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Management Updates: Sep 9, 2016

What's in Your Backyard?
Sep 9, 2016

Sod webworms

I was mowing my lawn late yesterday afternoon, and was struck by the number of sod webworm adults that were flying aimlessly about, just above the turf canopy. This was by far the largest flight of webworms I have ever noticed in my yard, although I see them every September. Interestingly, Whitney Cranshaw (my counterpart at Colorado State University) had recently reported a similar outbreak in Colorado. He and I are in agreement that the heavy flight should be viewed more as a curiosity than a point of concern. Given the number of adults I saw flying, there must have been a considerable number of caterpillars feeding about two or three weeks ago, and yet I did not see any damage in my lawn that could be attributed to caterpillar feeding. (There was plenty of drought stress and dormant turf but no obvious damage from webworms.) So I do not believe the heavy moth flight warrants any action at this time. I will monitor carefully next spring to see whether there is an increase in caterpillar activity in April or May, but I doubt there will be.

Turfgrass ants

I also saw very large numbers of turfgrass ants emerging from mounds in my lawn. When I got out my camera with the macro-lens and looked closely, I could see that there was a line of adults bubbling to the top of the burrow and stumbling out into the air. All of the ants were winged. This was that annual "nuptial flight". In most cases the ants emerge within a very short period of time from a given colony (often within a 24 hour period) and mate. The males do not live long after mating, while the females shed their wings and burrow a foot or more into the soil. They will begin to produce a new colony the following spring.

Some of my colleagues have suggested treating turf areas during a nuptial flight, with the hope of eliminating the emerging queens, but I personally believe it makes more sense to wait until next spring and treat new mounds as soon as they become apparent, if treatment is deemed necessary. Remember that turfgrass  ants spend much of their time preying on eggs and tiny larvae of some grubs and caterpillars, among other things, and so could be considered beneficial insects. If only we could teach them to stop producing the disruptive mounds!!!
And note that turfgrass ant mounding activity is normally only a problem on short-mown turf like golf course fairways, tees, and edges of greens.  While some people occasionally express concern about turfgrass ant activity in home lawns, I urge those folks to consider the benefits of predatory ants. Because the height of cut on a lawn is so much higher, the mounding activity should be minimally disruptive. (European fire ants are a very different species and can cause very painful stings, but appear to be fairly sporadic in their distribution in southern New England.)

Grub update

I received grub samples from two very different settings this week, and they have confirmed what I was suspecting.

The first sample came from an unirrigated rough at a golf course near Amherst. There were very few grubs in the area, and the only ones we found were near a sprinkler head. The ground otherwise was powder-dry. The grubs were late first instars and early second instars. Another sample came from irrigated athletic fields in the 495 corridor just south of the Turnpike. The affected areas were very heavily infested - at least 15 to 20 grubs per square foot. More than half the grubs were already third instars, feeding very aggressively. So... if you are managing irrigated turf, check NOW to see whether grubs are active on your properties. You are running out of time to apply a curative treatment. The larger the grubs are, the harder they will be to control. If you are managing unirrigated turf, this is also a good time to monitor to see whether you have any small grubs present. They are resilient critters, and if we get a little relief and some rain, the potential is there for some outbreaks.

Submitted by: Dr. Pat Vittum