Observations on the host plants of oystershell scale (Diaspidiotus ostreaeformis: Hemiptera: Diaspididae)

Abstract

Oystershell scale, Diaspidiotus ostreaeformis, is a pest of fruit crops in Otago and Canterbury. Spray programmes provide effective control of this pest in apple orchards but invasion of the crop from external host plants causes fruit infestation. Alternative hosts include deciduous tree species, many of which are used as orchard shelter belts. The abundance of oystershell scale was recorded on a range of deciduous and evergreen tree species in Otago in 1999-2000 as part of experiments on the management of oystershell scale on shelter. Scale insects on the trees were either counted during timed searches or scale crawlers were trapped and counted on sticky bands. Experimental design did not permit rigorous statistical analysis but the data indicated the potential susceptibility or resistance of the trees to oystershell scale. The majority of Betula, Alnus and Sorbus species studied were susceptible but resistance was indicated in B. papyrifera selections and B. platyphylla japonica. The hornbeam, Carpinus betulus, appeared resistant and no oystershell scale insects were found on any of the conifers studied. © 2011 The Royal Society of New Zealand.