Your greenhouse should be a sanctuary for plants, not a buffet for pests! While these unwanted visitors are inevitable, catching them early and using natural solutions can save your crops without harsh chemicals. Let’s explore the usual suspects-and how to send them packing.
The 5 Most Common Greenhouse Pests (and How to Fight Back)
1. Aphids: The Sticky Invaders
Spot them: Clusters of green/black bugs under leaves, sticky honeydew, and curled foliage.
Natural fixes:
- Release ladybugs (Harmonia conformis-our native species) or lacewings.
- Garlic spray: Blend 3 crushed garlic cloves + 1L water + a dash of eco-detergent.
- Attract predators: Plant yarrow or dill near entry points.
Local Tip: Order beneficial insects from Bugs for Bugs (QLD) or Biological Services (SA).
2. Whiteflies: The Greenhouse Ghosts
Spot them: Clouds of tiny white insects when you brush plants.
Solutions:
- Yellow sticky traps (hang at plant height).
- Neem oil (available at Bunnings)-spray undersides of leaves.
- Encarsia formosa parasitic wasps (works best in temps above 20°C).
Warning: Whiteflies spread tomato leaf curl virus-quarantine infested plants!
3. Two-Spotted Mites (Red Spider Mites)
Spot them: Yellow speckles on leaves + fine webbing (worst in hot, dry areas).
Solutions:
- Mist plants daily (mites hate humidity).
- Phytoseiulus persimilis predatory mites (thrive in 15-30°C).
- Wipe leaves with damp cloth + a few drops of eucalyptus oil.
Did You Know? Mites explode in population during heatwaves-shade cloth can help.
4. Slugs & Snails: The Slimy Midnight Raiders
Spot them: Ragged holes + glittery trails (especially in QLD/NSW coastal areas).
Solutions:
- Copper tape around pots (try Yates Copper Tape at Bunnings).
- Beer traps (use a cheap stubby buried to the rim).
- Handpick at dusk (a torchlit ‘slug patrol’ works!).
Native Alternative: Encourage blue-tongue lizards with rock piles near your greenhouse.
5. Fungus Gnats: The Soil Nuisance
Spot them: Tiny black flies buzzing around potting mix.
Solutions:
- Let soil dry out between waterings.
- Sand topping: 1cm of sharp sand over potting mix blocks egg-laying.
- Mosquito Dunk tablets (contain BTI-approved for AU organic gardening).
Prevention: Build a Resilient Greenhouse
🌿 Companion Planting for Our Climate
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Native companions:
- Lemon myrtle deters flies.
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Bush basil repels thrips.
- Trap crops: Plant nasturtiums away from veggies to lure aphids.
🌱 Soil Health
- Amend soil with kangaroo manure (low-odor and nutrient-rich).
- Boost microbes with worm tea from your compost bin.
🐞 Beneficial Bugs Down Under
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Dedicate a corner to flowering natives (Scaevola, Grevillea) to attract:
- Hoverflies (aphid eaters).
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Predatory wasps (whitefly assassins).
Pro Tip: Avoid pesticides-they kill good bugs too!
🧹 Greenhouse Hygiene
- Disinfect with vinegar (1:3 vinegar/water) between seasons.
- Check plants weekly-early mornings are best for pest spotting.
When to Call for Backup
For severe infestations (like Queensland fruit fly), consult your state’s agriculture department:
- NSW: DPI Biosecurity
- QLD: Business Queensland
