Meats, A., & Wheeler, S. 2010 Dispersion, contagion, and population stability of red scale, Aonidiella aurantii, in citrus orchards with low or zero insecticide use. Entomologia Experimentalis et Applicata 138: 146–153

Notes: Red scale, Aonidiella aurantii Maskell (Hemiptera: Diaspididae), has a contagious distribution among fruit and among trees largely due to the fact that most young settle on the same fruit as their mothers. The pattern of distribution and degree of dispersion of red scale within various sets of contiguous citrus trees in several orchards were recorded each autumn for 4 years. Changes in density and site occupancy within trees and within contiguous groups of trees were made to assess the strength of any link between populations and their dynamics on different trees. Aonidiella aurantii was found to have a very clumped distribution whereby trees with a level of scale infestation well above average for their block could be adjacent to trees with few or no detectable scale. However, patches of high density on a given tree usually did not recur for more than 2 years but were replaced with above average infestations on other trees. The stability of the red scale populations varied from block to block. Some blocks had few or no infested trees over the study period whereas others had widely fluctuating levels of infestation. Dispersion coefficients at ‘within tree’ and ‘within block’ levels were similar. Theoretical and statisticalmodels of the relation of average scale levels to the percentage of fruit or trees infested were less precise than they are for other pests because of high variation of clumping intensity of scale within any block.