Northern Masked Chafer

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Pair of northern masked chafers mating at night in turf.
Mature third instar northern masked chafer grub.
All masked chafer grubs have a random pattern of bristles on the raster area.
  • Scientific Name: Cyclocephala borealis Arrow [Phylum Arthropoda: Class Insecta: Order Coleoptera: Family Scarabaeidae]


  • Common Names: northern masked chafer


  • Climatic Zone: temperate


  • Geographic Distribution: The northern masked chafer is commonly a pest in cool-season turf from New England across to Illinois. This species is claimed to have been collected from eastern Canada across to Nebraska, down to the Gulf States and even California, but regular infestations are common in the Northeastern States and eastern Canadian provinces.


  • Damaging Stage: larva


  • Hosts: The northern masked chafer usually attacks cool-season turf, especially if Japanese beetle grubs have been suppressed. 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, racoons 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 typical scarab annual life cycles with a complete metamorphosis. Larvae and adults of all of the Cyclocephala are difficult to determine to species 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, increase diameter and have a nearly spherical shape.

Larvae: First instars are about 3/16-inch (4.5 mm) long at hatching and reach one inch (22 to 25 mm) when mature third instars. The mouthparts must be dissected to distinguish between the northern and southern masked chafers. The larvae have an 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 adults emerge. 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 compared to the southern masked chafers which have 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 which is used to grasp the female.


  • Life Cycle 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. 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 which 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. 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 °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 °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 upper level of soil 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 which splits down the center line. The pupa takes about 17 days to mature.


  • Control Approaches:

Cultural Control - Habitat Modification - Since the eggs require moisture for development, restricting irrigation in July and early August may significantly reduce survival. 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.

Natural Control - Milky Diseases and Parasites - Milky diseases caused by strains of Bacillus popilliae are known but commercial preparations do not contain masked chafer-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.

Biological Control - Insect Parasitic Nematodes - The insect parasitic nematode, Steinernema glaseri Steiner, was used before 1940 and had considerable promise but this agent was not developed further because of problems of rearing and expense. This nematode may be economically available in the future. Commercially available products containing strains of S. carpocapsae have been marginally effective. Preparations containing Heterorhabditis spp. seem to be the most effective of the currently available nematodes. Nematodes should be applied when white grubs are in the second instar. Irrigation before and after nematode application with 1/4 inch of water minimum increases efficacy.

Chemical Control - Insecticides -

Targeted Treatments: As with most soil-inhabiting insects, insecticides are most effective when small stage grubs are the target. For masked chafer species, the small first instar grubs are present July through early August. Applying an insecticides at this time, followed by sufficient irrigation to move the insecticide to the grubs usually yields satisfactory results. First instar grubs molt into second instars that feed from mid-August through September. These middle stage larvae are also very susceptible to control, but if not controlled, turf damage may begin to appear by late August. From early September to October, masked chafer grubs reach the third instar stage and are 40 to 60 times the body weight of the newly hatched, first instars. By this time, significant damage may be caused by skunks and racoons who dig up infested turf to feed on the grubs.

Curative Treatments: Insecticide applications made in late September and October yield poor control of third instar grubs. At this time, insecticides known to have rapid action and are least affected by thatch binding are effective. In late April and May, masked chafer grubs return to the upper soil level to briefly feed. Though grub damage may be evident at this time, skunk and racoon damage is usually the major problem. If necessary, insecticides with rapid action may be used.

Preventive Treatments: The recent labeling of long residual (>120 days) neonicotinoid and diacylhydrazine insecticides has made it possible to obtain grub control with a single application in May, June, July or August. Depending upon the time of application, some of these new insecticides simultaneously provide control of a broad range of insect pests other than grubs. Unlike carbamate or organophosphate insecticides, these new materials have low impact on beneficial organisms that live in the turf. Both liquid and granular formulations are available. Some require posttreatment irrigation, others do not. Read and follow label instructions for optimum results. Preventive treatments are most warranted where the risk of grub infestation is greatest. Recent research has shown that turf areas that have experienced a damaging grub infestation are more likely to experience a reoccurring damaging infestation. Likewise, certain golf course areas and lawns in neighborhoods often have reoccurring infestations. These are likely candidates for preventive treatments.

Monitoring

The adults can be monitored using 15 Watt black light traps. Trap counts can be plotted on graph of numbers versus date. When the trap capture has decreased for ten days, mark the date of peak activity. The grubs will be most susceptible to controls about six weeks after this peak. A simple method of monitoring adult occurrence is to suspend a 60 Watt light bulb over a dish or small plastic wading pool. Beetles attracted to the light fall into the water and are easily counted and removed each morning. Grub infestations should be evaluated as early as possible by monitoring, accurate identification and mapping of infested areas. The standard golf course cup cutter is a convenient tool to survey for infestations in golf courses, sports turf and home lawns. If care is exercised, sampling can be done with minimal damage to the turf. Once removed, samples can be examined carefully on the spot. Each soil and turf core is placed back in the hole made by the sampler. The sample does not have to be completely torn apart to determine the number of grubs present. If the soil is dry, it is advisable to add water to the sample hole before replacing the sample to improve the turf survival. The standard cup cutter is 4-1/4 inch in diameter. Therefore, to convert the number of grubs found per sample to the number of grubs per square foot, multiply the average per sample by a factor of 10.15.

Degree-Day Timing

Northern masked chafers emerge slightly before southern masked chafers, however, their activity periods overlap considerably. The first adults of the northern masked chafer should emerge between 898 and 905 DDbase50F and 90% of the adults should be finished laying eggs between 1377 and 1579 DDbase50F. Curative grub treatments can be applied about 15 to 20 days after the 90% adult activity.

Thresholds

Many books and extension publications on grub management often mention “population thresholds.” Thresholds are the numbers of pest insects present in a given area (usually per square foot) that warrant control. The idea behind using thresholds is to reinforce the IPM principle that application of a pesticide is not always warranted simply if pests are present. Pests must be present at populations high enough to eventually cause damage. The generally accepted level for masked chafer larvae is 6 to 8 grubs/ft2 before control is warranted. However, well maintained turfgrass with regular irrigation and fertilization can “tolerate” much higher grub populations. On the other hand, moles, skunks and racoons often find less than six grubs per square foot sufficient to dig up the turf in search of them. Thresholds must be adjusted for each turf situation. For golf courses, damage in roughs is more tolerable than damage in fairways, and damage in fairways is more tolerable than damage on tees and greens. Likewise, some course or home owners demand high turf standards while others may tolerate some periodic, localized damage.