Field application of biopolymer-coated Beauveria bassiana F418 for clover root weevil ( Sitona lepidus ) control in Waikato and Manawatu

Clover root weevil (CRW) (Sitona lepidus) continues to have a severe impact on white clover in pastures in the North Island of New Zealand. Trials were established in October 2005 as part of a continuing evaluation of the insect-pathogenic fungus Beauveria bassiana F418 strain for management of this pest. F418 was applied as a rice + biopolymer formulation, targeting CRW larvae in the clover root feeding zone (3-5 cm below the surface). Overall, there was a reduction in CRW numbers at all of the test sites. The number of larvae recovered was significantly lower in F418-treated than control plots after 3 weeks, and the number of pupae was similarly lower in F418 than control plots after 6 weeks. Higher levels of fungal propagules were recovered from 0-6 cm in the soil profile than 6-10 cm.