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New Zealand Plant Protection 65 (2012): 290

Measuring kiwifruit resistance to armoured scale insect pests

M.G. Hill, N.A. Mauchline and K.A. Stannard

ABSTRACT

A bioassay for assessing relative susceptibility of kiwifruit germplasm to latania scale (Hemiberlesia lataniae) has been developed and validated. The method uses cut canes collected from dormant kiwifruit vines in winter. Canes are held in coolstore (0C) until required. Lengths of cane (40 cm) are held with one end in water at 20C and scale insect crawlers from laboratory cultures are encouraged to settle beneath wool wrapped around the cane. Percentage crawler settlement, numbers of insects surviving to adulthood and their size are determined and used to assess the relative susceptibility of the plant. This method has been validated for H. lataniae and used to study kiwifruit resistance and defensive responses. The bioassay did not work satisfactorily for greedy scale (H. rapax) as crawler settlement was very low. Further research has identified cane age as an important determinant of H. rapax crawler settlement. Young canes harvested in summer enable good settlement of H. rapax but canes of this age do not last long enough for the insects to mature (10-12 weeks). Canes harvested in autumn while still green will survive to support H. rapax settlement, growth and survival, and can be used to compare kiwifruit resistance to both scale species.

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