Soil Feeders - Oriental Beetle

ORIENTAL BEETLE (OB)

FIELD KEYS
Hosts: Most grass species
Site symptoms: Turf wilting under heat stress despite adequate available moisture. Wilted turf dies in irregular patches. Removed sod of dead or wilted turf reveals grubs feeding at 1-inch soil depth.
Plant symptoms: Above-ground structures show no obvious damage or other symptoms, however root system shows extensive damage at 1-inch depth from grub feeding. Nearby ornamental plant roots may also be damaged.
Site keys: Sunny well managed short and tall cut turf sites locations with adequate soil moisture and organic content.

SPECIMEN ID
Immatures are six-legged white grubs with light tan heads that range in size from 1/6 inch for newly hatched first instars to 1-inch fully grown third instars. Adults are a wide bodied tan to black colored, 1/2 inch beetles often with tan and black mottled markings on wing covers.

SCOUTING TIPS
OB over-winters at soil depths of 8 to 16 inches mostly as a third instar grub that begins to move up in soil to feed when soil temperatures reach 45°F. After pupation adults emerge in early to mid-summer. Adults are not strong fliers (usually less than 50 yards) and are usually seen during warm days with strong sunlight. At night adults can be found crawling on turf under lights. Grub sampling should begin at OB vulnerable sites 3 -4 weeks after adult emergence. Late second instars may over-winter for a second year when soils cool below 50°F. Vulnerable sites with over-wintering second and third instars may show early feeding damage in heat or moisture-stressed springs.

CONTROL STRATEGIES
Cultural: If possible, limit supplemental watering at OB vulnerable sites (to increase egg and first instar mortality) starting 3 weeks after adult emergence. Increase drainage at wet sites and manage turf for maximum root production.
Chemical: Once regular grub sampling indicates that the per square foot grub population has reached 8-10, consider making control applications to asymptomatic sites. At more vulnerable sites applications may need to begin once grubs populations reach 3-5 per square foot.
Growth stages: egg - grub (three instars)* - pupa - adult
* - treatable stages

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