Common citrus problems
Citrus grow well in many parts of New Zealand, especially in the warmer northern regions.
Citrus are hardy and very forgiving of neglect but they can be affected by a number of pests and diseases. Most problems are relatively easy to control but the key lies in identifying the problem in the first place. Here are some of the most common:
Scales - There are many different types of scale insects that come in a range of shapes and colours, but they’re all characterised by the protective coating the sapsucking insects create over themselves. Underneath each coating a pest is busily sucking the sugar from the plant. Sometimes the excess sugar produced by the scale causes black sooty mould to grow on the leaves. All types of scale on citrus can be treated with a spraying oil. After the scale has died, the sooty mould will gradually flake off.
Aphids - Like scales, aphids are sap-sucking pests that cluster on the sweet, tender growing tips. Small infestations can be squashed but, if numbers start to get out of control, it may be necessary to use a spraying oil or Yates Nature’s Way Insect Spray.
Borer - The first obvious sign of borer activity is the sawdust that appears in branch junctions. Closer inspection will reveal the hole where the borer has entered the branch.
Prune off badly affected branches and burn or bin the clippings to get rid of the pest. If the problem’s not too severe, clear the entrance to the holes and spray with Yates Nature’s Way Pyrethrum.
Verrucosis - Pictured. This fungal disease causes irregular scabby, wart-like growths to de- velop on the fruit and, occasionally, on the stems. Although the fruit is still usable, the problem will gradually get worse if it’s not treated. Affected plants can drop large numbers of immature fruit.
Prune off the worst-affected stems and spray all over the tree with Copper Oxychloride or Yates Champ DP. This is most effective if carried out when the plant is about midway through flowering. A follow up spray is helpful.