What Defenses Do Grapevines Have Against Piercing and Sucking Insects?
Lydia Murphy, Andras Keszei, Richard Poire, and Paul
Cooper*
*The Australian National University, EE, Bld 46, Research School
of Biology,
The Australian National University, Canberra/A.C.T./2601,
Australia
(paul.cooper@anu.edu.au)
Anthropogenic climate change increases mean temperatures, leading to increased humidity and unusual weather patterns. Scale insects are piercing and sucking pests that occur on certain cultivars in high numbers in Australian vineyards. As these scale insects feed on grapevine leaves, they may be affecting vine growth and fruit production. Scale insects also produce honeydew as their excreta, which can initiate growth of sooty mold on both leaves and fruit, reducing photosynthesis and affecting grape value. Our work aimed to describe the natural defenses present in grapevines against piercing and sucking insects, which could reduce pesticide use in the future, when these insects may be present in greater densities. Rootlings of Cabernet Sauvignon (CS) and Sauvignon blanc (SB) (resistant to scale insects) and Shiraz (S) and Chardonnay (Char) (susceptible to scale insects) were grown in greenhouses to measure growth, fruiting, and volatile organic compound (VOC) production when these cultivars were exposed to scale insects. At harvest, the number of scales per five leaves were counted, the number of grape bunches and grape mass were measured, and dried root and shoot masses were recorded. We found an increase in growth of SB with high numbers of scale and a decrease in benzyl alcohol, but no effect in Char. Within the CS and S comparison, leaves imported anthocyanin from another location in the plant within four weeks of scale insect infection. The presence of anthocyanin corresponded to an increase in leaf abscission in CS plants. Dropped leaves had several scale insects present and on other still-attached leaves, many scales had died. Although S did not drop leaves as well as CS did, their leaves also appeared to import anthocyanin.
Funding Support: Research School of Biology, Australian National University
