Development and feeding effect of frosted scale Parthenolecanium pruinosum Cocquillet (Hemiptera: Coccidae) on selected Vitis vinifera L. cultivars

Abstract

Background and Aims: Frosted scale is a sap-sucking insect pest that feeds on several commercial Vitis vinifera cultivars across several wine regions of Australia. The ability to develop and the impact of its feeding activity on grapevines have not been documented. We have closed this knowledge gap through a study that examined the development and feeding effect of frosted scale on Pinot Noir, Riesling and Sauvignon Blanc. Methods and Results: A replicated glasshouse experiment was established by allocating the potted rootlings of the three cultivars into two treatment regimes, control (uninfested) and treated (infested with frosted scale) grapevines in the summer months between November 2011 and March 2012. Frosted scale population was relatively high on Riesling, moderate on Pinot Noir and least on Sauvignon Blanc. The presence of frosted scale significantly reduced leaf chlorophyll concentration and the number of internodes per vine. An increasing number of scales did not significantly affect the chlorophyll concentration in any cultivar. An increasing number of scales did significantly decrease the number of internodes per vine. The proportion of dropped leaves in all cultivars exposed to frosted scale was higher than that of control plants. Riesling dropped more leaves than Pinot Noir or Sauvignon Blanc. Conclusions: An increase in first and second instar populations of frosted scale feeding mainly on grapevine leaves was observed. This feeding may reduce leaf chlorophyll and the number of internodes per vine. Pinot Noir, Riesling and Sauvignon Blanc were all susceptible to frosted scale feeding under glasshouse conditions, but individual cultivar performance varied. Significance of the Study: Grapegrowers could expect frosted scale population and loss of vine vigour to increase on highly susceptible cultivars, such as Riesling. Further studies regarding cultivar differences in response to frosted scale feeding are necessary to clarify these results.