I don't know the answer to your timing question. And timing is everything when it comes to using beneficial nematodes.

You might see if your extension service people can answer you. Or, call one of the internet locations that sell them. There are several. They won't sell them to you unless it's an appropriate time in your part of the country. Cold temps can do them in.

You also need to know that beneficial nematode application doesn't work in all parts of the country, nor in all kinds of soils. I'd 'think' that your extension office might be a good place to begin your research, though these biological control sources can offer terrific advice and information.

Be sure to let us know what you find out!

Here is a link that might be useful: Just a litte more background

What I have seen over many years is that grubs are a bigger problem in lawns that are fed with synthetic fertilizers that have very little organic matter in the soil. Spending money on Beneficial Nematodes is usually not very effective unless steps are taken to correct the soil related problems and usually when the soil is made into a good, healthy soil the problems that did exist pretty much self correct.

Not true, kimmsr. The beetle species that lay their eggs in turf grass are more than happy to do so in 'good, healthy' soils, rich with organic matter. As a matter of fact, the larvae FEED on organic matter when very young, not starting on the plant roots until they mature somewhat.

What IS true, is a turf stand that has been managed properly (proper mowing, fertilizing, watering, soil care, etc.) can withstand some grub damage and can recuperate quickly. Whether the fertilizer is synthetic or not has nothing to do with it.