Home-made sprays: neem, garlic and friends

Organic does not mean harmless. Neem and soap kill beneficial insects too and can burn leaves in the heat, so spray only what you need, only where you need it.

Spraying rules for Qatar

• Spray at dusk or first light, never in sun, above about 32 °C, or in wind.
• Test a mix on a few leaves and wait 24 hours before spraying the whole plant.
• Cover both sides of the leaf; the underside is where whitefly, aphids and mites live.
• Mix only what you need; most of these lose strength within a day.
• Do not spray open flowers; bees visit them.

Neem oil emulsion

5 ml neem oil, 2–5 ml mild liquid soap and 1 litre of lukewarm water. Mix the soap into the water very well first, then add it to the neem oil, stir hard and spray at once. Do not store it. It helps against whitefly, aphids, mites, thrips and young caterpillars. Repeat every five to seven days, three times.

Neem and garlic emulsion

20 ml neem oil, 20 g garlic, 5 g plain bar soap (grated) and 80 ml water in all. Dissolve the soap in 50 ml of lukewarm water. Crush the garlic and extract it in 30 ml of water. Pour the soap solution slowly into the neem oil, stirring hard, to get a milky emulsion, then stir in the garlic extract. Dilute this in 900 ml of water and spray.

Leaf curl

A traditional treatment is a spray of 1 cup of curd, 2 cups of water and ¼ tsp of turmeric, mixed very well, or 10 ml of hydrogen peroxide in 1 litre of water, sprayed on the leaves on alternate days for at least three days.

But be realistic: leaf curl on tomato and chilli is usually a virus spread by whitefly, or damage from mites and thrips. No spray cures a virus. These sprays may help if mites or thrips are the cause, but the dependable fix is to control the insect that carries it (yellow traps and insect mesh), and to pull and destroy a badly affected plant rather than feed it.

Organic fungicides

• Asafoetida, turmeric and baking soda: 10 g asafoetida, 8 g turmeric powder and 2 g baking soda in 2.5 litres of water, as a foliar spray.
• Baking soda spray: 500 ml water, 2 tsp baking soda, 1 tsp cooking oil and ½ tsp liquid soap.
• Milk spray: one part milk to nine parts water weekly, good against powdery mildew.

Repeat every five to seven days, up to three sprays, and stop if the leaves show burn. Baking soda is a salt, so do not drench the soil with it. These work mainly on powdery mildew and light fungal problems; for serious infections, strip the affected leaves first.

When spraying is a waste of time

If a plant is heavily infected by a virus — curled, mottled, stunted leaves that keep getting worse — no spray will save it. Pull it, bag it, and do not put it in the compost.