1. Good Organic Gardening - January-February 2016
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1. Good Organic Gardening - January-February 2016

1. Good Organic Gardening - January-February 2016 1. Good Organic Gardening - January-February 2016

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PLANT HEALTH | Disease distress Mango anthracnose GARDEN FIRST AID In addition to insect attack, summer humidity can bring with it a range of fungal diseases that will go straight for your precious plants if you’re not vigilant and proactive Words & photos Claire Bickle If it’s not the insect population or four-legged marsupials, it’s some plant disease or virus attacking your prize edibles and floral delights in the garden. What are the key problems we have to deal with at this time, and how do we go about eradicating them — or preventing them taking hold in the first place — without using nasty chemicals? Here are some of the commonest fungal diseases that home gardeners often come across in their patch. Anthracnose This disease is a serious problem, requiring both pre- and post-harvest sprays. The main species the home gardener has to worry about is Colletotrichum spp. It will affect mangoes, avocadoes, tomatoes, passionfruit, capsicums, chillies, bananas and a large range of tropical crops. Symptoms include a variety of black spots: recessed black spots on fruit to raised small clusters of spots, depending on plant species affected, as well as black discolouration on flower buds and spikes, black spots and yellowing on leaves. Flowers and buds can drop, meaning poor fruit set and limited crops. The spores overwinter in the soil and anthracnose can even be seed-borne. It spreads via water droplets and is far worse in warm and/or cool humid conditions. During dry weather, anthracnose is virtually non-existent. Treatment Apply a copper spray just before flowering and during the early stages of fruit set. Shutterstock 54 | Good Organic Gardening

Remove any infected fruit and foliage. Remove any dead wood and twigs, and burn if possible. Practise crop rotation with annuals. Avoid overhead irrigation and improve air circulation. Choose disease-resistant varieties. Black spot (roses & pawpaws) Black spot is a broadly used common name for a variety of fungal issues that — you guessed it — exhibit black spots on foliage, flowers and fruit. Roses are renowned for black spot fungal issues and, even though not often eaten (well, the flowers and hips can be), they are such an important and widely grown flowering plant in gardens across the world that people are always looking for organic options when it comes to controlling pests and diseases. Black spot can be more prevalent on roses in warm, humid subtropical areas. The signs, of course, are the tell-tale black spots and yellowing of foliage, which can then drop off. It can even attack the stems of the rose and cause dieback. With all this going on, the plant can become weakened, prone to other diseases and insect attack, and produce fewer and smaller blooms. As for pawpaws, it’s the onset of cooler winter weather that can bring on a nasty case of black spot. Control Choose varieties that are diseaseresistant if possible; in warmer climates some of the old-fashioned teas and China roses do remarkably well. Spray with an organic fungicide such as Eco-fungicide to not only kill existing spores but also change the pH on the surface of the leaves and plant stems, making them more alkaline and less habitable for fungal diseases. Use a small of amount of Eco-oil mixed into the spray to help it stick to the plant. Copper and sulphur-based sprays can also be used. Remove any disease-affected leaves and throw them into the bin. Make sure you are giving your plants the right growing conditions with the required hours of sun a day and good airflow. This will help prevent fungal problems. Avoid watering the foliage, especially in the late afternoon. Keep plants healthy and less vulnerable to disease attack by feeding with recommended organic fertilisers throughout the growing seasons and when recommended. Applications of seaweed will also be of benefit and act as a preventive, strengthening the cell walls of the plant and encouraging stronger, healthier growth. Consider spraying the ground around the plant with fungicide as well, to catch any spores lingering there. Pawpaws lacking in potassium, magnesium or phosphorus can be more susceptible. Add potassium (sulphate of potash), phosphorus (rock dust minerals and/or magnesium (Epsom salts) to the feeding regime to ensure no deficiencies. Disease distress | PLANT HEALTH Peach leaf curl This fungal disease affects peaches and nectarines in cooler climates. Symptoms include puckering of foliage and sometimes even quite severe distortion with a pinkish blotching or discolouration. The leaves will usually drop prematurely. This, in turn, affects fruit production. Leaf curl remains secretly dormant on these deciduous fruit trees, appearing and infecting foliage as soon as the first shoots appear. Control There is no effective treatment for it once this disease has a foothold, so prevention is the key. Spray trees with a copper-based spray just as the growth buds start to swell. Be sure to spray the branches and trunk as well, to catch any spores that have been resting dormant over winter. Trees that are infected need all the help they can get, so keep up the applications of liquid seaweed as a foliar spray. Regular watering and the application of organic fertilisers will help the tree to survive through the growing season. After leaf drop in winter, gather up all the old foliage and follow the above directions in late winter and again early spring. Applications of gypsum for added calcium will also strengthen the plant cell walls against disease attack. Black spot on roses Peach leaf curl needs preventive treatment Good Organic Gardening | 55

PLANT HEALTH | Disease distress<br />

Mango anthracnose<br />

GARDEN FIRST AID<br />

In addition to insect attack, summer humidity can bring<br />

with it a range of fungal diseases that will go straight for your<br />

precious plants if you’re not vigilant and proactive<br />

Words & photos Claire Bickle<br />

If it’s not the insect population or<br />

four-legged marsupials, it’s some plant<br />

disease or virus attacking your prize<br />

edibles and floral delights in the garden.<br />

What are the key problems we have to<br />

deal with at this time, and how do we go<br />

about eradicating them — or preventing<br />

them taking hold in the first place — without<br />

using nasty chemicals?<br />

Here are some of the commonest fungal<br />

diseases that home gardeners often come<br />

across in their patch.<br />

Anthracnose<br />

This disease is a serious problem, requiring<br />

both pre- and post-harvest sprays. The main<br />

species the home gardener has to worry<br />

about is Colletotrichum spp. It will affect<br />

mangoes, avocadoes, tomatoes, passionfruit,<br />

capsicums, chillies, bananas and a large<br />

range of tropical crops.<br />

Symptoms include a variety of black spots:<br />

recessed black spots on fruit to raised small<br />

clusters of spots, depending on plant species<br />

affected, as well as black discolouration on<br />

flower buds and spikes, black spots and<br />

yellowing on leaves. Flowers and buds<br />

can drop, meaning poor fruit set and<br />

limited crops.<br />

The spores overwinter in the soil and<br />

anthracnose can even be seed-borne. It<br />

spreads via water droplets and is far worse<br />

in warm and/or cool humid conditions.<br />

During dry weather, anthracnose is virtually<br />

non-existent.<br />

Treatment<br />

Apply a copper spray just before<br />

flowering and during the early stages<br />

of fruit set.<br />

Shutterstock<br />

54 | <strong>Good</strong> <strong>Organic</strong> <strong>Gardening</strong>

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