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How to Manage Pests
UC Pest Management Guidelines
Turfgrass
Sod Webworms
(Reviewed 6/03,
updated 6/03)
In this Guideline:
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DESCRIPTION OF THE PESTS
Adult sod webworms, called lawn
moths, are typical snout moths: they have sensory appendages called labial
palps that extend in front of the head. The moth holds its wings close to and
over its body at rest, giving it a slender appearance. When disturbed, the moth
makes a short flight close to the grass. At night, these moths drop their eggs
indiscriminately on to turf. The creamy larvae have a distinctive double row of
brown or black spots down their backs, located at the base of long bristles.
The Lucerne moth larva is somewhat larger than the other sod webworm larvae.
During the day larvae reside in silk-lined burrows, writhing when disturbed. At
night they emerge to feed.
SUSCEPTIBLE SPECIES
Bluegrasses and bentgrasses often suffer the most damage, while perennial
ryegrasses and turf-type tall fescues infected with endophytes (symbiotic
fungi) and warm-season turfgrasses are more resistant.
DAMAGE
First instar sod webworm larvae are leaf skeletonizers. Later instars notch or
cut off leaf blades and pull them into the burrow. Heavily infested turf (more
than 100/sq yd) quickly appears moth eaten, with irregular patches of brown
grass or bare areas. Significant damage can occur on drought-affected bluegrass
and on bentgrass green and tee areas. Lucerne moths are primarily a problem
where clover and dichondra are mixed with turfgrass.
MANAGEMENT
When sod webworms are present, dethatching the turfgrass may help. Monitor to
determine if treatment is needed. Treatment choices include parasitic nematodes
and Bacillus thuringiensis (B.t.).
Biological Control
Natural enemies in California include a parasitic tachinid fly and two
parasitic braconid wasps, along with
earwig,
rove beetle,
robber fly,
paper wasp, ant, and vertebrate
predators. The extensive soil or thatch contact of sod webworms makes
Steinernema carpocapsae nematodes a valuable control measure.
Bacillus thuringiensis subsp. kurstaki (Bt), a microbial
insecticide, can be used but it breaks down rapidly in sunlight, washes readily
off leaves, and is ineffective against late instar larvae.
Cultural Control
Thatch removal can assist in removing sod webworm habitat, although larvae do
not require a thatch layer to be present in very high numbers. Control of
clover and dichondra may help minimize damage.
Monitoring and Treatment Decisions
Monitor for these pests from June to early October. Consider treating only when
a drench test (see section on MONITORING under
GENERAL INFORMATION) indicates there are more than 5
larvae per square yard on stressed greens or 15 larvae per square yard in other
situations. If Bt is used, apply it when there are predominantly early instar
larvae. Other materials should be effective on both small and large larvae.
Mow and irrigate the site before applying insecticide and do not mow or irrigate
the turfgrass for at least 24 hours after treatment unless nematodes were
applied, in which case apply a post-treatment irrigation. When Bt is applied,
do not irrigate for 2 days after treatment.
| Common name |
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| (trade name) |
Amount/1000 sq ft**
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Many of these products are available for use by licensed applicators only and cannot be used by home gardeners.
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| A. |
ACEPHATE |
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(Orthene Turf, Tree, and |
0.5-1 oz |
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Ornamental Spray) |
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COMMENTS: For use on golf courses and sod farms only.
Odorous. |
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| B. |
AZADIRACHTIN |
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(Ornazin, etc.) |
Label rates |
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COMMENTS: Can be used on both warm and cool-season grasses. |
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| C. |
BACILLUS THURINGIENSIS ssp. KURSTAKI |
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(various products) |
Label rates |
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COMMENTS: Slow acting stomach poison; only effective on
early instar larvae. Breaks down rapidly in sunlight and washes readily
off leaves. |
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| D. |
CARBARYL* |
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(Chipco Sevin) 80WSP |
Label rates |
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| E. |
CHLORPYRIFOS |
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(Dursban Pro) |
1.5 fl oz |
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(Dursban) 50W WSP* |
0.75 oz |
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COMMENTS: For use in turfgrass production and on golf
courses only. This product is highly toxic to birds and aquatic invertebrates.
State and federal agencies have determined that waterways have been
impaired by the use of this material. Do not apply in such a manner
that it will get into storm water drains. |
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| F. |
CYFLUTHRIN* |
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(Tempo) 20WP |
0.176 oz (5 grams) |
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| G |
DELTAMETHRIN |
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(DeltaGard T & O) 5SC |
0.2-0.4 fl oz |
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COMMENTS: Not for use on sod farms or in commercial seed
production. Apply as a broadcast spray in a minimum of 2 gal water/1,000
sq ft. Delay irrigation or mowing for 24 hours after application. |
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| H. |
PERMETHRIN |
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(Astro, Permethrin Pro) |
0.4-0.8 fl oz |
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COMMENTS: Apply using sufficient water to provide adequate
coverage. |
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| I. |
SPINOSAD |
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(Conserve SC) |
0.25 fl oz |
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COMMENTS: Apply late afternoon or early evening to maximize
control. Delay watering or mowing of treated area for 12-24 hours
after treatment. |
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| J. |
STEINERNEMA CARPOCAPSAE |
25 million |
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COMMENTS: Store nematodes properly before use as directed.
Apply to warm, moist, but not soggy soil. Several irrigations may
be needed during 2 weeks after application to keep soil moist. Apply
during the coolest time of day in hot areas. |
| ** |
Apply in 2-5 gal water/1000 sq ft |
| * |
Permit required from county agricultural commissioner for purchase or use. |
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UC IPM Pest Management Guidelines: Turfgrass
UC ANR Publication 3365-T
Insects and Mites
H. S. Costa, Entomology, UC Riverside
R. S. Cowles, Entomology, Connecticut Agricultural Experiment Station, Windsor, CT
M. A. Harivandi, UC Cooperative Extension, Alameda Co.
J. Hartin, UC Cooperative Extension, San Bernardino Co.
H. K. Kaya, Nematology, UC Davis
Acknowledgment for contributions to the insect and mite section:
K. Kido, Entomology, UC Riverside
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