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New Zealand Plant Protection 68 (2015): 441

The application of 980 degree days as a trigger for rapid increases in Bactericera cockerelli in Hawke's Bay solanaceae crops

N.M. Taylor, R.C. Butler and J. Vereijssen


During 2007-08, the tomato potato psyllid (TPP, Bactericera cockerelli) was observed in outdoor tomato and potato crops in Hawke's Bay. Many crops were heavily infested, resulting in severe yield losses and in some cases crop abandonment. Since then, growers have been proactive in plant monitoring and sticky trap use, but these methods are expensive and quite often a calendar spray programme is begun once the first adult TPP have been observed in traps. It has been proposed that 980 degree-days (DDs) from 1 July is used as an indicator of when TPP numbers are about to increase rapidly in North Island crops. This study describes the application of 980 DDs to recent sticky trap data from Hawke's Bay. For most sites, 980 DDs occurred just before rapid increases in adult TPP numbers. However, there were a small number of sites where this was not so. The presence of non-crop TPP host plants bordering these sites may explain rapid increases in TPP trap catches well before reaching 980 DDs.

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