Good question but I think your question should be directed to the ACT parks service (whatever their name is now) at the South Side Depot. Canberra Connect should be able to put you through. I’m interested in their response as I’m sure lots of other members are too.
My understanding is that the chemical used has to be taken down into the root system to kill the whole plant otherwise it will shoot again. The plant starts shutting down around mid-summer and sending nutrients down into the roots for the next spring growth and the chemical can be taken down then. I don’t know when the plants shut down for the winter but it is obviously useless to spray after they have shut down.
They may be able to start spraying after the berries are finished but it may not leave them much of a window.
From: casburnj [
Sent: Wednesday, 12 February 2014 12:51 PM
Subject: [canberrabirds] Blackberry spraying - will birds die?
Today along lower Molongolo river, norhtern side there are signs warning “Not to eat the Blackberrys” as spraying is in process. There are many small birds in this area that thrive on the Blackberries.
Does anyone know why spraying needs to be done while the Berries are on the bushes? Surely the spray will kill some of the birds?
Would it be better to spray when the bushes are getting new leaves?