Life in the swan plant patch

  • Creator
  • #52624


    Ants, aphids and swan plants

    When you get hooked on monarch butterflies you start learning a lot about swan plants… and all of the other life that lives in the monarch/milkweed community.
    At this time of the year a lot of questions are being asked about aphids. To rid our plants of aphids, we need to understand them… to understand aphids, we need to understand ants.

    Ants not only like the nectar-rich flowers of the swan plant but they have a symbiotic relationship with oleander aphids (Aphis nerii), both insects receiving some benefit from their association. In fact, ants actually ‘milk’ aphids by stroking their abdomen and collecting the honeydew. Their unique relationship provides protection for the aphids and food for the ants, with the ants taking it back to the nest to feed their larvae.

    Each spring winged female aphids come looking for their favoured plants (milkweed). The first offspring are female aphids without wings. These aphids give live birth to more aphids until conditions cause winged forms to be produced.

    Just like monarch caterpillars, these aphids pick up the toxic cardiac glycosides from the milkweed in their bodies. Their bright yellow-orange colour serves as a warning to anything that tries to eat them.

    (As a side-note, monarch caterpillars do not appear to be affected by aphids and according to observers, it would seem that on occasion aphids do get eaten by monarch caterpillars.)

    The presence of ants indicate large infestations of aphids. In fact, the aphids will allow themselves to be moved if the ants need to take them elsewhere! So managing ants is the first step in controlling the aphid population. Ant bait stations (such as Neverong, NO Ants and Raid) are effective. Ants carry the bait back to the main colony and then die. Ants in the nest eat the poisoned ants and die, ending more of them until the whole colony is destroyed or seriously depleted.

    Another tip is to wrap double-sided adhesive tape or similar around the base of swan plants (if of course the plants are stand alone and not touching other plants or walls etc. With less ants aphid numbers will drop.

    If left untouched to get out of hand the honeydew excreted by the aphids will turn black with the presence of sooty mould fungus. This generally does not harm the plant or monarch caterpillars unless there is too much of a build-up, which will kill the swan plant(s).

    An effective control for aphids is tiny parasitic wasps (Aphidius colemanii), the mummies of which can be bought from Bioforce. These will not harm humans – they do not sting.

    Female A. colemanii lay their eggs by inserting their ovipositors into aphids. The wasp’s larva then eats the aphid’s insides. The body of the aphid turns black and stiff, often referred to as a ‘mummy’ until the wasp cuts a hole in the aphid’s shell, emerges and continues to breed. These wasps will very quickly clean up your aphids.

    Ladybirds are another excellent predator of aphids. I have read that a single ladybird will eat 5,000 aphids during its lifetime – and in its larval stage it will eat about 400 aphids. Bear in mind, though, that when there are no aphids they could also eat monarch eggs. But when your aphids have gone, the ladybirds will generally move on too.

    There are some great photos of aphids and ants etc on the internet. I was enjoying checking my facts here and there tonight on the internet… and came across THIS page – and then I noticed that they’d featured a video I filmed (and my daughter-in-law put to music) here.

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  • Author
  • #52663


    I watched a video on Youtube where an aphid so annoyed a cat whilst in its “J” that the poor cat died. I haven’t seen any aphids in my swan plants, I think they are too busy sucking the life out of my vegie patch.


    rob cooper

    any ideas whats going on cheers


    rob cooper

    thanx for reply


    rob cooper

    lost 2 today err


    rob cooper

    intersesting jaqcki we have a major prob here now our big cage got infested with the aphids lost about 10 pillers our small went a bit funny lost about 9 piller so have bought fresh swan plants inside but our pillers wont eat them errrrrrrr have done a trial on big cage again sprayed it with a good oil over a week ago and kept it watered put a piller in there 3 days ago seems to be doing ok so i have no choice but put our inside one out in there tomorrow or we will lose them

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