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Depending on which part of the world you’re in, there are many plant diseases that can attack and quite often destroy the wonderful vegetable crops that we’ve so lovingly planted and cared for. And the challenge can be even greater if you’re like me and love to grow heritage plants. Here are a couple of diseases that can be challenging to your green thumb.
Powdery Mildew
One of the most common plant diseases, powdery mildew mainly attacks plants like zucchini, cucumbers, squash, pumpkins, peas and beans. However, I’ve even found some on my silver-beet/swiss chard. It looks like a powdery substance that covers the leaves, stems, flowers and sometimes even fruit.
It’s a fungus and the fungal spores are easily spread by wind. The best way to solve this problem is to try and prevent it from appearing on your vegetables in the first place. Make sure there is plenty of air circulation around your plants. And, ensure that as much of the plant is exposed to sunlight as possible. This naturally inhibits spore growth.
If you notice any infestation, pick off the affected parts of the plant and put them in the garbage. Only put them into the compost if it gets hot enough to kill the fungal spores. You need to be very diligent with this so the fungus doesn’t get a chance to spread.
You can also try spraying the leaves with some baking soda mixed with water as this raises the pH of the plant making it undesirable for the fungus.
Another way to control this unsightly disease is by visiting your local garden center or hardware store and checking to see if they have any organic sprays containing potassium bicarbonate. I’ve read that this works an absolute treat. For Australian readers there’s a product called Eco Fungicide, however, I’m not sure if it’s available elsewhere in the world. You could try googling it and see what you can find. I’ll be purchasing some the next time I’m in my local hardware store. And the best part is you only need to apply it once a week!
Tip – if you add some oil, Neem oil or even vegetable oil to your spray mixture it will help to coat the leaves and also stop the salt from the potassium bicarbonate accumulating in the soil.
Rust
This is another fungal disease and can be identified by yellow patches on leaves with orange/brown pustules on the underside of the 
leaves. Like most fungal diseases Rust favors warm, humid conditions and can weaken your plants by taking nutrients from the leaves.
Once again, prevention is better than cure, so make sure there’s plenty of airflow around your plants and if you do happen to see any signs, remove the infected plant part and destroy.
You can control this disease using the same spray as for the powdery mildew. Just remember to make sure you cover all the areas of the plant well including the underside of the leaves and to re-apply when needed.
Another way to assist your vegetables to resist the growth of fungus diseases is to spray the foliage with seaweed spray every 2 – 3 weeks. This will provide the plant with trace elements that it needs to be super healthy and resist disease infestation. The seaweed spray changes the pH of the leaves and strengthens the cell walls which makes the plant less attractive to fungal spores.
As a general rule, the healthier your plants are, the more disease-resistant they will be. So make sure you feed them well. Also, try to water in the morning to avoid moisture remaining on the plants in the cool of the evening.
