By: Teo Spengler
You don’t have to be a plant expert to recognize powdery mildew on barley. The barley leaves are sprinkled with white fungal spores that resemble powder. Ultimately, the foliage yellows and dies. If you grow barley in your home garden, it’s important to learn to recognize the symptoms of barley with powdery mildew. Read on for more information on powdery mildew, as well as tips on barley powdery mildew control.
Powdery mildew on barley is a fungal disease. You can recognize it by looking for fluffy white patches on the leaf surface of your barley plants. These spots get more gray as they mature. Barley with powdery mildew can appear as small isolated areas of white. But the disease can also cover the entire leaf surface as fungal spores germinate and infect the leaf.
When you see powdery mildew on barley, remember that the spores are using up the nutrients the plant requires to grow, reducing photosynthesis. This means that barley with powdery mildew won’t have much vigor and may stop growing entirely. The barley leaves can also die prematurely.
If you are wondering how to treat barley powdery mildew, unfortunately, it is not easily done. There is no magic wand to cure the problem and treating barley powdery mildew is difficult in a home garden. While it is possible to buy foliar fungicides that provide some barley powdery mildew barley control, this is expensive. And you have to apply it at least twice and sometimes even more often.
Instead of treating barley powdery mildew, experts recommend managing the disease with good cultural practices. Perhaps most important is to select a barley cultivar carefully, planting only those that are resistant to powdery mildew.
In addition to planting resistant cultivars, you can take other steps to prevent this disease from attacking your barley crop. Since barley that is planted early has a higher risk for infection, it’s a good idea to plant later rather than earlier.
Crop rotation, good garden clean-up and keeping down nearby weeds can also help prevent the overwintering of spores. It will also help if you don’t plant barley in dense stands or fertilize with high amounts of fertilizer.
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Sometimes. If powdery mildew has just appeared, you can sometimes kill it with natural substances. The best option is to remove visibly affected plants altogether, and then to stop further infection in its tracks with one or more of these natural treatments:
Copper sulfate both kills and controls powdery mildew and other bacterial and fungal infections. However, you should only apply copper sulfate before the flowering stage, and dilute it for use on young plants so that it doesn’t burn them. In addition, apply only when temperatures are below 85 degrees Fahrenheit so that leaves don’t yellow and drop off. Follow label instructions for use.
Barley straw rafts and pellets
Barley straw rafts and pellets can often inhibit the growth of powdery mildew and other organisms. While it won’t kill existing spores, it will prevent the growth of new.
That familiar brown bottle in your grocery store, 3% strength hydrogen peroxide, is a good natural treatment for powdery mildew. You can use a mix of hydrogen peroxide and water to control disease. Apply directly to the soil and mist on leaves for best control. You can also add hydrogen peroxide to your hydroponic solution.
Milk has natural “good” bacteria that can very effectively prevent powdery mildew. Use one part milk to nine parts water. It can significantly reduce current powdery mildew infections, and will prevent new ones from taking hold.
Background and rationale
Some of the major devastating diseases affecting crops, and therefore, threatening food security are caused by obligate pathogens. These include rusts (Basidiomycota fungi), powdery mildews (Ascomycota fungi) or Phytophthoras (Oomycetes). In particular Blumeria graminis is the cause of powdery mildew in cereal crops such as wheat and barley. Obligate pathogens, such as those mentioned above produce haustoria, which are specific structures at the heart of biotrophy: Haustoria are involved in acquiring nutrients from their host and they secret effectors proteins to promote virulence (Pliego et al, 2013) and interact with host proteins to compromise plant immunity Pennington et al, 2016, Lambertucci et al, 2019). Although haustoria are mostly of fungal origin, a plant extrahaustorial membrane (EHM) is formed in continuum but of different nature from the host plasma membrane. It is believed to facilitate susceptibility by accommodating the haustorium, while maintaining the invaded cell alive. So far, large scale -omic descriptions of haustoria have been limited to fungal transcriptomics (Bindschedler et al, 2016). Focusing on barley powdery mildew, a first pilot proteomics analysis described barley haustoria associated proteins (HAPs), some of which are predicted to be localised to the Extrahaustorial membrane (EHM Lambertucci et al, 2019). It was then shown that it is possible to use a novel transient gene silencing approaches to validate HAPs candidates for their role in modulating plant immunity. Similarly, the gene silencing approach can be used for validating the virulence role of candidate secreted effector proteins (CSEPs). Such studies largely disregarded more common haustoria core proteins, that might be equally important in maintaining the pathogenicity of the invading filamentous pathogens. Core functions, such as sugar and amino acid transport driven by functional ATPases, is already documented. Additional core proteins/enzymes of haustoria specific genes such as effectors) might be suitable “druggable” or “silencing” targets for disease control, as they are likely to be accessible for inhibition or silencing via the host, since haustoria are at the epicentre of intense molecular exchange and contact between the plant and the pathogen.
Aim and objectives
Further in-depth characterisation of the barley and Blumeria graminis haustorial structures and comparison with other haustoria bearing pathogens, will allow to unravel the essential core components required for disease success and biotrophy. This include the identification and validation of plant susceptibility factors and fungal proteins required for virulence during barley, wheat pea or strawberry powdery mildew infection. This PhD project will allow to contribute to this aim, by undertaking a mass spectrometry based multi-omics approach, to investigate the proteomes and metabolomes first of barley powdery mildew, and if successful of other powdery mildews, to characterise further specific and core components of haustoria. Haustoria and hyphae metabolomes and proteomes will be compared. Similarly, extrahaustorial membranes will be compared to host plasma membrane of infected cells. This will allow to identify haustoria associated metabolites (HAMs) and haustoria associated proteins (HAPs), in different powdery mildew pathosystems, in an effort to unravel key components of biotrophy, virulence, or modulators of immunity. In particular, common HAPs, constituting the core haustoria proteome, are likely to be required to convey full susceptibility or to modulate immunity. Therefore, a choice of interesting candidates will be selected. They will be further characterised using a functional genomics approaches, such as gene silencing strategies, to query their role in modulating immunity or promoting virulence. Ultimately, such research will serve to devise new strategies to reduce crop damage caused by biotrophic microorganisms.
When applying, specify the project ID (project code) in your application and mention this Find-a-PhD. Shortlisted candidates will be contacted by the end of May. Interviews will be held online in the first week of June or shortly thereafter. Project supervisors welcome informal project enquiries via email.
Powdery mildew is a disease that causes minimal long-term damage to trees in a forested environment. The forestry industry has traditionally dismissed the impact of this disease as a problem due to its minor effect upon the economic value of harvested stands. It is, however, a very real concern to growers of ornamental woody and herbaceous perennial plants, annuals, vegetables, fruits, grains and turf grasses. Within these industries, powdery mildew causes economic loss by weakening plants, promoting poor growth, and decreasing yields. In ornamental plants, powdery mildew detracts from the value of plants through the malformation and discoloration of leaves, destruction of fruit and flowers and overall decreased plant growth.
Powdery mildew disease is so common, widespread, and ever-present that the total losses in plant growth and crop yields most likely surpasses those losses caused by any other singular plant disease. Powdery mildew fungi do not typically kill their host, but instead interfere with normal plant growth by utilizing the host's nutrients, decreasing photosynthesis, increasing respiration, and increasing transpiration.
Signs and Symptoms of Powdery Mildew Disease
Make sure the soil around your plant is properly drained. Without proper drainage, your planting area can be a ripe breeding ground for disease organisms.
Adding organic materials through composting will generate beneficial microorganism activity which fights away disease and other garden problems.
Keep leaves as dry as possible. Water plants at the base instead of the leaves.
Remove all diseased leaves or branches throughout the season and once again before winter. Remove all diseased leaves and canes from the plant and surrounding areas.