Onion Black Mold Info: Managing Black Mold On Onions

by johnah on November 26, 2020

Mold on Red Onions: What Is White Mould?

White mold on onions is not just a fungus or bacteria. It’s actually a type of microorganism called Bacillus thuringiensis (Bt). Bt is commonly found in soil and water, but it can also grow in the environment where onions are grown. When onions are harvested, they have been sprayed with pesticides. These chemicals kill off any harmful organisms that might otherwise live on the onion before it reaches your plate. However, these same chemicals can also cause other problems such as killing beneficial microbes that make up the onion’s natural defense system. These beneficial microorganisms include yeasts and molds which help keep the onion healthy and prevent disease from developing in the first place!

The problem is when these beneficial microorganisms die off, the onion becomes susceptible to diseases like black mold. Black mold on onions causes yellowing and brown spots all over the surface of the onion. Sometimes the spot will turn completely black. While some people may think that eating spoiled food is bad for them, this is actually worse than eating rotten meat because it can lead to death!

Black Mold On Red Onions: How To Prevent It From Happening To You!

You can prevent the growth of black mold on onions by making sure blossom end rot does not occur.

Why does blossom end rot occur?

Blossom end rot occurs in plants when there is a lack of calcium within the plant’s cells. Without calcium within the cell walls, the plant is greatly weakened and cannot function properly.

To prevent blossom end rot from occurring, follow these steps:

1. Add 1 tablespoon of Epsom salt to a watering can.

2. Fill the rest of the can with water.

3. Water your plants as usual.

This process is known as “foliar feeding”. By providing a small amount of nutrients directly to the leaves of the plant, you can prevent blossom end rot from occurring in the first place. Foliar feeding will not prevent the growth of mold if the conditions are otherwise ideal (i.e. it’s very humid and warm), however foliar feeding on a regular basis will provide your onions with some basic nutrients that will help to keep them alive longer and deter the growth of mold.

If you are growing your onions from seeds, you can prevent blossom end rot by providing the seeds with a small amount of calcium. You can do this by adding some eggshells to the soil before you plant the seed. Be sure to crush the eggshells up into tiny pieces first. This process is known as “priming” the soil.

Onion Black Mold Info: Managing Black Mold On Onions - Image

Black Mold On Onions: Prevention And Treatment

How do you prevent black mold on onions?

You can prevent black mold on onions by following these steps:

1. Keep the soil around your plants well ventilated by intermittent deep watering.

Onions need a lot of water, but too much water can cause the roots to become soggy and encourage mold growth.

2. Space out your plantings.

Black mold is more likely to develop when a lot of plants are in close proximity to one another. Keeping your plants spaced apart will give them more air circulation which will prevent black mold from occurring.

3. Avoid planting your onion sets or seeds in soil that has previously grown onions for at least three years.

The same applies to gardeners who use the same plot each year. It takes time for harmful organisms to build up within the soil and having fresh soil every few years prevents this from happening.

4. Make sure you plant your onions in a well-ventilated area.

Onions (especially sets) need a lot of air circulation. Be sure to plant them in an area that gets a decent amount of wind so that the plants are not surrounded by still air.

5. Use mulch to help regulate soil moisture and keep down weeds, but be careful that the mulch you use (such as wood chips) do not retain too much moisture.

6. Avoid planting your onions in soil that is prone to retaining moisture such as that found in a floodplain.

7. Finally, make sure you plant your sets or seeds at the right time.

In other words, wait until the soil has warmed up a bit before planting. Temperature and moisture play an important role in deterring the growth of mold.

If you are unfortunate enough to have black mold develop on your onions despite taking all the right precautions, do not despair. There are ways to treat black mold on onions successfully.

The first way to treat black mold on onions successfully is to remove all of the infected plants and discard them. All of the soil should be removed and some experts even recommend burning it. Next, treat the area with a fungicide to ensure that all of the mold is killed off.

The second way is almost the opposite of the first. Instead of removing everything and starting over, some gardeners will only remove part of the infected plants. The idea is that by leaving some of the plants in place, the mold will not have enough time to grow back as long as you replant quickly. To do this, discar

Sources & references used in this article:

Analysis of Onion Management Practices as they relate to levels of Aspergillus niger (Black Mold) and Development of IPM scouting protocols for Black mold by T Rusinek, J Mishanec – 2000 – ecommons.cornell.edu

Nature and source of inoculum of Aspergillus niger causing the Aspergillus black mold disease of onions in New York by JW Lorbeer, VE Ransom, JJ Tuffley – 2000 – ecommons.cornell.edu

Onion Rule Based System for Disorders Diagnosis and Treatment by MA Alajrami, SS Abu-Naser – 2018 – dstore.alazhar.edu.ps

Management of black mold rot of onion. by AH Wani – Mycopath, 2011 – cabdirect.org

… of Plant Compost Leachates to Control Black Mold (Aspergillus niger) and to Induce the Accumulation of Antifungal Compounds in Onion Following Seed Treatment by N Özer, ND Köycü – BioControl, 2006 – Springer



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