Organic sprays
Organic sprays. Photo: Sol Morgan
In an ideal world, your fruit trees, roses, vegetables and ornamentals would all grow healthily without any pest and disease problems. But that’s doesn’t happen in most cases, for several reasons.
Firstly we want to grow plants not always suitable for the conditions. Our climate here in Golden Bay is pretty wet and warm, making it ideal for the proliferation of fungal diseases like brown rot, canker, silverleaf and leaf curl. That makes the environment for growing stonefruit trees like apricots and peaches, which prefer hot dry summers and cold winters, marginal at best.
Therefore select the best microclimates on your property for exotics, especially fruit trees.
When soil health is not up to scratch, then fruit and vegetable crops in particular will suffer first. Feeding the soil to maintain plant health is important. But stress happens, caused either by seasonal fluctuations (like a drought or too much rain), or lack of care (like forgetting to irrigate). These upset the balance and contribute to pest and disease outbreaks.
Sprays become the last resort in helping our beloved crops, fruit trees or flowers stay in reasonable health. So what options do the least harm to the environment?
Copper oxychloride or cupric hydroxide: These are protectant fungicides that control a wide range of fungal and bacterial diseases on fruit, vegetables and ornamentals. Copper works when its toxic ion is absorbed by the germinating fungal spore and disrupts its cellular proteins. For best results, copper must be reapplied as plants grow to maintain coverage and prevent disease establishment. Its application is recommended at bud burst and green tip (September), leaf fall (May) and during winter dormancy. Copper oxychloride comes as a wettable powder (eg, Yates Copper Oxychloride). Cupric hydroxide (Champ DP) comes as water-dispersable granules. Pre-mix in a small volume of water to form a slurry before adding to remaining water. Ensure thorough spray coverage of all foliage, buds and stems. Apply when foliage and weather conditions are dry, but avoid hot sunshine. Avoid mixing it with other sprays. Copper is a heavy metal and will harm soil and aquatic life, microorganisms and bees, so caution required.
Lime sulphur: A multipurpose spray that controls a range of pests and diseases on fruit trees and ornamental plants, and also controls moss and lichen on deciduous plants. It works by forming a protective film that prevents the entry of fungus into plant cells. Yates Lime sulphur contains 15 per cent sulphur as polysulphides of lime in the form of an aqueous concentrate. It has an unpleasant rotten-egg smell, so protect yourself. Spray fruit trees and roses during winter to control hard-to-kill pests and diseases like scale, mites and black spot. Apply in the morning or late afternoon when it is not too hot.
Neem oil: This comes from the pressed seed of the neem tree. Azadirachtin and clarified hydrophobic extract of neem oil are the active ingredients. Growers have found that neem is effective as a repellent, insecticide, miticide and fungicide. It also functions as an anti-feedant, discouraging insects’ feeding patterns. As an organic insecticide, it kills some pests after they’ve eaten leaves sprayed with it, while it repels others with its strong smell. Pests controlled include whitefly, aphids, moth larvae, scale and spider mites. Sprays containing clarified hydrophobic extract of neem oil are also used as fungicides against rust, black spot, mildew, leaf spot, scab, anthracnose, blight and botrytis. Mix the specified amount with water and a little soap before you spray. Cover the complete plant, including the soil or potting media. Avoid spraying in full sun.
Garlic and pyrethrum spray: This contains pyrethrins, which are extracted from dried daisy flowers. Pyrethrins are well known for their rapid action, broad-spectrum activity and lack of persistence, and don’t create insect immunity. Garlic has its own insecticidal activity and is a proven repellent. This product is safe to the environment, is non-residual and has very low mammalian toxicity (it’s one of the least-toxic domestic insecticides available). It controls a wide variety of insect pests on vegetables, flowers and ornamentals. For example, Betta Crop Garlic and Pyrethrum controls thrips, aphids, ants, fruit fly, codlin moth, leaf hoppers, pear slug, and caterpillars – with the highest kill rate (98.4%) of 10 products tested by MAF.
Sprays, however useful, don’t replace good cultural practices like hygiene (cleaning up diseased fruit), pruning for good airflow, plantings to attract beneficial insects and feeding the soil with mulches, etc.
Let’s hope the cold weather we’re having now is enough to limit pest or disease outbreaks in the coming season.
Sol Morgan
