Biology and ecology of grapevine scale parthenolecanium persicae (fabricius) and frosted scale parthenolecanium pruinosum (Cocquillet) (Hemiptera : Coccidae) on Grapevines Vitis Vinifera L.

Abstract

Grapevine scale (Parthenolecanium persicae Fabricius) and frosted scale (Parthenolecanium pruinosum Cocquillet) (Hemiptera: Coccidae) are significant economic pests of several deciduous fruit trees and ornamentals worldwide, including grapevines in Australia. Management using biological control and pesticides can control these scale insects however sporadic outbreaks can still occur across wine zones and districts. This thesis addressed aspects of the biology and ecology of these scales and examined possible responses of Vitis vinifera L. varieties to scale feeding activity. A non-hierarchical cluster analysis of morphological characteristics identified three K-groups that corresponded to first instars, second instars and adults in frosted scale. Four K-groups were identified in grapevine scale; first instars, second instars, third instars and adults. Only female scales were present in the populations, and the second and third instars of frosted and grapevine scales respectively were the overwintering stages. Increased growth of appendages did not match total body development, so that the legs, antennae and stylets were relatively shorter as scales matured. Stylet lengths for frosted scale suggested that feeding site did not vary, although location of feeding changed from leaf for first instars to woody branches for later life stages. Females of grapevine scale had a similarly high fecundity on both Chardonnay and Riesling grapevine varieties. Females of frosted scale had reduced fecundity when present on V. vinifera Sauvignon Blanc compared with individuals present on V. vinifera Chardonnay and Riesling varieties. The differences in fecundity of frosted scale were not a result of reduced body size, although smaller individuals were present on Sauvignon Blanc and Riesling. Fertility was at least 94% for both species and was not affected by grape variety. The pest status of grapevine and frosted scales across the wine zones does not appear to be associated with climate. Vineyard size and monoculture and/or mixed cropping of grapevine varieties differed with locale in the pest status of scales, as more small vineyards in the Hunter Valley had infestations, but mixed cropping reduced the incidence of scale in northeastern Victoria. More scales were apparent on white wine grape varieties compared to red wine grape varieties across the regions. Field and glasshouse studies identified that grapevine and frosted scales exhibit different responses on grapevine varieties. In field studies, population growth of grapevine and frosted scales were much higher on established vines of Riesling and Chardonnay compared to vines of Pinot Noir and Sauvignon Blanc. In greenhouse studies on the response of rootlings of Pinot Noir, Riesling and Sauvignon Blanc, the presence of frosted scale insects reduced chlorophyll content and internode, but only the number of internodes per branch was further reduced as the number of scale insects increased. This thesis provided several findings that can be used in future studies to address further questions on pest persistence, outbreaks, monitoring and management. Future research on grapevine and frosted scales pest population response and grapevine damage may need to consider the interaction between grapevine nutrition and secondary metabolites, and the differences that are present among grapevine varieties. Show more