Treating mint rust - Ask Extension
I have 4 mint plants in their own individual mini beds in my larger garden bed. (I sunk edging around them last year to limit their spread. This is ju...
Knowledgebase
Treating mint rust #331371
Asked June 11, 2016, 9:10 PM EDT
I have 4 mint plants in their own individual mini beds in my larger garden bed. (I sunk edging around them last year to limit their spread. This is just their second summer.) Plants 1 and 3 have mint rust, with plant 1 being the worst hit and noticeably stunted. They're all planted at about 5 feet intervals. I made a spray of of aspirin and water, but most research says to remove and bag the whole of each affected plant, and burn the roots and surrounding area to kill spores in the soil. I've also been advised to then quarantine the healthy plants. How do I go about doing this? The whole bed is mulched with wood. Should I apply a fungicide to the entire bed? How large an area around each plant should I quarantine and how should I seclude them?
Oakland County Michigan
Expert Response
Hello,
Mint rust often is a problem when leaves stay wet too long. Use drip irrigation or, if you must water overhead, do so early morning so that leaves dry quickly in the sun.
Rust spores are always in the environment and travel on the wind. You speak of flaming(burning), which is a technique used by commercial growers to destroy plant debris. You may be able to hire a professional, who must have the correct equipment and have legal permits to do so. If you are in a residential area, burning or flaming may be prohibited.
It sounds like you have your plants far enough apart. You want them spaced for good air circulation. Plants should not touch and you should be able to see the breeze moving the branches as the wind blows. Barriers need to go 10-12 inches deep to prevent spread.
I believe the quarantine recommendation may be for indoor growers, such as greenhouses. Spores can move farther than your property boundaries, so they will always be present out-of-doors.
No home remedies or off-label uses of chemicals is recommended unless peer-reviewed research has shown effectiveness. So, I can't recommend use of aspirin, even though researchers are looking at how plants that produce salicylic acid internally trigger their immune response.
Some dish soaps have been shown to burn and damage some plants. Insecticidal soap is not the same chemical, and is safe to use as directed by the label. Here are the details on dish soap used in plant care---
Here is an article with recommendations for growing mint---
And here is an article on organic fungicides, should you need it---
Here is a list of fungicides available to home gardeners. The same fungicides used for rust on beans can be used on mints---
In summary, these are recommendations from extension publications to control rust in mint---
1 Keep the foliage as dry as possible. Do not work around the plants when they are wet.
2 When conditions become wet in spring or fall, use a fungicide labeled for vegetables, follow label instructions. Sulfur is an organic fungicide and gives some control of rust.
3 Remove all debris from plants during the season and in the fall after harvest.
4 Don't fertilize plants in early spring when wet conditions make rust more likely. Wait until after the rainy season, then fertilize.
5 Use a fresh mulch each year to prevent rain from splashing soil up onto leaves.
6 Remove any wild mint from your property. Rust spores from these blow onto your crop.
7 Remove mulch from the garden around the diseased plants. Turn bare soil over at the end of the season or when replanting. This buries the surface soil and helps prevent spores on the soil surface from reaching plants next season.
8 Do not compost diseased plant material. Bag it and throw it away.
Mints are perennial so, if you can prune off and remove the infected material, then treat the remainder of the plant with fungicide, you may be able to regrow a clean plant. Work when the ground and the plants are dry. Change the mulch around this plant. Treat all mint plants with the fungicide since all have been exposed to spores.
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