Lots of people have been asking how to deal with pests and diseases organically recently so I’ve listed below a few ‘recipes’ to deal with most of the common ones.

However, even organic pesticides and herbicides should be used as a last resort, and are generally never recommended for use in polytunnels and greenhouses.

In the long term encouraging a garden full of biodiversity is the aim.  Planting hedges and flowers that will provide hiding places and food for natural predators as well as providing bird boxes and areas with water will all help to create a more balanced environment.

Traps and barriers work well if you put them up early – for instance adding netting will prevent butterflies landing on the brassicas before they become a problem.  Turn a terracotta plant pot upside down, stuff it with straw and balance it on a bamboo stick - this will attract earwigs that can be collected and disposed of easily.

Crop rotation and companion planting should be used too eg moving potatoes to a new area each year will help prevent the build up of potato eel worm and planting alliums and carrots/parsnips together will benefit both species.  Blasting aphids off with a hose or squashing them between your fingers works whilst colonies are small and keeping greenhouses hosed down will help to keep red spider mite at bay. Learning to recognise pests and their cycles is important too. 

However, until you’ve built up the ‘good’ insect population in your garden, you may have to resort to more instant control, so here goes: (its a good idea to test a small amount on a plant 2 or 3 days before use to check that it doesn’t damage the plant).


Pesticides


NOTE: Most insecticides kill beneficial insects as well as their predators so use with caution. It’s often advised to spray in the evening when the beneficial insects will not be as active (for instance if you spray soap to kill greenfly, you may kill the hoverfly larvae that would eventually eat the greenfly).  As with any chemical, organic or otherwise, wear gloves and avoid breathing in the spray.

Insecticidal Soaps – Control aphids, thrips, spider mite


Buy from organic suppliers or make your own:

Soap Spray


2 tbsp (30ml) phosphate free washing up liquid (label may say safe in septic tanks)
2.2 lts water


Avoid spraying in bright sun as it can scorch foliage. Test a few leaves a couple of days before use as it may damage the plant. Will have to repeat every 24 – 48 hrs.

Rhubarb Leaves - All leaf eating insects

Rhubarb leaves are poisonous as they contain large quantities of oxalic acid. Wash vegetables thoroughly that have been sprayed before eating them.

1kg rhubarb leaves (can use tomato, elder or nettle leaves instead)

1lt water


Mix together, leave for a week, strain and use as a liquid spray.


Or


450g rhubarb leaves
1.1lt water

15ml soap flakes

Boil for 30 mins, topping up to allow for evaporation. Allow to cool and add soap flakes as a wetting agent. Strain and use as an undiluted spray.

Elder Shoots - Controls aphids and caterpillars


450g young Elder shoots
3lt water

Mix in large pan and boil for 30 mins. Strain and cool. Can be bottled while hot and will keep for 3 months.

 Cinnamon Power – Deters ants

Sprinkle at the entrance to their nest and they will move away.

Garlic Spray – Kills many insect pests and friends

Note: Do not use metallic containers with garlic sprays as they may react with the mixture.



1. Non oily version



1-2 garlic bulbs
Boiling water
1ltr soap spray


Chop garlic bulbs and cover with boiling water in a lidded jar. Leave to soak overnight. Strain and add to soap spray. Unused spray will decay but it can be frozen to preserve it.

2. Oily Version

100g chopped garlic

30ml liquid paraffin or baby oil

500ml water

5ml liquid soap (phosphate free)



Soak garlic for at least 24 hours in paraffin or oil in a sealed jar. Add water and liquid soap and stir well to emulsify the oil. This should keep well. Use 30ml of preparation in 500ml to spray plants.


3. Powdered dry garlic bulbs

Sprinkle the powder over affected plants or mix with water to make a spray.


Wormwood Tea – Controls aphids, caterpillars, flea beetles & moths


225 g wormwood (Artemisia absinthium)
2.25 lts water

1 tsp soft soap


Simmer for 30 minutes, strain and add soft soap and add to spray bottle. Alternatively place dried sprigs beside carrots & onions to mask their scent.

Sulphur - Spider mites, thrips

Fungicides

Fungal infections are usually visible to the naked eye and include mildews, leaf spots and rusts. They are spread by spores. Carefully removing infected leaves immediately they are infected will help to control the infection.




Sodium Bicarbonate – Powdery Mildew

5g baking soda
1lt water


Mix together for a spray

Or

Blackspot & mildew on roses

3 tsp baking soda
1 heaped tsp soluble fertiliser
Few drops phosphorous free washing up liquid
4.5 lts water


Mix first three ingredients together thoroughly with 200ml water. Add to the remaining water in a watering can. This can be watered over the foliage every two weeks, starting in early spring and continuing throughout the growing season.


Or


Downy mildew

100g washing soda
4 lts water
50g soft soap

Dissolve washing soda in water then add soft soap to a spray bottle


Or




Powdery mildew, blackspot

20g baking soda
15ml citrus oil
2.2 lts water


Mix and spray foliage lightly, including the undersides. Do not pour or spray this mix directly into the soil.

Milk - Mildew

300ml milk
700ml water

The enzymes of fresh milk sprayed on plants will attack mildew. A stronger solution will result in a foul smell as the milk goes rancid.

Elder Spray – Mildew and black spot

Same as pesticides:


450g young Elder shoots
3lt water


Mix in large pan and boil for 30 mins. Strain and cool. Can be bottled while hot and will keep for 3 months.


Dock Spray – Mildew


15g mature docks
1 lt water

Puree docks and mix with water. Leave to soak for an hour and spray.

Garlic Spray – For scab, mildew, bean rust & tomato blight.

See pesticide preparation above.

10g crushed garlic or – Powdery mildew.
15g crushed onions
1lt water






Horsetail - Mildew on crops and some rusts, eg., celery

Preventative against potato blight.



28g horsetail (can use all parts of the plant, including rhizomes)
1 lt water
Mix together and allow to stand for 24 hours. Strain and use undiluted as a spray.

Finally:

DISCLAIMER: The control methods are suggested here as a matter of general information. Under Irish and EU law it is illegal to use any preparation as a pesticide/fugicide/herbicide that is not approved for such use. The author and the website accepts no responsibility for how a user may mix, use, store, or any effects the mixture or its elements may have on people, plants or the environment. The information here is for reference only and does not imply a recommendation for use. If you disregard this warning and make any of the preparations, you do so entirely at your own risk.