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Seeking sustainable protection against garden weevil
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A boost to efforts in Western Australia to develop practical, effective and sustainable management of garden weevil has been provided through GWRDC Regional Development Initiative funding. The Australian & New Zealand Grapegrower & Winemaker reported in its February issue that the principal partners are the WA Department of Agriculture and Curtin University.
The funding assists a range of activities, including: further investigation of environmental variables to predict the timing and emergence of adult weevils; assessment of the main drivers of populations of the pest in vineyards (with attention being given to ground covers, cultivation practices, exclusion barriers, birds and use of insecticides); and clarification of the potential, through use of insecticides, to increase risks of secondary pest outbreaks.
Chief investigator for the project, Stewart Learmonth, said the aim was to be able to recommend appropriate vineyard management practices in an integrated pest management framework that would mean sustainable management of garden weevil.
“It is a major problem in WA and a significant pest in parts of SA, Victoria and Tasmania,” he said.
“Feeding by adult weevils can kill newly planted vines, reduce yield in mature vines by up to 70% and increase propensity for secondary infestations, while there can also be long term effects on vine structure and bud development. “Broad spectrum insecticides such as butt drench and foliar sprays, are available but give only temporary protection and may cause build-up of secondary pests, most notably longtailed mealybug.”
Work towards better, sustainable, solutions began last August with a workshop to review current knowledge on weevil biology and management.
On the research front Curtin University of Technology is studying the timing of emergence of adult weevils at infested vineyards in relation to soil temperature, examining the relationship between weevil abundance and cover crop plants on the vineyard floor, and looking at the long term seasonal changes in weevil abundance. The WA Department of Agriculture is fostering industry liaison through an internet based activity called Garden Weevil watch. There are 22 participating growers who contribute information on weevil numbers and insecticide use that is posted on the department’s web site each week.
Field trials have commenced on studying the damage the weevil can cause to winegrapes, as well as physical and chemical exclusion methods that prevent the weevils from entering the canopy of grapevines. A new exclusion method that is already showing promise is the use of Barrier Glue® in South Africa. Also, the use of Surround® (particle film technology) is showing some weevil control when used as a foliar spray).