My experience is that most people who have weed problems actually have poor grass problems. Anuual weeds are oportunistic, they'll grow where nothing is already growing. They tend to produce millions of tiny seeds that spread everywhere. Small seeds tend to only germinate in the presence of sunlight. The best long term plan against them is to establish a thick turf. My suggestion is to kill or pull the stiltgrass ASAP and then put down some grass seed this fall.

kidhorn, we mowed the large patches of stiltgrass to the ground 10 days ago. Most of them were getting ready to flower so I think the mowing left them not enough energy to regrow this fall. I also hand dug up smaller spots of them then I overseeded with a turf type fescue lawn seeds. So far the new grass is growing nicely (1.5 inches tall) and the stiltgrass is browning and dying.

However the question remains as what preemergent you will recommend for next year. My neighbors all have stiltgrass in their lawn and I am down wind and down rain run off from many of them.

I'm not sure I want to get in the middle of this, but Corn Gluten Meal (CGM) will stop seeds from growing of probably 90 percent of plant species, whether they're annual or perennial weeds, or annual or perennial grasses. Siduron, for example, can't do that. Siduron (brand name Tupersan) is only effective against warm-season grassy weeds, like crabgrass.

So for siduron to work, your target has to meet 3 criteria:

(1) Be a warm-season weed, not a cool-season weed (so siduron isn't useful against the weed called Annual Bluegrass).

(2) Be a grassy weed, not a Broadleaf weed--so forget about henbit, which is neither a Grassy weed nor a warm-season weed.

AND

(3) Be an annual weed, not a perennial weed.

Corn Gluten Meal doesn't care. It will affect all the weed seeds and grass seeds above, perennial or annual. Yes, CGM won't hurt already established weeds, but it can hurt the dropped seeds of those established weeds if its time for the seeds to germinate.

By the way, you shouldn't use siduron if you have Zoysia or bermuda, because siduron will hurt those grasses. So siduron / Tupersan is really just useful during spring seeding of cool-season grasses like Kentucky bluegrass, fescue, and rye. As our friendly Iowa State professor notes:

"[Siduron] has the unique ability to inhibit the establishment of warm-season weeds without damaging the germination of cool-season grasses."

Professor Nick wrote that in 2007. Of course, today, there's something called Tenacity, but Tenacity is very new.

I'd follow kidhorn's advice. It seems very sound to me.

Don't know if it's effective against Japanese Stiltgrass, but here's some good info from the government:

First documented in Tennessee around 1919, stiltgrass may have accidentally escaped as a result of its use as a packing material for porcelain.

Individual plants may produce 100 to 1,000 seeds that fall close to the parent plant from both self-fertilizing and cross-fertilizing flowers.

Stiltgrass seed remains viable in the soil for five or more years and germinates readily.

[Here's the good stuff - how to get rid of it]

Stiltgrass is a shallow-rooted annual that can be pulled by hand throughout the growing season, especially when the soil is moist and entire plants with roots can be removed. Pulling is easier and probably more effective in mid-to-late summer when the plants are much taller and more branched. At this stage, entire plants can be easily removed by grabbing the basal portion of a plant and pulling firmly. In short time, a fair amount of stiltgrass can be pulled and piled up to dehydrate on site. If plants are already in the fruiting stage, they should be bagged and disposed of offsite to prevent dispersal of seed. Also, try to avoid pulling native grasses like Virginia cutgrass (Leersia virginia) that often grow intermingled with stiltgrass and may be difficult to distinguish from it. Because hand pulling plants disturbs the soil and may expose stiltgrass seed from previous seasons, late season pulling will avoid the likelihood of seed germination. Hand pulling of plants will need to repeated and continued for many seasons until the seed bank is exhausted.

Stiltgrass can be mowed in late summer (i.e., August through September) when the plants are flowering but preferably before seed is produced. This can be done using a lawn mower or "Weed Whacker" type machine or a scythe. Because stiltgrass is primarily an annual plant, cutting late in the season before the plants would die back naturally avoids the possibility of regrowth. Recent information suggests that stiltgrass plants that are cut early in the summer respond by regrowing and flowering soon after cutting, much earlier than they would normally flower. This is another reason to consider cutting in late summer to fall rather than during the early summer months.

The info comes from the National Park Service web site at

http://www.nps.gov/plants/alien/fact/mivi1.htm

It's a pretty good page about Stiltgrass. You may have already seen it.

My problem is next year when the seeds from my neighbors' yard come into ours. I used corn gluten meal for last year and this year and they didn't seem to do anything for the stiltgrass. I am pretty sure we applied them correctly although only one application per year. Should I have applied it more often?