Threat to Tweedia!

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  • #14898


    How do you feel about Environment Waikato importing a beetle to destroy moth plant and tweedia?

    I subscribe to the "Get Growing" email from NZ Gardener ( and the latest edition says that Environment Waikato will soon apply to the Environmental Risk Management Authority for permission to introduce a biological control agent to attack moth plant and to help control it.

    Richard Hill from Plant and Food will be writing the application for Landcare Research, the science advisors to Environment Waikato. The research to determine whether this root-feeding beetle is safe to be introduced has been completed. It shows that the beetle is restricted to a very narrow range of host plants, and that no native species are at risk. Swan plants (which are closely-related to moth plants) are also immune from attack. However, the closest relative to moth plant present in New Zealand is tweedia, an old-fashioned garden ornamental, and the tests show that the beetle is likely to attack tweedia too.

    Richard Hill’s role is to present the case for and against introduction. He wants to find out whether possible damage to tweedia would be a significant concern to the New Zealand public so that ERMA can weigh up the costs and benefits of introducing the beetle.

    email Richard with Tweedia in the subject line to have your say!

Viewing 12 replies - 26 through 37 (of 37 total)
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  • #27887


    Thanks Darren,
    Saves us members of MBTNZ the worry about loss of swan plants, if had the beetles were allowed to be imported to NZ, that would means very few monarch butterflies and Lesser Wanderer butterflies won’t breed here if no swan plants.
    No swan plants = no monarch butterflies.
    To import the caterpillars / pupaes of Monarch butterfly from USA, could be very difficult, due to diseases and health reasons to replace our monarch butterflies that become extinct if beetles were allowed to be imported to NZ.



    I really hope we can have the Plain tiger (Danaus erippus) introduced into New Zealand!! It would be the perfect tonic…the cousin of the Monarch! Question though, would it survive our winters? I believe it would because Argentina is quite cold although it would be much easier to fly north to over winter in South america than it would in New Zealand.
    You guys think its a great idea?



    I believe the scientists have got the research right! But then again, I Believe the earth is flat, the majority of politicians are honest and I was sent here on a hyperspace bypass from planet Zog!



    Researching this issue further led me to an interesting source… Our own September 2008 newsletter!

    The Argentinian Monarch Butterfly (Danaus erippus) (sometimes referred to as the ?Black Monarch?) is on a list of potential insect agents for moth plant (Araujia sericifera) which is becoming quite a pest plant in NZ.
    ?We have discovered that this Monarch and D. plexippus are not able to interbreed and form hybrids, which is one obstacle out of the way,? said Lynley Hayes, Project Leader at Landcare Research.

    ?We still have questions about how serious parasitism and predation might be, which will require further study.? An application to ERMA is being prepared to import four species on insect into containment at Landcare, Lincoln for further study. They are Rhyssomatus diversicollis and Araptus araujiae ? both fruit-feeding weevils, Colaspis argentinensis ? foliage and root-feeding beetle, and D. erippus ? foliage-feeding butterfly.

    Lynley said that the team is commissioning further research on these insects in Argentina.

    ?The next step would be to import colonies for study which would not likely happen for at least a year. It is likely that with further study the long list will be reduced to 1-2 insect species.?

    Lynley pointed out that colonies of potential biocontrol agents would need to be imported to check their host range and ensure that they will not harm any desirable species. The team is also studying several plant diseases which
    keep moth plant under control in its native range.



    I agree Bernie! I should perhaps have pointed out that I was drawing from another article, not stating my opinion. Besides which, there is a saying that “absence of evidence is NOT evidence of absence”. In other words it is very hard to conclusively proove a negative. A hundred trials showing no evidence of this bettle attacking swanplant would be worthless if the 101st showed they did.

    And does “swanplant” include all the varieties of monarch host plant grown in NZ? Did they test G.fruticosus or G.physocarpus? And what about A.incarnarta and A.curassivca?



    Good one Bernie – top marks.



    I have e mailed Mr. Hill and asked him to send me the scientific evidence to back up the conclusion that these beetles do not attack the swan plant.



    I would like to see the evidence that leads them to say that whilst these beetles attack both cruel plant and poor old tweedia,they apparently do not attack the swan plant.
    Until they produce scientific evidence to back it up ,quite frankly,I am sceptical to the point of disbelief.



    I don’t Heather but feel free to pass it on!




    Jacqui, do you have Redfire Nursery email, they might be interested in that info too.



    Good work, Darren, thanks for your vigilance. I will send off an email too – and thanks for making it easy for us.





    I have sent the following to and

    Dear Richard Hill,
    I am a member of the Monarch Butterfly New Zealand Trust. Thank you for the heads-up about Environment Waikato wanting to import a beetle to destroy moth plant and tweedia.

    In 1933 the wasp Pteromalus puparum was introduced to control the Cabbage White Butterfly. It also attacks our native Yellow Admiral and Red Admiral butterflies. The Red Admiral Butterfly is only found in New Zealand.

    I am extremely concerned about any plans to import another exotic pest, particularly one which attacks foodplants of the beloved Monarch Butterfly.

    Since caterpillars of The Monarch Butterfly eat mothplant we already have a biological control for mothplant. I consider the threat to the existing Monarch Butterfly does not justify importing another exotic pest.

    I would prefer education such as weedbusters already performs to control mothplant.


    Darren Gedye

Viewing 12 replies - 26 through 37 (of 37 total)

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