What Is Mint Rust: How To Treat Rust On Mint Plants


By: Kristi Waterworth

A kitchen garden feels empty without a decent collection of herbs, including many varieties of mint. These hardy plants are capable of producing a wide range of flavors for drinks and bakery goods and require little care. For keepers of mint, rust fungus is just one of a few serious diseases to bear in mind. Keep reading for information on mint rust symptoms and how to treat this disease.

What is Mint Rust Fungus?

Mint rust is caused by a fungus, Puccinia menthae, which only infects plants in the mint family, especially spearmint and peppermint. It is encouraged by overhead irrigation, which frequently allows water to stand on plant leaves long enough for the fungal spores to germinate. Closely planted mints, or those that need to be thinned, are at a heightened risk due to increased humidity around the plants.

What Does Mint Rust Look Like?

Rust on mint plants looks similar to other rusts in later stages, with orange to rust-colored spots covering the undersides of lower leaves in early spring. Mint rust symptoms may progress, manifesting as leaves that turn completely brown and drop from affected plants. In late summer and early fall, when these dropped leaves regrow, darker spots often appear instead. The very early stages of mint rust may appear as white bumps on mint leaves.

Controlling Mint Rust

There are many ways to control mint rust, depending on your preferred method of management. Organic gardeners and those looking to preserve beneficial insects may want to destroy infected mint plants or remove infected leaves if the disease is mild. Any rust-infected tissues should be immediately burned or double bagged, and all plant debris kept away from your mint to discourage re-infestation.

Thinning your mint stand will allow better air circulation that can dry out rust fungus without the use of fungicide. Changing the way you water will slow or even stop rust fungus; always water mint at the base, never on the leaves, and do it early in the day so water will evaporate quickly. Potted mints shoved into corners should be brought away from walls and fences.

Fungicidal Treatments for Rust on Mint Plants

When cultural modifications fail, you may want to consider chemical control. You’ll have to wait a number of days, anywhere from a week to about three months to harvest leaves after the final treatment, so only apply fungicide when absolutely necessary. Give cultural controls a week or more to work before moving to stronger control methods.

Azoxystrobin can be applied to infested leaves and only requires a week between treatment and harvest, though it may work more effectively when rotated with myclobutanil or propiconazole (both require a month before safe harvest). Ornamental mints can be treated with chlorothalonil; the 80-day wait to harvest won’t render the plants useless.

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How to Grow Mint Without It Taking Over Your Whole Garden

Plant this herb and you'll always have its bright, refreshing scent and flavor around to enjoy. But it also has a tendency to quickly spread, so here's what you need to know to keep this vigorous plant contained.

Mint has tons of different uses: Its fresh green leaves add a tangy punch to fruit salads, ice cream, sherbet, and brewed tea. It's a flavorful addition to a simple glass of still or sparkling water. And whoever heard of a mint julep without the mint? When you grow your own mint in your garden, you'll have a constant supply of this tasty, versatile herb. This perennial is tough and easy to grow, but the downside of its hardiness is that it can spread aggressively and become a weedy problem if you're not careful. Here's how to grow mint without letting it take over your entire garden and crowd your other plants


How to Treat Rust on Plants

Ugly—but seldom deadly—rust can be tough to eliminate. Follow these steps to treat plant rust and keep it from spreading in your garden.

Related To:

Plant Rust

Rust is also a disease that can harm your plants. But it isn’t just one disease it’s actually a group of fungal diseases that attack many different kinds of plants, including—but not limited to—roses, daylilies, carnations, snapdragons, mums, tomatoes, beans, pines, spruce trees and cypress. It can even attack your grass.

Photo by: Shutterstock/Margrit Hirsch

It’s easy to spot rust on a trowel or garden hoe. It’s that reddish-orange, flaky stuff that forms on iron and steel when they react with oxygen and moisture.

Rust is also a disease that can harm your plants. But it isn’t just one disease it’s actually a group of fungal diseases that attack many different kinds of plants, including—but not limited to—roses, daylilies, carnations, snapdragons, mums, tomatoes, beans, pines, spruce trees and cypress. It can even attack your grass.

The first signs of rust are tiny specks or spots on leaves that range in color from orange to rusty-brown, brownish-yellow, purple and red. Left untreated, the spots get bigger and turn into bumpy-looking pustules. Eventually, the pustules break open and release spores that are spread by wind or splashing water. As they land on other plants, the spores infect them, too.

Rust isn’t usually fatal, but it can cause your plants to decline. You may see stunted growth, dead branches and yellowing leaves that drop prematurely. Lawns take on a reddish tinge, and you may stir up orange dust when you mow or walk around.

Hot, humid weather is prime time for rust to attack, and it can be tough to eliminate.

But as always, it’s easier to prevent a problem than fix one. Try these steps to discourage it from taking hold in your garden:

  • Rust loves damp conditions, so avoid overwatering your plants. Use a soaker hose or drip irrigation to keep water off the foliage. (As a bonus, they’ll deliver water more efficiently than sprinklers or spray nozzles, saving money on your utility bills.)
  • If you water overhead, do so early in the day, so foliage has time to dry before nighttime.
  • Look for rust-resistant cultivars of the plants you want to grow. However, be aware that some of the fungal pathogens that cause rust can mutate, so some cultivars may be affected anyway.
  • Make sure that any new plants you buy or bring home are disease-free. If in doubt, isolate them from the rest of your garden for about three weeks to be sure they’re healthy.
  • When you plant, space the plants as recommended. Good air circulation can help prevent many diseases.

If rust appears anyway, try tackling the disease in one or more of these ways:


Rust Fungus: Controlling and Preventing Infection in the Garden

Written by The Seed Collection Pty Ltd Date Posted: 28 June 2019

Rust fungus is one of the most common diseases a gardener will come across. It can be a major concern in agriculture, but its appearance in a home garden also spells trouble.

Left unchecked, it can kill younger plants while stunting the growth of established ones. It's extremely difficult to treat, and all but impossible to eradicate completely.

Most of this difficulty stems from the huge number of fungus species which can cause the infection. There are an estimated 7,000 unique rust fungus pathogens, most of which only affect a narrow range of host plants.

Nonetheless, no matter which variety of rust fungus you encounter, the methods for controlling and preventing infection are broadly the same.

What Causes Rust Infection?

The various species of rust fungus prefer a specific set of conditions to infect a plant and begin reproducing. First, they need a period of relative dark, damp, and warm weather for the spores to attach to the plant and germinate.

Next, a period of hotter, dryer weather will start the fungus multiplying as the leaves dry out. Because of this, the greatest risk of rust is when the weather is changeable.

The first infection in a garden will usually be caused by spores being blown in on the breeze, or carried in on animal fur. However, once established, the spores can spread by being splashed up from the soil during watering, contagion by contact between plants, and even through the use of contaminated tools.

Diagnosing a Rust Infection

In the early stages, rust can be identified by small black specks on the undersides of leaves, or less frequently on the plant stems. These specks then become surrounded by rust-coloured blotches, which can range from yellow through red to brown. As the infection grows, these blotches form pustules, which look a little like clusters of aphid or spider mite eggs.

If left untreated, the rust will spread and the upper side of infected leaves will start to turn yellow, and they'll eventually wilt and drop. At all stages, the rust interferes with photosynthesis, reducing the vigour of the host plants.

Which Plants Does Rust Affect?

The vast number of rust fungus species means there are many different plants at risk. Anything from small annuals to large trees can be infected, but the infection won't often pass from one species of plant to another within a garden.

Some of the most common plants affected include roses, geraniums, snapdragons, pelargoniums, fuchsias, frangipani, myrtles, tomatoes, garlic and beans.

Treating Rust Infection

Unfortunately, there's no sure-fire solution to a rust infection. Chemical fungicide sprays can be effective, but with such a wide range of rust species to deal with, results can be hit and miss.

If you decide to go down this route, look for a product specifically recommended for your infected plants' species. Alternatively, use a more general purpose spray such as copper or lime sulphur, which can work by reducing the germination rates of fungal spores.

Before using any fungicide or other spray, read the label carefully to guard against unexpected side effects both for your plants and for the wider eco-system.

However, the more effective, longer-term strategy for dealing with rust is to contain it, reduce the risk of it spreading through your garden, and minimise the damage it does to your plants.

Controlling Rust Fungus Infections

If you spot a rust infection, it's important to act quickly. Remove all affected leaves, or the entire plant if the infection is severe.

Don't add infected material to your compost, as only the hottest of heaps are certain to kill off the spores. Burning or bagging up for disposal is a much safer way of handling the waste, even if it goes against the grain of sustainable gardening practice.

Importantly, take care not to spread spores to healthy plants when removing diseased ones, and be sure to thoroughly clean any tools you use afterwards to prevent transmission.

Once the initial problem has been dealt with, take ongoing action to reduce the risks of reinfection. Together, the following tips will help keep a rust problem under control, even when complete eradication isn't realistic.

  • Many plants have rust-resistant cultivars available. If possible, choose these when buying new plants or seeds. As well as providing protection for the individual plant, it'll keep overall spore counts down across the garden.
  • Check for signs of rust infection before buying seedlings or plants, to avoid bringing the spores home into your garden. Importantly, keep checking new arrivals for rust symptoms, as the fungus can lie dormant for lengthy periods until the right conditions for germination are met.
  • As with most pathogen problems, good gardening hygiene is crucial. Clean your tools after every use, and if you know you've been working with rust-infected plants, sterilise them with a mix of one part household bleach to nine parts water.
  • Use a crop rotation system to break the infection cycle, and to avoid fungal spores building up in the same spot over the years.
  • Don't overcrowd your plants, and don't let weeds invade. The more contact there is between leaves, the easier infections spread. Overcrowding also allows dampness to develop more easily by reducing ventilation.
  • If necessary, support taller plants to prevent contamination by leaning into each other.
  • Ensure the soil is well-draining to keep damp conditions under control. Add a layer of mulch if surface waterlogging is a problem.
  • Water the soil around the base of the plant rather than from above, to prevent the leaves from getting damp. However, be gentle to avoid splashing soil upward.
  • Beware of overusing nitrogen-based fertilisers, as these encourage the excessive leafy growth which rust fungus loves to feed on. If nitrogen is needed, consider a slow-release product to space out its impact.
  • In infected locations, rake the soil thoroughly to remove any debris, and add a mulch to reduce leaf contact with the earth.
  • Remove the lower leaves on large bushy plants, again to reduce soil contact, but also to improve air flow.
  • At the end of every growing season, clear your beds of all debris. In infected areas, burn or bag the materials rather than composting.
  • Never use seeds or bulbs from infected plants to produce the next year's generation.
  • Practice good soil management, adding plenty of non-infected organic material consistently. A healthy soil full of microorganisms helps to keep fungal infections in check, and also gives plants greater strength to resist the damage the fungus causes.

Rust fungus is very difficult to completely clear from a garden, thanks largely to the huge number of different species behind the infection. However, good garden hygiene and proactive control measures can keep the damage to a minimum.


Growing Mint - advice on how to grow Mint

Mint is a herbaceous perennial which dies back in late Autumn but burst back into life in Spring. The vigorous nature of Mint makes it a relatively easy plant to grow. However it is also a very invasive plant that will spread through the plot if left to its own devices.

Mint sends out lateral root runners under the soil that enable it to surface in another part of your plot and at the same time compete with your other plants for water, nutrients and light.

In this article we examine how to grow Mint successfully without letting it dominate your garden.

Preparation

The ability to encroach into the space of other herbs and plants in the garden is normally overcome by either growing Mint in containers or by taking measures to prevent the spread of the roots.

If you wish to grow your Mint in the soil rather than in a container on the patio / decking then use the following trick for restricting the sprawl of Mint. Use a large plastic plant pot (at least 15 inches deep) with the bottom cut out of it that enables the roots to grow downwards but not sideways.

Dig a hole in the herb garden / soil where you want to locate the Mint and put the container with no bottom into this hole. Leave around an inch of the rim of the container above soil level. The pot will act as a barrier to the lateral spreading of the Mint root runners and so keep the plant in check.

You could also use brick / pot / stones to form mini barrier walls under the soil between the mint and the next herb in your herb garden. However beware that if there are any cracks left in such a wall then the Mint roots will find their way through the cracks!

Sowing

Mint can be grown from seed although growing from seed is not always successful. Because Mint is so easy to propagate from cuttings this is often the chosen
method of obtaining more Mint plants.

If growing from Sow seed thinly in 3 inch pots and cover with a 1/2 cm layer of fine compost. Water the compost and place a clear plastic bag (sandwich bags
are ideal) upside down over the pot to help retain moisture. Secure the plastic bag with an elastic band.

Growing Mint from cuttings

If growing from cuttings it is vital that you inspect the plant you propose to take the cuttings from before you do so. If the plant shows any sign of being affected by pest or disease then do not use that plant to propagate from. The most common Mint disease is the fungal Mint Rust (see below).

Use a sharp knife or sharp scissors to take a cutting just below a leaf node (where leaves are emerging from the stem).

The cutting should be about 8-10cm in length.

Remove any established leaves from the bottom half of the cutting.

Cut the growing tip off the stem (found at the top of the cutting). Make sure to handle the cutting carefully, not squashing its main stem in any way.

You can now choose to place the cutting into either water or compost.

Growing in a glass of water can be great fun if your kids are involved as they can see the roots forming in the water). Simply make sure that at least the bottom half of the cuttings are submerged in the water, after about a week you will see roots starting to form. Wait another week or so and then pot the cuttings on into the containers you wish them to grow in. Throughout this period ensure that you keep the water level topped up as required.

You can alternatively put the cuttings into seed modules, 3 inch pots or directly into 7 inch or 12 inch pots which saves having to transplant again when the cuttings have taken root.

For seed modules or larger containers simply fill the container with compost, make a hole in the compost the depth of at least half the cutting length. Use a dibber or pencil to do this.

Put the bottom half of the cutting into the hole. Use the dibber/pencil to firm the compost around the cutting taking care not to crush the stem.

Mint does not like to dry out so it is essential to keep the compost moist whilst your seedlings are establishing. When your cutting is in pots you can help moisture retention by using an upturned clear plastic bag over the pot as described when planting from seed.

Position

Mint will thrive in a sunny position but will also tolerate some shade.

Growing more than one type of Mint

Although Mint will co-exist with other varieties of Mint it is widely believed that the qualities of the flavour and scent of the plants are reduced when doing so. Therefore if you want to have different varieties in a large container then plant the varieties in small sub containers and place these containers in the larger container.

Soil type

Mint likes a rich, soil that is fairly free draining although it does not like the soil to dry out.

Tending

When growing Mint in containers - cnce the root system has filled the pot or container then the plant can be lifted out of the pot and then divided into 3 or 4 plants and then each plant re-potted in the center of a new pot with additional compost to backfill the container.

Do this in spring and these plants will soon put on vigorous growth in their new container. This will help keep your plant healthy and enable it to expand its root system even though it is in a restricted space.

If you find your Mint plants have put on so much growth that you can't use it all then you can either preserve it (see below) for use over winter or at the very least make sure to keep cutting the growing tips back. This encourages bushy growth rather than having a long straggly plant.

Mint does not like to dry out so make sure to water regularly, especially if in terracotta pots which lose a lot of water through thepot walls. You can line your terracotta pots with old compost bags to help retain moisture.

Harvesting

Before winter you can cut the stems back to a couple of inches above the soil. This will give you a bumper crop of Mint that you can preserve by either:

  • Chopping into pieces small enough to put in ice cubes trays, top up with water and freeze. You can then add the required number of ice cubes to drinks (fantastic with Apple juice) or for adding to Gravies / mint sauce etc.
  • Tying around the bottom of the stems to create bunches of Mint that can be hung in a ventilated dry space to air dry them. See Preserving Herbs for more information.

Varieties

There are many varieties of Mint and each type has it's own strengths.

Spearmint is a perennial that is hardy and will grow to a height of about 45-50cm. As with other varieties it will spread laterally if not contained.

Moroccan Mint -the Moroccan variety is well known for its use in making great tasting tea.

Pineapple Mint - variegated (white/cream and green leaves)

Diseases

Mint Rust is a fungus that appears as small rust (orange) coloured patches that appear on the underside of the leaves of the plant.

If you have a plant showing signs of Mint Rust then remove it from the garden and destroy it. This is because it can easily spread to other plants and the soil thus affecting plants introduced in the future.

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