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How to Manage Pests
UC Pest Management Guidelines
Turfgrass
Masked Chafers (White Grubs)
Scientific Names: Cyclocephala hirta, C. pasadenae
(Reviewed 6/03,
updated 6/03)
In this Guideline:
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DESCRIPTION OF THE PESTS
Masked chafers are large C-shaped beetle larvae that feed on roots of turfgrass
plants. These grubs are white, up to 1 inch (2.5 cm) in length, with dark
translucent dorsal stripes, brown head capsules and legs, and a characteristic
pattern of bristles on the underside of the posterior end of the abdomen (the
raster). Masked chafers have a scattering of bristles, while less commonly
encountered May or June beetles have
two parallel rows of bristles. Masked chafers are larger than
black turfgrass ataenius grubs and have
a slight constriction at the forward portion of the abdomen, which helps
distinguish them. Adult beetles are
golden brown, hairy on the underside of the thorax, and have a darker brown
head. Cyclocephala hirta is common throughout California; C.
pasadenae is found in southern California. Both species complete one
generation per year overwintering as mature larvae, which form earthen cells in
soil where they pupate. Adult males are attracted to lights at night, mostly
from mid-June through July.
SUSCEPTIBLE SPECIES
All turfgrass species are susceptible to masked chafer damage. Damage is
usually more serious on ryegrass and bluegrass turfgrasses, whereas fescues are
somewhat less affected. Warm-season grasses tend to be the most tolerant of
grub feeding.
DAMAGE
Masked chafer grubs feed on roots, resulting in
irregular dead patches. Symptoms
resemble drought stress and persist even where there is sufficient irrigation.
Grub activity can cause the ground to feel spongy; extensive root feeding
sometimes allows the turf to be rolled back like a carpet. Most damage usually
takes place in late summer or early fall. Digging by vertebrate predators, such
as crows, raccoons, skunks, and coyotes, is a common indication of high grub
populations.
MANAGEMENT
For turfgrass infested with masked chafers, biological and cultural
controls may help reduce their number. If monitoring indicates a need,
treatment may be warranted. Commercially available parasitic nematodes
are among the treatment options.
Biological Control
Tiphiid wasps are common parasites
of masked chafers, but may not consistently be effective in reducing grub
populations below damage thresholds. Heterorhabditis bacteriophora are
commercially available parasitic nematodes that can effectively control masked
chafers. Steinernema carpocapsae nematodes are not effective.
Cultural Control
Establishing warm-season grasses may reduce white
grub damage. Thorough spike-aeration of turf also kills significant portions
of white grub populations when they are feeding close to the soil surface.
Monitoring and Treatment Decisions
Carefully dig around roots
of grass to detect white grubs. If the infestation is heavy, the turf
may be loose and easy to roll back like a carpet. (For more information
on monitoring, see GENERAL INFORMATION.)
Threshold levels on greens are low; if you detect more than one grub per
square foot on greens, treatment should be undertaken. In other turfgrass
settings, up to six grubs per square foot can usually be tolerated.
Current chemical control options are most effective against
early instar larvae (less than 0.5 inch
long). Grubs may take up to 10 days to die following contact with an
insecticide, so wait at least this long to evaluate insecticide efficacy. Adult
activity generally occurs during the period from mid-June to July. Optimum
timing for treatment is 3 to 4 weeks following peak adult activity. Because
applied insecticides bind to the leaf blades and thatch, remove thatch before
and irrigate immediately following application to obtain good results.
| Common name |
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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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CARBARYL* |
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(Sevin) 80WSP |
6 fl oz |
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| B. |
CHLORPYRIFOS |
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(Dursban Pro) |
3-6 fl oz |
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(Dursban) 50W WSP* |
1.5-3 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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| C. |
HETERORHABDITIS BACTERIOPHORA |
25 million |
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COMMENTS: Apply during late spring/early summer before
adults emerge, or early fall when most chafers are in the susceptible
stages. Irrigate before and after applying nematodes. Store nematodes
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 cool time of day in hot areas. |
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| D. |
IMIDACLOPRID |
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(Merit) 75 WP |
3 teaspoons (0.15 oz) |
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(Merit) 75 WSP |
0.15 oz (1 packet/11,000 sq ft) |
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COMMENTS: Maximum of 1 application/year. Applications
cannot exceed 8.6 oz/acre/year (0.19 oz/1000 sq ft). Optimum control
will be achieved when applications are made before egg hatch of target
pests followed by sufficient irrigation or rainfall. Applications
should not be made when turfgrass areas are waterlogged or soil is
saturated with water. |
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Apply in 25 gal water/1000 sq ft |
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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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