Laboratory bioassays of new synthetic and microbial insecticides to control Eucalyptus tortoise beetle Paropsis charybdis

Paropsis charybdis, or eucalyptus tortoise beetle, is (one of) the most signiicant pests of eucalypts in New Zealand. It severely defoliates Eucalyptus nitens and Eucalyptus globulus plantations, leaving heavily-damaged trees with reduced growth and poor form. Laboratory bioassays of new synthetic and microbial insecticides were undertaken to identify management options compatible with biological control. The current insecticide used for operational control, alpha-cypermethrin, was a positive control. Of the products tested, spinetoram (Sparta) gave the most promising results (100% mortality after 14 days) for control of adult P. charybdis. Spinetoram and spinosad (Success Naturalyte), the microbial control agents Beauveria bassiana (F305 ex Botanigard) and Bacillus thuringiensis var tenebrionis, and the enterobacterium Yersinia entomophaga, all resulted in high mortality of larval P. charybdis after 4 days. Targeting larvae alone may not be economically viable, leaving spinetoram as the only possible additional insecticide for managing P. charybdis. Potential barriers of cost, application and non-target impacts are yet to be addressed.