Black scale in olive tree (Saissetia oleae Olivier, 1791), is one of the most important pests in the olive grove.
Saissetia oleae, is also commonly known for tizne mealybug or carapace.
In addition to the olive tree, citrus fruits ( orange, lemon, mandarin…) are also sensitive to suffer the attack of this black scale.
This species has important differences with the violet olive scale (Parlatoria oleae), plague less frequent and of importance secondary.
Damages caused by the black scale olive tree
With enough presence in the olive grove, the black scale olive tree is one of the three main phytophagous pests that olive growers face.
The mealybug of the blight, like the aphid, excretes a significant amount of molasses during the digestion process.
This molasses is the base that supports the bold fungus. This fungus forms a black layer that stands between the sun and the olive leaf. This, reduces photosynthetic activity and indirectly the vigor of the olive tree. The bold stains the olives and is complex to eliminate, depreciating the value of the olives for greening.
In addition to collateral damage caused by the presence of the fungus. black scale itself as a sap sucking insect, consumes olive resources. When the infestation is high, the black scale can cause the tree decay, being necessary to perform phytosanitary treatments with insecticides and fungicides (when there is a presence of bold), to alleviate the situation.
Biological cycle of Saissetia oleae
We can differentiate between black scale states between several phases. Adult female, adult female with eggs and black scale larvae.
Adult female mealybug with eggs
It is dark brown (with eggs present), it has a convex shape with an H-shaped embossed mark. Its size is between 1 and 4 mm wide and 2 to 5mm in length. Each female lays about 1000-2000 pink eggs and size between 0.3 and 0.8mm.
Female mealybug without eggs
It differs by its smaller size, more flattened shape and lighter brown color.
Male of Saissetia oleae
There are no males of Saissetia oleae, being the parthenogenetic reproduction.
Black olive scale larvae
Around the month of May larvae are born initially mobile, but they end up being fixed “like a barnacle” to the branches or leaves of the olive tree. During the development process, the larvae make two molts between which they can make slight movements. Finally, the larvae pass to the nymph state that gives rise to the adult black scale and c complete the generation in late summer.
In autumn some of the more mature adults develop a second generation of a partial character.
This generation is developed until April and provides adult females for the May generation. The black scale is considered to have an annual generation and a half.
Saissetia Oleae treatment
There are three control measures for black scale (saissetia oleae treatment). The natural control through parasitic or predatory insects, the cultural measures and the phytosanitary treatments.
Natural control of the mealybug black scale
It is also essential to control some species of parasitic or predatory insects such as: Chilocorus bipustulatus, Metaphycus helvolus, Scutellista cyanea and Coccophagus lycimnia.
Cultural measures against black scale
The high temperatures and the environmental dryness of the summer, can allow us to end with a 95% of black scale larvae. Aerated planting frames, thinning prunings, irrigation control and balanced nutrition (without excess nitrogen).
Phytosanitary treatments against black scale olive tree
Infected branch of black scale and Negrilla
The chemical treatments against black scale should be the last option. They should only be carried out when after applying the previous techniques, there is a black scale population above the admissible level. The authorized treatments by the ministry will be applied in the dose and conditions indicated by the manufacturer.
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