Towards Improved Early Detection of Grapevine Phylloxera ('Daktulosphaira vitifoliae' Fitch) Using a Risk-Based Assessment

Abstract

Grapevine phylloxera ('Daktulosphaira vitifoliae' Fitch) is a significant threat to the Australian viticulture industry, with over 80% of grapevines planted on highly susceptible, ungrafted 'Vitis Vinifera' L. Early detection of phylloxera is critical as it can spread unnoticed in the early years of infestation when vine foliar symptoms may not reflect subterranean root damage. Management strategies such as phylloxera exclusion zones (PEZ) and a number of quarantine protocols relating to movement of machinery and grape materials are already established within Australia in an attempt to contain proliferation throughout viticultural regions. Such measures are particularly important for regions like the Hunter Valley in New South Wales, Australia and the Barossa Valley in South Australia, which are phylloxera-free and sustain a high volume of viticultural production. Currently, early detection protocols include labour-intensive, systematic sampling of vine roots to inspect for the presence of phylloxera and multispectral aerial imagery to identify potentially stressed vines. Airborne remote sensing identifies weak spots in the vineyard that are not necessarily due to phylloxera infestation, rather the expression of non-specific water or nutrient related symptoms. Healthy, vigorously growing canopies may also disguise the early expression of above-ground signs of phylloxera-induced root degradation. The delayed appearance of visible symptoms, coupled with the dynamics of phylloxera infestation means current detection methods could be significantly improved through development of a risk-based monitoring strategy to indicate the potential susceptibility of vineyards to phylloxera infestation. This paper presents the targeted use of several primary and secondary detection techniques already being utilised across the viticulture industry, including EM38, Greenseeker™ and a soil-based DNA assay specific for phylloxera.