Soil Feeders - European Chafer (EC)

EUROPEAN CHAFER (EC)
scientific name: Rhizotrogus majalis

FIELD KEYS
Hosts: Most grass species
Site symptoms: Turf wilting under heat stress despite adequate available moisture. Wilted turf rapidly dies in irregular patches. Removing dead or wilted turf reveals grubs feeding at the soilthatch interface.
Plant symptoms: Above-ground plant structure shows no obvious damage or other symptoms, however root system shows extensive damage at the soil-thatch interface from grub feeding.
Site keys: Any sunny location with adequate soil moisture and organic content, managed or unmanaged.

SPECIMEN ID
Immatures are six-legged white grubs with tan heads. Third in-stars can reach 1 inch when fully grown. Adults are slightly shiny chestnut brown colored, 5/8 inch-long beetles.

SCOUTING TIPS
Over-wintering third instar grubs become active as soon as the soil thaws and continue to feed until late spring. Actively feeding over-wintering third instars may produce severe turf damage by late spring or early summer during hot or dry springs. After pupation, adults emerge on mating flights for several hours after dusk when temperatures are greater than 66°F. Mating occurs in trees and several hundred beetles can be shaken from trees or caught in sweep nets at peak flight times. Grub sampling at vulnerable sites should begin three to four weeks after adults begin to appear in light traps. EC grubs are very active feeders often continuing feeding until the ground freezes and may resume during thaws in warmer winter periods.

CONTROL STRATEGIES
Cultural: Improve drainage at wet sites and manage turf for maximum root production. Maintain turf so thatch accumulation is kept to less than 1/2 inch.
Chemical: Once regular grub sampling indicates that the per square foot grub population has reached 8-10, consider making control applications to asymptomatic managed sites. Unmanaged sites as well as highly vulnerable managed sites may show damage 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