Influence of pasture renewal, soil factors and climate on black beetle abundance in Waikato and Bay of Plenty

Abstract

An outbreak of the sporadic pest black beetle caused major damage on farms throughout Waikato and Bay of Plenty regions from 2007 to 2010. Two projects were initiated in these regions to gain an understanding of the interaction of black beetle with endophyte/ cultivar combinations and pasture renewal strategies. Monitoring of black beetle populations on the project farms showed that overall, abundance steadily declined from 2009 to 2013, possibly due to cool temperatures, and in the case of Bay of Plenty, high rainfall in 2010. In Waikato, pasture renewal in 2012 had no significant effect on beetle abundance in the following year compared to the unrenewed paddocks. Greater population levels in the Waikato sites were associated with lower soil pH. El Niño and La Niña weather events appear to be associated with changes in black beetle population levels, which may assist prediction of future outbreaks and damage risk. Keywords: Heteronychus arator, pasture, La Niña