i wonder if there is any experience among readers with blackberry leaf rust (for blackberry control of course) and Scoth thistle beetle (for Scotch thistle, perhaps not surprisingly!). I have identified only one distributor in the whole of Australia, which is something of a worry, given these tow biological controls are widely publicised. I would expect many if the approach was definitive.
Sorry no experience with blackberry or scotch thistle but was involved with bridle creeper biological control. In the Adelaide Hills two methods were tried. The first was an insect, forget exactly what. It was a total fail. But they knew it would be so why they went to all the hoop la of releasing it I don't know. It works in the Eastern states because the bridle creeper stays green all year and gives the bug something to eat. When it was released in the Hills with the Minister of the Environment and a whole lot of press people the guys running the trial quietly said to myself and neighbours could you please water this patch of creeper so it will stay green and the bug can live otherwise it will die. How stupid to do a big photo opportunity releasing something you know is useless. Anyway next was a rust. Not anything as impressive on a photo so no Pollie or press but the rust was great. All you had to do was find a bit of creeper that has rust spots on the underside of its leaves, pick off some rusty leaves and rub them over your healthy plants and pretty soon you would see rust on yours. Took several years to really kill off big patches but it stopped it spreading within a year and after a few years even a big patch would start to die and disappear. So biological control can be a winner if the research is done right
Blackberry Rust (Phragmidium violaceum) will defoliate blackberry canes but it rarely results in death of the plant since it is very rare for the rust to infect the canes themselves. This would make it a questionable control method. Orange Rust Gymnoconia sp. and Arthuriomyces sp. might be a viable control but should you need to eradicate it, you would need to completely remove the infected bush, roots and all. Both of these fungi tend to be systemic but neither actually kill the host plant, rather they just completely infect the plant. The Scottish thistle beetle feeds on various Asteraceae, incl. thistle (Carduus, Cirsium, Onopordum) and knapweed (Centaurea). They are not considered viable as a biological control method since they do feed on some economically important species. Most countries do not allow them to be used as a biological control.
I'm sure goats are fine in the paddock situation, but not for the creek line area I'm grappling with. The blackberry leaf rust will hopefully complement the tube stock I'm hoping to plant into the area ( I've already attacked with the brushcutter), whereas the goats would not. Bryant, can you tell me what crops would Scotch thistle attack?
globe artichoke (Cynara scolymus) and safflower (Carthamus tinctoria). are the two main cash crops they will attack. However they have only been documented attacking these plants when there is a lack of thistle plants.
Was just wondering if you had any update on sourcing those beetles and success in eradicating the thistles? I have a few on our farm too.
Hi Jason I did use the blackberry rust, combined this with regular slashing, seemed to get a benefit. I haven’t followed up on thistle beetle, but intend to, especially because the neighbour insists on neglecting his! Regards Peter
Thanks for the update Peter. We just bought a small farm that had been neglected for a number of years and there is one paddock quote thick with thistles. Our approach is to spray them out to get on top of it then use natural control in subsequent years (gazing, desirable pasture competition, etc). Also have a patch of bracken to work on. Geoff's video on weeds was quite interesting with respect to that. Where are you based? We're in South West Australia.