Citrus Whitefly is a sneaky garden pest. Often you won’t notice it until the adult whiteflies appear on the underside of your citrus tree leaves. Discover different ways to control and treat Citrus Whitefly on your homegrown citrus trees. It’s usually possible to treat these little white pests naturally without chemical sprays before they cause too much trouble.
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What are Citrus Whiteflies?
There are many different species of whitefly, with over 100 in Australia alone. Whiteflies that are known to affect citrus trees include the Australian Citrus Whitefly (Orchamoplatus citrus (Takahashi)) and Aleurocanthus Whitefly, and the Citrus Whitefly (Dialeurodes citri) in the US.
Where I live in Australia we also have a large problem with the Ash Whitefly (Siphoninus phillyeae), which are often found on fruit trees. They tend to affect deciduous fruit trees like apples and pears over spring and summer and move to other trees like citrus and olive in Autumn.
Whiteflies are not actually flies, but are sap sucking insects like scale, mealybug and aphids. They are very small, measuring 1-2mm, and are named for their white wings.
Citrus Whiteflies lay oval shaped yellowish eggs on the back of leaves, up to 30 or 4 at a time. When the eggs hatch, the tiny scale like nymphs move around before finding a place to attach. The nymphs stay hidden on the back of the leaves so they are very easy to miss until they mature. Immature Whiteflies suck sap from citrus leaves and excrete sticky honeydew. The lifecycle of a Citrus Whitefly takes about 4 weeks to mature from egg, through the various stages of the nymph moulting to an adult insect.
Whitefly can affect all types of citrus trees including lemon, lime, orange, mandarin and grapefruit.
How can I tell if my citrus tree is affected by Whiteflies?
I recently found Citrus Whiteflies on a few leaves of my potted lime. I first noticed two leaves at the back of the tree that weren’t looking very healthy, with some yellow mottling and curling of the leaves. On the underside I discovered that Citrus Whitefly had come, laid eggs and gone without me noticing. All that was left was the remains and some Sooty Mould formed on the sweet honeydew they left behind. On closer inspection of the rest of the lime tree, I found just 3 adult Whiteflies, but they were busy laying eggs.
Sticky honeydew deposits or black Sooty Mould may be the first thing to alert you to a Whitefly problem.
Unfortunately it’s hard to find Citrus Whitefly infestations early unless you see the small white adults. The eggs and pupae are very small and difficult to notice. However, you may be lucky to spot the eggs or like me, an adult busy at work laying them. Adult Citrus Whiteflies lay eggs on the underside of leaves, often in a circular pattern.
Problems caused by citrus whiteflies
Citrus Whiteflies are an annoying garden pest but can also damaging to your citrus tree. As whitefly larvae and adults are sap sucking insects they will affect your citrus tree leaves. The sweet honeydew they excrete can also cause black Sooty Mould to form. All of this can affect your tree’s overall health by affecting photosynthesis.
A citrus tree with a Whitefly infestation may produce less fruit and not grow as well. Unhealthy trees can also be more vulnerable to other citrus pests. Damaged leaves can also be unsightly.
The other reason to treat Citrus Whiteflies is to prevent them from spreading to other citrus trees or other plants in your garden. Depending on the species, some Whiteflies can affect other plants from from ornamental trees and shrubs to vegetables (especially broccoli, kale and tomato) and herbs.
How to treat citrus whitefly
There are several ways to treat and prevent Citrus Whiteflies, and luckily some of these don’t involve using heavy chemical insecticides.
Natural predators can be a great way to reduce whitefly numbers. Green Lacewings, Ladybirds and Hover Fly larvae are pests commonly found in the garden that will help by feeding on Whiteflies. There are also naturally occurring tiny parasitic wasps that feed on Whitefly eggs and larvae.
Physically remove pests
Depending on the size of your citrus tree, it is often possibly to manually remove white flies. This is often easier for potted citrus trees. Physical ways to manage whiteflies include:
- using a hose to spray the leaves to remove any whiteflies that are present;
- vacuuming adult whiteflies from leaves with a hand-held vacuum (odd but surprisingly effective,); and
- picking off any leaves that are very heavily infested white citrus whitefly nymphs.
Some people recommend using yellow sticky traps to catch whiteflies, but these do not discriminate between harmful and beneficial pests and I personally think they are best avoided.
Avoid using insecticide sprays if possible
If you do decide to treat your trees with a spray for Citrus Whitefly, please think carefully about using an insecticide. You might end up killing the good insects that help keep your tree healthy.
If you need to spray
If you have a more severe infestation, you could spray with a horticultural oil. The oil will smother the Whitefly nymphs and and adults. Be aware that oil can still affect the beneficial insects too.
When using an oil treatment, make sure to spray your citrus trees in the early morning to minimise harm to beneficial insects. Don’t spray when the weather is too hot, windy or when it’s going to rain.
Disclaimer: These notes about spraying are for general information only. If you have any questions about whether a product is suitable for your needs, speak to your local garden centre or contact the manufacturer. Please also make sure to read and carefully follow any instructions on the labels of citrus pest sprays.
Try a homemade alternative to chemical sprays
Rather than buying a commercial horticultural oil, try making your own at home with:
- half a cup of vegetable oil or neem oil;
- half a Tablespoon of dishwashing liquid detergent;
- 5 litres of water.
For a small tree, fill up a spray bottle and soak the foliage of your citrus tree. Make sure to cover the underside of the leaves too. For a larger tree, you’ll need a spray pack. You will need to spray your tree every 3 to 5 days with homemade soap and oil spray for this to be effective.
Prevention is better than cure
You can discourage whiteflies by keeping your garden weed-free, especially around fruits trees and vegetables.
Protect your citrus from Whiteflies by keeping them healthy. Weak or unhealthy citrus trees are more prone to attack from pests in general. Look after your citrus trees well by feeding and watering regularly.
Encourage beneficial insects in your garden to help to keep pests at bay and avoid the need to use any sprays, even natural or organic ones.
Finally, make sure you regularly inspect your citrus trees for any signs of pests like whitefly so that you can treat the problem early.
References and more information
For more information about citrus whiteflies, see the following references we’ve referred to in this post:
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