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Milkweed and the Evil Yellow Aphids!

Milkweed and the Evil Yellow Aphids!  Bob Sussman 7/23/19

This is the time our year your native milkweed plants should be growing quickly and waiting for the fall arrival of the monarch butterflies (and queen butterflies too). All is easy and good except for a non-native visitor, that arrives out of no where and will eat/suck the life out of your milkweed plants. The “evil yellow aphids” have arrived.

You have to get rid of these little trouble makers. You can’t use “bug” spray because that will make the milkweed toxic for months and kill your caterpillars. Lady bugs are great aphid eaters but they fly away. I’ve tried neem oil but it’s hard to keep water and oil mixed for applying. Diluted alcohol? You may as well remove them by hand. 

Ok, here’s what we do….we use dish washing soap and water at a rate of 1 to 1-1/2 oz/gallon of water mix it in a sprayer and spray them. It’s easy to apply, doesn’t poison the plant, and works really well.  Downside? you have to repeat the spraying about every 10 days and the soap can build up but we water the field about twice / week and that takes care of that. Once you see the monarchs you have to stop and go to plan “B”, much less efficient means of control because the soapy water kill the aphids it’s not too good for the baby caterpillars. At that point however the milkweed plants are large and healthy- you can spray them off with water or go by some lady bugs.

1000 words? Maybe?

Some of our narrow leaf milkweed.

The narrow leaf milkweed – Asclepias fascicularis- waiting for their new homes and the monarch caterpillars.

Here come the “evil yellow aphids”

If left alone they will cover the plant until it’s pretty much near death – sometimes rescued by other bugs but the rescue might be too late.

Chemical warfare?

Dawn is good one but you can use “store” brand just fine. Use at a rate of 1 to 1-1/2 oz/gallon – much more than that you’ll begin to burn the leaves.

The results!

Next day the aphids begin to turn black and drop off the milkweed plants.

And in a few weeks you’ll be seeing these and it’s all good!



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Iris 'Dr. Richie'

Common Name

Dr. Richie


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1' tall × 2' wide

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Filtered Sun / Part Shade / Shade


Drought Tolerant / Occasional
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