Aphids on swan plant


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  • #36728


    Please help… my swan plants are covered in caterpillars and chrysalis but also millions of aphids which are now causing black soot all aver the plant.

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    No the sooty mould and the aphids doesn’t directly affect the monarch caterpillars but it does affect the health of the swan plant (or milkweed) and of course caterpillars fed on poor quality food are more susceptible to disease etc.

    Build up the health of your plants.



    We’ve got aphids and the black soot but it doesn’t seem to bother the plant much. Are they a problem for the caterpillars or butterflies?



    Do you still have aphids?

    If you do, please try spraying them with a spray made up of 5% milk (regular, ordinary milk) and 95% warm water. Shake well. You may care to wash it off after 30 minutes. Repeat the next day to catch the aphids that you missed. Word from overseas is that works really well, and doesn’t affect monarch caterpillars or the plants!

    I wish I could try it out (I’m currently aphid-free) but if you DO have aphids and try it, please let us know how you get on.

    See picture here of aphids at their peak!

    Aphids will destroy this milkweed in a matter of days



    Shirls, thanks for the tip on worm juice. I have some and will try that. No ladybirds around in my Seatoun, Wellington garden sadly.



    During spring I lost 1 mature plant and 2 of my others took an absolute hammering due to aphids.
    I did the following to get them under control:-
    Lots of chicken manure and water – I read about someone using worm juice because of the strong “flavour” it put aphids off the plant.
    Manual removal – I can’t tell you how many hours I spent out there; or how many pairs of latex gloves I went through!
    Strong hosing while watering in the chicken manure… this works well until you have Caterpillars on your plants… they don’t swim well!
    Lady birds… they have done an awesome job in culling the aphids!



    I have tried a few things but have decided if the lady birds won’t get them I will wash them off. Gently rub them off using fingers and a hose. Seems to work well. Not permanent but not toxic either.



    If you have aphids, our friends in the Northern Hemisphere are laughing:




    I cut reasonable size branches and they seem to stay there, sometimes swapping to the other branch, and the skins just drop off onto the paper towel I have under the vase.
    I sqash the ends of the branches which seems to help water absorption. When the cats are big I change the paper towels, but flick the guano into the garden as I’m sure it is good fertiliser, even if small. All helps!



    Hi, So you have the branches in water in vases? What happens when the caterpillars
    want to leave the plant to shed their skins? I have tried to keep leaves moist which had eggs on them but failed.



    Must be a bad summer for aphids, as I didn’t have any last summer, but they are sure arriving on the tips of branches on my 2nd season big plant now. I’ve been cutting off the tips, but at last the ladybirds have arrived, so I will leave them to cope while I am away for 10 days. When I see a butterfly laying eggs I cut that branch off and keep it inside so the eggs can hatch safely. But when I had 3 large and 2 small caterpillars on branches in a vase, the biggest started harassing the smaller ones, even tho I thought I had plenty of leaves for all. I finally had to separate into several vases, until the big cats finally turned.
    Always a new trick to learn!



    Right!!! Off outside armed with scissors to chop off the tops of the branches which are laden with aphids… and will try to water blast as well.. I have about 15 large plants that are about two years old…so lots of food and lots of caterpillars. Have saved seeds for next year. Looking closely I can see that some chrysalis have started dying!!! HOpe it was not because i sprayed with soapy water 🙁



    I have just found this info Nola.


    ”If you are raising Monarch butterflies, think about employing another good anti-Aphid control: the Ladybug or Ladybird Beetle. These little critters are great because they eat the Aphids! Their larvae (babies) also eat Aphids so having them around is a plus.

    *Just keep in mind that Ladybugs will also eat butterfly eggs and young caterpillars!”



    Good stuff Nola.

    One of my plants went down to an aphid attack earlier this season and I took the plunge and cut off all the shoots that were covered with aphids. (What I could have done – if I had lots of caterpillars – is I could have washed the cut tips well to rid them of the aphids and then put caterpillars on them to eat the greenery, but fortunately I didn’t have a lot of Monarch caterpillars and did have plenty of other food.)

    It’s also necessary to control the ants around those plants as they only exacerbate the problem. They have a symbiotic relationship with aphids as you’ll read in the information sheet under Species/Pests above. So I put ant poison down around the plant and cleaned up the ants.

    Also feed the plant well – compost, covered with lots of mulch so that the plant isn’t going to dry out.

    You don’t say how old the plants are, but if you can get them into the second year and let some go to seed, you will probably never need to buy another swan plant as they will come up all over the garden. Then you can put caterpillars on the badly placed ones, or even pull them up and put them in water, leaving the caterpillars to eat them to death.

    Hope that’s helpful. And good luck!



    Hi taniab, I have got the same problem, although not the black soot as yet, just millions of aphids, so I spent from 1am to 4am last night researching this forum. There is a lot of helpful information on aphids. Look to the right and click on the ‘aphids’ tag and start reading all the posts going back years, for some great safe spray recipes and other ways of getting rid of them. Also, some people advocate leaving them and explain why. It will take a while to read through all the posts, but very worth while….. I went out today with an artists’ brush and started wholesale removal of aphids – until – I noticed lady birds eating them for me, so I have now left these helpful bugs to sort the problem out for me. All except in the greenhouse where the aphids have got on the tiny seedlings I have grown, with no lady birds in there, so they came in for a blast of water, then a brushing and I realise that I may have to do this again and again as I keep the greenhouse door open during sunny days. I’m much more relaxed about aphids now that I know what damage they can do and how to sort them. Good Luck.

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