Whiteflies are not good news for gardenia growers. Your attractive foliage is under attack – tiny whiteflies are sucking up the sap and depositing honey on which black mold thrives.
They are not easy to control because the flies fly away if disturbed, and they lay their eggs on the undersides of leaves, so they are hard to get at to kill. Also, they breed fast – egg to mature egg-laying adult can take as little as 16 days in hot weather.
And the damage is not confined to the direct damage the whitefly does – they are also the vectors of pathological plant viruses, which may also attack your gardenias.
Caring for your gardenia
Many people find gardenia plants challenging to grow. But by taking care, they will reward you with highly scented showy flowers and glossy foliage. Whiteflies find them attractive, too. For a detailed look at how to care for your gardenia, you might like to look at this information from the RHS – all you need to know to grow healthy plants, but you will need to keep the whitefly in check.
Identifying whitefly on Your gardenia
You may notice a black, sooty covering in the leaves of your gardenia, together with tiny whiteflies – these are the signs of whitefly infestation. You can find pictures on this website here. The whiteflies suck up the sap from the leaves. They excrete honeydew that falls onto the leaves, and sooty mold fungus takes over and covers the leaves. The honeydew is not harmful, but when there is a lot of it, it stops the sun from getting through to the chlorophyll in the leaves. Blocking the sun means the plant cannot synthesize the sugars it needs to grow and flourish.
You may see not only whiteflies on the leaves but under the leaves are the grey-white eggs and immature forms of the whitefly. They are immobile, so at least they do not fly away.
How to prevent a whitefly infestation on your gardenias
- Attract beneficial insects to your garden. A tiny parasitic wasp – that will not sting you – will kill the whitefly as it lays its eggs inside them. Spiders, small birds, ladybugs, and lacewings all prey on whiteflies.
- Buy beneficial bugs – you can buy lacewings, for example, here – Green Lacewing 5000 Eggs - Good Bugs.
- Plant flowers to attract the whitefly predators.
- Take care not to purchase, or otherwise bring into your space, plants which have an infestation. Inspect them thoroughly, especially the undersides of the leaves.
- Place sticky traps around your garden – yellow colors will attract the adults and divert them away from your gardenias.
- Use slow-release fertilizers – it’s best not to overfeed your plants as this may result in more enhanced growth and yet more juicy leaves for the hungry whitefly.
- Excessive pruning stimulates new growth – and the whiteflies like that. But do cut off badly infested areas.
How to get rid of whiteflies on gardenias
You must attack the adults and the eggs and nymphs on the undersides of the leaves. There is a YouTube video here that shows one man’s attack on whiteflies. Here are some more ways you can tackle them:
Hose off the eggs and mold gently
If your gardenia is sturdy, you can hose off the eggs, the mold, and the honeydew. You won’t get all the adults – some will escape.
Vacuum up the whiteflies
You can vacuum the flies off before they get going in the morning while it’s still cool. Empty the vacuum bag into a sealed container like a plastic bag and refrigerate overnight to kill the whiteflies.
Prune (a little)
Prune away badly infested parts.
Spray with insecticidal soap
Take care to spray the undersides of the leaves. You can find one here – No products found. that is ready to use and contains specially selected soaps (fatty acid salts) to provide effective pest control.
Spray with Neem Oil
Neem oil (like this one – Pure PetraTools Neem Oil for Plants - Organic Neem Oil Spray for Plants,100% Cold Pressed Neem Oil, Pure Neem Oil, All-Natural Neem Oil Concentrate Leaf Polish for Plants - (17 Oz)) is very effective, but you have to repeat the application every 5-7 days to keep on top of the whitefly population. It does not harm beneficial insects, and the whitefly eggs are resistant – hence the need for repeated applications.
Whitefly like yellow things and a yellow trap will divert some of the adult whiteflies. You can buy ready-made ones here – No products found., or make your own (you can vary the shape). Cover a yellow surface with petroleum gel mixed with the same amount of liquid soap and place them around the plants. It’s a good idea to make sure the part you insert into the earth is not covered with glue!
DIY Vinegar traps – soak a bit of cotton wool in vinegar and wrap it in clingfilm. Then punch a few holes in it and leave it near the gardenia. The insects seem to like the smell – and it does get less after a short while so that it won’t be a nuisance for you. The flies fly in, and then they cannot find the way out.
Insecticides – a last resort
You can use powerful insecticides to get rid of these pesky pests. However, the chemical ingredients can harm other insects, including whitefly predators – and the whitefly population is beginning to show resistance to some pesticides. You are much better off using the alternatives, even though they need repeated applications.
Gardenias are beautiful plants, but they do need the care to thrive. Unfortunately, whiteflies also find them attractive, and they are the second most crucial vector for viruses which can also damage your plants.
However, by attacking the eggs and larvae on the leaves’ undersides and laying traps for the adults, you can control the sooty mold and the whiteflies on gardenia. Being alert and treating as soon as you notice any tiny whiteflies and repeated applications of your chosen treatment are key elements – even better if you can prevent them coming in the first place!
Where are whiteflies found?
Whiteflies lay their eggs on the underside of leaves, but the adults can be all over the plant. They may lift off in a white cloud if the plant is disturbed and the infestation is heavy.
Will dish soap kill whiteflies?
Yes – dish soap will kill whiteflies. Add a tablespoon of liquid soap to a liter of water and mix well. Spray on the undersides of the leaves. Repeat every few days.