Armoured scale (Hemiptera : Diaspididae) distribution in kiwifruit blocks with reference to shelter

Armoured scale insect (Hemiptera: Diaspididae) leaf infestations were monit ored from rows of kiwifruit (Actinidia deliciosa (A.Chev.) C.F. Liang et A. R. Ferguson var. deliciosa) vines in three blocks at each of 11 sites, at 3 -8 times from December until May. The relationship of scale leaf infestatio n with distance across kiwifruit blocks (scale distribution) was analysed u sing different regression models. Scale distributions were best described u sing linear models for 26 kiwifruit blocks and for seven blocks using quadr atic models. Scale distributions derived using live scale followed similar patterns to those derived from total scale. Overall 53% of sites or blocks had significant linear or quadratic scale distributions. Kiwifruit blocks w ith high scale infestations invariably had significant scale distributions whereas those with low infestations had non-significant distributions. The finding of significant relationships using regression models with parallel lines or curves for different sampling times at some sites, showed scale di stributions hold throughout the season. In the simplest situation scale inf estations were highest in kiwifruit rows adjacent to alternative host plant s and declined linearly away from the scale source. These findings were con sistent with the hypothesis that scale distributions were caused by the aer ial dispersal of crawlers from alternative host plants.