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Masked Chafers

by David J. Shetlar    

Species

Distribution

Masked chafers are natives of North America. The southern masked chafer is most common in the southern states and has been collected from Central and South America. It has been recently reported as a more common pest in southern Indiana, Illinois, Iowa and Nebraska. The northern masked chafer is commonly a pest in the Kentucky bluegrass and tall fescue growing regions from New England across to Illinois. Specimens have been collected from Maine across to Nebraska and California.

Hosts

The southern masked chafer commonly attacks turfgrasses in the transition zones (Kentucky bluegrass and tall fescues) and in southern bermudagrass areas. The northern masked chafer usually attacks cool season turf, especially if Japanese beetle grubs have been suppressed. Both species attack the roots of field crops such as wheat, oats and corn. The adults do not feed.

Damage Symptoms

Turf begins to show drought stress in late summer into fall or spring and does not rapidly recover after rain or irrigation. Heavy infestations result in turf dying in irregular patches. Birds, skunks, raccoons and opossums commonly dig up turf around the dead patches. Moles may tunnel extensively where grub populations are high. Infested turf feels spongy under foot and is easily lifted because of the absence of roots. The adults do not feed on ornamental plants or turf.

Description of Stages

Masked Chafers have a typical annual scarab life cycle with a complete metamorphosis. Determining the species of larvae and adults of all of the Cyclocephala is difficult without the assistance of a taxonomist.

• Eggs: The eggs are oval when laid and are about 1/16 inch (1.7 mm) long by 3/64 inch (1.2 mm) wide. These pearly white eggs absorb moisture from surrounding soil and increase to 2.1 mm in diameter and have a nearly spherical shape.
• Larvae: First instars are about 3/16 inch (4.5 mm) long at hatching and reach 1 inch (22 to 25 mm) when maturing as third instars. The mouthparts must be dissected to distinguish between the northern and southern masked chafers. The larvae have the irregular pattern of bristles on the raster which is typical of all Cyclocephala larvae.
• Pupae: The 5/8 inch (17 mm) long by 1/4 inch (8 mm) wide pupae are first creamy white and gradually change to reddish-brown just before the adult emerges. Female and male pupae can be separated by looking at the lower surface of the ninth abdominal segment. The males have a pair of conspicuous lobes while females have the segment partially divided below the genital pore.
• Adults: The adults are a dull dark yellow-ocher and have darker brownish-black markings on the heads and eyes. Adults of the northern masked chafer have conspicuous hair on the thorax and wing covers. The southern masked chafer has sparse hair. The adults are 1/2 inch (11 to 14 mm) long by 1/4 inch (6 to 7 mm) wide. Males have an enlarged fifth tarsal segment on the fore legs that is used to grasp the female. In C. lurida males, the antennal club is shorter or equal to the combined length of the other antennal segments. C. borealis males have a longer club .

Adult Southern Masked Chafers (top), Larvae (bottom left), Raster Pattern (bottom right)

Life Cycle and Habits

The northern and southern masked chafers have very similar life histories and habits. Adult beetles usually begin emergence in mid-June and are active into mid-July. Males come to the soil surface after dark before females emerge. The southern masked chafer is apparently active earlier in the evening than its sibling species, the northern masked chafer. Southern masked chafer males begin to emerge just before sunset and skim the ground surface in search of unmated females. Northern masked chafer maximum activity occurs around midnight. Unmated females come to the soil surface, climb upon a grass blade and begin releasing a sex pheromone that attracts the males. Many males often cluster around calling females and the successful male clasps the female with his modified legs during copulation. Mated females and males fly at night and are strongly attracted to lights. The males tend to fly within two feet of the ground while females seem to fly at higher altitudes. Most of the mating and flying activity of the southern masked chafer is finished by midnight. Northern masked chafers are active until a few hours before sun rise. Neither males nor females feed on plant material but merely mate and disperse at night. Mated females dig down four to six inches and lay 11 to 14 eggs. If soil moistures are sufficient, the eggs swell within eight days and hatch in 14 to 18 days at 70 to 75 degrees F. The young larvae burrow to the soil surface in search of plant roots. The larvae also eat general organic material in the soil as well as thatch. The larvae grow rapidly when adequate moisture and food are present. The second instars are reached in 20 to 24 days at 80 degrees F and third instars are common by September. It's during this time of the season that most of the damage occurs. As the soil temperatures begin to drop in the fall, the larvae begin to dig downwards to hibernate. Larvae may dig down 12 inches but most are within 3 to 6 inches, at least in southern states. Grubs surviving the winter, return to the soil surface in late-April and May to feed. The larvae again move down slightly in late-May and early-June to pupate. A mature larva ready to pupate voids all residue from the gut and the abdomen becomes very translucent. The pupa is formed within the old exoskeleton that splits down the center line. The pupa takes about 17 days to mature.

Northern masked chafer life cycle

Control Strategies

See: White Grubs in Turfgrass (HYG-2500)

Option 1: Cultural Control - Environmental Modification - Since the eggs require moisture for development, restricting irrigation in July and early-August may significantly reduce survival. Since the adults are attracted to lights at night and damage is common under street lights, replace the lights with sodium vapor or yellow lights to reduce their attractiveness.

Option 2: Biological Control - Milky Diseases - Milky diseases caused by strains of Bacillus popilliae are known but most commercial preparations do not contain these host specific strains. Larvae are also commonly attacked by Tiphia wasps but these wasps may require several seasons to build up populations sufficient to control this pest.

Option 3: Chemical Control - Timing of Insecticides by Trapping - Consult, HYG-- 2500, White Grubs in Turfgrass for insecticide use recommendations. Bulletin L-187 lists the pesticides currently registered. The adults can be monitored using 15 Watt black light traps. Trap counts can be graphed showing the number of adults versus the date counted. When the trap capture has decreased for ten days, record the date of peak activity. The grubs will be most susceptible to chemical controls about six weeks after this peak.

Option 4: Chemical Control - Timing of Insecticides by Degree-days - Northern masked chafers emerge slightly before southern masked chafers. However, activity periods overlap considerably. The first adults of the northern masked chafer should emerge between 898 and 905 DD₅₀F and 90% of the adults should be finished laying eggs between 1377 and 1579 DD₅₀F. The first adults of the southern masked chafer should emerge between 1000 and 1109 DD₅₀F and 90% of the adults should be finished laying eggs between 1526 and 1679 DD₅₀F. Grub treatments can be applied about 15 to 20 days after the 90% adult activity period.

This publication contains pesticide recommendations that are subject to change at any time. These recommendations are provided only as a guide. It is always the pesticide applicator's responsibility, by law, to read and follow all current label directions for the specific pesticide being used. Due to constantly changing labels and product registration, some of the recommendations given in this writing may no longer be legal by the time you read them. If any information in these recommendations disagrees with the label, the recommendation must be disregarded. No endorsement is intended for products mentioned, nor is criticism meant for products not mentioned. The author, The Ohio State University and the Ohio Cooperative Extension Service assume no liability resulting from the use of these recommendations.


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