Olive tree - recognize + combat common diseases & pests


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Olive tree - Olea europaea

Far away from the sun-drenched, mild regions of the Mediterranean, the Central European climate sometimes brings an olive tree into distress. Wet, cold winters and rainy summers weaken his resilience, so that he can not defend himself against attacks by pathogenic agents on his own. Anyone who is familiar with the potential dangers as an olive gardener can stand by his noble wood in good time. Familiarize yourself with common diseases and pests. How to recognize the symptoms and combat them effectively, read here.

Summary overview

An olive tree will confront you with diseases and pests of various origins. The following overview shows the harmful effects of this guide in detail:
Common diseases:
  • Eye blotch (Spilocaea oleagina)
  • Olive crayfish (Pseudomonas syringae)
  • Feuerbakterium (Xylella fastidiosa)
  • Leaf yellowing (chlorosis)
Common pests:
  • Scale insects (Coccoidea)
  • Black-backed weevil (Otiorhynchus)
  • Meadow foam cicada (Philaenus spumarius)
So that you can enjoy olives from our own harvest later on, the recommended control measures concentrate on environmentally and health-friendly methods. Only when an ecological approach has proven to be unsuccessful, chemical-based resources will become the focus.

Eye blotch (Spilocaea oleagina)

Ophthalmopathy is feared, as this fungal infection is widespread and can affect the large olive groves in the Mediterranean. From these symptoms you recognize the disease:
  • On infected leaves dark brown spots appear with a bright border
  • In the advanced stage, a leaf completely turns yellow and dies
  • Wet summer weather intensifies the infestation pressure
In the first step of the fight you remove all infested leaves, in order to dispose of them in the dustbin. Because the fungal spores specifically seek the path from living leaf to live leaf, they insulate the infection in this way. For the sake of caution, the fallen leaves should also be eliminated. Since the infection spreads only very slowly, a consistent action can spare further control measures. If eye-spot disease has already infected the entire crown, use a fungicide. The two preparations Fungisan Rose and Vegetable Mushroom-Free and Atempo Mushroom-Free Neudorff have proven themselves well in practice.

Olive crayfish (Pseudomonas syringae)

Olive tree - Olea europaea

In Europe as far as South Africa and North America, a bacterium makes life difficult for commercial and private olive growers. The rod-shaped Pseudomonas syringae spares neither herbaceous nor woody plants and also has its olive tree in sight. Every tiny wound uses the pathogen as an entrance gate to nest deep in the tissue. As a result, cancerous growths form. First symptoms occur before:
  • Brown discoloration on the branch bark, which tears open lengthwise
  • Thin branches die off, thicker branches stop the growth of thickness
  • Black or dark red lesions form on the trunk, which gradually sink in
  • In the advanced stage, the cells of the cambium grow outward
Immediately effective control agents are not available, neither in ecological nor in chemical form. Affected plant parts should be cut out and burned. Since the infection often occurs on unclean scissors and knives, they should always be disinfected. A rain sheltered location and avoidance of overhead irrigation also help prevent the pathogens of olive crabs from attacking. Further, if you have a cut, make a choice in spring when the wounds heal quickly. If frost damage occurs in the form of cracks in winter, use a wound closure agent to prevent bacteria from accessing your olive tree.

Feuerbakterium (Xylella fastidiosa)

The Feuerbacterium has already caused so many devastating damages in olive groves that the European Commission has intervened. Since 2015, commercial olive growers in all European Member States have been obliged to dispose of all olive trees within 100 meters of a plant infected with Xylella fastidiosa, regardless of their state of health. The experts were forced to take this drastic measure, as there are no control measures against this destructive disease. In 2016, the Feuerbakterium was also detected in Germany. The symptoms are easy to diagnose:
  • The bacterium settles in the xylem of the olive tree
  • The running here pathways are clogged
  • The supply of water and nutrients is prevented
  • Leaves, shoots and flowers turn yellow, dry out and die
An affected olive tree shows at first glance all signs of drought stress. Unfortunately, the first symptoms do not appear until weeks and months after the infection. The main carriers are meadow foam cicadas and other insects. The Feuerbakterium is not limited to olive trees. Among the more than 200 host plants are almond, peach and lemon trees as well as oleander and other Mediterranean plants. Already in case of suspected disease, the olive tree should be completely cleared and burned.

Leaf yellowing (chlorosis)

The olive tree is one of the few lime-tolerant plants in the Mediterranean garden. If, on the other hand, the lime content in the soil or container substrate becomes excessive, the leaves turn yellow. The reason for this is not a plant disease, but a lack of iron and magnesium. Although these micronutrients are present in sufficient quantities in the earth. An excessively high calcium content in the alkaline range greater than 8 blocks the absorption of the trace elements. The signs of leaf chlorosis are unmistakable:
  • The leaf surfaces turn yellow from the tips and edges
  • The leaf veins retain their green color, creating a mosaic pattern
  • In the course of the foliage turns brown and falls off
To compensate for the deficiency in the short term, we recommend foliar application with an iron chelate fertilizer, such as Ferramin from Neudorff or Fetrilon from Compo. To permanently eliminate the nutrient deficit, turn an olive tree in a bucket into fresh substrate with a pH between 7 and 8. On a planted Olea europaea, loosen up the soil and work in peat, peat soil or foliage compost.

Scale insects (Coccoidea)

Olive tree - Olea europaea

An olive tree in a permanent room culture offers shield lice with an evergreen leaves a popular destination. This applies equally to lid, cup and lubricating lice. With their pronounced mouthparts, the pests sting the leaf tissue in order to reach the coveted plant sap. If no action is taken against this activity, the tree slowly dies under the growing infestation pressure. The presence of scale insects can be recognized by these indications:
  • Small green or brown bumps on the tops and bottoms of the leaves
  • Mealybugs weave white webs on the foliage and in the leaf axils
  • Mealybugs hide under white cotton buds on the foliage
  • Cripple leaves and flowers
  • Shoots and branches crust and deform
By setting up your olive tree in the open air until the first frost, avoid this plague without further action. If the scale insects have already discovered the wood for themselves, rub off the populated leaves with an alcohol-soaked, soft cloth. Hard-to-reach areas of infection are repeatedly dabbed with cotton swabs that you have previously dipped in spirit. Furthermore, the classic soap solution prepares at least the lice without shield and lid the end. The shielded lice equipped with a tank are naturally combated effectively with diatomaceous earth, a powder of sedimentary rock.
Tip: An infestation with scale insects can be confused at first glance with olive crayfish. Before worrying about clearing your olive tree, carefully examine the areas in question by looking closely with a magnifying glass.

Black-backed weevil (Otiorhynchus)

They are black, 10 mm long and move out at dusk to look for food in the garden. An olive tree with its dense, evergreen leaves dress the Dickmaulr├╝ssler not left it. How to detect an infestation of leaky perennials:
  • Adult beetles leave the characteristic bark-feeding on the leaves
  • Females lay up to 800 eggs at the roots, which nibble on the roots as larvae
  • Under high pressure of infection occur on the olive tree deficiency symptoms, such as drooping leaves and shoots
There is a whole arsenal of environmentally sound means available for fighting. The voracious larvae are reliably destroyed with nematodes. These nematodes are spread using the watering can or a crop protection syringe and parasitize the larvae. For optimal success, repeated use is required. Bait traps can be laid out against adult fat weevils whose grooves are filled with a gel of nematodes.
If you do not want to condemn the beetles to death, hang buckets filled with wood wool in the garden. The inviting retreat, the weevils can not resist, crawl inside and can be relocated by day to a safe location.
If the control with nematodes is too time-consuming, Neempresskuchen works in the substrate. The neem oil contained therein is absorbed by the roots of the olive tree and causes a feeding stop in larvae and beetles. It is important to note that nematodes and neem must not be used at the same time because no oil is poisonous to the beneficial organisms.

Meadow foam cicada (Philaenus spumarius)

Until a few years ago, the meadow foam cicada did not play a significant role in the ranking of common pests on the olive tree. Only when the larvae appeared in masses and sucked on the leaves, they were rinsed with a sharp stream of water. Since the insects have been identified as the main transporter of the Feuerbakterium, a consistent fight comes into the focus. How to detect an infestation:
  • In May and June, the green larvae wrap themselves in a white foam
  • Suction activity causes pustules on leaves, shoots and branches in rows
  • Adult insects are oblong-broad in shape and pale brown to dark brown with light spots

Olive tree - Olea europaea

By suspending sticky traps in the olive tree immediately after being weighed out, the females are prevented from oviposition. Since the larvae are among the prey scheme of ants, you can draw attention to the beneficial organisms with sugar water on the tree. Where the white foam forms, it is shed with water. With an environmentally friendly neem oil-based insecticide, you can effectively combat the meadow foam cicadas and their larvae.

Resistant olive varieties

Since olive trees have been cultivated for centuries, today a wide range of proven varieties is available. Naturally, the focus in the German ornamental garden is on a reliable winter hardiness. This is not contradicted by the fact that some established breeds have also proven to be largely resistant to disease. The following selection introduces you to recommended olive varieties:
leccino
One of the leading olive varieties comes from Tuscany and enjoys worldwide popularity. The outstanding attributes are a good winter hardiness down to - 11.9 degrees Celsius, a vigorous growth, tasty fruits and a reliable resistance to diseases.
Hojiblanca
The large variety of olive trees cultivated in Spain is also increasingly common in Central European gardens. Trust in their hardiness to -9.9 degrees Celsius gave a scientific study of the University of Cordoba. Properly cared for in full sun, Andalusian premium breeding acquires sufficient defenses against diseases and pests.
Aglandaou
The lover is based in France. Aglandou is the ideal olive tree for a pronounced alkaline soil with a pH of 8 to 8.5. The highly branched root system contributes significantly to a reliable frost tolerance. The healthy foliage knows how to ward off diseases and pests, as long as it is not exposed to continuous rain. The French breeder Olivier d'Auge sends young plants from own breeding on request by parcel delivery to Germany.
Arbequina
This olive variety from Catalonia can bear temperatures up to - 11.8 degrees Celsius. Their small fruits are ideal for fresh consumption and produce a premium quality oil. Unmistakable is their corkscrew-like winding trunk, which attracts everyone's attention. Arbequina is one of the selected varieties that are to be discovered in the German specialist trade, because they only rarely cause diseases and pests.
Tip: In the wild, olive trees like to find a location with a high salt content in the air. By sprinkling the wood in the spring with a light saline solution of 15 grams of salt to 1 liter of water, the Mediterranean ideal conditions of the salty Mediterranean climate are simulated.
Conclusion
Skilled hibernation is not the only challenge in the cultivation of olive trees. If an Olea europaea is weakened by neglect of care or frost damage, diseases and pests use the favor of the hour. Excessive humidity causes eye-spot disease or olive cancer. Completely new to the list of common diseases, the Feuerbakterium has found, against which all control strategies so far go nowhere. After all, leaf chlorosis can be remedied with simple means, such as foliar fertilization with iron. With pests, such as scale insects, olive growers are rarely confronted, as long as the woodland at least for some time experiences temperatures around the freezing point. In summer, of course, the appetite of the weevil may not be underestimated. At the same time as the Feuerbakterium, the meadow-foam cicada, previously classified as harmless, has come into focus, since it is considered as the carrier of the pathogen.

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