How can I get rid of the infestation of aphids on our milkweed without hurting the Monarch caterpillars?

Question

It's a terrible paradox...I got the milkweed for our garden to have butterflies. I've tried/tested a soap/oily mixture and sprayed on one of our milkweeds, it killed the aphids, but the "lady" Monarchs didn't lay eggs on it because of the film it left on the plant...even after 3 weeks! Our other 2 milkweed plants have literally thousands of aphids on each plant...AGH! ...HELP! Thank you... :)

Answer 1

Your best and safest way to remove aphids is simply water pressure... hose spray. They even sell a special hose end sprayer gadget for that purpose (check with your local nursery). It sprays water in a rotary sort of way so it gets on top of and even under the leaves where aphids are. But even just a strong hose spray will work, you just have to remember to get under the leaves, too! Spray directly at the aphids and like magic they are gone. So whenever or wherever you see them just spray them off with water.

And it doesn't cost any money, time to prepare or accidental loss of any beneficial  insects.

But if you must spray something... here is a formula that will also do the trick.

I like the smell of this spray, and your not using harmful chemicals! It actually attacks the aphids nervous system.

Citrus Killer for Aphids...

1 pint water

rind from one lemon, grated (you can also use grapefruit or orange rinds)

pump spray bottle

Directions...

1. Bring water to boil. Remove from heat and add grated lemon rind

2. Allow the mixture to steep over night.

3. Strain the mixture through cheese cloth, and pour into your pump spray bottle.

4. Apply the mixture to just the plant leaves that are under attack by aphids, on top and underneath the infected leaf. The spray must come in contact with the aphids bodies to be effective. But keep in mind to just spray it directly on 'only' the aphid infected leaves because this spray will kill any soft bodied insects, (like any aphid killer will), if you spray the whole plant.

Answer 2

You are truly stuck in a catch 22. What I would do is hit the plants with insecticidal soap (the same thing you used or a store brand) give it a day or two to kill the aphids and then hose it off the plants.  This will not have as good of an effect on the aphids since you will be washing it off, but at least it will lower their numbers. You may want to hit the surrounding plants as well to slow down the aphids return. I would not use the citrus idea because the citrus itself will keep the insects you want to move in away from your plants.

Answer 3

Go to your local garden store and ask if they have lady bugs for sale. I live in southern California and our local Green Thumb nursery has them in plastic bags. There are about 100 to 200 in a bag. Each bug will eat dozens in a day.