for grubs. Fortunately, I didn't see it at first and only put it down at the 2 lb. rate. Whew! But with all my research I learned all about milky spore and that's what my plan is the first sign of grubs. Still learning and I so appreciate the advice!

[NW CT gardener]

When you're thinking of using Sevin, Grub-ex, and the multitude of other nasty chemicals to kill grubs - STOP - they are temporary, toxic, and will result in the death of beneficial earth dwellers (earthworms), are connected to Colony Collapse in Bees - toxic in groundwater run-off and home wells - Will cost a fortune to re-establish your lawn with yet more chemicals - pamper your earthworms, they'll do much of the work for you - put down some Milky Spore and beneficial nematodes - these are long term grub predators - expensive first year, multiply by themselves over time - add lime - grubs hate it -