Sprayed swan plants from garden centre

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  • #52036


    We ran out of most of our home grown swan plants with caterpillar onslaught so bought a big, very expensive plant from a Wellington garden shop.
    It took a while to dawn on us why our lovely big – and smaller – caterpillars disappeared. No sign of wasps yet apart from a paper wasp in the house.
    Then we noticed drops of inky black exudate and about 3 deformed, writhing, skinny caterpillars that died.
    Only one, and hopefully a second, chrysalid, probably because those caterpillars were on our own plant alongside.
    Lost at least a dozen caterpillars – some rescued from stripped plants.
    Question – is this consistent with plants sprayed either by the grower or by the garden shop?
    I intend to return the plant and have a forceful discussion about the shop ensuring their supplier doesn’t spray and they don’t spray themselves, or at least cover any swan plants. I will also seek a refund.
    We found this upsetting as we enjoy rearing Monarchs.
    Our other outside plants, grown by us, have chrysalids fortunately.
    PS The shop was not the garden centre at New World Thorndon. They are meticulous about buying in unsprayed plants but unfortunately this summer their supplier has been hit by white fly (proof they don’t use spray!) and they don’t have fresh stocks.

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  • #52085


    I’m prepared to bet the plants I got from Miramar have been fertilized with something unsuitable that’s changed the chemical balance of the plant. The caterpillars are happy to sneak on to it (go out of their way) and are fine for up to a day or even a bit longer. If you get them off fast enough they are good even if they have started to show signs of not being well.
    The fertilizer theory would explain what the garden centres are saying i.e. not sprayed but have a different chemical makeup in the short term. I’m watering the plants day and night, have sprayed them with water and they are out of bounds for another week or so at least.



    Mattie, please water the new plants well and persevere with them, and keep us informed of progress. Do the plants look similar, i.e. similar leaves, to the old ones? There are different forms of milkweed but I don’t think any of the growers are using other forms – just your ordinary common Gomphocarpus fruticosus, swan plant.

    Could you also please contact me, jacqui@monarch.org.nz, as this is something we would like to do something about.




    Hi JaniceS I had the same problem. Bought three plants on Thursday as going away for the weekend and placed them next to my cuttings. The cats moved over on their own accord but then I started to see them dying. Rung the Plant Centre who said they had only come in on Tuesday and definately hadn’t been sprayed. The only thing I can put it down to is that the new plants were naturally more toxic then the ones I had been using.



    Good call, Rob!


    rob cooper

    now is the time to grow more plants for next year if your serios about getting them away no spray no nothing so yea we now have heaps for next year



    all so true … I really thought I’d be ok this year as I have quite a few very big plants and had plenty coming on. Well instead of a small problem I got a very big one lol. No doubt you still have to keep an eye on things and cull those eggs if necessary. So here I am in January with all my giant plants stripped to the bone and nearly all my backup plants pretty well tested … and I’ve had to go an buy some anyway. At least I can leave them for a couple of weeks. And yes I’m watering them and they will go out in the first rain this week (we hope). I’ve certainly noticed aphids are worse with indoor plants so my coverings are net based except for a few in my hothouse that has the windows and door open. In the next week I should be releasing at least 50 butterflys if all goes well, so the cycle starts again.



    Copying this info. from this page here, and I have made certain parts of it bold FYI. And also, because I’ve cut and pasted from the original information, the links won’t work but you can find them by going to the original page:


    The relationship between monarchs and milkweed (such as swan plants) is fascinating. Consider the predators, parasites and pathogens that affect monarchs. If people loved swan plants as they do rose-bushes, then we would see the monarch as a pest!

    It is not a simple exercise for a commercial operation to grow swan plants. The plants need to be in a good condition when they go on sale. The two main challenges are monarchs and aphids. After all garden centres won’t want to sell plants that are covered with aphids or are bereft of leaves.

    Some growers resort to using pesticides. Hopefully they don’t release their plants for sale until the chemicals are no longer active.

    A female monarch lays on average of 700 eggs (one was recorded as laying 1179 eggs). After the caterpillar emerges from its egg it will grow almost 3000 times in size over the following two weeks. So one day you have lots of leaves, a week later and the plants can just be leafless stalks.

    If you grow your own plants from seed you will know for certain that the leaves are safe for caterpillars. We encourage everyone to hold plants over from previous years. When a plant is over 1.5 metres in height, and if it is well fertilised and kept healthy, the growth in the spring and summer will almost keep up with the caterpillars.

    So if you haven’t bought your plants this year, get twice as many and protect some for next year’s monarchs. Also get some seed – Yates gives the MBNZT a donation for each packet sold – and grow more plants. If seedlings sprout up in inconvenient places leave them until you need food. Pull out the plant, or cut it off at the stem and put it in a bucket of water, splitting the bottom of the stem before you do so it will better absorb water.

    Here are some more tips to help you raise your Monarchs so that they become beautiful butterflies.

    Between egg and chrysalis the caterpillar or larva is going to shed its skin five times. When they are shedding their skin it is important not to disturb them. We suggest that you observe the life cycle but do not touch or interfere. Monarchs have been undergoing metamorphosis for hundreds of years and do not usually need our help.

    If your larvae need more food we suggest you let them move themselves to the new plant. A potted plant can be placed next to an existing plant. Or, if the existing plant has no leaves, then prune it and put the stems you have cut off (with caterpillars) at the base of the new plant.

    By the way, milkweed and Monarchs are poisonous so be careful when handling them. There is more information about this HERE. Monarch larvae store toxic steroids (known as cardenolides) from the milkweed they eat and use these cardenolides as a defence against predators such as birds. The bad taste and toxicity of both the larvae and adults are advertised by their warning colour. When a bird predator tastes a Monarch it learns to associate their colour and pattern with the bad taste and avoids preying on them in the future. (Interestingly, the Shining Cuckoo is not affected and will eat them.)

    Be aware that there are different types of milkweed and the new plant(s) may not immediately appeal to your larvae. Water the plant well so that if there is an imbalance of cardenolides, they will be diluted.

    If you are buying new plants as food for your caterpillars you should be careful about buying plants that have pesticide spray residue on them as this will affect and may even kill your brood. Ask your supplier if they are spray-free – or better yet have a go at planting next year’s in advance from seed. Seed is available on our website HERE.

    Pesticides include fly sprays, plug-in insect controls and flea collars on pets so bear this in mind if you bring your larvae indoors.

    If you are concerned that your caterpillars are dying, we suggest that you look in the forum HERE to see if there have been other similar reports – or add your own post. Don’t forget to add details like your locality, if the plants or new or well-established, number of caterpillars affected, if you have neighbours who spray and anything else you think is relevant.

    Now, that being said, I think it’s a wonderful “cop-out” for some growers/garden centres to point the finger at the difference in the chemical composition of the leaves on different plants as being the thing that is upsetting the caterpillars. If you water the “new” plant well and put it alongside the old plant then the caterpillars should transfer over okay – but in this hot weather it will be more difficult.

    Commercial growers will find it virtually impossible to grow large numbers of swan plants without resorting to pesticides, even if they’re under cover. The monarchs can smell them from 2 km away so they’ll be keen to lay eggs on their plants. If the plants are shut away in glasshouses or greenhouses, aphids can still get in and that’s a perfect place for them, as well as thrips and then sooty mould.

    So if they spray their plants and IF they adhere to the withholding period(s) then who is to say that those “withholding periods” are correct. And if they’ve used Product X for thrips and Product Y for something else, the mix can make an even deadlier combination for which no-one knows the “withholding period”.

    PLUS get some cowboy with a spraypack and they want to spray everything in sight. Unless you had seen a plant grow from a seedling to maturity, you can never be sure how “safe” it is. Even in our own garden(s) there could be spray drift from neighbours’ places…

    It really is wise to grow your own. And IMHO, after 40 or so years of doing it, I’m learning to live with the “bigger picture” – the ecology, the community of flora and fauna that exists in your natural garden is much more appealing than having hundreds of monarch butterflies and getting upset by “starving caterpillars” or wasps, ants and aphids etc.

    Just my 2c worth!



    Its somewhat perilous buying plants it seems. I bought 12 from Palmers in Miramar on Friday. To their credit they warned me that people have had problems putting caterpillars on them and to let the caterpillars choose the plant themselves, in the short term at least. Trouble is of course a lot of us are in dire need of fresh plants.

    Interestingly I got the same spiel from Mitre10 Crofton Downs. I believe its best to leave them 2 weeks?

    They, (both garden centres) insisted the plants are not sprayed and in fact I found an egg on one of them. They said it was to do with the active ingredient of the plants being different .. kind of makes sense. But no help for the immediate problems. I’m able to leave my new plants for now and they are in with other plants.

    fortunately my hungry masses are almost all pupating now … good luck with yours.

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