Millipedes - An unwanted visitor in vineyards

As vintage continues across the state, you might have noticed a few unwanted visitors in amongst your grapes. The black Portuguese millipede is a common sight around the house and relatively harmless. But did you know that millipedes may cause damage to grape berries and wine taint if they are fermented with grapes at harvest?
 
Luckily our resident viticulture expert Mary Retallack has some management tips so growers are better able to manage the impact of millipedes in their vineyard.
 
Background
The black Portuguese millipede was introduced near Port Lincoln in 1953 and again in Bridgewater in 1964 and is now widespread across southern Australia. Mary says, ‘The conditions in South Australia are perfect for these exotic and invasive millipedes. They prefer our climate of moderate temperatures, lower annual rainfall and have a higher tolerance to drier conditions than native millipedes.’
 
Issues
Mary explains why these tiny creatures can be such an issue at harvest in some locations. ‘Millipedes are an unwelcome pest at harvest due to their capacity to cause damage to grapes and wine taint. They may damage the skins of berries by feeding on them, which has the potential to cause Botrytis and other bunch rots. This may result in a quality downgrade or rejection of fruit from the vineyard.’
 
The other big issue with black Portuguese millipedes is their defensive nature. Mary says, ‘These millipedes are less susceptible to predation as they excrete chemical compounds when attacked which make them inedible to most natural enemies and birds.’
 
It is these defensive chemical compounds that often result in wine taint if millipedes are accidentally fermented with grapes. The excretions produce unpleasant flavour compounds which are noticeable when tasting contaminated wine.

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Image - Millipedes in a grape bin at vintage and outside a building

Millipedes in vineyards 
Mary says, ‘Even though millipedes do not move much more than several hundred metres a year they have the capacity to colonise areas quickly and grape berries may provide an attractive source of food. It is important that if you have experienced a millipede problem in the past, to take preventative action.’
 
Mary’s research in vineyards in the Adelaide Hills and Barossa revealed that millipedes were found in the greatest numbers early in the growing season and declined during the warmer months. However, following rainfall events in February, the millipede population increased again.
 
Solutions
One method of controlling millipedes, which is successful in domestic situations, could provide a long-term biocontrol option for vineyards. Mary explains ‘It is possible to control millipede populations in domestic backyards via the release of the parasitic nematode Rhabditis necromena which occurs naturally near Bridgewater, SA. The nematodes are released via a series of baiting stations which attract the millipedes. The millipedes then ingest the nematodes which bore through their gut wall lining. Bacteria from the gut then infects the millipedes, which kills them.’ Further research is required to assess their potential use and efficacy in broader scale applications such as vineyards.
 
There are a number of chemical control options registered for the control of millipedes. However, pesticides have a limited active life, must be re-applied for ongoing control, are not registered for use in vineyards or are restricted for use by some wineries. The use of broad-spectrum pesticides may also have unintended consequences, leading to the death of natural enemies or facilitate secondary pest outbreaks.
 
Growers are encouraged to maintain vigilance. If they have experienced a millipede issue in the past on a particular site, then consider an integrated and long-term approach to pest control using the points above as a guide.
 
If you have any questions about the topics covered in this email, send an email to admin@wgcsa.com.au