Mortality of grape phylloxera in composting organics

Abstract

The effects of windrow and in-vessel Vertical Composting Unit (VCU) systems on the mortality of grape phylloxera, Daktulosphaira vitifolii (Fitch) (Hemiptera: Phylloxeridae) infesting European grapevine (Vitis vinifera L.) root systems were tested in three experiments. No phylloxera survived the first three-week windrow period of a 12-week, four-turn, composting cycle at a representative depth of 0.75-1.0 m with temperatures between 62.2°C and 66.5°C. Some root systems survived on the windrow surface and produced new growth after 12 weeks. Phylloxera survived on these root systems for no longer than 6 weeks at temperatures between 25.5°C and 29.4°C, which are well below the upper thermal survival limit of 36°C to 40.0°C for phylloxera. Root systems surviving on the surface were destroyed when buried at 0.75-1.0 m. No phylloxera or root systems survived when exposed to shallower burial (1.0 to 0.25 m), reduced times of exposure (21 to 4 days) and lower temperatures (66.5°C to 50.8°C) in three successive windrows. This included one treatment equating to the requirements of the current Australian Standard (AS 4454) for composted products. In a third experiment, phylloxera were allowed to pass passively through a bench scale test-cell that simulated composting in a VCU. Temperatures ranged between 54.6°C and 61.4°C in the top two-thirds of the tower where phylloxera were exposed for 12-21 days. No phylloxera or root systems survived the VCU. Temperatures in both composting systems were sufficiently high to cause complete mortality of phylloxera provided that turning regimens for windrows ensure that all material is mixed to the Australian Standard. Factors other than temperature may also contribute to phylloxera mortality during composting.