Pseudaulacaspis pentagona
(mulberry scale)

P. pentagona originated in eastern Asia. It was accidentally introduced to Italy in the nineteenth century, and subsequently, to other regions: for example, USA, Argentina and Australia. It is currently widely distributed in the Palearctic and Nearctic Regions (Kozar, 1990a). There are many publications concerning its detailed distribution and importance in different parts of the world (Konstantinova, 1976; Kozar and Konstantinova, 1981; Davidson and Miller, 1990; Kozar et al., 1994; Anon., 1996).

This species is probably intercepted in most countries; however, interceptions go largely unreported. The species is thermophilous, so it only lives indoors in colder countries (for example, Sweden). In the past 20 years it has started to spread northwards in Europe in field conditions; this could be as a result of climate change. Where 'eradication' has been reported, P. pentagona may have died out locally because of unsuitable conditions, or it may persist at low densities. Under these circumstances, monitoring using pheromone traps may be advisable.

P. pentagona is the subject of quarantine regulations in many countries (Anon., 1976, 1993), but not in EU countries.

P. pentagona is a polyphagous species. The host plant range could be much wider than is listed. However, P. pentagonia cannot complete development on some of the hosts listed, which indicates that some may not be true host plants. P. pentagonia is mainly a pest of deciduous fruits, including peach, currant, grape, kiwi, walnut; it also attacks some woody ornamental plants, including Morus, Sophora, Syringa, Catalpa, Euonymus and Paulownia (APPPC, 1987; Borchsenius, 1966; Konstantinova, 1976; Davidson and Miller, 1990; Kozar, 1990a; Kosztarab, 1996).

P. pentagona has between one and four generations per year in different parts of the world. Development under local conditions are described by Bobb et al. (1973); Shinano et al. (1976); Paloukis (1979); Stimmel (1982); Park and Kim (1990), Hanks and Denno (1993), and Erkilic and Uygun (1997a). It overwinters in cold countries as adult females. In Central Europe, egg-laying starts during mid-May. In Southern Europe, egg-laying starts 1 month earlier. Crawlers appear after 1-2 months. Females each lay ca 100 eggs (Ball, 1980). Males of the first generation start to fly at the begining of July, and the second generation flies in mid-September in Central Europe (Kosztarab and Kozar, 1988). In South Europe, flight commences about 1 month earlier.

P. pentagona is attacked by a large number of parasitoids and predators, which have been studied in detail especially in the Palaearctic region (Trapitzin, 1978; Kosztarab and Kozar, 1988). Studies of natural enemies of P. pentagona include: Zaets (1970); Rosen and DeBach (1976); Gordon (1978); Yasuda (1981); Darling and Johnson (1984); Noyes and Hui (1987); Liebregts et al. (1989); Gordon and Hilburn (1990); Habibian (1991); Li (1991), and Hanks and Denno (1993). A comprehensive list of the natural enemies of P. pentagona is provided by Waterhouse and Norris (1987).

These natural enemies are efficient regulators of P. pentagona; they keep pest density down in natural habitats. Where chemical control has been used against P. pentagona in orchards, its natural enemies can be killed causing local outbreaks. P. pentagona has caused major problems in areas where it was accidentally introduced, in the absence of its natural regulators. The efficiency of natural enemies is reduced in urban areas by pollution. Consequently, P. pentagona can cause severe damage to ornamental plants in towns and cities.

There have been a number of successful biological control programmes against P. pentagona in different parts of the world, especially in the USA, Europe and Russia. Usually Encarsia (Prospaltella) berlesei is reared, released, and established, according to the protocols of Rosen (1991) (see also Greathead, 1976). E. berlesei was released in several European countries, and spread into neighbouring countries. Encarsia diaspidicola has been successfully released in Western Samoa (Sands et al., 1990).

Many of the listed parasitoids of P. pentagona may also be hyperparasitoids.

Heavy infestations on the bark of trees produce large, visible white colonies of female and male scales. Some infestations may be confirmed by laboratory examination with stereomicroscopic analyses of the branches, following the survey system described in detail by Kozar (1990b,c).

The structure and composition of the P. pentagona pheromone is known. P. pentagona pheromones are emitted by females and attract males, but not parasitoids. Pheromone traps are widely used for detection in newly infested regions, especially in Europe (Kozar et al., 1997). Colour and sticky traps were have also been developed to monitor the flight and dispersal of males and parasitoids (Kozar, 1990c, and Kozar et al., 1995).

Only microscopic characteristics can be used to identify the species definitively. Kosztarab and Kozar (1988) and Williams and Watson (1988) describe the methodology of slide mounting. This species can be differentiated from P. prunicola according to the number and shape of plates. P. pentagona has mostly bifurcated plates, whilst P. prunicola usually has spine-like plates. These characters show great variability depending on temperature, geographic locality and host plant (Danzig, 1993).

Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.

Regulatory Control

For details of quarantine regulations for P. pentagona see Anon. (1976, 1993). Quarantine recommendations and requirements for the treatment of seedlings and other nursery materials have included irradiation, fumigation, cold-treatment and heat-treatment (Angerilli and Fitzgibbon, 1990; Balsari and Tamagnone, 1997).

Cultural Control and Sanitary Methods

Obtaining scale-free nursery material is very important, because young plants can die very quickly after infestation. The removal of heavily infested parts of the trees and the cleaning of bark from infestation can improve the efficacy of chemical treatments. Surrounding vegetation can be a source of re-infestation by pests and/or a refugium for natural enemies.

Host-Plant Resistance

There are no varieties that exhibit real resistance to this pest (Arru, 1976). There are several tolerant varieties of different fruit tree species, but these varieties are not usually marketable.

Biological Control

The biological control of P. pentagona is well-studied (see Natural Enemies). Coccinellids and a number of parasitoids including Encarsia berlesei can be effective control agents. However, the effect of biological control programmes can only be observed over a relatively long period, and only in the absence of insecticides. The use of a range of different introduced parasitoid agents and predators, along with the encouragement of indigenous natural enemies can increase the efficacy of control. However, biological control is unlikely to be of significant use in controlling infestations on stressed ornamental plants in urban areas in Europe at times when the weather favours pest development.

Chemical Control

Fumigation of seedlings has traditionally been the most important means by which early infestation by P. pentagona is prevented.

Oil sprays have proved effective for the treatment of infested plantations (Meyer and Nalepa, 1991). Other insecticides may have different efficacy in different parts of the world (Torrel et al., 1987; Isufi and Mirtha, 1996; Erkilic and Uygun, 1997b). In orchards, insecticides (organophosphates, carbamates and pyrethroids) are very efficient against crawlers. These chemicals are often used in the summer against other orchard pests, such as codling moth (Cydia pomonella), leafrollers, leafminers and mites. However, chemical control should be avoided if biological control is in place, to avoid killing natural enemies of the scale.

Early Warning Systems

Kozar (1990b,c) studied monitoring and forecasting systems for P. pentagona in detail. Yellow sticky traps are useful for monitoring males and parasitoids, and pheromone traps collect males. The percentage of infested fruit can be monitored, with control being implemented when infestation levels pass a threshold.

IPM programmes

IPM programmes against orchard pests including scale insects have been developed by Kozar and Varjas (1976), Darvas and Zseller (1985), Parisot (1990), Semisi et al. (1992), Paloukis and Navzoridis (1995), and Jenser et al. (1997). These programmes incorporate the use of insect growth regulators (Rosen, 1991) which are effective against scale insects.