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White Rust Disease – Controlling White Rust Fungus In The Garden

White Rust Disease – Controlling White Rust Fungus In The Garden


By: Jackie Rhoades

Also called Staghead or white blister, white rust disease affects cruciferous plants. These plants are all members of the cabbage family (Brassicaceae) and include such vegetables as broccoli, cauliflower, Brussels sprouts, and kale and can ruin your crop.

White Rust Disease – What is White Rust?

What is white rust? It’s a disease that causes distinctive chalky white spore masses sometimes referred to as pustules that first show up on the underside of leaves. These blister-like masses, called sori, form under the leaf’s dermis (skin) and can’t be scraped off without damaging the leaf. The stem and leaves can become twisted and deformed. White rust disease can and will infect the floral parts as well. Broccoli and cauliflower, in particular, will produce grossly deformed heads and for those gardeners who collect seed for the following year’s planting, those seeds will be sterile.

White rust is one of several species of the fungus Albugo. It commonly occurs when nights are cool and damp and days are warm. The perfect time for growing cruciferous vegetables also provides the perfect growing conditions for Albugo. Controlling white rust fungus would be easy if we could control those spring and fall temperatures since it flourishes between 57 and 68 degrees F. (14-20 C.). Unfortunately, we can’t control temperature any more than we can control the spring rains or the dewy mornings this fungus adores.

White Rust Treatment

If your garden has been plagued by white rust disease in the past, you should look for resistant strains in the future. There are no fungicides specific to white rust treatment and once the disease becomes rampant, there is little to be done. That being said, fungicides used to treat downy mildew are sometimes effective against white rust, particularly the more leafy crops. Treatment must begin at the first signs of infection. The methods for controlling white rust fungus or how to prevent white rust are largely organic.

The control of white rust fungus depends on the understanding of the life cycle of fungi in general. Fungi reproduce by producing spores, tiny microscopic cells, each of which is capable of becoming a fungi and thus establishing a new colony– what we see on the leaf or stem. Due to their minuscule size, these spores are carried easily from plant to plant, or garden to garden, by wind or water. Since there is a protective coating, many of these spores can lay dormant for long periods of time, surviving in both cold and arid conditions. When conditions are right again, they ‘blossom.’

The secret to how to prevent white rust is two-fold. First is the removal of the places where the spores hide. Garden debris should never be left to overwinter. Even plant growth that looks healthy may be harboring spores waiting to spread the disease the following spring. Obviously infected debris should be disposed of away from the garden area. As it is almost impossible to collect and destroy every scrap of debris, consider tilling it under as another form of white rust treatment. While tilling won’t destroy the spores, it can prevent them from being exposed to the growing conditions they require.

The second step in controlling white rust fungus is crop rotation. Infected beds should not be replanted with cruciferous vegetables for at least three years.

Remember, good garden housekeeping is essential in controlling white rust fungus as well as many other garden diseases, therefore, it should be a regular part of your gardening calendar. That old adage remains true: An ounce of prevention is worth a pound of cure.

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Read more about Plant Diseases


What is rust plant disease? This fungal disease affects a wide range of woody and herbaceous plants. Even though it rarely kills plants, it reduces a plant’s health, vigor, and flower production.

What Causes Rust?

Rust disease is caused by a fungal parasite that needs living plants to survive. Rust diseases occur most often in mild, moist conditions. Rust is spread by spores that are transferred from infected plants to healthy plants. These spores can be transferred either by the wind or by water, which is why rust disease often spreads after watering. Wet surfaces are also needed to cause infections.


How to Get Rid of Rust on Beans

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Bean rust is a fungus that attacks the leaves, pods and shoots of bean plants. The fungal spores spread quickly and can take down an entire garden of beans if left unchecked. The most common symptom of rust is seen in the leaves, which become covered in a mix of yellow, brown and red. The use of fungicides and controlling conditions that lead to bean rust are the best ways to prevent the fungus from attacking your garden.

Use pruning shears to cut away entire shoots that have affected leaves and bean pods. While it's possible to prevent the spread of the fungus by removing individually affected leaves and pods, the fungus may have already spread to an adjacent leaf. It's safer to remove entire shoots.

Apply fungicides at the first sign of rust. Fungicides are only effective if applied before the rust overruns the bean plants. Dilute all fungicides in water, according to the manufacturer's instructions, unless the solution is ready to use. The University of California suggests applying sulfur in the spring, even before the first indication of rust.

Remove and replant any plants that are touching the beans or reducing airflow around the beans. Bean rust spreads easier when humidity rises, so keeping a nice flow of air around the plants better defends against the fungus.

Use a watering can to water the beans. Sprinklers and hoses can cause water to splash from an infected plant to another plant, causing the fungal spores to spread. If you must use a hose, do so in calm conditions and with low hose pressure. Do not spray water during windy conditions.

Check for spider mites. What looks like bean rust could be an infestation of spider mites. If left alone, spider mites will destroy leaves, turning them to a yellowish-brown, similar to what bean rust looks like. Spider mites are tiny red insects that create webs that look like dust on leaves. Miticides and sulfur both work well at keeping spider mites at bay.

Located in Pittsburgh, Chris Miksen has been writing instructional articles on a wide range of topics for online publications since 2007. He currently owns and operates a vending business. Miksen has written a variety of technical and business articles throughout his writing career. He studied journalism at the Community College of Allegheny County.


Disease Control

Examine spinach plants regularly for any changes or abnormalities. Identify diseases before treating for optimal results. Contact a licensed professional or local county extension agent for diagnostic assistance if you are uncertain which disease is plaguing the spinach plant.

Search spinach leaves for symptoms of downy mildew disease. Look for yellow spots on leaves that grow and fade to a light brown hue. Search the undersides of leaves for a fuzzy growth in a purple hue.

Remove and destroy spinach plants affected by downy mildew. Apply a fungicide to plants not yet showing symptoms of disease. Spray spinach with a fungicide containing an active ingredient such as mefenoxam for effective control of mildew.

Examine plants for white rust disease, a common problem on spinach. Search first for the presence of tiny yellow specks on leaf surfaces. Look for "chalk-white, cheesy, raised spore masses (sori) which occur mostly on the underleaf surfaces," according to the University of Illinois Extension.

Spray young infected plants with a fungicide immediately upon symptom development. Spray a fungicide with an active ingredient such as Pyraclostrobin during cool, humid weather once every one to two weeks. Remove and destroy mature infected plants, as fungicides cannot reverse advanced white rust damage.


Cultural Controls

The lack of fungicides registered to control white rust on turnips limits your options to cultural controls. One of the key ones is to buy high quality seed that is produced in a dry climate!

Since the organism can overwinter in plant debris in the soil, try to plant your seed in a well-drained bed that doesn’t have any plant residues in it.

It is important to eliminate any cruciferous weeds like mustard or shepherd’s purse near your plants, since they can harbor the disease. If you can, rotate your turnips with a non-cruciferous crop for at least two years to purge the soil of infective spores.

Try to minimize overhead sprinkling. That will not prevent the rust from causing disease, but it may minimize its severity.

After you have harvested your turnips, incorporate any remaining crop residue into the soil as soon as possible, so it will decompose and reduce the chances of the spores surviving.