Soil Feeders - Asiatic Garden Beetle (AGB)

ASIATIC GARDEN BEETLE (AGB)
scientific name: Maladera castanea

FIELD KEYS
Hosts: Most grass species
Site symptoms: Turf wilting under heat stress despite adequate available moisture. Wilted turf dies in irregular patches. Removed dead or wilted turf reveals grubs feeding at 2-3 inch soil depth.
Plant symptoms: Above-ground plant structure shows no obvious damage or other symptoms, however root system shows extensive damage at 2 to 3 inch depth from grub feeding.
Site keys: Sunny locations with adequate soil moisture and organic content near flowering shrubs, fruit-bearing trees, vegetable gardens, or lights that are kept on at night.

SPECIMEN ID
Immatures are six-legged white grubs with tan heads that range in size from 1/16 inch for newly hatched first instars to 3/4 inch for fully grown third instars. Adults are chestnut to medium brown colored, 7/16 inch-long beetles with slightly iridescent wing covers.

SCOUTING TIPS
AGB over-winters at soil depths of 8 to 16 inches as a third instar grub that pupates and then emerges as an adult when nighttime temperatures exceed 70°F. Night-feeding adults, which damage flowering shrubs, tree fruits, and some vegetables, can be captured using light traps. Monitor adult capture numbers and begin grub sampling at vulnerable sites 2 to 3 weeks after the number of captures declines for 7 to 10 days.

CONTROL STRATEGIES
Cultural: Limit supplemental watering at vulnerable sites (to increase egg and first instar mortality) starting when adult captures decline. Increase drainage at wet sites and manage turf for maximum root production. Turn off any lights at night near vulnerable sites.
Chemical: Once regular grub sampling indicates that the per square foot grub population has reached 8-15, consider making control applications to asymptomatic sites. At more vulnerable sites, applications may need to begin once grubs populations reach 5-8 per square foot.
Growth stages: egg - grub (three instars)* - pupa - adult*
* - treatable stages

Life cycle:1 year life cycle (multiple generations)
Sequence: grub - pupa - adult - egg - grub