Bacteria are tiny organisms that cause damage in the following ways: Rots—which involve the decay of leaves, stems, branches and tubers.

Blockage of a plant's vascular system can cause wilting—and galls, that are a result of an over-growth of the affected cells.

Bacterial problems are encouraged by wet soil, high humidity and high night-time temperatures. The use of disease-free seed and resistant varieties can help control bacterial disease.

Infected plants should be removed immediately from the garden and burnt. Crop rotation can also be a good preventative measure.


Fungi are often visible to the eye, with fungus diseases named for their appearance.

Downy mildew

Fungi Diseases Plants

Downy mildew on grape leaves

Downy mildew grows from within a plant and sends out branches through the victim's stomata to create pale patches on leaves.

Powdery mildew

Powdery mildews live on the surface, and send hollow tubes into the plant to suck out nutrients.

Powdery mildew on strawberry plants

This mildew can spread rapidly since the disease cycle can be completed in as little as 72 hours.

However, it commonly takes 7 to 10 days from the time of infection to the development of symptoms and secondary spore production.

Preventative measures

Try to grow powdery mildew resistance varieties. Plant in full sunlight in a well-drained area. Don't crowd plants. Avoid using too much high nitrogen fertiliser which can promote tender leaf formation.

Remove and destroy plants that are infected. Water plants in the morning to give the plants the rest of the day to dry off, discouraging establishment of fungus diseases.

Organic sprays

Sulphur is highly effective against powdery mildew. Apply a sulphur-based fungicide at first evidence of mildew, and repeat applications as necessary.

However, sulphur can be damaging to some squash and melon varieties. Another option is to spray once a week with a solution of baking soda.

Baking soda increases the surface pi I of the leaf making it unsuitable for the growth of powdery mildew spores. Be sure to spray the undersides of leaves as w ell as the upper surfaces when using any of these sprays.

Home-made baking soda spray

One teaspoon baking soda, one litre water A few drops of liquid detergent—which acts as a surfactant and encourages the mixture to stick to the leaves.

Garlic contains high levels of sulphur and a few cloves crushed in water can be used to make a home-made spray.

Other plant diseases

Rust is named for the colour imparted to leaves. Leaf spot causes yellow-green spots. Soil-inhabiting fungi causes damping-off.

Spacing plants to allow for good air circulation can help to control some fungus diseases. Spraying plants with liquid seaweed foliar spray can also be helpful.

Environmental problems

Environmental problems such as heavy unseasonat rain, exceptionally hot sunshine, strong winds and consistent high temperatures can also contribute to the development of fungus diseases.

A soil rich in soil organisms is the best insurance against plant diseases, providing conditions favourable to vigorous growth.

Beneficial fungi and bacteria which feed on destructive species can keep soil bacteria and fungi in balance.

Many diseases of plants can also be eliminated by careful observation and taking appropriate action before the situation gets out of control.

Smokers should not handle plants without first washing their hands because of the risk of spreading tobacco mosaic disease which is often found in tobacco.

To protect tomatoes from viruses, it is best to isolate them from potatoes and cucumbers.

Bordeaux fungicide Discovered in 1882

In Medoc in southern France, many acres of grapes were grown.

But young boys often used to snatch and carry off the grapes that grew by the roadside.

The owners of the vineyards, becoming increasingly annoyed, had resorted to splattering the broad green leaves of the vines with a lime and water slurry to resemble bird droppings. They did this in the hope that it would deter the boys from stealing the fruit.

Some owners, a little more vindictive, added some bluestone, a substance well-known to be poisonous. This blue-white, sickly-looking concoction would stick to the grapes and foliage even through the heaviest rainstorms.

The summer of 1882 was particularly wet and mildew rotted the grapes, threatening to destroy the vines themselves.

Late that season, Dr. Pierre Millardet, a professor of botany, was inspecting the devastated vineyards in the area, lie noticed that the few plants near the roadway were healthy, and heavy with well-ripened grapes.

Those further back in the vineyard were defoliated and the grapes were shrivelled, rotten, or unripened.

Dr. Millardet learned of the composition of the concoction that remained splattered on the sound leaves and fmit. During the next two years, he experimented with mixtures of lime, iron, and copper salts, but found the original combination of ingredients worked best.

He then calculated the most effective proportions and published his findings in 1885—naming the new spray 'Bordeaux mixture'.

The new fungicide was later improved with the addition of copper sulphate. Although found by chance, it is still in use today.

Non-toxic fungicides used by organic gardeners are:

Bordeaux mixture

Home made recipe: Stir 90g copper sulphate into 4'/2 litres of hot water and leave overnight. Next day, mix 125g garden lime with 4.5 litres of cold water. Mix with the copper sulphate and use immediately. Baking soda: For mildews and rusts. 500 g baking soda, 15 litres water, 250 g soap. Mix thoroughly. Can also be used to control scale. Copper-oxycloride

A commercially available preparation, useful for treating all types of fungus diseases.

Chamomile tea: Make up as a drinkable tea, allow; to cool and spray over plants.

Chive tea: For scab and mildew. Use dried chives. Pour 500ml of boiling water over the dried chives and infuse them for an hour.

Strain through an old nylon stocking. Dilute one part spray with two parts water and use.

Epsom Salts—(Magnesium sulphate)

Mix 1 tablespoon into 2 litres of water. Effective against mildews and also has the added advantage of adding magnesium to the soil.

Milk: Use one part fresh milk to nine parts water. This solution is also effective for controlling Red Spider mite.

Potassium Permanganate (Condy's Crystals).

A useful general insecticide and fungicidc, acting as a contact poison. Depleted within 4 hours.

Dissolve 10 grams Condy's crystals into 4 litres of water.

Liquid seaweed: Applied in a foliar application is very effective against all types of moulds and fungus diseases.

Vinegar Fungicide

Mix 3 tablespoons of natural apple cider vinegar in 3 litres of water. Spray during the cool part of the day. Use to control black spot on roses and other fungal diseases. Adding 1 tablespoon of molasses to the water will also be beneficial. El

Chamomile tea: Make up as a drinkable tea, allow; to cool and spray over plants.



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  • askalu
    Does condes crystals help with fungus mildew rust on plants spray the tips with?
    8 years ago

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