The higher taxonomy of scale insects (Hemiptera: Coccoidea) is under debate. They are generally considered in the Order Hemiptera, Suborder Sternorrhyncha, and Superfamily Coccoidea (Gullan 2001).
There are an estimated 7355 species of scale insect in 1050 genera and 28 families. Three families account for an estimated 6 073 of these species. These are the Diaspididae (2409), Pseudococcidae (2215) and Coccidae (1149) (Ben-Dov et al. 2005).
A number of scale insects are well known as quarantine pests. Several of these species are distributed widely and are established in a range of production areas, whereas others have limited geographic distributions.
Scale insects are regularly detected upon plant and plant product commodities in international trade. Detection of scale insects on these commodities may result in phytosanitary measure(s) being applied.
Whilst evidence is limited, it is considered that the spread of many of these species has been mainly through the unregulated trade of propagative plant materials and plants (nursery stock), rather than via regulated trade in fresh fruits and vegetables for human consumption.
Although scale insects generally have limited mobility, they may be transferred passively by animal and human activities (e.g. transport of contaminated equipment and plant material) and by wind. The presence of scale insects on the pathway of commodities for human consumption provides a restricted opportunity for these pests to establish and spread compared to that associated with nursery stock. The developmental biology of scale insects may be a factor that mitigates phytosanitary risk.
ISPM No. 11, Pest risk analysis for quarantine pests including analysis of environmental risks and living modified organisms, 2004 provides guidance for undertaking a pest risk analysis (PRA) to determine the quarantine status of a given pest. It describes the integrated processes to be used for risk assessment as well as the selection of risk management options. This standard supplements ISPM No. 11 in regard to PRA for scale insects.
Certain scale insects may be important pests on specific commodities for some countries, but evaluation of the probability of introduction and spread of these pests and of the associated economic consequence may conclude that they may not establish or spread on commodities for human consumption. The critical factor supporting this conclusion is their low mobility of the scale insect and the fact that the host is likely to be consumed and the skin either eaten or discarded relatively soon after harvest. The combination of these factors is likely to provide few opportunities for establishment or spread for scales of low mobility associated with commodities for human consumption.
This standard provides guidelines for considering the risk from scale insects on the pathway associated with fresh fruit and vegetables for human consumption. It provides guidelines on: