Development and mortality of greedy scale (Homoptera : Diaspididae) at constant temperatures

Developmental times and mortality were determined for four stages of greedy scale Hemiberlesia rapax (Comstock), a key pest of kiwifruit, Actinidia de liciosa (A. Chevalier) C. F. Liang et A. R. Ferguson variety deliciosa, in New Zealand. Scale were reared on potato tubers at seven constant temperatu res and developmental stage and mortality were assessed at regular interval s. This required the removal of the scale cover to enable stage and mortali ty to be accurately determined. High numbers of scale (>1,400) were require d at each temperature to sustain a frequent destructive sampling regime. Sc ale survival to the reproductive stage ranged from 0% at <12.3<degrees>C to 45% at 24.6 degreesC. The time for 50% of the live scale population to rea ch each developmental stage was determined using a Bayesian smoothing progr am. A linear model of scale development war; developed for each stage based on a single, temperature-independent distribution of normalized developmen tal time. A linear regression of development rate against temperature was u sed to estimate developmental thresholds that were 9.6, 9.7, 10.3, and 10.6 degreesC and it took 257, 552, 882, and 992 degree-days (DD) to reach the second, third instar, mature, and first reproductive stages, respectively.