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Sunday, 12 June 2011

Organic pest and disease control

Pests and diseases can completely eradicate a crop. Commercial growers combat these problems by use of a large array of chemicals but the organic approach is to provide the optimum growing conditions to ensure healthy plants and accept some losses will occur. 

Before we examine the main pests and diseases, it is worth focusing on methods of prevention. Firstly, ensure your soil contains plenty of humus and is fertile, contains all the necessary nutrients and moisture levels required by individual plants and pH levels are correct. Secondly, keep your plot clean as possible to avoid pests and diseases by removing rubbish, decaying weeds and vegetables and fallen leaves. Thirdly, remove weeds frequently from beds and paths as these may harbour pests. And finally, remove any diseased plants immediately and chop and bury deeply or burn. 

Certain other practices can also promote a healthy environment for plant growth. Firstly, crop rotation can reduce the build up of pests and diseases which effect a particular vegetable family. Secondly, keep all your equipment clean which includes your footwear, tools, plant containers and propagator. Thirdly, always follow guidelines for planting times, spacing, feeding and watering to discourage pests and diseases. Fourthly, always use disease resistant varieties when available. And finally, undertake, if time permits, a daily inspection of your plot to catch problems early and which will allow you to deal with problems at an early stage.

Organic chemical controls are available which quickly breakdown into non-toxic compounds but like standard chemicals they can, however, be harmful to some beneficial insects and natural pest predators. And I would, therefore, recommend usage only as a last resort as pests have a habit of becoming resistant to any chemical frequently used. If spraying is required ensure you follow product guidelines; use as little spay as possible and wash your hands and any equipment used thoroughly after spraying is completed. The following are the chemicals which have been approved for use by organic growers: derris, pyrethrum and insecticidal soaps. All of which are effective on blackfly, greenfly and aphids.

Alternatively, you could try making your own natural insecticides and pesticides. (1) Boil 40g of garlic and 10g of onion skins and leave to cool, filter and add biodegradable washing-up liquid and mix thoroughly. Use the mixture diluted in 1.5 litres of water in a spray bottle for any crops or fruit trees affected by fungal attack; (2) You may also use biodegradable washing-up liquid on its own which is effective against blackfly and greenfly; (3) Mix 250ml of vegetable oil with 1 tablespoon of biodegradable washing-up liquid. Use 2.5 tablespoons of the mixture in 250ml of water in a spray bottle against immature bugs and eggs and (4) Cut up five hot chilli peppers and crush four garlic cloves, place in a jar, seal and leave in the sunny location for a day or two. Filter the mixture, add water and use in a spray bottle against most bugs.

Planting nectar supplying flowers can attract beneficial insects to your garden which may naturally deal with any pests present. For example, attract ladybirds to your garden which eat aphids and blackfly.

The most common Cypriots pests and diseases

Ants: These take away newly planted seeds. If possible, locate the nest by following their trail and pour boiling water into their holes. Moist beds also act as a deterrent.

Aphids: Can destroy plants by sucking the sap out of young plants. Plant ladybird attracting plants such as fennel, dill and caraway and the ladybirds will consume large amounts of aphids daily.

Greenfly: Can attack legumes, spray with liquid seaweed twice weekly to eradicate this pest.

Whitefly: Mainly effect brassicas and can be sprayed with liquid seaweed or diluted biodegradable washing-up liquid twice weekly to destroy the whitefly.

Blackfly: Can effect broad beans and spinach. Pinch out the tender shoots on broad beans to deter or spray with diluted biodegradable washing-up liquid.

Bean and Pea Weevil: These pests will burrow into pods and lay eggs which will hatch and feed on your crop. If a particular plant is badly affected it is best to remove the plant and burn it. However, if the damage is minimal you will have some sorting to do when harvesting to take out damaged peas and beans and discard those with holes. We spent ages doing this last year with our black eyed bean crop.

Mildew: Can effect tomatoes, cucumbers, onions, peppers, garlic and aubergines. Try to avoid wetting plants when watering and remove any badly affected vegetables.

Fungal Diseases: These can be in the form of rust, rot or blight. The first two mainly affect the onion family and legumes and can be minimised by not over watering and ensuring good drainage. Blight mainly affects vegetables of the potato and tomato family and if particular plants become badly affected it is best to remove and burn.

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