SOUTHERN AND NORTHERN MASKED CHAFERS: Contents:
Introduction
Masked chafers are in the
Scarabaeidae family and within the Cyclocephala
genus. Two species present in Maryland are the northern masked
chafer, Cyclocephala borealis,
and the southern masked
chafer, Cycloaphala
lurida.
White grubs are the larval stage of adult beetles within this family. Damage is due to larval feeding on the root systems of turfgrasses. Masked chafers are considered to be a key pest of turfgrasses in Maryland.
Identification
Adults are reddish brown in color and will reach lengths
of 11-14mm (1/2"). Their common name "masked" refers to a darkened
area around their eyes and head. The two species can be separated
based on the amount of hair on the front wing or elytra. Northern
masked chafers will have hair on their front wings while southern
masked chafers will lack this trait.
Larvae will be C-shaped, white with a reddish brown head and six legs. Larvae, known as white grubs, will vary in size from 3mm (.12") as first instars to 23-25mm (1") as third instars. A distinctive rastral pattern for these species is lacking.
Distribution
A broad overlapping distribution
occurs between both of these species in the Mid-Atlantic states.
Because the grub feeding damage and life histories are similar
both species are frequently referred to as masked chafer grubs. A
grub species shift is occurring in many Mid-Atlantic areas where
they overlap with the Japanese beetle. For reasons not fully
understood, urban neighborhoods that previously hosted 80-100%
Japanese beetle populations are now reversing to a predominately
masked chafer population. Selective natural control by milky
disease and other Japanese beetle specific pathogens may be part
of the explanation for the shift. Masked chafers are not affected
by the Japanese beetle milky disease.
Hosts
All cool season and warm season
turfgrasses found in Maryland can be attacked by masked chafer
grubs. Differences in damage levels are observed with respect to
the size and depth of the root system. Turfgrasses with extensive
root systems tolerate higher levels of white grub feeding activity
than do shallow rooted grasses.
Life Cycle
Masked chafers have one
generation per year and will overwinter as third instar grubs
below the frost line. Eggs are laid in the upper 2" of soil during
July and grubs begin to develop by early to mid-August. Larval
feeding damage can be observed by late August and through October.
Larvae will move deeper into the soil by late October and November
and overwinter in earthen cells.
Larval feeding activity will continue in the spring, April-May period, with pupation occurring in late May to early June.
Based on light trap results in the Maryland area, adult emergence occurs during the first week of July.
Damage
Adults do not feed, and
grub
damage is identical to Japanese
beetle. Populations of 10-15 grubs per square foot can
severely
damage turf. The adults of both
species can be monitored with black light traps. Southern masked
chafers fly just after sundown and activity stops around 12:00.
Northern masked chafers start their flight activity at 2:00 and
continue until sunrise. Both are highly attracted to irrigated
lawns during the dry weather and both flight and egg laying
activities will increase significantly after rainstorms.
Masked chafer grubs more so than the Japanese beetle also feed on organic matter. This results in higher population thresholds for these species. Potter (1982) indicated damage thresholds at 9-10 grubs per square foot for moisture stressed turf and 15-20 per square foot for irrigated turf not stressed. Similar to the Japanese beetle, masked chafers are frequently found with other annual white grub species.
Unlike the day flying and feeding Japanese beetles that can alert turf managers to possible future problems, the masked chafers fly at night and cause no feeding damage. Frequently turf managers have no prior warning of an outbreak. Many outbreaks are frequently misdiagnosed as Japanese beetle problems particularly in areas that have historically been treated with milky disease spores.
Biological-Biorational Control
Natural enemies of masked chafer grubs include entomophathogenic nematodes, fungal pathogens, parasitic flies and wasps, and ground beetles. A new strain of milky disease specific for masked chafer grubs has been discovered but is not commercially available as yet.The entomophathogenic nematode, Heterorhabditis bacteriophora , has shown good activity against white grubs and is commercially available as Cruiser.
A new product which mimics the insect molting hormone, ecdysone, and causes premature molting is Mach 2 (halofenozide). This product has shown consistent and excellent control for a number of white grub species.
Cultural Control
Females prefer to oviposit in moist soils that are high in organic matter. Avoiding irrigation during egg laying in July will increase mortality of eggs. However, the use of irrigation during August-September can mask larval feeding damage.
Chemical Control
Insecticidal control may be warranted if threshold levels of 10 grubs per square foot exist. Improved control will occur if the following conditions are met; proper timing of insecticide application, sufficient irrigation after application (1/2") and removing excessive thatch layers (more than 1/2"). The preferred timing for a majority of the recommended insecticides is in late summer to early fall when damage is first noticed. The other time period is in the Spring from April to mid-May.The following insecticides have labeling for white grub control however a number of these products have restrictive labeling and may require a certified applicator to apply them.
Organophosphates: Dylox, Proxol, Mocap*, Mainstay, Crusade*, Oftanol*, Triumph*, and Diazinon*
Carbamates: Sevin and Turcam*
*Restrictive Labeling
A new product for white grub control which was released in 1996 is Merit. This product can be applied earlier in the season (May-early August) due to its longer residual activity. However, it does not perform well on later instar or on older grubs and is not recommended for application after mid to late August in this area.
by Dr. Lee Hellman, Department of Entomology and Dr. J. Kevin Mathias, Institute of Applied Agriculture