Buddleia pests

This topic contains 66 replies, has 14 voices, and was last updated by  Anna 5 years, 8 months ago.

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  • #14137

    NormTwigge
    Keymaster

    Today I noticed the leaves on my Nanho blue buddleia were looking like something was chewing at them. Close inspection revealed an advanced infestation of maggot-like grubs on both sides of the leaves. Putting two and two together I did a search and sure enough they proved to be Cleopus japonicus, a biological control brought in from China to help eradicate the Buddleia davidii which grows rife on riverbanks, roadsides and plantation forest margins.

    The insect is a weevil which lays its eggs on the leaves of buddleia bushes. These hatch out and grow into a maggot-like legless grub, a yellow jelly-like blob which eats away at the leaves, defoliating the plant, stunting its growth, and probably eventually killing it. The grub will grow to about 5 mm in length, and then pupates in a cocoon on the leaf,finally emerging as the adult weevil to mate and start all over again.

    The authorities are more than happy with the results, and advised gardeners to spray their plants if the weevil became troublesome to ornamentals.

    I will post some shots to the Photo section.

Viewing 25 replies - 26 through 50 (of 66 total)
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  • #30157

    NormTwigge
    Keymaster

    Anna – re your previous post, the autumn pruning last year halted the weevil larvae, but late summer this year the leaves were being skeletonised before the flowering had finished. Once the bush had finished flowering I gave it its annual prune (severe hack back) and then a spray with Yates Target, a systemic spray. I hate using sprays so I used it strictly according to directions. It eradicated the weevil larvae but just lately I had noticed the adult weevils are about, and realised that while the spraying killed the larvae it did not kill the cocoons in which the adult weevil was developing. The weevils mate and the females lay the eggs in cracks and crevices of the branches so it is difficult to control all stages. The weevil is extremely efficient in doing its job of defoliating, which is the reason why it was introduced. A slight movement or touch and the weevil will immediately drop to the ground, so the wasps may have a hard job to get them, plus they have a hard shell exoskeleton which would probably be impervious to a wasp sting.

    #30148

    Anna
    Participant

    I have noticed an asian wasp hovering near a branch with a few weevils on this morning. It will be interesting to see if it carries one of them off.
    (I have found weevils on more bushes now) The infestation has been light so far, so I have just had to pick off any leaves or the odd branch that I find with them on.

    #30140

    Darren
    Participant

    I’ve just been releasing tagged butterflies at the Maleme Street Butterfly Sanctuary, and was most intrigued to see what had happened to the three Buddleias I had planted there.

    Rob Herd donated two to the project, which were labelled as “red” and “yellow”. They are now now covered with brown lacework instead of leaves, most disappointing.

    However in between them was the first Buddleia I planted there, a Silver Anniversary which was one of the Trust’s “Twelve Buddleias of Christmas”. It was completely untouched, and on closer inspection I couldn’t find a single C. japonicus on it.

    Regarding Pteromalus puparium, it was introduced in 1933. The awareness of potential non-target problems is much greater today. Which is not to say that mistakes can’t happen, but it is hopefully much less likely.

    Interestingly Barron’s 2004 thesis “Population ecology of the red admiral butterfly (Bassaris gonerilla) and the effects of non-target parasitism by Pteromalus puparum” concluded that more damage was being done to the Red Admirals by the parasitic wasp Echthromorpha intricatoria which seems to have found its own way here from Australia in the 1900s.

    #30138

    Anna
    Participant

    …forgot to add…Norm, from post 1, did the Nanho Blue get reinfested?
    I’ve got rid of all the grubs I can find, but will have to be pretty vigilent to keep on top of them so I don’t have to resort to sprays:(

    #30137

    Anna
    Participant

    I can’t but help think of the pteromalus puparium wasp, and when it was released it was bought in to control the white butterfly, but ended up affecting Admirals and that wasn’t forseen, so fingers crossed the weevil sticks to what it is supposed to do.
    I think some go overboard re: native plants though … not all people are natives here, but add to the diversity of the place, and so it should be with plants.
    The pine forests could hardly be called native but add a lot to the country, and so it should be with Buddleia cultivars and the like.

    #30123

    Jane
    Participant

    Thanks for the link to that paper Darren. Very interesting. I see that there have been no releases near here yet, but the spread rate seems quite fast and it’s only a matter of time really.

    I can’t say I’m devastated by this news though. When you see what Buddleia has done in the wild in NZ, it is truely shocking, and for that reason I won’t be tragic about it going. It is gorgeous in the butterfly garden, and from that perspective it will be a bit of a pity, but it has made some shocking impacts on our wild spaces. As mlusk points out further up in this thread, it is enormously invasive, and like mlusk, I have seen it in our forest parks where it has become the dominant species and altered the landscape, thereby having a negative impact on our forest ecology and laying waste to thousands of hectares of riverbed where it has altered the course of our waterways in many places.

    As most of us here know, buddleia has a magnetic effect when it comes to butterflies. We must try and remember though that in it’s absence the butterflies will nectar on hundreds of other species that are not having a massive impact on our native habitats. Many native plants are terrific for nectar, AND were here before any of our exotic species of plants were introduced.

    I won’t be protecting buddleia when the weevil gets here. There is a bigger picture to be kept in mind. I care about butterflies (they won’t die without buddleia), but other biomes and habitats that creatures depend on too.

    #30122

    Darren
    Participant

    A systemic insecticide should do the trick. But I tend not to have things like that lying around as I prefer more environmentally friendly solutions when possible. And on my budget buying some for use on a few plants isn’t a priority, especially when they are in such close proximity to my milkweeds.

    I doubt Cleopus japonicus will totally wipe out Buddlejas here, after all it hasn’t in its homeland. Initially they will have a population explosion, but as the wild Buddlejas get fewer and further apart the weevils will start to starve and an equilibrium will be reached.

    But growing garden Buddleja species certainly won’t be as easy in the future.

    #30121

    Anna
    Participant

    Thanks Jacqui.
    Does anyone know of an effective spray for the Buddleia weevil? Darren said Super Shield doesn’t kill them:(

    #30118

    Jacqui
    Keymaster

    The Wiri Collection are always good, if you can find them: Wiri Charm, Wiri Prince, Wiri Spears, Wiri Vision. The Wiri Collection were all bred by Jack Hobbs at the Auckland Botanic Gardens, and for sure they’re loaded with nectar. I like the rich colours of the abovenamed varieties.

    Wiri Blush, Wiri Dawn, Wiri Desire, Wiri Joy…

    Got weary yet? 🙂 They’re all wery colourful…

    http://www.teara.govt.nz/en/horticultural-use-of-native-plants/3/2

    #30117

    Anna
    Participant

    It doesn’t look good for the Buddleia does it. Once all the buddleia are gone I wonder if the weevil will die out…or head for another food source…hopefully not feijoas!

    Anyone know the best hebes to plant that would give the same amount of nectar??

    #30116

    Darren
    Participant

    Jane, details here

    Cleopus japonicus: releases and distribution of the buddleia biological control agent in New Zealand
    M.C. Watson, T.M. Withers and M. Heaphy pp. 155-159
    http://www.nzpps.org/journal/64/nzpp_641550.pdf

    #30114

    Jane
    Participant

    Hi Charlotte and Anna,

    I hope that by cutting down at this time of year they will not reach the same height that they did this year. I would like to keep them under 1 – 1.2m at most if possible. There are plenty of shoots at the base, so it is a bit of an experiment.

    We don’t seem to have the weevil yet, but I imagine it is only a matter of time.

    What were the release sites of the weevil around NZ? Can anyone tell me?

    #30113

    Anna
    Participant

    Char…I hope the weevil doesn’t find your place, though when I looked up some of the release sites I noticed Auckland was one of them.
    Has anyone found a spray that would kill the weevil grubs…but not make the flowers toxic for other insects? I guess there may be a way of spraying them when there are no flowers, then hoping the witholding period is over before they come into flower.
    I have been trying not to use spray:(

    With the buddleia, I have noticed that if I pinch out the growing tips often for a start, you end up with a much bushier, flower covered plant, as they flower on new growth.
    Also if they are in pots, it keeps them under control, and they still give lots of flowers.
    I’m loving having mine!…so have the butterflies this season.

    #30110

    Charlotte
    Participant

    We have no sign of the weevil up here in Auckland as yet.

    Our Buddleias are flowering again for the third time this season. We were about to cut them right back and low and behold they have started flowering like mad again!

    A few of our B. davidii types are like your plants Jane and have managed to get very tall and lanky and falling over in the winds.. The Buddleias that have stopped flowering we will cut right back like you Jane, as this year they have gone crazy…

    #30108

    Jane
    Participant

    Hi Anna,

    No I haven’t pruned in autumn before, but this year many of the buddleia were over 2 metres tall and it was very difficult to deadhead them on the far side as this was down the bank…..soooo… I decided to take them to within 2 feet of the ground so that hopefully I can always deadhead them. I have quite a few buddleia that are not pests like the weyeriana, lindleyana and colvillei, and they are unlikely to become pests. HOWEVER I’m also aware that all the B. davidii types like white profusion, pink delight, Black knight, royal red etc will seed if not deadheaded, and will proliferate and exacerbate the weed problems especially as mine are all planted on railway land adjacent to waste areas that can be corridors for weed spread. In short I try to keep them from seeding!

    #30107

    Jacqui
    Keymaster

    “The Brook Waimarama Sanctuary is a community-based initiative working to create a pest-free wildlife sanctuary close to the Nelson city centre.”

    Hmmm… interesting expression, “pest free”.

    #30105

    Anna
    Participant

    Heres a link to three photos of the weevils damage at the brook sanctuary….and they seem happy about it!

    Cleopus japonicus, beetle larvae

    What about the nectar source it has been for the insects???

    #30104

    Anna
    Participant

    Thanks Darren…I haven’t seen an adult weevil as yet, so its good to see the photos.

    ps/ The ladybird hasn’t touched the 5 weevil larvae I gave her yesterday:(

    #30102

    Anna
    Participant

    Jane…I was wondering whether to prune mine at this time of the year, or whether you are supposed to wait till spring. Do you usually give them an Autumn prune, then another one in spring?

    #30100

    Darren
    Participant
    #30097

    Jane
    Participant

    I have seen no sign of the weevil here, but I have just cut nearly all my buddleias that have finished flowering to within a foot of the ground in an effort to tidy them up for next seasons growth. They were getting very tall and straggly and too high to deadhead.

    I wonder if this method would disrupt the lifecycle of the weevil. Does the weevil spend it’s entire lifecylce on the buddleia?

    #30093

    NormTwigge
    Keymaster

    Cleopus japonicus has now been released to over 30 sites throughout New Zealand and has become well established. With the ability to fly the weevil is also expanding its territory naturally and is regarded as a success story of an introduced biological control in its ability to defoliate buddleia.
    I have been picking off mating weeevils from my bushes by the dozens, and many have probably already laid eggs which will not be affected by sprays.

    #30092

    Anna
    Participant
    #30091

    Anna
    Participant

    I’ve put a ladybird in with five weevil grubs, to see if she will eat them…fingers crossed.
    What a pity that the weevil is here now. The ones I have as captives at the moment move pretty fast when they want to. I have since found some on other buddleias, so I have been picking off and destroying any affected leaves as well as squashing the grubs.

    #30078

    Pepetuna
    Keymaster

    I have discovered Cleopus japonicus on my Buddleia Weyeriana “Sungold” too. First year seen here (I’m near Hamilton in Waikato District). Same as Anna reported, it’s not on the other buddleias yet.

    I was going to try to destroy all the globby-looking larvae before they pupated…but might be too late. I don’t want to spray the plants because they are still flowering (so danger to bees and butterflies) and also I have pots of Asclepias curassavica directly beneath the affected buddleias.

    Darren, thanks for reporting re Super Shield: did you find anything else effective?

Viewing 25 replies - 26 through 50 (of 66 total)

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