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Plantwise Technical Factsheet

olive scale (Saissetia oleae)

Host plants / species affected
Aralia
Asparagus officinalis (asparagus)
Cajanus cajan (pigeon pea)
Catharanthus roseus (Madagascar periwinkle)
Citrus
Citrus reticulata (mandarin)
Citrus sinensis (navel orange)
Coffea (coffee)
Coffea arabica (arabica coffee)
Cycas revoluta (sago cycas)
Erica (heaths)
Euphorbia pulcherrima (poinsettia)
Ficus benjamina (weeping fig)
Gossypium (cotton)
Ilex (Holly)
Korthalsella
Laurus nobilis (sweet bay)
Nerium (oleander)
Olea (olive)
Olea europaea subsp. europaea (European olive)
Pelargonium zonale hybrids
Persea americana (avocado)
Pistacia
Pistacia vera (pistachio)
Prunus (stone fruit)
Psidium (guava)
Psidium guajava (guava)
Punica granatum (pomegranate)
Pyrus (pears)
Rosmarinus officinalis (rosemary)
Spondias (purple mombin)
Tamarix (tamarisk)
List of symptoms/signs
Leaves  -  abnormal leaf fall
Leaves  -  abnormal leaf fall
Leaves  -  honeydew or sooty mould
Leaves  -  honeydew or sooty mould
Leaves  -  wilting
Stems  -  external feeding
Symptoms
S. oleae colonies extract large quantities of sap, causing general host debilitation and build-up of sticky honeydew deposits on nearby surfaces. The honeydew may attract attendant ants. Sooty moulds grow on the sugary deposits. Badly fouled leaves may be dropped prematurely. The older insects are usually quite easy to see as dark grey or brown-to-black lumps on leaf undersides and stems.
Prevention and control
Regulatory Control

Planting material of host-plant species of S. oleae should be inspected in the growing season before shipment and should be free of infestation. A phytosanitary certificate should guarantee absence of the pest from consignments of either planting material or produce.

Chemical Control

Due to the variable regulations around (de-)registration of pesticides, we are for the moment not including any specific chemical control recommendations. For further information, we recommend you visit the following resources:
- PAN pesticide database (www.pesticideinfo.org)
- Your national pesticide guide

Biological Control

As an introduced pest in most of the countries where it occurs, S. oleae is particularly suitable for classical biological control. However, ants attracted to the scales by honeydew may deter natural enemies from attacking them. The biological control of S. oleae in California is discussed by Bartlett (1978).

Biological control of S. oleae in Florida is discussed by Browning (1994), who reports that the most important natural enemy of Saissetia species there is Scutellista caerulea. However, biological control is not completely effective because problems in identifying Saissetia species have resulted in unsuccessful introductions of parasitoids that were inappropriate to the target pest species. S. oleae is less important on citrus than S. neglecta in Florida.

The following information is from Bartlett (1978). Numerous natural enemies have been introduced to California but relatively few species are important control agents for S. oleae there now. In coastal areas, Metaphycus helvolus is a successful control agent, but inland it does not prosper because of intolerance of the colder winters. In these areas, control by M. lounsburyi, Scutellista caerulea and Coccophagus lycimnia is rather less successful. M. lounsburyi does best in areas where the scale is bivoltine, as in univoltine scale populations there is a severe shortage of hosts at an appropriate stage for 7 months of the year.

From California, Metaphycus helvolus has been introduced successfully to Greece, Crete and Iran to control S. oleae. This parasitoid is also the most effective introduced natural enemy of the scale in Chile.

The situation in California has changed recently with the introduction of M. bartletti in 1986. M. bartletti has now become the most important control agent in the coastal region. Likewise when M. bartletti was introduced into European countries and Israel it displaced M. helvolus and became the most effective parasitoid (Lampson and Morse, 1992; Argov and Rossler, 1993).

In Australia, control of S. oleae is mainly by Metaphycus lounsburyi, Scutellista caerulea, M. helvolus and the native ladybird, Rhyzobius forestieri. Details of the life history of Scutellista caerulea are given by Jadhav and Ajri (1984).
Impact
S. oleae is one of the most important pests of citrus in the Mediterranean Basin, Florida, California and South America (Bartlett, 1978). Gill (1988) considered it to be the most injurious soft scale in California, and the most important pest of citrus there until 1940; he also reports it as a serious pest of olives. Removal of large quantities of sap debilitate the plant and can cause wilting, desiccation of tissues and dieback. Sooty mould growth on honeydew deposits screen light and air from the leaves and impair photosynthesis, promoting premature leaf drop. Such damage reduces overall yield and quality of produce.
Related treatment support
 
External factsheets
IVIA factsheets, Instituto valenciano de investigaciones agrarias, Spain, 2015, Spanish language
Department of Agriculture and Food Western Australia Farmnotes, Government of Western Australia, 2011, English language
TNAU Agritech Portal Crop Protection Factsheets, Tamil Nadu Agricultural University, English language
TNAU Agritech Portal Crop Protection Factsheets, Tamil Nadu Agricultural University, Tamil language
University of California IPM Pest Management Guidelines, University of California, 2007, English language
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