Our Blog

Garlic Cloves
Pests and Diseases Nutrient hydroponics

Posted By: Plant Magic

Diseases That Affect Garlic: Leek Rust and Onion White Rot

Garlic is a heavy feeder, which means that plants require hydroponic nutrients such as phosphorus and potassium. Knowing how to grow garlic efficiently will require you to keep an eye on your plants to make sure they are free of pests and diseases - and that new plants don’t contaminate existing ones.

Leek rust and onion white rot are two of the most common diseases that can affect garlic, and it’s vital to know the signs of infection in plants before they spread.


Leek Rust

Common in leeks, this fungal disease can affect chives, onions, and garlic. Puccinia allii is a pathogen that rarely affects onions severely in the UK, but garlic plants require extra attention. These fungi are biotrophs, which means they live within plants’ living tissues and extract their nutrients without killing the plants.

As the disease is incapable of living in dead plant tissues, leek rust can be controlled between growing seasons. Leek rust attacks often begin around mid-spring until early-summer, with the rust spores from infected plants being released. Spore germination and release typically occurs when temperatures are at a range between 10ºC and 20ºC.

Between early-summer until late-autumn, the rust fungus germinates in infected plants and begins presenting symptoms as early as a week after germination. The following symptoms occur in plants:

When the disease is severe, leaves can become less vigorous and they eventually shrivel.

Leaves gain bright orange pustules on both sides, which with time break open and release dusty, orange airborne spores.  

Our recommendation: Essence Leaf is a great way to help cure leaf diseases from fungal pathogens. BioSIlicon helps to strengthen plants’ leaves and stems for higher resistance to fungi diseases.

Bunch of Garlic Cloves

Onion White Rot

Onion white rot is a big threat to onion family plants, affecting all alliums like shallots, onions, leeks, and garlic. This serious fungal disease, Stromatinia cepivora, can remain in the soil for many years. The sclerotia, round and black structures of approximately 0.5mm of diameter, stays dormant until an allium is planted.

Sclerotia has the ability to detect some of alliums’ unique volatile chemicals, proceeding to germinate and produce the fungal growth that directly attacks the roots.The soil is re-contaminated when more sclerotia is formed on the rotting bulbs.

Should the white rot have a low incidence in the garden, the infected plants are usually easily culled and destroyed. A widespread infection, however, requires you to completely restart your crop in a different location.

In the UK, temperatures above 20ºC don’t allow for fungal growth or sclerotia germination of onion white rot. Wet and cool summers are problematic, with symptoms typically appear around mid-season to harvest. You may notice the following:

  • Onion white rot starts by attacking the roots, which become rotten, before invading the bulbs.
  • A fungus growth on the garlic bulb base, appearing white and fluffy, eventually turns into small and black structures.
  • The foliage presents wilting and yellowing as the first symptom.
  • In wet weather, this disease can make garlic plants become loose instead of wilting.

Healthy Garlic Cloves

Prevention is the best medicine when it comes to onion white rot and, as such, it’s vital to make sure that all equipment used is properly disinfected. A quarantine area for new plants allows for you to see if the garlic plants are infected before planting them and potentially infecting your soil. If you’re wondering how to plant garlic effectively, growing from seeds can be a great way to prevent this disease.

Our recommendation: Oldtimer Granules provide garlic plants with improved stress tolerance and helps to form a protection barrier against root diseases.

Making sure that plants have all of their needed nutrients as they grow provides them with the best chances at being healthy and disease-free. Contact us to know more about our range of products and how they can help plants.

Our Blog: Hydroponic Tips & Tricks

Whether you are an expert who already has a thriving crop of healthy plants, or you are trying to grow your very first hydroponic yield, we can help you to grow the strong and healthy crops you have always wanted.

Here at Plant Magic Plus, our team of gardening experts work very hard behind the scenes to provide you with the high quality nutrients, additives and growing media that will help you to get the most out of your growing plants.

But we understand that successful horticulture is about more than just having good quality chemicals, nutrients or fetilisers, that's why we have written this blog to provide you with the insights, tips and techniques you will need to give your garden that extra magic touch.

From helpful advice about watering your plants in soil and a guide to magnesium nutrients, to top tips about growing hydroponic vegetables and a comprehensive overview of microbes, we’ve got everything covered.


Search through our previous blog posts by month.

View All


If you have a question or query about a product of ours, or you want to know more about the fascinating plant growing cycle, why not contact us via our contact form or reach out to us on our Facebook page? Or do you want to suggest a new blog topic for to us to write about? If we haven’t covered a topic that you want to learn more about, we want to know!

Alternatively, you can read through our extensive list of the most frequently asked questions in our FAQ section.

Plant Magic horticulture nutrients promoting healthy plant growth logo

Feel free to contact us for any advice you may need.

Paddock Road
Skelmersdale WN8 9PL

Tel: 01695 554 080
Company No. 06745959
VAT No. GB 942806906

Copyright ©2019 Plant Magic Plus Ltd.