Cold hardiness and effect of winter chilling on mortality of passionvine hopper (<i>Scolypopa australis</i>) eggs
Passionvine hopper (PVH; Scolypopa australis) is a significant production pest of kiwifruit in New Zealand and an occasional pest of some other crops. It is also associated with toxic honey. Estimated losses of kiwifruit due to sooty mould associated with feeding by PVH varies from c. 0.5–3% of Class-1 fruit packed, depending on year. Mortality of overwintering eggs due to winter chill may contribute to this inter-annual variation. After cold-hardening under ambient winter conditions, eggs were exposed to six temperatures between -11°C and 0°C. The median minimum lethal temperatures for a 1-h exposure was -9.1°C. Longer exposures (up to 24 h) did not strongly influence mortality at different sub-zero temperatures. Mortality of eggs held at a range of North Island sites was most strongly correlated with the sum of chilling hour degrees (CHD) below a threshold of 10°C in August (r=0.89).