Olive tingit – Plerochila australis (Lace Bug)
This is a small grey-brown sucking insect about 4mm in length. They feed on the underside of leaves by sucking the plant sap, destroying the leaf tissue. As a result yellow spots appear on the leaf or, in the case of heavy infestation; the whole leaf turns yellow and dies
There are two types of olive scale that normally attack olive trees. Soft scale species include The Black Olive Scale as well as Soft Brown Scale. Armored species include Oleander Scale, Red Scale and Olive Scale. The eggs hatch into tiny yellow crawlers with legs. Crawlers walk all over the tree surface and can spread to neighboring trees by people or birds or are blown by wind to other trees.
Armored scales settle down permanently after a day or two in the crawler stage, molt and begin to form the characteristic covers. Soft scales move around longer but also settle down eventually at permanent sites.
Scale occurs on both the branches, leaves and the fruit. On the fruit scales causes deformation, delayed ripening and changes in colour where they feed on the fruit.
Peacock eye (spot) – Spilocaea oleagina
This is also known as olive leaf spot or birds-eye spot. It is less of a problem in the dryer olive growing regions.
The first signs of peacock spot are black sooty looking blotches on the leaf that cannot be rubbed off with a finger. These develop into muddy green to almost black circular spots. A yellow halo around the spot sometimes occurs, resembling the spots on a peacock tail, hence the name. Where there are a number of these spots on a leaf, it will turn yellow and drop of.
Olive larvae – Agropistes sexvittatus
On hatching the yellow larvae of the olive beetle, burrow into the leaves, normally attacking the new growth first, and then feed between the leaf surfaces. They can
cause major damage in a very short term if left untreated.
Olive beetle – Agropistes olea
Olive Beatles resembles Ladybirds in shape and size. They normally are either yellow with black stripes or completely shiny black. When disturbed they have a habit of jumping instead of flying. The adult beetles attack the fruit and leave scars on the fruit. They lay their yellow eggs underneath the leaves, sometimes covered with excrement.
Anthracnose – Gloeosporium (Soapy Olives)
This fungal disease is encouraged by rainy or humid conditions. The name Anthracnose means “coal-like”.
The first sign of infection appears on the flowers in the form of rust brown spots. Before the flowers can open it dies. On the fruit it appears as small circular or oval, brown coloured, depressed spots which grows larger very quickly. The disease spreads very quickly even in harvested fruit and steps to contain it should be taken as soon as the first signs appear. Infected fruit is useless for processing.
Olive fly – Bactrocera olea
The fly is slightly smaller than the housefly, but darker in colour. It has a characteristic yellow-white shield on the underside of its body. This is a very serious pest and steps should be taken keep orchards free from it. The fly lays a single egg beneath the skin of the fruit, usually from January. Sting marks can be seen on green fruit and cutting open the fruit will reveal the maggot burrowed into the flesh.
Mature larva drops to the ground under the tree where it pupates and stays in the soil through the winter. Fruit invested by olive fly larva is completely spoilt and cannot be used for table olive processing or the production of good quality olive oil.
This fungus attacks the root system, or the rotting may spread to the lower stem of the tree, causing collar rot. It is also possible to have collar rot without the roots being infected. The first signs are reduced growth in the spring, thin/sparse canopies, yellow, wilted leaves and shoot tip dieback. In larger trees the disease may not be immediately noticeable and the tree can even take 1 to 2 years to die. The disease can be identified from a soil or tissue sample from the roots or infected stem. This disease can be prevented by planting your trees in well drained soil.
Olive psylla – Euphyllura olivine
It is a small sucking insect related to aphids. The eggs are laid on new growth and the nymphs secrete a white wax resembling cotton wool as well as honeydew.
Animals eating the trees
In the drier regions of South Africa, some farmers have problems with rabbits, hare and other small animals eating the leaves. Using a tree guard will protect the tree from hungry animals, herbicide drift and will help finding the trees if weeds get out of control (which you shouldn’t allow to happen). It also creates a mini green house environment for the tree. However if you do not have animals eating your trees, don’t go to the bother and expense of putting tree guards on.
In the drier regions termites can damage young trees by nesting in the root systems and by feeding on twigs and leaves.
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