Susceptibility of redheaded cockchafer <i>Adoryphorus couloni</i> in New Zealand to <i>Metarhizium anisopliae</i> strain DATF001 (Chaferguard)

Abstract

The Australian pasture pest Adoryphorus couloni (redheaded cockchafer RHCC) continues to slowly spread from the Port Hills and Banks Peninsula through Christchurch towards productive agricultural land on the Canterbury Plains There are currently no products chemical or biological registered in New Zealand to control this pest In Christchurch several parks used extensively for human recreation were badly damaged by RHCC grubs in the autumn/early winter of 2008 and had to be treated with chemical insecticides (diazinon) Laboratory trials were thus carried out to assess the susceptibility of New Zealand populations of RHCC to a microbial biocontrol agent Metarhizium anisopliae DATF001 (ChaferGuard) registered in Australia Fungal activity was directly influenced by temperature and mode of application Infection and mortality occurred faster at 20C than 15C High mortality levels (90100 after 7 weeks) were obtained when larvae were treated by topical application (105 conidia/grub) or exposure to the dry ChaferGuard formulation in soil; >80 of the cadavers in these treatments were mycosed Direct incorporation of conidia into soil was the least effective treatment Grass grub (Costelytra zealandica) was unaffected by the fungus This trial confirmed the efficacy of DATF001 and its potential for use against New Zealand populations of RHCC