What is killing my St. Augustine grass? (UPDATE 9/26)

Probably webworms, heard they’re bad this year.

Looks to be sod webworm damage - you can see insect related blade damage (chewed leaf blades) in the last photo - not sure if something else may be in play as well. There are a couple threads on the first page of this board, probably another 2 or 3 threads in the first few pages. It is a major issues for many homeowners right now.

ETA: LINK

I have the same issue and part of it I know is sod webworms, but OP has the entire leaf dead also which I also have is that sod webworms also? It seems more like a fungus to me? My webworms damage is healing it’s growing back. But I have spots where it looks like my dog pee spots where the whole leaf is there but dead which I don’t think is webworms? Then there are other spots with the gray leaf spot that’s obvious and webworms where you can see the leaf is eaten.

My dang new sod has been fricked with everything this year.

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Looks to be sod webworm damage - you can see insect related blade damage (chewed leaf blades) in the last photo

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Thanks. I had some Spectracide Triazicide in the garage and put that down. I'm hoping it makes a difference.

The white moths, are they related I am guessing or is that something else.

Yes those are the adults (they don’t eat grass blades) that lay the eggs that develop into worms/caterpillars that cause the damage to the grass. Chemical control needs to target the “worms” not the adult moths.

Here are excerpts from a article from from an LSU AgCenter horticultural extension specialist (sorry I can’t post a link as it’s not posted on the internet)

“ USING SOAPY WATER
To find the caterpillars in the lawn, you have to look carefully through the green grass at the edge of a brown area. But, just looking carefully through the grass during the day may not turn up any webworms. It helps to make up a gallon or two of soapy solution (one ounce dishwashing liquid – lemon scented is best – per gallon of water) and pour it in the green grass right at the edge of the brown area. This should cause the tropical sod webworms to start moving, making them easier to spot.

CONTROL OPTIONS FOR TROPICAL SOD WEBWORM
To make sure the eggs have hatched (the insecticides are not effective on the eggs), you need to wait for the first signs of damage to appear before treatment (don’t treat the moths). When you see damage appearing in the lawn, treat as soon as possible. A variety of insecticides are effective. Follow label directions carefully.

Spinosad (an organic insecticide) – Monterey Organic Garden Insect Spray; Ferti-lome Borer, Bagworm, Tent Caterpillar and Leafminer Spray; Green Light Spinosad Lawn and Garden Spray; Dow Spinosad Home and Garden, Success Naturalyte, Bonide Captain Jack’s Deadbug Brew and other brands.

Bifenthrin (a pyrethroid) – Talstar; Bifenthrin, Ortho Home Defense and other brands.

Acephate (systemic) – Acephate; Orthene and other brands.

Carbaryl – Carbaryl, Sevin

WHAT CAN YOU DO ABOUT TURF RECOVERY
There is some good news in this. The caterpillars only eat the blades of grass. They do not damage the runners, roots or growing points. As a result, as bad as the lawn looks recovery is generally reliable.

When damage occurs in mid to late summer, fertilizing with a lawn fertilizer containing nitrogen should help the sod webworm damaged turfgrass recover. In most cases, turf grows back with plenty of moisture and fertilizer.

However, weak St. Augustinegrass may not recover from tropical sod webworm damage, and newly emerging seeded bermudagrasses can be seriously damaged.

The later in the season the damage happens, the less recovery you will see in the lawn before winter dormancy. Lawns damaged in October, for instance, will not recover as fast as lawns damaged in July or August.

Sod webworm outbreaks do not tend to occur every year. Many years may go by between outbreaks. So, this is not something you should expect on an annual basis. But, when large numbers of small moths show up in lawns and shrubbery in mid to late summer, now you know what is going on and what to do.

Prepared by:
Dan Gill
LSU AgCenter
Consumer Horticulture Specialist

With information provided by:
Dr. Ron Strahan
LSU AgCenter
Turf Specialist”

Is webworm what causes the dead grass in the OP also? I know they eat the leaves and you can see some chewed on leaves. But I have patches of dead whole leaves that aren’t chewed on. Maybe they just chewed them off at the base?

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I'll say chinch bugs.

This is good information. I wonder why bifenthrin (Talstar) isn't mentioned for the worm control? I see it used a lot here, but haven't seen much success albeit temporary for moths. I looked at the product I apply, Anderson's Duocide, and it does contain Carbaryl as it's primary ingredient with a smaller % of bifenthrin. It practically instakills the larvae.