If new leaves on Camellia plants become thick and very pale green or pink, and the underside of the leaf starts becoming white – the plant is suffering from ‘Camellia leaf gall’. This is a fungal disease that affects tender new growth of Camellia sasanqua (and sometimes Camellia reticulata), especially in very humid or wet, shady conditions. Fungal diseases are a sign that growing conditions are stressing your plants and their immune system is compromised. There is no organic or chemical treatment for this disease. However, an application of seaweed extract tea will help to strengthen the cell walls of the affected plants and make them more resistant to disease.
But, first the affected growth must be removed, preferably before the undersides of leaves develop white spores. You will need a baked bean tin containing about 5 cm of methylated spirits to sterilize secateurs blades, and a large garbage bag for the prunings. Prune off all affected growth (swish the open secateurs in the spirits often while pruning) and place it directly into the garbage bag. Also collect in the bag any fallen leaves as they can harbour the fungal spores that will activate this disease again when conditions are suitable. Seal the bag and put it in the garbage if you are unable to burn the leaves. Do not compost them. Then give the soil around the plants a drink of seaweed extract at the recommended strength, and protect the soil surface with 3–5 cm of fresh mulch. Make sure your camellias are watered when the top centimetre of soil is dry, but afford watering the foliage. Also give the plants an annual application of compost or complete organic fertiliser and seaweed extract tea in late winter.
See below, how affected new growth appears, and close-up of affected leaves.
Soil fungi that affect the water-carrying parts of plants cause wilt diseases that can affect a wide range of vegetables, grains, and ornamentals. Fruit trees can also be affected.
Wilt diseases are commonly caused by not practicing a proper crop rotation. Adding organic matter to soil helps to limit soil-borne diseases because the beneficial fungi in organic matter out compete the pathogens. Avoid using glyphosate because it has been shown to affect the microorganisms in soil that assist in keeping diseases under control.
To find out which fungus is affecting your plants, pull out (if possible) one of the affected plants and cut open the stem near the roots.
If it’s Fusarium wilt, the inside of the stem (in most plants) will be pink to reddish brown. In beans, the inside of the stem will be dark brown with reddish roots. According to research recently published by the US Department of Agriculture, Fusarium diseases are becoming a serious problem in GM crops that have been engineered to be glyphosate-resistant. The research found that glyphosate exuding from the roots of this type of GM crops stimulates Fusarium fungi in soil. In wheat, these fungi cause Fusarium Head Blight. Fusarium produces several toxins in plants that are not destroyed by cooking. These become a health problem when present in large quantities. One type causes vomiting. Another type causes cancer and birth defects, while a third type of toxin is lethal. It is important to act to prevent the establishment of Fusarium in garden and agricultural soils.
If it’s Verticillium wilt, the outside of the stem appears normal but the inside of the stem will be dark brown to black. This disease is more common where drainage is poor. Improve drainage and control weeds. Give any unaffected plants in the bed a drink of seaweed extract tea as potassium and trace elements in this tea assist in building resistance to disease.
TREATING FUNGAL WILT DISEASES
Remove all weeds and affected plants and burn them or dispose of them in a sealed plastic bag. Do this carefully, as spores can be spread by shoes, and gardening tools. Wear rubber boots and wash them and all tools after working in infected soil. Then dry these in direct sunlight. Bio-fumigation
When soil temperature is 14° C. or higher, grow a green manure crop of bio-fumigants such as Green Harvest’s BQ Mulch, yellow mustard, or radish. The peppery members of the Brassica family produce good quantities of glycosinolate that breaks down in wet soil to produce a gas that is effective against fungal pathogens and nematodes. Slash the green manure before it flowers, and hoe it into the topsoil. Then water the bed and cover it thickly with mulch. Solarization
Recent Spanish research has shown that, during summer, solarization is effective in treating these diseases. Place clear plastic sheets over irrigated beds and leave them in position for a minimum of 2 months.
Then grow a green manure crop of corn or maize and slash it when it is knee high and dig it into the topsoil. Wilt diseases are more common where soil is low in broken down or decomposed organic matter, and bio-fumigation will also affect beneficial mycorrhiza fungi in soil. Replacement of organic matter through green manures and as much compost as you can spare will encourage the re-establishment of mycorrhiza and other beneficial fungi and bacteria that can control soil pathogens when organic cultivation methods are used.
You will also need to practice a long crop rotation for different plant families until your soil is free of disease.