Rust on green beans

Rust Spots On Bean Plants: How To Treat Rust Fungus On Beans

There is nothing more frustrating than putting your blood, sweat and tears into creating a perfect vegetable garden, only to lose plants to pests and disease. While there is a lot of information available for blights that affect vegetable plants such as tomatoesand potatoes, fungal diseases of beansare not mentioned very often. This article will address what causes rust on bean plants and how to treat rust fungus on beans.

Rust Spots on Bean Plants

Rust spots on bean plants can look like a reddish-brown powder. Sometimes these red-brown patches may have a yellow halo around them. Rust fungus can appear on the plant’s leaves, pods, shoots or stems. A field of beans affected by rust fungus may look like it has been burned or badly scorched.

Other symptoms of rust fungus are wilted foliage and small, deformed bean pods. An infection of rust fungus can lead to other disease and pest problems. Weakened diseased plants are often vulnerable to other diseases and pest infestations.

Like many other fungal diseases, rust spots on bean plants are spread by airborne spores. These spores infect the plant tissues then reproduce in hot, humid weather, making more spores. It is these new spores that appear as a reddish-brown or rust colored powder on the plants.

Generally, these fungal spores are most abundant in the heat and humidity of summer months. In milder climates, where plants do not die back to the ground in autumn, these spores can over winter on plant tissues. They can also over winter in garden debris.

How to Treat Rust Fungus on Beans

As a preventative measure against rust fungus, many bean growers will add lime sulphur to the soil around bean plants in early spring. Some other ways to prevent rust spots on bean plants are:

  • Properly spacing plants to allow for air flow and prevent infected plant tissues from rubbing against other plants.
  • Watering bean plants with a slow trickle directly at the root zone of the plant. Splashing water can spread fungal spores.
  • Keeping garden clean of debris that can be a breeding ground for pests and disease.

If you suspect that your bean plants have fungal rust, remove and dispose of all infected tissues of the plant. Always use sharp, sanitized pruners when pruning plants. To reduce the spread of disease, it is recommended that you dip pruners in a mixture of bleach and water between each cut.

After infected tissues have been removed, treat the whole plant with a fungicide, such as copper fungicide or neem oil. Be sure to get all surfaces of the plant and also spray the soil around the plant crown. Regularly inspect the plant for any sign that the disease has returned.

International Journal of Pest Management

Rust control and ethylenebisdithiocarbamate (EBDC) residues in green beans ( Phaseolus vulgaris L. ‘Morgan’) were evaluated in two seasons of 1993 in Dschang, Cameroon. Four weekly applications of mancozeb (2.8 kg ha- 1), sulphur (2.24 kg ha- 1), or mancozeb+sulphur (1.4+1.12 kg ha- 1) were initiated from initial rust symptoms. In both seasons, treatments with mancozeb alone resulted in a low area under pustule count progress curve (AUPPC) and a significant increase in leaf area index, and pod and green fodder yields. Pod yields were negatively correlated with AUPPC. Pod yield loss was estimated at 61% and 32% in the early and late seasons, respectively, while losses in green fodder yields were 57% and 24% respectively. EBDC residue levels decreased significantly with a delay in pod harvestand when pods were washed in running tap water. Residue levels were high in the late season, possibly due to low rainfall. Pods exposed to the combined fungicidal treatments accumulated higher levels of residues than those sprayed with mancozeb alone, suggesting a potential risk of EBDC accumulation on pods when EBDCs are mixed with sulphur.

Signs of Rust (And What Causes Them)

Rust: if your car has it, you’re probably not happy about it. But, when left unchecked, a rust spot can quickly grow until it causes a structural problem. In many states a car with rust holes in the body won’t pass inspection, regardless where the spots are located or how serious they are.

For these and other reasons, it’s best to deal with the problem as soon as you spot it. Understanding the rusting process, the problematic areas, and the ways to address trouble are crucial to repairing rust before it’s a serious issue. In this first article, we’ll discuss the types of rust and what causes them.

Types of Rust

Rust is the layman’s term “oxidation,” or the breakdown of iron-based metals. Given enough time and exposure to the elements, most types of iron and steel will completely reduce to iron oxide through the rusting process. Since these metals are commonly used in cars, there are three main types of rust for drivers to be concerned about:

1) Surface Rust

The first signs of surface rust usually appear in the paint. This type of rust preys on small nicks, cracks, and scratches. As the clear coat wears you paint also becomes vulnerable to wear and abrasions. Once water penetrates the unprotected metal, it oxidizes. Pure iron and aluminum don’t oxidize as aggressively but steal tends to have impurities in the metal that accelerate the rusting process.

2) Scale Rust

Exposed steel rusts at different rates depending on a few variables: alloy components, thickness, the environment the steel is in, and the type of heat treating the steel undergoes. Scale refers to the oxides of iron that are formed on wrought, or worked, metals as a result of mill operations (usually from high temperature rolling or furnace treatment). These chemical processes corrupt the surface and reduce the metal’s strength, making it more vulnerable to oxidation. Over time, water can react to the chemicals used in a heat treatment creating scale rust. Scale is usually hard but brittle and flaky.

3) Penetrating Rust

After prolonged exposure to the elements, oxidized steel is typically converted to brittle iron oxide and holes form. Automakers do a lot to try to prevent this severe type of corrosion, and many vehicles now have a thick coating on the underside which chemically seals the steel against oxidizing agents. But those dips and coatings wear off over time, especially on the road side of the vehicle where salt and other elements cause excessive wear on the metal. Penetrating rust can usually be prevented if it’s caught and treated early enough.

At V&F

Just a little extra vigilance reduces rust to no more of a problem than any other regular maintenance issue. At V&F, our expert mechanics use latest diagnostic equipment, and high-quality CARQUEST auto parts, to make sure we get the job done right. Call us today at (413) 314-2280 or schedule an appointment online.

How does rust work?

­R­ust is the common name for a very common compound, iron oxide. Iron oxide, the chemical Fe2O3, is common because iron combines very readily with oxygen — so readily, in fact, that pure iron is only rarely found in nature. Iron (or steel) rusting is an example of corrosion — an electrochemical process involving an anode (a piece of metal that readily gives up electrons), an electrolyte (a liquid that helps electrons move) and a cathode (a piece of metal that readily accepts electrons). When a piece of metal corrodes, the electrolyte helps provide oxygen to the anode. As oxygen combines with the metal, electrons are liberated. When they flow through the electrolyte to the cathode, the metal of the anode disappears, swept away by the electrical flow or converted into metal cations in a form such as rust.

­For iron to become iron oxide, three things are required: iron, water and oxygen. Here’s what happens when the three get together:


When a drop of water hits an iron object, two things begin to happen almost immediately. First, the water, a good electrolyte, combines with carbon dioxide in the air to form a weak carbonic acid, an even better electrolyte. As the acid is formed and the iron dissolved, some of the water will begin to break down into its component pieces — hydrogen and oxygen. The free oxygen and dissolved iron bond into iron oxide, in the process freeing electrons. The electrons liberated from the anode portion of the iron flow to the cathode, which may be a piece of a metal less electrically reactive than iron, or another point on the piece of iron itself.

The chemical compounds found in liquids like acid rain, seawater and the salt-loaded spray from snow-belt roads make them better electrolytes than pure water, allowing their presence to speed the process of rusting on iron and other forms of corrosion on other metals.

On the following page, you can check out more links about rust.

Hollyhock Rust

Hollyhock rust causes orange to yellow spots on leaves of hollyhock & other plants in the mallow family.(Pic – Stephanie Porter)

Nicole Uelmen*, UW-Madison Plant Pathology
Revised: 3/6/2014
Item number: XHT1231

What is hollyhock rust? Hollyhock rust is the most common fungal leaf disease of hollyhocks (Alcea rosea). Many other ornamentals (e.g., flowering maple, rose mallow) and weeds (e.g., common mallow) in the mallow family are also susceptible. Hollyhock rust can quickly spread, causing stunting of plants and premature leaf drop. In rare instances, hollyhock rust can result in plant death

What does hollyhock rust look like? Initial symptoms of hollyhock rust are orange to yellow spots (roughly ⅛ to ¼ inches in diameter) on lower leaves. Irregular brown areas may also develop on stems. As the disease progresses, brown to dark-red raised “bumps” (fungal reproductive structures called pustules) develop on the undersides of leaves beneath the orange/yellow spots. Severely affected leaves often develop holes that give them a lacy appearance. These leaves may eventually shrivel and die.

Where does hollyhock rust come from? Hollyhock rust is caused by the fungus, Puccinia malvacearum which can be introduced into a garden by windborne spores or on infected transplants. Further localized spread of spores is possible by wind, by splashing rain, or by splashing water from a sprinkler. Warm and humid temperatures favor the growth of the fungus. P. malvacearum can survive the winter in hollyhock leaf and stem debris.

How do I save a plant with hollyhock rust? Once symptoms of hollyhock rust appear, control can be difficult. If you observe the disease very early in its development, remove symptomatic leaves and dispose of them in your municipal garbage (where allowed) or by deep burying them. Consider follow-up fungicide treatments (although such treatments will be most effective when applied before any symptoms appear). If you decide to use fungicides for control, select products that are labeled for use on hollyhocks (or more generally on ornamental flowering plants) and contain the active ingredients chlorothalonil, mancozeb, myclobutanil, tebuconazole, or triticonazole. When making more than one application, DO NOT use the same active ingredient for all treatments. Instead, alternate the use of at least two active ingredients with different modes of action to help minimize problems with fungicide-resistant variants of the hollyhock rust fungus. Myclobutanil, tebuconazole and triticonazole have similar modes of action and should NOT be alternated with one another. Be sure to read and follow all label instructions of the fungicides that you select to ensure that you use products in the safest and most effective manner possible.

How do I avoid problems with hollyhock rust in the future? Remove weedy mallow plants (especially common mallow) from your garden; they can serve as a source of P. malvacearum spores. Also, be sure to remove all hollyhock debris in the fall to eliminate another place where the fungus can overwinter. Weeds and plant debris can be disposed of as described above. DO NOT use seeds from infected plants and inspect new hollyhock plants for rust symptoms prior to purchase. Some hollyhock varieties are resistant to some, but not all, variants of P. malvacearum. Thus use of resistant varieties may not be a reliable method for control of hollyhock rust in all situations. Avoid planting hollyhocks densely to allow better air circulation that will promote more rapid drying of plants, as well as reduced humidity. Water and fertilize properly to promote optimal growth of your hollyhocks. DO NOT water with a sprinkler as this will wet leaves; use a soaker or drip hose that applies water directly to the soil. Fertilize only when needed based on a soil fertility test.


Additional Images

Brown to dark-red bumps on the undersurface of leaves is typical of hollyhock rust. (Pic- Tom Creswell, Purdue Univ)
Tags: disease, rust Categories: Flower Problems, Flowers

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