Sod webworms

Sod webworms may cause damage to closely mowed turfgrass early in the spring. Damage, similar to that depicted in the photos below, may be seen on golf tees and greens.

The overwintered caterpillars become active when the temperatures warm up in the spring and begin to tunnel and feed. They are mostly active at night, so they often elude inspection. The absence of an obvious insect makes the diagnosis difficult, - but look for patches of close-cropped turf as well as the tiny trails or tunnels in the thatch. Often the soil (and sand topdressing material) in these trails is bound together with silken material to create a cover or cap, hence the name “webworm”. Along with the damage, these tunnels help provide evidence of sod webworm activity. A soap flush is a sure method of verifying sod webworm presence.

To flush suspect areas, mix one full tablespoon of lemon scented Joy dishwashing liquid in two gallons of water and dispense the solution through a sprinkling can over 1 square meter of turf. It is best to mix the detergent into the proper amount of water by hand in order to minimize the formation of foam which can make it much more difficult to find emerging insects. Allow 10-15 minutes for the sod webworms to appear on the surface as it may take a while for the soapy water to penetrate the silk-lined tunnels these insects create.

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1158Gibb24iMac:Users:gibbs:Desktop:Sod webworm folder:IMG_20110511_095944.jpg

Healthy and vigorously growing turfgrass will often ‘outgrow’ damage from sod webworms. However, if the damage is unsightly and controls are warranted, use a pesticide that is labeled for sod webworms and apply at the recommended rates. Mach 2 and Conserve are both labeled for sod webworms as well as a host of conventional insecticides. Do not irrigate after application so that the insecticide stays on the blades and in the thatch where the webworms reside and feed.
The following photo, taken two days after treatment shows the resulting dead larva.

Tim Gibb, Turfgrass Entomologist
Doug Richmond, Turfgrass Entomologist
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Educational Opportunity:

Turf Field Day
Tuesday, July 19, 2011
Daniel Turf Center, West Lafayette, IN
Attendee Registration Form
Exhibitor Registration Form
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If you are interested in periodic assessments of turf disease threats in Indiana, then you should check out our TURFCAST website. The website offers daily risk assessments for certain diseases (dollar spot, brown patch, and Pythium blight) and weekly comments by me at "Turf Disease Watch" this is based on my observations at Purdue¹s Daniel Turf Center and out in the state. It also includes a chart of soil temperatures recorded here in West Lafayette, which I use to comment on the timing for fungicide applications for summer patch control.

You can access TURFCAST through our Purdue Turf website (, or simply Google "Purdue TURFCAST".

Rick Latin, Turfgrass Pathologist

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Flooding on turf

April was a wet month in Indiana with rainfall totaling 2-10 inches more than normal in April for areas of Indiana (see precipitation map below). Heavy rainfall can cause flooding stress on turf. Flooding reduces oxygen to the plants from the soil and could ultimately lead to plant death without oxygen. If water saturation is only around the roots in the soil while shoots (leaves) are exposed to air, the damage to turf is much less than when plants are submerged under water. In addition, soil erosion and deposition, debris, and the accumulation of toxic substances can also kill turf following flooding events.

Plant survival depends on several factors: turfgrass species, submergence depth and duration, and water temperatures. When submersion occurs simultaneously with high temperatures, plants can die quickly due to a lack of the energy production to sustain plant growth. Plant survival can be either through fast growth to above the water to obtain oxygen or slow growth to reduce carbohydrate consumption. For common turf species, creeping bentgrass and bermudagrass are most tolerant of flooding. Kentucky bluegrass and tall fescue are fairly tolerant. Annual bluegrass, perennial ryegrass, and red fescue are least tolerant.

Turf discoloration and yellowing is a common symptom of flooding stress due to loss of chlorophyll and nitrogen uptake. Once water has receded, a light fertilizer application will help grass recovery. Soil cultivation improves the physical condition of soil and increases oxygen concentration to the roots, which will benefit the regrowth of the turf. Walk-mowing with lightweight equipment in moist or saturated soils will help reduce soil structure damage compared to heavier ride-on equipment.

Yiwei Jiang, Turfgrass Physiologist

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