It wouldn’t be a Kiwi garden without a citrus tree! They can quite easily thrive in the garden, but sometimes they can run in to a few problems. If you want to grow spectacular citrus, our top tip is to keep your tree well fed and healthy as they are less likely to be plagued by pests and diseases.
We look at the most common pests and diseases that can afflict your citrus trees, along with symptoms and control options.
- Distorted buds and leaves
- Sticky “honeydew”
- Black sooty mould growing on the honeydew
- Clusters of black, yellow, green or brown insects on leaves
- Ants crawling on the plants and feeding on the honeydew
Most likely cause: Aphids
Aphids are unmistakable in the garden. Easy to spot, aphids are tiny, pear-shaped, sucking insects that love to feed on new growth. There are several species and they may be yellow, green, brown or blackish. They can be referred to as greenfly or blackfly, but they are not actually flies.
Although a single aphid is not a big threat, aphid colonies can grow shockingly quickly and you will easily be able to see them in clusters on shoots, buds and leaves. As they feed, the plant will become brittle and yellow and the plants will slip into decline.
Since aphids are such tiny, tender insects, you can often control them by hosing them off with a strong blast of water. You will need to get all areas of the plant, including the undersides of the leaves, and you will need to do this more than once.
If water does not seem to be controlling them, you can try insecticidal soap. Make sure the plant is completely coated. The soap needs to make contact with the aphid.
Another natural/organic option is Yates Nature’s Way Citrus, Vegie and Ornamental Spray, which controls aphids on contact. Yates Conqueror Oil concentrate is another option.
- Poor growth
- Leaf drop
- Pale, dehydrated leaves
- Small and dry fruit
- Hard, scale-like insects on woody and green stems
Most likely cause: Scale
Scale are sap sucking insects that can be white, brown, black or even pink in colour. They look like patches or raised bumps that appear on stems or the underside of leaves. Scale quickly multiples in dry seasons.
Citrus scale pests can spread rapidly so act as soon as you notice a problem. A natural/organic option is Yates Nature’s Way Citrus, Vegie and Ornamental Spray, which controls scale on contact. Yates Conqueror Oil concentrate is another option.
- Black, sooty mould
- Small insects found in protected cavities
Most likely cause: Mealybugs
Mealy bugs are small sap sucking insects that have a furry white coating. A natural/organic option is Yates Nature’s Way Citrus, Vegie and Ornamental Spray, which controls scale on contact. Yates Conqueror Oil concentrate is another option.
A natural/organic option is Yates Nature’s Way Citrus, Vegie and Ornamental Spray, which controls scale on contact. Yates Nature’s Way Pyrethrum concentrate is another option.
- Rough skin on fruit, stems and leaves
- Wart like lesions on the outside of fruit
- Fruit drop often occurs.
Most likely cause: Citrus Scab (Verrucosis)
This fungal disease is usually encouraged by damp, cool weather. Although the fruit is unaffected on the inside, this disease needs to be controlled as it will gradually reduce the vigour of the tree.
A natural/organic option is Yates Nature’s Way Fungus Spray, a sulphur and copper fungicide to control citrus scab. Yates Copper Oxychloride concentrate is another option.
- Severely deformed leaves
- Leaves changed colour
- Curled leaves
Most likely cause: Leaf Curl
Citrus leaves can curl when temperatures are cold or extremely hot, some insect infestations such as scale, mealy bug, mites or aphids will cause leaves to curl. Over-watering can also cause this. Other times it is leaf curl disease. Leaf curl overwinters in buds of infected trees. Collect up any infected leaves that fall and burn or dispose of, do not compost as this will spread the disease.
A natural/organic option is Yates Nature’s Way Fungus Spray, a sulphur and copper fungicide to control leaf curl. Yates Copper Oxychloride concentrate is another option.
- Loss of leaves
Most likely cause: Leaf Drop
Citrus trees naturally shed their leaves from time to time, usually having a life span of 3-4 years. If a lot drop off at once, or over a short period of time, this usually indicates that something isn’t right.
Leaves will drop after a sharp decrease in temperature, so if you’re citrus tree is in a pot, move under cover or to a warmer area of your property. If plants are receiving too much, or not enough water, known as water stress, this can also lead to leaf drop. Root bound plants can also drop their leaves, so if your citrus tree is in a pot or container and you’re watering correctly, this may be the cause.
- Small sized fruits dropping from the tree
Most likely cause: Fruit drop
Fruit drop can be a common occurrence among citrus trees. A part of that is normal – it happens when a tree sets more fruit than it can support (often in young trees). First, blossoms drop without setting fruit, then pea-size fruit falls from the tree, then fruit the size of golf balls may fall off. This can all be normal. Continuous fruit drop, however, is not. This can be brought on by many factors, though typically it’s a result of environmental stress (cold wind, sudden changes in temperature, inadequate nutrition, lack of moisture) or poor pollination.
Adequate moisture during the early stages of fruit development is crucial. If rain is scarce, regular watering is necessary. Apply a layer of mulch to conserve moisture in the soil, though keep the mulch away from the trunk or it may rot. Clear away any weeds too as these compete for water and nutrients. In cooler areas, keep your plants sheltered from cold winds. If moving them to a protected spot over winter, do so gradually to give the plant time to adjust.