Milkweed Yellows Phytoplasma

There have been a number of questions in the MEI group about phytoplasma, or "milkweed yellows'.

This is the best explanation I can come up with after an extensive search. It comes from this .pdf


Photo courtesy of Julie Ross, MEI member

Phytoplasmas are bacteria; they do not have a cell wall and are enclosed by a single membrane. They cause diseases in plants and are spread by insect vectors (primarily leafhoppers). 

Leafhoppers aren't the only insect that can spread phytoplasma, but most of the known vectors are in the insect order Hemiptera. Their piercing/sucking mouthparts allow them to feed on the phloem of plants, where phytoplasmas live. These phloem-feeding insect vectors can transfer diseases such as milkweed yellows phytoplasma by feeding on an infected plant, allowing an incubation period during which the phytoplasma cells replicate and eventually reach the insect’s salivary glands, and then moving to a healthy plant and injecting phytoplasma cells into it during feeding.

How do you know if your milkweed has a phytoplasma disease?
There are a few symptoms to look for, according to the Phytoplasma Resource Center found on the USDA Agricultural Research Service website:
- Phyllody—development of leaf-like growths in place of normal flower parts
- Virescence—development of green color in place of normal flower color
- Witches Broom—abnormal, excessive proliferation of axillary shoots resulting in a broom-like growth
- Yellowing—leaves lose normal green color, becoming yellow
- Little leaf—development of abnormally small leaves
- Proliferation—abnormal growth of numerous stems
- Necrosis—death of cells and/or tissues - Dieback
- death of branches
- Stunting—overall reduction of plant height
- Bunch top—shortening of internodes at and near the tip of a branch, resulting in bunched growth at the end of the branch

Photo courtesy of Julie Ross, MEI member

What should you do if you suspect phytoplasma in your milkweed patch?

Since the disease is spread by insect vectors, one way to get phytoplasma under control is to quickly and effectively eliminate any milkweeds suspected of phytoplasma, at the first sign of disease. By digging out an infected plant, you reduce the chances of other insects feeding on that plant and becoming vectors of the disease. 

Debbie Jackson, Monarch Watch Conservation Specialist, says ... 

Milkweed can be affected by a killer disease called phytoplasm. Signs: the leaves are wrinkled, like they're shrunken between the leaf veins, tissue near the veins is yellow, the plants are shorter and the stems are clustered too closely together than normal.

 - Please try to get all the root out to kill it. The entire milkweed planting may be affected because it is spread through the rhizome root system. You can't save part of it, you have to remove it all. The largest one I've seen was about 50' in diameter.

 - If you have monarch caterpillars to feed, you can dig it up, cut off the leaves, rinse & pat them dry, then refrigerate the leaves for up to 2-3 weeks to use for food.

Photo from Debbie Jackson
- The photo on the right is from my mom's garden in Marion, IA ....
pencil-thin stems packed together radiating from a node on the rhizome. 

 - Phyto kills milkweed and there is no cure. Leafhoppers suck up the disease and transfer it as they bite into other plants. Prevent it's spread by removing the affected plants. A friend of mine saw a clone of 200 common milkweeds die in 2 years from phytoplasm!

 - It has also been suggested to cover the milkweed plants with a mesh or tulle cover to avoid leaf hoppers getting to it and spreading the disease.

View more photos of phytoplasma at

You can also run a search for milkweed phytoplasma and then click "images" to see photos.


2021 was a good year

Monarchs in Eastern Iowa members did a great job raising monarchs from eggs and caterpillars again this year.

Below are the 2021 totals as well as totals since we started in 2014. 

In addition, many of our members give eggs and caterpillars away to friends and neighbors to raise, and some of those people end up joining our group and getting in on the action!

Congratulations on another good year!


A thank you

Monarchs in Eastern Iowa received an email from Rose, a student with the environmental club, OLSCA (Old Louisville Student Conservation Association, sent by a volunteer, Hannah, on her behalf.

Hannah wrote: Rose has been working on a project about how people interact with the environment, so she was doing research and ended up on the links page on this blog. It was a wonderful find because she was able to get some wonderful info from the sites on there & we're going to get a lot of use out of the links we bookmarked! She thought you might appreciate hearing how you helped us.

Rose also found an awesome page on photosynthesis for kids, at - https://www.lgcypower.com/solar-energy-and-photosynthesis/. It's a fun overview of the process with some vocab words. Rose was in charge of the plants this summer at her house, and she had the idea that we could include this in our thank-you note as a way of returning the favor! She thinks it's so cool how plants make their own food . She thought it would be a useful link for you, for other kids & students during this time, like us! Hopefully it's helpful!

 - Hannah and Rose


It is wonderful to hear that you found our site useful. Best of luck in your research! And thank you, Hannah, for the volunteer work you do with OLSCA, which looks like a wonderful club!

All the best!
Barb, Monarchs in Eastern Iowa