The aphid is the most common pest in the greenhouse. It reproduces explosively, one female in 3 weeks 80 offspring. Quick reaction is crucial, but pesticides are not the only way. In this article, we will show you 6 natural methods that work.
How to identify aphids
Aphids are 1-3 mm long insects, usually green, yellow, or black. They inhabit:
- The underside of young leaves
- The tips of shoots and young stems
- Flowers (especially marigolds)
Signs of infestation: curled leaves, sticky liquid (honeydew), black sooty mold, ants on the plant. Ants "graze" aphids and protect them, if you see ants, always check for aphids.
Soap, the first line of defense
The simplest and most effective method. Soap solution:
- 1 L of water + 2 tablespoons of liquid Marseille soap (or potassium soap)
- If necessary, add 1 teaspoon of olive oil (better adhesion)
- Spray abundantly on all leaves (especially the lower ones)
- Repeat every 3-5 days, until the population is under control
Repellent plants, natural protection
Planting certain plants in the greenhouse or around it repels aphids:
- Basil, excellent with tomatoes
- Garlic, strong smell repels aphids and ants
- Calendula, attracts beneficial insects
- Mint, very strong, but invasive (plant in a pot)
- Nasturtium, "trap" plant, aphids prefer it
Beneficial insects, biological control
Ladybugs (Coccinella) are natural enemies of aphids. One ladybug eats up to 5000 aphids in its lifetime. Other beneficial insects:
- Lacewings (Chrysoperla), even more effective than ladybugs
- Hoverflies (Syrphidae), larvae eat aphids
- Parasitic wasps (Aphidius colemani), lay eggs in aphids
In Slovenia, you can buy ladybugs and lacewings at eco garden centers (Bistra, Agroline). Price: 10-20 €/100 individuals.
Prevention for next year
The best battle is the one that doesn't need to be fought. Prevention:
- Clean up all old plants from the greenhouse in the fall (eggs overwinter on them)
- Plant calendulas near every bed
- Thoughtful fertilization (too much nitrogen = soft leaves = attractiveness to aphids)
- Ventilate the greenhouse, aphids don't like drafts
- Cold winter in the greenhouse, open ventilators for 2 weeks in Dec-Jan
"A gardener who observes plants every day sees aphids immediately. A gardener who looks only once a week doesn't catch them anymore.", Old gardener from Kras
Make yourself an automatic monitoring system: yellow sticky traps (at garden centers) in the greenhouse catch flying females and give a signal for the start of the attack.
Closed system = fewer pests
Our greenhouses have double doors and ventilation screens that hinder the entry of insects from the outside.
Termoplast greenhouses