Phylloxera infested grapevines have reduced chlorophyll and increased photoprotective pigment content – can leaf pigment composition aid pest detection?

Grape phylloxera is a root-feeding pest of grapevines. In Australia, phylloxera infested vineyards are subjected to quarantine restrictions and early detection remains vital for the timely implementation of post-outbreak quarantine protocols. Current detection methods rely on time-consuming ground surveying which involves detailed examination of grapevine (Vitis vinifera L.) root systems. Leaf pigment composition is often a sensitive indicator of plant stress. The increasing popularity of remote sensing systems, which exploit those changes in pigments observed with plant stress, offers a real possibility for the development of a phylloxera specific remote detection system. Our objective was to investigate changes in grapevine leaf pigments associated with phylloxera infestation and relate any changes to appropriate reflectance indices. This was achieved through a glasshouse experiment where the response of two vine cultivars (Cabernet Sauvignon and Shiraz) to phylloxera infestation was compared to their response to waterand nitrogen-deficiency. The response of leaf pigments to phylloxera infestation was also investigated in Pinot Noir and Cabernet Sauvignon grapevines grown under field conditions. A reduction in the leaf chlorophyll content and an increase in photoprotective pigment concentrations were observed in leaves of phylloxera infested grapevines compared to uninfested vines. The photochemical reflectance index (PRI) was found to be most closely associated with the ratio of total carotenoid to chlorophyll in these vines