Citrus trees remain popular among gardeners, offering a rich assortment of fruits, including oranges, lemons, limes, grapefruits, and tangerines. Despite being relatively easy to grow, these trees are prone to various diseases and pests.
WATCH: Graham Ross on how to get the most out fo your citrus
The best defence against diseases and pests is a healthy citrus tree, so make sure you’re watering your trees regularly and feeding them with a citrus fertiliser during their growing season.
Common citrus diseases and pests
Here are some common citrus diseases and pests and how to get rid of them.
1. Citrus leaf miner
A common citrus enemy is the citrus leaf miner, a nocturnal moth with a small wingspan that lays eggs on citrus trees, creating translucent tunnels in the leaves.
Kevin Parker is a senior horticulturist at The Greenery Garden and Home. He previously told BHG the biggest mistake people make with their citrus trees is waiting until the insect appears to do something about it.
“You can’t control it [citrus leafminer] when you see it. You’ve got to spray preventively when new growth starts,” says Kevin.
When you see new growth on your citrus trees, spray using an oil-based solution like white oil, eco-oil, or neem oil.
Read more about citrus leaf miner.
2. Scale
Scale, a persistent insect, manifests in hard or soft shell-like coverings and can be challenging to control if left unchecked. Treatment involves using white oil, horticultural oil, eco-oil, or neem oil.
Read more about scale.
3. Aphids
Aphids are small sap-sucking insects prevalent during spring and summer and can be managed organically using products like Yates Nature’s Way citrus and ornamental spray or neem oil.
Read more about aphids.
4. Stink bugs
Stink bugs, recognised for their foul odour and affinity for citrus, may require companion plants or natural predators like ladybugs and parasitic wasps. In severe cases, chemical control methods can be considered.
Read more about stink bugs on citrus.
5. Fruit flies
Rising temperatures bring about fruit flies, which lay eggs beneath the fruit’s skin, causing rot. Natural solutions like pheromone-based traps or targeted insecticides like Yates Nature’s Way Fruit Fly Control can help manage fruit fly populations.
Read more about fruit flies.
6. Lemon tree gall wasps
Lemon tree gall wasps affect citrus trees by laying eggs in developing stems, forming galls. Prune and destroy galls using a knife or a potato peeler in winter before the larvae can mature. This helps reduce the population and prevent the emergence of new wasps.
Alternatively, you can hang sticky traps in the tree during the wasp’s flying season to capture adult wasps and reduce the likelihood of egg-laying.
7. Sooty mould
Sooty mould, a consequence of honeydew-excreting insects, can be prevented by keeping aphids, soft scales, and mealybugs away from citrus trees.
8. Melanose
Melanose, a common fungal disease affecting citrus trees in wet weather, is caused by the pathogen Diaporthe citri. This disease is characterised by small, raised lesions with a dark brown to black colour, displaying a distinctive cracked or alligator skin-like appearance on citrus leaves, fruit, and stems.
Melanose is more likely to attack citrus foliage, fruit and twigs while still very immature. Practical strategies to manage melanose include pruning infected material and applying copper-based fungicides.
9. Lemon scab
Citrus trees in coastal areas may encounter lemon scabs caused by the fungus Sphaceloma fawcettii var. Scabiosa. The good news is that you can still use the juice from your citrus but not the zest from the skin. But there’s a chance your tree is on the way out.
A copper-based antifungal spray on leaves and bark, repeated every three weeks for nine weeks, is an effective control method.
10. Collar rot
Collar rot is a fungal disease caused by various soilborne pathogens, including Phytophthora spp. The disease primarily affects the base of the citrus tree, particularly the area above the bud union. Signs of collar rot include sap seeping from a lesion on the trunk. Place a copper-based fungicide below the lesion.
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